rhBMP-2-Coated Acellular Dermal Graft for Chronic Rotator Cuff Healing: Translational Tendon Repair Research

*Kwang-Il Lee, Ju-Woong Jang and Kwang-Won Lee*

#### **Abstract**

A rotator cuff tear is a common shoulder injury in sports medicine. However, a rotator cuff repair still has the high failure rate (57%) in large torn (>8 cm2 ) rotator cuff cases. One of the main reasons is failing at suture-tendon cause of continuous tensional and torsional stresses even after surgery, and thus, an ideal biologic augmentation to overcome large tears is an essential challenge. The ECM graft, the biological material can be useful for augment repair of large torn rotator cuff. Recombinant human bone morphogenetic protein 2 (rhBMP-2), which belongs to transforming growth factor-β superfamily, is well known as an osteoinductive growth factor. It plays an important role in the development of bone and cartilage. rhBMP-2 also facilitates chemotaxis in the host tissue. In this study, rhBMP-2 coated acellular dermal graft, which is isolated from human cadaveric donor, was transplanted in the rabbit with the chronic rotator cuff injury. The radiologic image, histomorphometric, histologic image analyses, and tensile test were performed to evaluate the effectiveness. The results showed the enhancement of increased host cell infiltration, new bone formation, and tensile mechanical property. The rhBMP-2-coated acellular dermal graft will be promising for chronic rotator cuff healing.

**Keywords:** rotator cuff, rhBMP-2, acellular dermis, tendon-bone healing, enthesis

#### **1. Introduction**

A rotator cuff plays an important role in shoulder movements and maintaining shoulder joint stability [1]. The rotator cuff is composed of supraspinatus muscle, subscapularis muscle, infraspinatus muscle, and teres minor muscle. The rotator cuff is connected between the scapula and the humeral bone head, forming a cuff at the shoulder joint. The rotator cuff tear, which is partial tear and full-thickness tear, mainly occurs in the supraspinatus tendon under the acromion [2]. A torn rotator cuff weakens shoulder's physical function. Almost 2 million people in the United States visit to see doctors cause of the painful rotator cuff at every year [3]. The rotator cuff repair requires reattachment of the rotator cuff tendon back to the humeral bone by using suture and fixation tools, which is non-biological technique [4, 5]. Rotator cuff repair has showed good long-term follow-up results so far. However, it still shows the high failure rate (57%) in the case of large tear

(more than 8 cm<sup>2</sup> ) size [6]. The main reason of the pain even after rotator cuff repair surgery is that the shoulder has stiff due to the limited movement [7]. During the surgery, the rotator cuff tendons are sutured to the upper humeral bone. In the case of large tear size, it will be much harder to suture the shortened tendon back to the bone than the repair of the small tear size [8]. More tensile stress will be applied to the sutured gap between the tendon and bone.

The limitations for rotator cuff healing maybe overcome by biological augmentation approaches. A bio-scaffold should have high initial fixation strength, mechanical stability, and biological healing of the tendon-bone interface. And a growth factor should induce host cell infiltration and new tissue formation. Those characteristics are strongly necessary for biological augmentation approaches [9–12]. The dermal graft, which has been used for wound coverage, maybe applicable for large rotator cuff tears. The dermal graft is an acellular dermal extracellular matrix (ECM) scaffold intended for supporting and covering the soft tissue repair. There are various types of the acellular ECM scaffold such as small intestinal submucosa, urinary bladder basement membrane, pericardium, and dermis [13–16]. The only dermal graft has the most thickness (maximum 4 mm), and this will be the only ECM scaffold that can cover the thickness of supraspinatus (avg. 4.9 mm) or infraspinatus (avg. 4.2 mm) tendon [17]. Dermal graft has been used as a grafting material in plastic, dental, and orthopedic surgeries [18–20].

Various growth factors have been applied for enthesis regeneration studies [21–25]. Recombinant human bone morphogenetic protein 2 (rhBMP-2) is an osteoinductive protein that induces differentiation of mesenchymal stem cells into osteoblasts and chondrocytes. rhBMP-2 has shown the potential to improve tendon-bone biomechanical strength during rotator cuff healing [26, 27]. In our previous studies, we found that injectable rhBMP-2 hydrogel increased the biomechanical properties and new bone formation at the tendon-tibia intra articular bone tunnel [28].

The purpose of this translational study is to investigate whether the rhBMP-2 coated dermal graft can improve rotator cuff healing using a rabbit chronic rotator cuff injury model.

#### **2. Materials and methods**

#### **2.1 Decellularization of human dermis and rhBMP-2 coating**

Dermis was procured from the back of human cadaver and cut into pieces (1 × 2 cm). The tissue pieces were digested in an enzyme cocktail (total 500 mL) mixed with 0.25%(v/v) trypsin, 7.5%(w/v) collagenase A, and 37.5%(w/v) protease in a shaking incubator at 120 rpm, 37°C for 4 hours [29]. The tissues were then washed with the same volume of saline solution at 120 rpm, 4°C for 1 hour. This washing step was repeated for three times and finished with the final saline washing for 12 hours. And then, the washing solution was replaced with the same volume of distilled water and the tissues were cleansed with ultrasonic waves at 240 W for 5 minutes. This step was repeated in fresh saline solution. The processed tissues were lyophilized and sterilized with ethylene oxide gas.

Chinese hamster ovary cell line-derived rhBMP-2 was reconstituted and diluted with distilled water to 50 ug/mL before coating on the scaffold. rhBMP-2 was covered on the both side of the dermal graft and, then, lyophilized.

#### **2.2 Surgery for making a chronic rotator cuff injury model**

Adult New Zealand white rabbits (n = 42, male, 5-month old, 3.0 kg) were used for the chronic rotator cuff tear model. All the animal surgical protocols were approved by

**51**

**Figure 1.**

*rhBMP-2-Coated Acellular Dermal Graft for Chronic Rotator Cuff Healing: Translational…*

for 8 weeks to check their mobility and the state of the surgical wound.

**2.3 Surgical procedure for dermal graft insertion**

surgery, and they were sacrificed at 4 or 8 weeks.

**and mineralized tissue generation**

the Committee of Experimental Animal Sciences. To make the chronic injury model, the rabbits were anesthetized with ketamine, 40 mg/kg IM and xylazine, 5 mg/kg IM, and the right shoulder joint compartment was exposed. The supraspinatus tendon was cut off from the right proximal humerus bone. The detached end of the tendon was placed in a silicon tube (10 mm length and 4 mm diameter) and fixed by suturing (**Figure 1**). The silicon tube-inserted tendon was relocated and sutured using 5-0 Vicryl. Postoperatively, the animals were allowed free movement without the use of any type of immobilization and had access to food and water from the first day onward. They were monitored daily

For dermal graft implantation, the supraspinatus repair by single-row repair technique was performed in this study. After 4 weeks, the silicon tube was removed from the cut supraspinatus tendon, and two holes (1 mm diameter) were made on the proximal humerus bone for the graft insertion (**Figure 2**). The rabbits were assigned to one of the following treatment groups: normal (n = 6); no grafting (n = 12), the cut supraspinatus tendon was inserted into the hole without graft and fixed by suturing; dermal graft insertion (n = 12), a sheet-shaped dermal graft (1 cm × 2 cm) was inserted and fixed by suturing between the tendon and bone; and rhBMP-2-coated dermal graft insertion (n = 12) with the same method. The animals were allowed to recover and monitored as described for chronic defect

**2.4 Micro-computed tomography (CT) analysis of bone mineral density (BMD)** 

A micro-CT system was used for quantitative analysis of BMD and mineralized tissue generation between the connected tendon and bone lesion. Rabbit shoulder

*The surgical procedure of chronic disease model. (a) After detaching the tendon from the proximal humeral bone; (b) the end of a tendon is inserted into the silicon tube; (c, d) they are sutured and fixed for 4 weeks.*

*DOI: http://dx.doi.org/10.5772/intechopen.82282*

*rhBMP-2-Coated Acellular Dermal Graft for Chronic Rotator Cuff Healing: Translational… DOI: http://dx.doi.org/10.5772/intechopen.82282*

the Committee of Experimental Animal Sciences. To make the chronic injury model, the rabbits were anesthetized with ketamine, 40 mg/kg IM and xylazine, 5 mg/kg IM, and the right shoulder joint compartment was exposed. The supraspinatus tendon was cut off from the right proximal humerus bone. The detached end of the tendon was placed in a silicon tube (10 mm length and 4 mm diameter) and fixed by suturing (**Figure 1**). The silicon tube-inserted tendon was relocated and sutured using 5-0 Vicryl. Postoperatively, the animals were allowed free movement without the use of any type of immobilization and had access to food and water from the first day onward. They were monitored daily for 8 weeks to check their mobility and the state of the surgical wound.

#### **2.3 Surgical procedure for dermal graft insertion**

*Biotechnology and Bioengineering*

) size [6]. The main reason of the pain even after rotator cuff

repair surgery is that the shoulder has stiff due to the limited movement [7]. During the surgery, the rotator cuff tendons are sutured to the upper humeral bone. In the case of large tear size, it will be much harder to suture the shortened tendon back to the bone than the repair of the small tear size [8]. More tensile

The limitations for rotator cuff healing maybe overcome by biological augmentation approaches. A bio-scaffold should have high initial fixation strength, mechanical stability, and biological healing of the tendon-bone interface. And a growth factor should induce host cell infiltration and new tissue formation. Those characteristics are strongly necessary for biological augmentation approaches [9–12]. The dermal graft, which has been used for wound coverage, maybe applicable for large rotator cuff tears. The dermal graft is an acellular dermal extracellular matrix (ECM) scaffold intended for supporting and covering the soft tissue repair. There are various types of the acellular ECM scaffold such as small intestinal submucosa, urinary bladder basement membrane, pericardium, and dermis [13–16]. The only dermal graft has the most thickness (maximum 4 mm), and this will be the only ECM scaffold that can cover the thickness of supraspinatus (avg. 4.9 mm) or infraspinatus (avg. 4.2 mm) tendon [17]. Dermal graft has been used as

stress will be applied to the sutured gap between the tendon and bone.

a grafting material in plastic, dental, and orthopedic surgeries [18–20].

new bone formation at the tendon-tibia intra articular bone tunnel [28].

**2.1 Decellularization of human dermis and rhBMP-2 coating**

were lyophilized and sterilized with ethylene oxide gas.

Various growth factors have been applied for enthesis regeneration studies [21–25]. Recombinant human bone morphogenetic protein 2 (rhBMP-2) is an osteoinductive protein that induces differentiation of mesenchymal stem cells into osteoblasts and chondrocytes. rhBMP-2 has shown the potential to improve tendon-bone biomechanical strength during rotator cuff healing [26, 27]. In our previous studies, we found that injectable rhBMP-2 hydrogel increased the biomechanical properties and

The purpose of this translational study is to investigate whether the rhBMP-2 coated dermal graft can improve rotator cuff healing using a rabbit chronic rotator

Dermis was procured from the back of human cadaver and cut into pieces (1 × 2 cm). The tissue pieces were digested in an enzyme cocktail (total 500 mL) mixed with 0.25%(v/v) trypsin, 7.5%(w/v) collagenase A, and 37.5%(w/v) protease in a shaking incubator at 120 rpm, 37°C for 4 hours [29]. The tissues were then washed with the same volume of saline solution at 120 rpm, 4°C for 1 hour. This washing step was repeated for three times and finished with the final saline washing for 12 hours. And then, the washing solution was replaced with the same volume of distilled water and the tissues were cleansed with ultrasonic waves at 240 W for 5 minutes. This step was repeated in fresh saline solution. The processed tissues

Chinese hamster ovary cell line-derived rhBMP-2 was reconstituted and diluted

Adult New Zealand white rabbits (n = 42, male, 5-month old, 3.0 kg) were used for the chronic rotator cuff tear model. All the animal surgical protocols were approved by

with distilled water to 50 ug/mL before coating on the scaffold. rhBMP-2 was

covered on the both side of the dermal graft and, then, lyophilized.

**2.2 Surgery for making a chronic rotator cuff injury model**

(more than 8 cm<sup>2</sup>

cuff injury model.

**2. Materials and methods**

**50**

For dermal graft implantation, the supraspinatus repair by single-row repair technique was performed in this study. After 4 weeks, the silicon tube was removed from the cut supraspinatus tendon, and two holes (1 mm diameter) were made on the proximal humerus bone for the graft insertion (**Figure 2**). The rabbits were assigned to one of the following treatment groups: normal (n = 6); no grafting (n = 12), the cut supraspinatus tendon was inserted into the hole without graft and fixed by suturing; dermal graft insertion (n = 12), a sheet-shaped dermal graft (1 cm × 2 cm) was inserted and fixed by suturing between the tendon and bone; and rhBMP-2-coated dermal graft insertion (n = 12) with the same method. The animals were allowed to recover and monitored as described for chronic defect surgery, and they were sacrificed at 4 or 8 weeks.

#### **2.4 Micro-computed tomography (CT) analysis of bone mineral density (BMD) and mineralized tissue generation**

A micro-CT system was used for quantitative analysis of BMD and mineralized tissue generation between the connected tendon and bone lesion. Rabbit shoulder

#### **Figure 1.**

*The surgical procedure of chronic disease model. (a) After detaching the tendon from the proximal humeral bone; (b) the end of a tendon is inserted into the silicon tube; (c, d) they are sutured and fixed for 4 weeks.*

#### **Figure 2.**

*The surgical procedure of patch insertion. (a) Finding the silicon tube-inserted tendon lesion after 4 weeks; (b) the removed tube from tendon; (c) making a hole for fixing with tendon; (d) the detached tendon is sutured with the bone through the holes; (e) the tendon is fixed with the bone; (f) each conditional dermal patch is inserted and fixed with suturing between the tendon and bone lesion.*

specimens were scanned and reconstructed using 3D reconstruction bundle software. To quantify the amount of newly formed mineralized tissue over time, the region of interest (ROI) was chosen and reconstructed using the 3D software. After thresholding, the BMD (mm3 ) of the ROI of mineralized tissue was calculated.

#### **2.5 Biomechanical testing**

Rabbit shoulder joints including the tendon-connected bone lesion were collected. To analyze the tensile mechanical properties, tensile strength was measured using a universal testing machine. The specimen was fixed vertically on a 5000 N load cell, and tensile strength was measured by pulling the sample at a loaddisplacement rate of 10 mm/min (**Figure 3**). The failure load and ultimate strength (N) were recorded.

#### **2.6 Histological and histomorphometric analysis**

Rabbit shoulder joints were collected and fixed in a neutralized formalin solution for 2 days and decalcified using 10% formic acid. Then, the specimens were

**53**

**Table 1.**

**2.7 Statistical analysis**

*rhBMP-2-Coated Acellular Dermal Graft for Chronic Rotator Cuff Healing: Translational…*

*3D-CT images and new bone formation of each experimental group 4 and 8 weeks after repair. (a) Intact group (PO 4 weeks); (b) defect group (PO 4 weeks); (c) repair group (PO 4 weeks); (d) dermal graft augmentation group (PO 4 weeks); (e) rhBMP-2-coated dermal graft augmentation group (PO 4 weeks); (f) intact group (PO 8 weeks); (g) defect group (PO 8 weeks); (h) repair group (PO 8 weeks); (i) dermal graft augmentation group (PO 8 weeks); (j) rhBMP-2-coated dermal graft augmentation group (PO 8 weeks); (k) quantitative* 

**Characteristics Points (maximum total of 9 points)**

*analysis of the new bone formation after rotator cuff surgery after 4 and 8 weeks.*

Abundant 3 Moderate 2 Slight 1 None 0

Abundant 3 Moderate 2 Slight 1 None 0

75–100% 3 50–75% 2 25–50% 1 0–25% 0

dehydrated in ethanol and embedded in paraffin. The 4-um-thick sections were stained with H&E and visualized using an optical microscope. Healing of the tendonbone connected lesion was graded histomorphologically by two observers blinded to treatment group. Histomorphometric analysis was performed to assess healing of the bone-tendon interface on the basis of three histomorphological criteria: fibrocartilage formation, new bone formation, and tendon graft bonding to adjacent tissue, which

*Histomorphometric scoring system used to assess healing of the tendon-patch grafts with the bone.*

The data are presented as the average from at least triplicate samples. The experiments were repeated three times to ensure the reproducibility of the methods

were scored on a scale of 0–3 (maximum total score of 9) in **Table 1**.

*DOI: http://dx.doi.org/10.5772/intechopen.82282*

**Figure 3.**

Fibrocartilage formation

New bone formation

Tendon allograft bonding to adjacent tissue

*rhBMP-2-Coated Acellular Dermal Graft for Chronic Rotator Cuff Healing: Translational… DOI: http://dx.doi.org/10.5772/intechopen.82282*

#### **Figure 3.**

*Biotechnology and Bioengineering*

specimens were scanned and reconstructed using 3D reconstruction bundle

*The surgical procedure of patch insertion. (a) Finding the silicon tube-inserted tendon lesion after 4 weeks; (b) the removed tube from tendon; (c) making a hole for fixing with tendon; (d) the detached tendon is sutured with the bone through the holes; (e) the tendon is fixed with the bone; (f) each conditional dermal patch is* 

software. To quantify the amount of newly formed mineralized tissue over time, the region of interest (ROI) was chosen and reconstructed using the 3D software. After

Rabbit shoulder joints including the tendon-connected bone lesion were collected. To analyze the tensile mechanical properties, tensile strength was measured using a universal testing machine. The specimen was fixed vertically on a 5000 N load cell, and tensile strength was measured by pulling the sample at a load-

displacement rate of 10 mm/min (**Figure 3**). The failure load and ultimate strength

Rabbit shoulder joints were collected and fixed in a neutralized formalin solution for 2 days and decalcified using 10% formic acid. Then, the specimens were

) of the ROI of mineralized tissue was calculated.

**52**

thresholding, the BMD (mm3

**2.6 Histological and histomorphometric analysis**

*inserted and fixed with suturing between the tendon and bone lesion.*

**2.5 Biomechanical testing**

**Figure 2.**

(N) were recorded.

*3D-CT images and new bone formation of each experimental group 4 and 8 weeks after repair. (a) Intact group (PO 4 weeks); (b) defect group (PO 4 weeks); (c) repair group (PO 4 weeks); (d) dermal graft augmentation group (PO 4 weeks); (e) rhBMP-2-coated dermal graft augmentation group (PO 4 weeks); (f) intact group (PO 8 weeks); (g) defect group (PO 8 weeks); (h) repair group (PO 8 weeks); (i) dermal graft augmentation group (PO 8 weeks); (j) rhBMP-2-coated dermal graft augmentation group (PO 8 weeks); (k) quantitative analysis of the new bone formation after rotator cuff surgery after 4 and 8 weeks.*


#### **Table 1.**

*Histomorphometric scoring system used to assess healing of the tendon-patch grafts with the bone.*

dehydrated in ethanol and embedded in paraffin. The 4-um-thick sections were stained with H&E and visualized using an optical microscope. Healing of the tendonbone connected lesion was graded histomorphologically by two observers blinded to treatment group. Histomorphometric analysis was performed to assess healing of the bone-tendon interface on the basis of three histomorphological criteria: fibrocartilage formation, new bone formation, and tendon graft bonding to adjacent tissue, which were scored on a scale of 0–3 (maximum total score of 9) in **Table 1**.

#### **2.7 Statistical analysis**

The data are presented as the average from at least triplicate samples. The experiments were repeated three times to ensure the reproducibility of the methods used. All statistical analyses were performed using SPSS (v.15.0). ANOVA was used to find overall differences among means. The post hoc Sheffé test was used to analyze differences between groups, with significance levels set at \*p < 0.05 and \*\* < p < 0.01.

### **3. Results**

In the postoperative 3D-CT images, the rhBMP-2-coated dermal graft inserted group showed significantly higher new bone formation than the other groups (**Figure 3**). The new bone volume in the rhBMP-2 group at 4- and 8-week postrepair surgery was 41.8 and 68.5 mm3 , respectively, which was ~11.5 times higher than in the control and dermal graft only inserted groups. The latter groups displayed less than 6 mm3 and, thus, did not show actual new bone formation.

#### **Figure 4.**

*The rabbit humeral bone is fixed with upper grip and the end of the detached tendon is fixed with lower grip. (a) Installed tissue specimen between the load cells for tensile test; (b) collected rabbit shoulder joint for tensile test; (c) ultimate tensile failure loads: A load-displacement rate was 10 mm/min and ultimate failure loads were measured from each group PO 4 and 8 weeks.*

#### **Figure 5.**

*The conditionally repaired groups in the rabbit tendon injury model. The repair group in which supraspinatus tendon and humeral bone were sutured at 4 weeks (a) and 8 weeks (d) post-surgery. The group that had received only a dermal patch, which covered the tendon-and-bone-suturing lesion, at 4 weeks (b) and 8 weeks (e) post-surgery. The group that had received the rhBMP-2-coated dermal patch, at 4 weeks (c) and 8 weeks (f) after repair. Images are shown at original magnification ×100. H&E, hematoxylin and eosin; T, tendon; HB, host bone; I, interface.*

**55**

**Figure 6.**

*Histomorphological scores of each group PO 4 and 8 weeks.*

*rhBMP-2-Coated Acellular Dermal Graft for Chronic Rotator Cuff Healing: Translational…*

The rhBMP-2-coated dermal graft effectively induced new bone formation in the

The ultimate tensile strength of the repaired tendon-bone interface was significantly higher in the rhBMP-2-coated dermal graft group and dermal graft only group than in the control group (suture only) at 4-week post repair surgery. However, there was a significant difference only in the rhBMP-2-coated dermal graft inserted group at 8-week post repair surgery (**Figure 4**). Moreover, the ultimate failure loads of specimens from the rhBMP-2-coated dermal graft group were similar to those of intact tissues at 8-week post-repair surgery. These results indicated not only that dermal patch provided good mechanical support but also that the rhBMP-2 increased the fusion rates of repaired lesion between the humeral

Histological analysis indicated that newly differentiated fibrochondrocytes were detected near the host bone in the rhBMP-2-coated dermal graft group at 8-week post-repair surgery (**Figure 5F**). The dermal graft only group showed lower cell penetration into the interface area, although the dermal graft was connected between the bone and tendon (**Figure 5B, E**). However, high cell penetration was observed near the host bone surface, and the interface between the bone and tendon was well connected without any space in the rhBMP-2-coated dermal graft

Quantitative histomorphometric analysis showed that the dermal graft coated with rhBMP-2 group had the highest analytic score (5.9) such as more fibrocartilage formation, new bone formation, and stronger attachment of the tendon to adjacent bone than the other groups (control group, 3.4; dermal graft only group, 3.9) after 8 weeks (**Figure 6**). As a result, the histological and histomorphometric analyses suggested that the rhBMP-2-coated dermal graft stimulated cell recruitment as well

*DOI: http://dx.doi.org/10.5772/intechopen.82282*

repaired lesion of the tendon and bone.

bone and supraspinatus tendon.

group (**Figure 5C, F**).

#### *rhBMP-2-Coated Acellular Dermal Graft for Chronic Rotator Cuff Healing: Translational… DOI: http://dx.doi.org/10.5772/intechopen.82282*

The rhBMP-2-coated dermal graft effectively induced new bone formation in the repaired lesion of the tendon and bone.

The ultimate tensile strength of the repaired tendon-bone interface was significantly higher in the rhBMP-2-coated dermal graft group and dermal graft only group than in the control group (suture only) at 4-week post repair surgery. However, there was a significant difference only in the rhBMP-2-coated dermal graft inserted group at 8-week post repair surgery (**Figure 4**). Moreover, the ultimate failure loads of specimens from the rhBMP-2-coated dermal graft group were similar to those of intact tissues at 8-week post-repair surgery. These results indicated not only that dermal patch provided good mechanical support but also that the rhBMP-2 increased the fusion rates of repaired lesion between the humeral bone and supraspinatus tendon.

Histological analysis indicated that newly differentiated fibrochondrocytes were detected near the host bone in the rhBMP-2-coated dermal graft group at 8-week post-repair surgery (**Figure 5F**). The dermal graft only group showed lower cell penetration into the interface area, although the dermal graft was connected between the bone and tendon (**Figure 5B, E**). However, high cell penetration was observed near the host bone surface, and the interface between the bone and tendon was well connected without any space in the rhBMP-2-coated dermal graft group (**Figure 5C, F**).

Quantitative histomorphometric analysis showed that the dermal graft coated with rhBMP-2 group had the highest analytic score (5.9) such as more fibrocartilage formation, new bone formation, and stronger attachment of the tendon to adjacent bone than the other groups (control group, 3.4; dermal graft only group, 3.9) after 8 weeks (**Figure 6**). As a result, the histological and histomorphometric analyses suggested that the rhBMP-2-coated dermal graft stimulated cell recruitment as well

**Figure 6.** *Histomorphological scores of each group PO 4 and 8 weeks.*

*Biotechnology and Bioengineering*

repair surgery was 41.8 and 68.5 mm3

*were measured from each group PO 4 and 8 weeks.*

displayed less than 6 mm3

\*\* < p < 0.01.

**3. Results**

**Figure 4.**

used. All statistical analyses were performed using SPSS (v.15.0). ANOVA was used to find overall differences among means. The post hoc Sheffé test was used to analyze differences between groups, with significance levels set at \*p < 0.05 and

In the postoperative 3D-CT images, the rhBMP-2-coated dermal graft inserted

, respectively, which was ~11.5 times higher

and, thus, did not show actual new bone formation.

group showed significantly higher new bone formation than the other groups (**Figure 3**). The new bone volume in the rhBMP-2 group at 4- and 8-week post-

than in the control and dermal graft only inserted groups. The latter groups

*The rabbit humeral bone is fixed with upper grip and the end of the detached tendon is fixed with lower grip. (a) Installed tissue specimen between the load cells for tensile test; (b) collected rabbit shoulder joint for tensile test; (c) ultimate tensile failure loads: A load-displacement rate was 10 mm/min and ultimate failure loads* 

*The conditionally repaired groups in the rabbit tendon injury model. The repair group in which supraspinatus tendon and humeral bone were sutured at 4 weeks (a) and 8 weeks (d) post-surgery. The group that had received only a dermal patch, which covered the tendon-and-bone-suturing lesion, at 4 weeks (b) and 8 weeks (e) post-surgery. The group that had received the rhBMP-2-coated dermal patch, at 4 weeks (c) and 8 weeks (f) after repair. Images are shown at original magnification ×100. H&E, hematoxylin and eosin; T, tendon;* 

**54**

**Figure 5.**

*HB, host bone; I, interface.*

as induced fibrochondrogenic differentiation of the undifferentiated mesenchymal cells in the junction between the bone and tendon.

#### **4. Discussion**

There have been a number of preclinical and clinical trials for the enhanced tendon-bone healing in the shoulder repair surgery [12, 21, 30]. The augmentation repair of rotator cuff by incorporating growth factors or stem cells into the scaffold is intended to enhance the repair process, improve the mechanical properties, and reduce the possibility of re-rupture [10, 24, 25].

Decellularized human dermis has better mechanical properties than any other ECM-based scaffolds in the previous studies [31, 32]. ECM-based grafts are attractive model for tissue regeneration. However, they may support only shortterm reinforcement and retard tissue regeneration [33]. For the enhanced healing process, the grafting material requires good mechanical properties as well as specific differentiation effects. rhBMP-2 has shown biological effectiveness for rotator cuff repair and for tendon-bone interface healing in extra-articular bone tunnel in the previous studies [28, 34]. However, there have been no preclinical and clinical studies on the rhBMP-2-coated acellular dermal graft for rotator cuff repair.

Many limitations of safety and effectiveness still remain for the clinical use of rhBMP-2. The considerations of biomechanical property for better morbidity of bone-tendon, the concentration of rhBMP-2 for the safety in the implanted area, and coating method for sustained release from the scaffold are necessary for growth factor application in the biological augmentation research.

Although the review articles suggested that dermal graft has good biomechanical properties and rhBMP-2 is effective for biological augmentation in bone-tendon, there was no original article that showed the composite of rhBMP-2 and an acellular dermal graft [35, 36]. For this initial study on rhBMP-2-coated dermal graft for rotator cuff repair, we generated a rabbit rotator cuff injury model by using a silicon tube, which covers the supraspinatus tendon that was detached from the humeral bone for 4 weeks. In our previous study, we showed the usability of rhBMP-2 application for tendon-tibia bone interface healing, using viscous collagen gel as an injectable carrier. rhBMP-2 needs to be embedded in a scaffold for an effective delivery to the targeted lesion. Thus, various types of carriers need to be tested for rhBMP-2 delivery.

Acellular dermal graft exhibits higher suture pullout strength than other ECMbased scaffolds. The rotator cuff area is subject to excessive and multidirectional loads by tendon-bone interface motion; therefore, healing following rotator cuff repair largely depends on robust mechanical properties of the junction between the bone and tendon.

On the basis of prior knowledge, rhBMP-2-coated acellular dermal graft was sutured between the rabbit supraspinatus tendon and humeral bone. The rhBMP-2-coated dermal graft group showed significant new bone formation as indicated by 3D-CT data recorded at 4 and 8 weeks after surgical treatment. The ultimate failure loads of the rhBMP-2/acellular dermal graft inserted tendon-bone interfaces increased to the mechanical properties of intact tissues at 8 weeks. The histological images demonstrated rich cell penetration into the tendon-bone interface by rhBMP-2, and the recruited cells induced fibrochondrogenic differentiation. The histomorphometric scores of the dermal graft coated with rhBMP-2 group were significantly higher than the other groups.

**57**

**Author details**

Republic of Korea

Republic of Korea

Kwang-Il Lee1

provided the original work is properly cited.

\*, Ju-Woong Jang2

1 The Scripps Research Institute, La Jolla, CA, United States

\*Address all correspondence to: jasonklee77@gmail.com

© 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

and Kwang-Won Lee3

2 The Institute of Biomaterials and Medical Engineering, Cellumed Co., Ltd., Seoul,

3 Department of Orthopedic Surgery, Eulji University Hospital, Daejeon,

*rhBMP-2-Coated Acellular Dermal Graft for Chronic Rotator Cuff Healing: Translational…*

chronic rotator cuff injury model. This study demonstrated that the combination of an acellular dermal graft and rhBMP-2 can be applied to that rotator cuff injured

*DOI: http://dx.doi.org/10.5772/intechopen.82282*

patients.

In conclusion, the grafting of rhBMP-2-coated human dermal graft enhanced new bone formation and the bone-tendon fusion rate in a rabbit *rhBMP-2-Coated Acellular Dermal Graft for Chronic Rotator Cuff Healing: Translational… DOI: http://dx.doi.org/10.5772/intechopen.82282*

chronic rotator cuff injury model. This study demonstrated that the combination of an acellular dermal graft and rhBMP-2 can be applied to that rotator cuff injured patients.

#### **Author details**

*Biotechnology and Bioengineering*

**4. Discussion**

repair.

cells in the junction between the bone and tendon.

reduce the possibility of re-rupture [10, 24, 25].

factor application in the biological augmentation research.

as induced fibrochondrogenic differentiation of the undifferentiated mesenchymal

There have been a number of preclinical and clinical trials for the enhanced tendon-bone healing in the shoulder repair surgery [12, 21, 30]. The augmentation repair of rotator cuff by incorporating growth factors or stem cells into the scaffold is intended to enhance the repair process, improve the mechanical properties, and

Decellularized human dermis has better mechanical properties than any other ECM-based scaffolds in the previous studies [31, 32]. ECM-based grafts are attractive model for tissue regeneration. However, they may support only shortterm reinforcement and retard tissue regeneration [33]. For the enhanced healing process, the grafting material requires good mechanical properties as well as specific differentiation effects. rhBMP-2 has shown biological effectiveness for rotator cuff repair and for tendon-bone interface healing in extra-articular bone tunnel in the previous studies [28, 34]. However, there have been no preclinical and clinical studies on the rhBMP-2-coated acellular dermal graft for rotator cuff

Many limitations of safety and effectiveness still remain for the clinical use of rhBMP-2. The considerations of biomechanical property for better morbidity of bone-tendon, the concentration of rhBMP-2 for the safety in the implanted area, and coating method for sustained release from the scaffold are necessary for growth

Although the review articles suggested that dermal graft has good biomechanical properties and rhBMP-2 is effective for biological augmentation in bone-tendon, there was no original article that showed the composite of rhBMP-2 and an acellular dermal graft [35, 36]. For this initial study on rhBMP-2-coated dermal graft for rotator cuff repair, we generated a rabbit rotator cuff injury model by using a silicon tube, which covers the supraspinatus tendon that was detached from the humeral bone for 4 weeks. In our previous study, we showed the usability of rhBMP-2 application for tendon-tibia bone interface healing, using viscous collagen gel as an injectable carrier. rhBMP-2 needs to be embedded in a scaffold for an effective delivery to the targeted lesion. Thus, various types of carriers need to be tested for rhBMP-2 delivery.

Acellular dermal graft exhibits higher suture pullout strength than other ECMbased scaffolds. The rotator cuff area is subject to excessive and multidirectional loads by tendon-bone interface motion; therefore, healing following rotator cuff repair largely depends on robust mechanical properties of the junction between the

On the basis of prior knowledge, rhBMP-2-coated acellular dermal graft was sutured between the rabbit supraspinatus tendon and humeral bone. The rhBMP-2-coated dermal graft group showed significant new bone formation as indicated by 3D-CT data recorded at 4 and 8 weeks after surgical treatment. The ultimate failure loads of the rhBMP-2/acellular dermal graft inserted tendon-bone interfaces increased to the mechanical properties of intact tissues at 8 weeks. The histological images demonstrated rich cell penetration into the tendon-bone interface by rhBMP-2, and the recruited cells induced fibrochondrogenic differentiation. The histomorphometric scores of the dermal graft coated with rhBMP-2 group were

In conclusion, the grafting of rhBMP-2-coated human dermal graft enhanced new bone formation and the bone-tendon fusion rate in a rabbit

**56**

bone and tendon.

significantly higher than the other groups.

Kwang-Il Lee1 \*, Ju-Woong Jang2 and Kwang-Won Lee3

1 The Scripps Research Institute, La Jolla, CA, United States

2 The Institute of Biomaterials and Medical Engineering, Cellumed Co., Ltd., Seoul, Republic of Korea

3 Department of Orthopedic Surgery, Eulji University Hospital, Daejeon, Republic of Korea

\*Address all correspondence to: jasonklee77@gmail.com

© 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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[4] UW Medicine Orthopaedics and Sports Medicine. Arthroscopic Shoulder Surgery for the Treatment of Rotator Cuff Tears [Internet]. 2018. http://www.orthop.washington. edu/?q=patient-care/articles/sports/ arthroscopic-shoulder-surgery-forthe-treatment-of-rotator-cuff-tears [Accessed: 23-10-2018]

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[9] Dejardin LM, Arnoczky SP, Ewers BJ, Haut RC, Clarke RB. Tissue-engineered rotator cuff tendon using porcine small intestine submucosa. Histologic and mechanical evaluation in dogs. The American Journal of Sports Medicine. 2001;**29**(2):175-184

[10] Prabhath A, Vernekar VN, Sanchez E, Laurencin CT. Growth factor delivery strategies for rotator cuff repair and regeneration. International Journal of Pharmaceutics. 2018;**544**(2):358-371

[11] Chainani A, Little D. Current status of tissue-engineered scaffolds for rotator cuff repair. Techniques in Orthopaedics. 2016;**31**(2):91-97

[12] Thangarajah T, Pendegrass CJ, Shahbazi S, Lambert S, Alexander S, Blunn GW. Augmentation of rotator cuff repair with soft tissue scaffolds. Orthopaedic Journal of Sports Medicine. 2015;**3**(6):2325967115587495. DOI: 10.1177/2325967115587495

[13] Adams JE, Zobitz ME, Reach JS Jr, An KN, Steinmann SP. Rotator cuff repair using an acellular dermal matrix graft: An in vivo study in a canine model. Arthroscopy. 2006;**22**(7):700-709

[14] Ide J, Kikukawa K, Hirose J, Iyama K, Sakamoto H, Mizuta H. Reconstruction of large rotator-cuff tears with acellular dermal matrix grafts in rats. Journal of Shoulder and Elbow Surgery. 2009;**18**(2):288-295. DOI: 10.1016/j.jse.2008.09.004

[15] Thangarajah T, Henshaw F, Sanghani-Kerai A, Lambert SM, Blunn GW, Pendegrass CJ. The effectiveness of demineralized cortical bone matrix in a chronic rotator cuff tear model. Journal of Shoulder and Elbow Surgery. 2017;**26**(4):619-626. DOI: 10.1016/j. jse.2017.01.003

**59**

*rhBMP-2-Coated Acellular Dermal Graft for Chronic Rotator Cuff Healing: Translational…*

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2011;**19**(3):218-226. DOI: 10.1097/

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morphogenetic protein-2 to enhance tendon healing in a bone tunnel. American Journal of Sports Medicine.

[27] Hashimoto Y, Yoshida G, Toyoda H, Takaoka K. Generation of tendon-tobone interface "enthesis" with use of recombinant BMP-2 in a rabbit model. Journal of Orthopaedic Research.

[28] Lee KW, Lee JS, Jang JW, Shim YB, Lee KI. Tendon-bone interface healing using an injectable rhBMP-2 containing collagen gel in a rabbit extra-articular bone tunnel model. Journal of Tissue Engineering and Regenerative Medicine. 2017;**11**(5):1435-1441. DOI: 10.1002/

[29] Lee KI, Lee JS, Kim JG, Kang KT, Jang JW, Shim YB, et al. Mechanical properties of decellularized tendon cultured by cyclic straining bioreactor. Journal of Biomedical Materials Research. Part A. 2013;**101**(11): 3152-3158. DOI: 10.1002/jbm.a.34624

[30] Atesok K, Fu FH, Wolf MR, Ochi M,

jazrawi LM, Doral NM, et al. Augmentation of tendon-to-bone healing. The Journal of Bone and Joint Surgery. American Volume. 2014;**96**(6):513-521. DOI: 10.2106/

JBJS.M.00009

JSA.0b013e3182250c78

Wozney J, Warren RF. Use of recombinant human bone

1999;**27**(4):476-488

2007;**25**(11):1415-1424

term.2041

*DOI: http://dx.doi.org/10.5772/intechopen.82282*

[16] Derwin KA, Badylak SF, Steinmann SP, Iannotti JP. Extracellular matrix scaffold devices for rotator cuff repair. Journal of Shoulder and Elbow Surgery. 2010;**19**(3):467-476. DOI: 10.1016/j.

[17] Sessions WC, Lawrence RL, Steubs JT, Ludewig PM, Braman JP. Thickness of the rotator cuff tendons at the articular margin: An anatomic cadaveric study. The Iowa Orthopaedic Journal. 2017;**37**:85-89

[18] Bello YM, Falabella AF, Eaglstein WH. Tissue-engineered skin. Current status in wound healing. American Journal of Clinical Dermatology.

[19] Schmidt J, Redwan B, Koesek V,

jse.2009.10.020

2001;**2**(5):305-313

Heitplatz B, Bedetti B, Aebert H, et al. Thoracic wall reconstruction with acellular porcine dermal collagen matrix. The Thoracic and Cardiovascular Surgeon. 2016;**64**(3):245-251. DOI:

10.1055/s-0034-1383512

2012;**21**(2):218-227

[20] Eppley BL, Summerlin DJ, Sadove AM. A potential biomaterial composite for dermal and subcutaneous

augmentation. Annals of Plastic Surgery. 1994;**32**(5):463-468

[21] Edwards SL, Lynch TS, Saltzman MD, Terry MA, Nuber GW. Biological and pharmacologic augmentation of rotator cuff repairs. The Journal of the American Academy of Orthopaedic Surgeons. 2011;**19**(10):583-589

[22] Bedi A, Maak T, Walsh C, Rodeo SA, Grande D, Dines DM, et al. Cytokines in rotator cuff degeneration and repair. Journal of Shoulder and Elbow Surgery.

[23] Wd G, Xu PC, Wu P, Hu K, Sun Y, Cheng B, et al. Advances in the treatment of rotator cuff lesions by cytokines. Frontiers in Bioscience (Landmark Edition). 2017;**22**:516-529

*rhBMP-2-Coated Acellular Dermal Graft for Chronic Rotator Cuff Healing: Translational… DOI: http://dx.doi.org/10.5772/intechopen.82282*

[16] Derwin KA, Badylak SF, Steinmann SP, Iannotti JP. Extracellular matrix scaffold devices for rotator cuff repair. Journal of Shoulder and Elbow Surgery. 2010;**19**(3):467-476. DOI: 10.1016/j. jse.2009.10.020

[17] Sessions WC, Lawrence RL, Steubs JT, Ludewig PM, Braman JP. Thickness of the rotator cuff tendons at the articular margin: An anatomic cadaveric study. The Iowa Orthopaedic Journal. 2017;**37**:85-89

[18] Bello YM, Falabella AF, Eaglstein WH. Tissue-engineered skin. Current status in wound healing. American Journal of Clinical Dermatology. 2001;**2**(5):305-313

[19] Schmidt J, Redwan B, Koesek V, Heitplatz B, Bedetti B, Aebert H, et al. Thoracic wall reconstruction with acellular porcine dermal collagen matrix. The Thoracic and Cardiovascular Surgeon. 2016;**64**(3):245-251. DOI: 10.1055/s-0034-1383512

[20] Eppley BL, Summerlin DJ, Sadove AM. A potential biomaterial composite for dermal and subcutaneous augmentation. Annals of Plastic Surgery. 1994;**32**(5):463-468

[21] Edwards SL, Lynch TS, Saltzman MD, Terry MA, Nuber GW. Biological and pharmacologic augmentation of rotator cuff repairs. The Journal of the American Academy of Orthopaedic Surgeons. 2011;**19**(10):583-589

[22] Bedi A, Maak T, Walsh C, Rodeo SA, Grande D, Dines DM, et al. Cytokines in rotator cuff degeneration and repair. Journal of Shoulder and Elbow Surgery. 2012;**21**(2):218-227

[23] Wd G, Xu PC, Wu P, Hu K, Sun Y, Cheng B, et al. Advances in the treatment of rotator cuff lesions by cytokines. Frontiers in Bioscience (Landmark Edition). 2017;**22**:516-529

[24] Cheung EV, Silverio L, Yao J. Delivered growth factor therapy to improve healing after rotator cuff repair. Stem Cells Cloning. 2010;**3**: 135-144. DOI: 10.2147/SCCAA.S7359

[25] Oliva F, Via AG, Maffulli N. Role of growth factors in rotator cuff healing. Sports Medicine and Arthroscopy Review. 2011;**19**(3):218-226. DOI: 10.1097/ JSA.0b013e3182250c78

[26] Rodeo SA, Suzuki K, Deng XH, Wozney J, Warren RF. Use of recombinant human bone morphogenetic protein-2 to enhance tendon healing in a bone tunnel. American Journal of Sports Medicine. 1999;**27**(4):476-488

[27] Hashimoto Y, Yoshida G, Toyoda H, Takaoka K. Generation of tendon-tobone interface "enthesis" with use of recombinant BMP-2 in a rabbit model. Journal of Orthopaedic Research. 2007;**25**(11):1415-1424

[28] Lee KW, Lee JS, Jang JW, Shim YB, Lee KI. Tendon-bone interface healing using an injectable rhBMP-2 containing collagen gel in a rabbit extra-articular bone tunnel model. Journal of Tissue Engineering and Regenerative Medicine. 2017;**11**(5):1435-1441. DOI: 10.1002/ term.2041

[29] Lee KI, Lee JS, Kim JG, Kang KT, Jang JW, Shim YB, et al. Mechanical properties of decellularized tendon cultured by cyclic straining bioreactor. Journal of Biomedical Materials Research. Part A. 2013;**101**(11): 3152-3158. DOI: 10.1002/jbm.a.34624

[30] Atesok K, Fu FH, Wolf MR, Ochi M, jazrawi LM, Doral NM, et al. Augmentation of tendon-to-bone healing. The Journal of Bone and Joint Surgery. American Volume. 2014;**96**(6):513-521. DOI: 10.2106/ JBJS.M.00009

**58**

*Biotechnology and Bioengineering*

2018. Available from: https:// en.wikipedia.org/wiki/Rotator\_cuff

[2] OrthoInfo. Rotator Cuff Tears [Internet]. 2018. Available from: https://orthoinfo.aaos.org/en/

[Accessed: 23-10-2018]

[Accessed: 23-10-2018]

Journal. 2014;**4**(3):309-314

[Accessed: 23-10-2018]

[Accessed: 23-10-2018]

[Accessed: 23-10-2018]

23-10-2018]

[7] Johns Hopkins Medicine.

[8] Lädermann A, Burkhart SS, Hoffmeyer P, Neyton L, Collin P, Yates E, et al. Classification of full-thickness rotator cuff lesions: A review. EFORT Open Reviews. 2017;**1**(12):420-430

[5] Arthrex. Rotator Cuff Repair [Internet]. 2018. https://www.arthrex. com/shoulder/rotator-cuff-repair

[6] Medscape. AAOS 2012 Annual Meeting [Internet]. 2012. https://www. medscape.com/viewarticle/758280

Orthopaedic Surgery [Internet]. 2018. https://www.hopkinsmedicine.org/ orthopaedic-surgery/specialty-areas/ shoulder/treatments-procedures/failedrotator-cuff-repairs.html [Accessed:

[4] UW Medicine Orthopaedics and Sports Medicine. Arthroscopic Shoulder Surgery for the Treatment of Rotator Cuff Tears [Internet]. 2018. http://www.orthop.washington. edu/?q=patient-care/articles/sports/ arthroscopic-shoulder-surgery-forthe-treatment-of-rotator-cuff-tears

[1] Wikipedia. Rotator Cuff [Internet].

[9] Dejardin LM, Arnoczky SP, Ewers BJ, Haut RC, Clarke RB. Tissue-engineered rotator cuff tendon using porcine small intestine submucosa. Histologic and mechanical evaluation in dogs. The American Journal of Sports Medicine.

[10] Prabhath A, Vernekar VN, Sanchez E, Laurencin CT. Growth factor delivery strategies for rotator cuff repair and regeneration. International Journal of Pharmaceutics. 2018;**544**(2):358-371

[11] Chainani A, Little D. Current status of tissue-engineered scaffolds for rotator cuff repair. Techniques in Orthopaedics. 2016;**31**(2):91-97

[12] Thangarajah T, Pendegrass CJ, Shahbazi S, Lambert S, Alexander S, Blunn GW. Augmentation of rotator cuff repair with soft tissue scaffolds. Orthopaedic Journal of Sports Medicine. 2015;**3**(6):2325967115587495. DOI:

[13] Adams JE, Zobitz ME, Reach JS Jr, An KN, Steinmann SP. Rotator cuff repair using an acellular dermal matrix graft: An in vivo study in a canine model. Arthroscopy.

[14] Ide J, Kikukawa K, Hirose J, Iyama

Reconstruction of large rotator-cuff tears with acellular dermal matrix grafts in rats. Journal of Shoulder and Elbow Surgery. 2009;**18**(2):288-295. DOI:

10.1177/2325967115587495

2006;**22**(7):700-709

K, Sakamoto H, Mizuta H.

10.1016/j.jse.2008.09.004

jse.2017.01.003

[15] Thangarajah T, Henshaw F,

Sanghani-Kerai A, Lambert SM, Blunn GW, Pendegrass CJ. The effectiveness of demineralized cortical bone matrix in a chronic rotator cuff tear model. Journal of Shoulder and Elbow Surgery. 2017;**26**(4):619-626. DOI: 10.1016/j.

2001;**29**(2):175-184

diseases-conditions/rotator-cuff-tears/

[3] Oliva F, Osti L, Padulo J, Maffulli N. Epidemiology of the rotator cuff tears: A new incidence related to thyroid disease. Muscle, Ligaments and Tendons

**References**

[31] Omae H, Steinmann SP, Zhao C, Zobitz ME, Wongtriratanachai P, Sperling JW, et al. Biomechanical effect of rotator cuff augmentation with an acellular dermal matrix graft: A cadaver study. Clinical Biomechanics (Bristol, Avon). 2012;**27**(8):789-792. DOI: 10.1016/J.clinbiomech.2012.05.001

[32] Nie X, Wang DA. Decellularized orthopaedic tissue-engineered grafts: Biomaterial scaffolds synthesized by therapeutic cells. Biomaterials Science. 2018;**24**(6):2798-2811. DOI: 10.1039/ c8bm00772a

[33] Sackett SD, Tremmel DM, Ma F, Feeney AK, Maguire RM, Brown ME, et al. Extracellular matrix scaffold and hydrogel derived from decellularized and delipidized human pancreas. Scientific Reports. 2018;**8**(1):10452. DOI: 10.1038/s41598-018-28857-1

[34] Lee KW, Lee JS, Kim YS, Shim YB, Jang JW, Lee KI. Effective healing of chronic rotator cuff injury using recombinant bone morphogenetic protein-2 coated dermal patch in vivo. Journal of Biomedical Materials Research. Part B, Applied Biomaterials. 2017;**105**(7):1840-1846. DOI: 10.1002/ jbm.b.33716

[35] Acevedo DC, Shore B, Mirzayan R. Orthopedic applications of acellular human dermal allograft for shoulder and elbow surgery. The Orthopedic Clinics of North America. 2015;**46**(3):377-388. DOI: 10.1016/j. ocl.2015.02.006

[36] Kim JG, Kim HJ, Kim SE, Bae JH, Ko YJ, Park JH. Enhancement of tendon-bone healing with the use of bone morphogenetic protein-2 inserted into the suture anchor hole in a rabbit patellar tendon model. Cytotherapy. 2014;**16**(6):857-867. DOI: 10.1016/j. jcyt.2013.12.012

**61**

**1. Introduction**

**Chapter 6**

**Abstract**

Scaffolds

Structural Design, Fabrication

Fiber-Based Tissue Engineering

*Martin W. King, Jiyang Chen, Monica Deshpande, Ting He,* 

The use of tissue engineering to regenerate viable tissue relies on selecting the appropriate cell line, developing a resorbable scaffold and optimizing the culture conditions including the use of biomolecular cues and sometimes mechanical stimulation. This review of the literature focuses on the required scaffold properties, including the polymer material, the structural design, the total porosity, pore size distribution, mechanical performance, physical integrity in multiphase structures as well as surface morphology, rate of resorption and biocompatibility. The chapter will explain the unique advantages of using textile technologies for tissue engineering scaffold fabrication, and will delineate the differences in design, fabrication and performance of woven, warp and weft knitted, braided, nonwoven and electrospun scaffolds. In addition, it will explain how different types of tissues can be regenerated by each textile technology for a particular clinical application. The use of different synthetic and natural resorbable polymer fibers will be discussed, as well as the need for specialized finishing techniques such as heat setting, cross linking, coating and impregnation, depending on the tissue engineering application.

*Harshini Ramakrishna, Yu Xie, Fan Zhang and Fan Zhao*

**Keywords:** resorbable polymer, tissue engineering scaffold, biocompatibility,

The field of tissue engineering and regenerative medicine was conceptualized about 35 years ago by Robert S. Langer, Institute Professor at Massachusetts Institute of Technology, together with Joseph P. Vacanti, MD a pediatric and transplantation surgeon-scientist at Massachusetts General Hospital and Harvard Medical School [1]. They recognized that in all fields of reconstructive surgery less than 30% of patients needing an organ transplant were able to obtain one [2], and that an alternative approach of engineering viable tissues and organs using cell culture techniques was needed to address this limited supply [3]. As a result, "an interdisciplinary field of research that applies the principles of engineering and the life sciences towards the development of biological substitutes that restore, maintain or improve tissue function" has been created with the ultimate goal of repairing injured and diseased organs [1].

cell culture, porosity, braiding, knitting, weaving, nonwoven web

and Evaluation of Resorbable

#### **Chapter 6**

*Biotechnology and Bioengineering*

[31] Omae H, Steinmann SP, Zhao C, Zobitz ME, Wongtriratanachai P, Sperling JW, et al. Biomechanical effect of rotator cuff augmentation with an acellular dermal matrix graft: A cadaver study. Clinical Biomechanics (Bristol, Avon). 2012;**27**(8):789-792. DOI: 10.1016/J.clinbiomech.2012.05.001

[32] Nie X, Wang DA. Decellularized orthopaedic tissue-engineered grafts: Biomaterial scaffolds synthesized by therapeutic cells. Biomaterials Science. 2018;**24**(6):2798-2811. DOI: 10.1039/

[33] Sackett SD, Tremmel DM, Ma F, Feeney AK, Maguire RM, Brown ME, et al. Extracellular matrix scaffold and hydrogel derived from decellularized and delipidized human pancreas. Scientific Reports. 2018;**8**(1):10452. DOI: 10.1038/s41598-018-28857-1

[34] Lee KW, Lee JS, Kim YS, Shim YB, Jang JW, Lee KI. Effective healing of chronic rotator cuff injury using recombinant bone morphogenetic protein-2 coated dermal patch in vivo. Journal of Biomedical Materials

Research. Part B, Applied Biomaterials. 2017;**105**(7):1840-1846. DOI: 10.1002/

[35] Acevedo DC, Shore B, Mirzayan R. Orthopedic applications of acellular

[36] Kim JG, Kim HJ, Kim SE, Bae JH, Ko YJ, Park JH. Enhancement of tendon-bone healing with the use of bone morphogenetic protein-2 inserted into the suture anchor hole in a rabbit patellar tendon model. Cytotherapy. 2014;**16**(6):857-867. DOI: 10.1016/j.

human dermal allograft for shoulder and elbow surgery. The Orthopedic Clinics of North America. 2015;**46**(3):377-388. DOI: 10.1016/j.

c8bm00772a

jbm.b.33716

ocl.2015.02.006

jcyt.2013.12.012

**60**
