**6. Current methods for cartilage tissue engineering and future perspectives**

#### **6.1. Autologous chondrocytes for tissue regeneration**

The hyaline articular cartilage is a highly specialized tissue and its main function is to protect the bone from friction in the joints [89, 90], once articular cartilage is damaged their ability to self-repair and regeneration is limited as mentioned above. Cartilage injuries are mainly associated with anterior cruciate ligament, patellar dislocation, followed by a meniscectomy [91]. Osteochondral lesions of the knee are determined mainly by arthroscopic knee surgery [92, 93], which is seen mainly in traumatic injuries, together with abnormal stresses on the knee.

To determine the treatment for the repair and regeneration of articular cartilage injury, have developed different techniques, the techniques described are focused on the repair, recon‐ struction or regeneration of tissue. The repair methods (drilling or microfracture) support the formation of new tissue fibrocartilaginous [94, 95] while the reconstructive method seeks to fill the defect with allografts (OATS) combining with miniarthrotomy arthroscopy. And finally the regenerative methods that rely on bioengineering techniques to develop a hyaline cartilage tissue graft or autologous chondrocyte cell matrices (Table1).


**Table 1.** Cartilage repair techniques

Each of these procedures is associated with improvement of these techniques with the use of biomaterials or with the use of growth factors. In the autologous chondrocyte implantation of the second generation is required arthrotomy so this technique becomes more complicated. In order to facilitate and improve the technique and quality of the tissue repair, has developed a method which has proved more effective and easy to implement in the knee joint [112, 113] develop and autologous chondrocyte implantation induced extracellular matrix of the third generation.

#### **6.2. Description of the technique of autologous chondrocyte implantation induced extracellular matrix (third generation).**

#### *6.2.1. Obtaining the tissue*

**Ref. Method Technique Results**

[97] Perform subchondral drilling of the lamina Tissue repair and pain relief

Perforation of the subchondral lamina by arthroscopy, it promotes the release of mesenchymal cells in the lesion, forming

Followed by a micro abrasion bill and placing a collagen scaffold on the defect, inducing the formation of fibrocartilage by migrating mesenchymal cells and the expression of cytokines and

Is based on obtaining osteochondral cylinder obtained from areas of low load from the distal femur, which are grafted into the

1st Generation: In this technique, cartilage cells are injected under

2nd. Generation: is replaced cover membrane or periosteum biomaterials, which can have different components

3rd. Generation: In this technique, autologous chondrocytes cultured on a three-dimensional artificial scaffold

a cover of periosteum is sutured into the defect.

Significant symptomatic improvementin 75% of patients

Avoids necrosis associated with the use of the drill and preserves the subchondral surface. The results observed in the medium term, mainly in young patients, about 20% of patients do not reach after five years.

Stimulation of bone marrow has limited mechanical strength and may even degrade the cartilage is repaired with fibrous tissue or fibrocartilage so that there is tissue degeneration.

The results are limited in large lesions due to donor site morbidity and healing of the seams in the recipient

It has been reported good results in most patients after 10-20 years

Has been used in the past two decades, with this type of membranes hypertrophy is reduced by 5%, after 3 to 6 months membrane is reabsorbed.

after implantation. In the second generation transplants with areas of fibrocartilage, possibly because of low cell density and lack of proliferative capacity. This technique replaces healthy cartilage to regularize the defect.

Removal of osteophytes and knee abrasion

[96]

[99, 100]

[101- 104]

[105- 107]

[108- 110]

[111]

Drilling with lavage and debridement

378 Regenerative Medicine and Tissue Engineering

Microfracture

Chondrogenesis induced stimulation of bone marrow (AMIC)

Mosaicplastyandt ransplantosteoch ondral allograft

Autologous chondrocyte implantation

Autologous chondrocyte implantation induces extracellular matrix

**Table 1.** Cartilage repair techniques

[98] Elimination of subchondral lamina

a plug of tissue

tissue repair

defect

This technique is mainly based on the autologous cultured chondrocytes on a biocompatible three-dimensional scaffold which is subsequently implanted into the defect. As in the techni‐ que of autologous chondrocyte implantation of the second generation, it requires a prior arthroscopic surgery where a piece of cartilage obtained from a zone of no load of the knee joint (intercondylar notch or the lateral edge of the trochlea) after obtaining the sample fragment is processed to obtain chondrocytes in culture.

#### *6.2.2. Implant preparation*

Cartilage fragments are disintegrated mechanically to obtain smallest fragment, is performed subsequent enzymatic digestion to release trapped chondrocytes in the matrix of collagen. Expansion of chondrocytes was performed in 8 weeks. Days before implantation chondrocytes are seeded on a scaffold or membrane [112] Rich in collagen, which is considered a threedimensional extracellular biomaterial consists mainly of collagen I and III, the scaffold contains glycosaminoglycans, proteoglycans and glycoproteins [111, 114, 115] cells are capable of synthesizing a typical matrix of chondrocytes facilitating cell adhesion and influence the morphology, migration and differentiation of cells.

#### **6.3. Advantages of autologous chondrocyte transplantation induced extracellular matrix (third generation) on the autologous chondrocyte implantation (second generation)**

The main advantages of autologous chondrocyte transplantation induced extracellular matrix (third generation) is that no cell loss is not presented hypertrophic tissue growth, requiring only a second incision is a safe procedure for treatment of injuries symptomatic articular cartilage surgery facilitates reducing the operating time and the need for open surgery compared to traditional surgery for autologous chondrocyte implantation (second generation). While in the second generation technique leads to form hyaline cartilage on the surface showing fibrosis and proliferation of small blood vessels (reactive fibrosis), by the use of periosteum, so that in this case it is advisable the use of membrane collagen
