**Abstract**

Osteoarthritis (OA) is one of the most common chronic, inflammatory, and degenerative diseases affecting the synovial joints, the hip, and the knee. OA is commonly managed clinically by treating pain with anti-inflammatory medicines using nonsteroidal anti-inflammatory drugs (NSAIDS) or analgesics. In severe OA patients, invasive knee replacement surgery is the last option. Treatment of OA using mesenchymal stromal cells (MSCs) has been widely explored due to their anti-inflammatory properties and chondrogenic differentiation potential. In this chapter, we comprehensively discuss in detail the in vitro OA potency development, OA preclinical studies, and clinical trials conducted using MSCs.

**Keywords:** osteoarthritis, pooled human bone marrow-derived mesenchymal stromal cells, potency assay, preclinical studies, clinical studies

### **1. Introduction**

Common factors linked to osteoarthritis (OA) occurrence are increasing age (>55 years) and obesity [1]. The gender also seems to play a major role, where the majority of OA patients are women and higher prevalence has been liked to menopause. Radiological evidence suggests that about 70% of women above the age of 65 years are affected by OA [2, 3]. Other factors such as genetic predisposition, extrinsic environmental factors, nutrition, and lack of exercise are reasons for the increased prevalence of OA. It has been reported by the World Health Organization (WHO) that 10–15% of the populations aged >60 years exhibit a certain degree of OA [4]. It has been reported by the National Health Portal of India that 22–39% of the Indian population are affected by OA. As reported by the United Nations Organization (UNO), 130 million people will be affected by OA with over 40 million people with severe disability due to disease progression [3].

The etiology of OA is believed to be multifactorial. Some of the main reasons include the biomechanical disease progression due to the narrowing of space in the joints, bone hypertrophy, and formation of new osteophytes in the articular margins causing stiffness and pain in the joints. In addition, an imbalance in the synthesis and release of cytokines by chondrocytes in the disease state could be the main reason for the continual inflammatory state in the joint. During the initial stages of OA, catabolic interleukins (IL) such as IL-1α and IL-1β and tumor necrosis factor α (TNFα) increase inflammation affecting cartilage metabolism and homeostasis. TNFα is a proinflammatory cytokine implicated in the degradation of matrix proteins synthesized by

chondrocytes and synoviocytes [5]. Further, increase in the levels of interferon γ (IFNγ) in the joint worsens the inflammatory state and structure of the joint leading to degradation of proteoglycans such as sulfated glycosaminoglycans (sGAG) [5, 6].

### **2. Current treatment options for osteoarthritis**

Currently, pain in OA is pharmacologically managed using nonsteroidal antiinflammatory drugs (NSAIDS), opioids, and analgesics. Corticosteroid injections have also been used for relieving severe pain in OA patients. Recent attempts have been made to use TNFα blockers as recent studies have proven the significant role of TNFα in contribution to the pathogenesis of OA [7]. Research by several groups has implicated the role of nerve growth factor (NGF) and its binding to tropomyosin receptor kinase A (trk A) which leads to downstream signaling and activation of peripheral and central pain molecules causing severe pain. The therapeutic efficiency of anti-NGF antibodies to block NGF or its antagonists has been studied by several groups for relieving pain. The pain-relieving effects of anti-NGF antibodies fasinumab and fulranumab manufactured by Regeneron Pharmaceuticals and Janssen Pharmaceutica, respectively, have been evaluated in phase III clinical trials [8]. In addition to pain relief, efforts have been made to halt further cartilage damage using slow-acting symptomatic drugs such as chondroitin sulfate and glucosamine sulfate. Orally administered chondroitin and glucosamine have shown to relieve joint pain equivalently compared to NSAIDs. These molecules, intact or broken, could be absorbed into the matrix of the joint and prevent cartilage degeneration. Although glucosamine and chondroitin sulfate have been clinically proven to be safe, their therapeutic efficacy in protecting the cartilage matrix was found to the variable [9]. In grade 4 OA (Kellgren and Lawrence classifications), patients are advised to opt for total knee replacement surgery [10]. Alternatively, autologous chondrocyte implantation (ACI) has been suggested and reported to be successful. In the ACI method, the chondrocytes from patients are taken, culture-expanded in vitro, and then implanted back into the knees of patients. This procedure is invasive and has a lesser success rate than total knee replacement surgeries [11].

Apart from ACI, the efficacy of autologous platelet-rich plasma (PRP) in providing pain relief and promoting cartilage regeneration has been recently investigated by several groups [12]. The PRP is rich in platelets that secrete several growth factors and cytokines such as platelet-derived growth factor (PDGF), hepatocyte growth factor (HGF), insulin-like growth factor 1 (IGF-1), vascular endothelial growth factor (VEGF), and prostaglandin E2 (PGE-2) [13]. Several research groups have reported that intra-articular injections of PRP primarily reduced inflammation mediated by PGE-2, HGF, and IGF-1. IGF-1 synthesized and secreted by platelets is shown to prevent leukocyte infiltration into the joint space, thereby reducing the levels of IL-1β and TNFα in the synovial fluid [13]. Overall intra-articular injection of PRP has been shown to maintain joint homeostasis. However, clinical trial data suggest that the effect of PRP seems to last for only 3 weeks and thereafter reduces. The symptoms of OA were seen to relapse after a period of 1 year. Although promising results were observed using PRP in the hydrogel, chitosan, or hyaluronic acid (HA) scaffolds [14], efficacy is yet to be shown in elaborate randomized clinical trials (RCTs).

#### **3. Mesenchymal stromal cells**

The history of mesenchymal stromal/stem cells (MSCs) dates back to 1960 when seminal studies conducted by Friedenstein showed the isolation of MSCs from bone

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**osteoarthritis**

*The Role of Mesenchymal Stromal Cells in the Management of Osteoarthritis of the Knee*

marrow (BM) which were capable of forming ectopic bone in vivo. This was found to be a non-hematopoietic fibroblast-like, colony-forming cell which primarily supported hematopoietic stem cells in the perivascular niche [15]. Owen and Friedenstein discovered that these cells were capable of differentiating into the osteogenic lineage [16]. Subsequently, the multipotent plasticity of that bone marrow MSCs (BMMSCs) was identified and shown that they were capable of differentiating into osteocytes, chondrocytes, and adipocytes in vitro [17]*.* In addition to the abovementioned three lineages, Caplan and colleagues demonstrated that these cells were capable of differentiating into cells of the muscle, tendons/ligaments, and connective tissue after which he coined the term "mesenchymal stem cells" [18]. Bianco and Gehron Robey deduced that *cbfa1* gene was the master regulator for directing the osteogenic fate of MSCs. Because of the ability of MSCs to form osteocytes, they named them skeletal stem cells [19]. In 2006, the International Society for Cellular Therapy (ISCT) proposed the name multipotent mesenchymal stromal cells and defined that MSCs must adhere to the criteria of being plastic adherent; express surface markers CD105, CD73, and CD90; lack the expression of hematopoietic markers CD45, CD34, CD14 or CD11b, CD79α or CD19, and HLA-DR; and differentiate into osteoblasts, chondrocytes, and adipocytes under suitable conditions in vitro [20]. In addition to their differentiation capacity, MSCs have been shown to elicit immunosuppressive and immunomodulatory effects on T lymphocytes, B cells, dendritic cells (DC), and natural killer (NK) cells either by cell-cell interactions or by secretion of anti-inflammatory molecules such as indoleamine 2,3-dioxygenase (IDO) and prostaglandin E2 (PGE-2), interleukin-4 (IL-4), interleukin-10 (IL-10), and transforming growth factor β (TGFβ) making them ideal cell types for treatment of diseases [21–23]. Because of their ability to differentiate into chondrocytes in vitro and with their anti-inflammatory and immunomodulatory functions, they were believed to be candidate cell type to treat diseases such as OA. MSCs have been isolated from over 18 different tissue sources. The most commonly used tissue sources for isolating MSCs apart from bone marrow are the adipose tissue, umbilical cord, placenta, and dental pulp. However, autologous or allogeneic BMMSCs are currently the most widely used cell type in clinical trials for various disease indications. They are considered the "gold standard" MSC type because of their extensive characterization that took place for over 5 decades.

**4. Possible mechanism of action (MoA) of BMMSCs for treatment of** 

The pathophysiology of OA is characterized by degradation of hyaline cartilage causing narrowing of joint space leading to subchondral sclerosis, subchondral cysts, hypertrophic chondrocytes, and formation of osteophytes. The friction caused by the rubbing of joints results in chronic pain in OA patients [24]. Degeneration of cartilage extracellular matrix (ECM) may be caused due to the increase in the levels of proteolytic enzymes such as matrix metalloproteases (MMPs) and aggrecanases mediated by IL-1β and TNFα [25]. BMMSCs express a wide range of properties that are anticipated to be beneficial for treating genetic, mechanical, and age-related degeneration in diseases such as OA. In our previous publication, we have in detail attempted to deduce the possible mechanism of action (MoA) of allogeneic pooled BMMSC population [25]. Briefly, BMMSCs are known to be immunomodulatory in nature, primarily because of their potential to significantly suppress the proliferation of inflammatory T cells, monocytes, and dendritic cells either by direct cell-to-cell contact. In addition, they secrete a wide range of anti-inflammatory molecules such as PGE-2, IDO, IL1Ra, and IL-10 [26, 27]. BMMSCs influence the local osteoarthritic microenvironment by stimulating

*DOI: http://dx.doi.org/10.5772/intechopen.86016*

#### *The Role of Mesenchymal Stromal Cells in the Management of Osteoarthritis of the Knee DOI: http://dx.doi.org/10.5772/intechopen.86016*

marrow (BM) which were capable of forming ectopic bone in vivo. This was found to be a non-hematopoietic fibroblast-like, colony-forming cell which primarily supported hematopoietic stem cells in the perivascular niche [15]. Owen and Friedenstein discovered that these cells were capable of differentiating into the osteogenic lineage [16]. Subsequently, the multipotent plasticity of that bone marrow MSCs (BMMSCs) was identified and shown that they were capable of differentiating into osteocytes, chondrocytes, and adipocytes in vitro [17]*.* In addition to the abovementioned three lineages, Caplan and colleagues demonstrated that these cells were capable of differentiating into cells of the muscle, tendons/ligaments, and connective tissue after which he coined the term "mesenchymal stem cells" [18]. Bianco and Gehron Robey deduced that *cbfa1* gene was the master regulator for directing the osteogenic fate of MSCs. Because of the ability of MSCs to form osteocytes, they named them skeletal stem cells [19]. In 2006, the International Society for Cellular Therapy (ISCT) proposed the name multipotent mesenchymal stromal cells and defined that MSCs must adhere to the criteria of being plastic adherent; express surface markers CD105, CD73, and CD90; lack the expression of hematopoietic markers CD45, CD34, CD14 or CD11b, CD79α or CD19, and HLA-DR; and differentiate into osteoblasts, chondrocytes, and adipocytes under suitable conditions in vitro [20]. In addition to their differentiation capacity, MSCs have been shown to elicit immunosuppressive and immunomodulatory effects on T lymphocytes, B cells, dendritic cells (DC), and natural killer (NK) cells either by cell-cell interactions or by secretion of anti-inflammatory molecules such as indoleamine 2,3-dioxygenase (IDO) and prostaglandin E2 (PGE-2), interleukin-4 (IL-4), interleukin-10 (IL-10), and transforming growth factor β (TGFβ) making them ideal cell types for treatment of diseases [21–23]. Because of their ability to differentiate into chondrocytes in vitro and with their anti-inflammatory and immunomodulatory functions, they were believed to be candidate cell type to treat diseases such as OA. MSCs have been isolated from over 18 different tissue sources. The most commonly used tissue sources for isolating MSCs apart from bone marrow are the adipose tissue, umbilical cord, placenta, and dental pulp. However, autologous or allogeneic BMMSCs are currently the most widely used cell type in clinical trials for various disease indications. They are considered the "gold standard" MSC type because of their extensive characterization that took place for over 5 decades.
