Autologous and Allogeneic Mesenchymal Stem Cell Therapy for Treating Osteoarthritis

Current treatments for osteoarthritis (OA) focus on relieving symptoms such as joint pain and inflammation and improving mobility. No therapies are available to reverse the progressive degeneration of articular (i.e., joint) cartilage that characterizes OA. To meet the need for such a treatment, researchers are evaluating whether injection or infusion of mesenchymal stem cells (MSCs) into affected joints can repair damaged cartilage in patients with OA. If MSC therapy is found to be safe and effective, it would represent the first regenerative therapy for OA.

MSCs are multipotent progenitor cells capable of differentiating into several different cell types, including cartilage, tendon, bone, and fat.1,2 Studies of animal models and microfracture surgery to treat cartilage defects in humans have suggested that MSCs might help regenerate articular cartilage.3 However, the exact mechanism by which MSCs promote cartilage regeneration remains unclear. Several theories may explain the role of MSCs in this process. MSCs might differentiate into chondrocytes (i.e., cells responsible for maintaining cartilage) to fill a cartilage defect. MSCs might also modulate the immune response to reduce inflammation, promote host cell survival, stimulate local angiogenesis (i.e., new blood vessel growth), and inhibit fibrosis (i.e., scar tissue formation).1,4

Researchers evaluating MSCs to treat OA have not yet standardized cell preparation techniques. MSCs can be isolated from several types of tissue, including bone marrow, skeletal muscle, adipose (i.e., fat), synovium (i.e., membrane lining articular joints), and periosteum (i.e., membrane covering the outer surface of bones).1 MSCs harvested from different tissue types have different attributes and may vary in their ability to proliferate and to differentiate into chondrocytes.1 MSCs are relatively rare compared to other cell types. Thus, investigators must concentrate MSC populations from tissue samples via centrifuge or culture them in a laboratory using cell expansion techniques to obtain a sufficient supply of MSCs for therapeutic applications.3,5 Laboratory culturing of MSCs exposes them to growth factors that could influence their nature and potentially alter the efficiency of MSCs for therapeutic uses. Furthermore, research has demonstrated that a patient's age and overall condition, including presence of OA, might influence the attributes of new MSCs produced, such as their ability to proliferate and differentiate into chondrocytes.1

Most research of MSCs to treat OA has involved autologous MSCs harvested from patients' own tissue. As of mid-2012, at least one company, Osiris Therapeutics, Inc. (Columbia, MD, USA), is developing an off-the-shelf, MSC-based product to treat OA that is derived from an allogeneic (i.e., donor) stem cell line. The company is conducting clinical trials of its Chondrogen® MSC-based therapeutic...