Assessing Stem Cell Potential for a Tmj Disc Construct

INTRODUCTION Jaw joint disorders affect more than 10 million Americans and can have a significant effect on quality of life. The Temporomandibular Joint, or TMJ, is behind the pain, clicking, and grinding of the jaw that so many individuals find aggravating and in some cases, debilitating. Up to 70% of patients with jaw joint disorders suffer from some displacement of the TMJ disc, which can lead to deterioration of the native joint tissue. (Farrar et. al., 1979). Like other cartilogenous tissues, the poor regenerative capabilities of the TMJ disc make it a good candidate for tissue engineering. For patients who must undergo discectomy, or removal of the TMJ disc, there is currently no available tissue engineered construct with which to replace the degenerated disc. Current research in the TMJ realm has turned to seeking cell sources that could be potentially developed into a TMJ disc construct. A healthy TMJ must withstand a biomechanical environment unique from other joints in the body, and as a result develops a distinctive extracellular matrix (ECM) composition. Mature chondrocytes extracted from the autologous site are in some ways promising because they display the imperative joint properties, but these show limited ability to expand in culture (Mao, 2005). A second cell source under consideration is mesenchymalderived stem cells. These show great capability of differentiating into multiple cell lineages, including cartilage, bone, and tendon (Pittenger et. al., 1999). Through combinations of scaffold choice, type of media, mechanical stimuli, and growth factors, these cells can be manipulated to display a directed phenotype upon culturing. One type of mesenchymal stem cells, adipose-derived stem cells (ASCs), are particularly promising due to their abundance, ease of attainability, and capability of undergoing differentiation into fibrocartilage. One study has already employed ASCs to examine their potential for tissue engineering the TMJ disc. This study by Mäenpää et. al. in 2010 showed limited success in getting the ASCs to show similar ECM composition as cells extracted from the TMJ disc. This indicated inadequate differentiation of the cells into fibrocartilage. This study employed the micromass and pellet seeding techniques on a poly(L/D)lactide (PLA) disc, which may have affected the outcome.