Identification And Characterization of Precursor Cells in Mouse Temporomandibular Joint

Objectives: Approximately 1-2 million people in the United States have degenerative diseases of the TMJ (TMJ-DD). Therefore, enhancing the repair of damaged cartilage constitutes a rational strategy for the treatment and/or prevention of TMJ-DD. However, the identification of precursors cells in the TMJ remains elusive. The purpose of this study is to identify the potential precursor cells in the TMJ. Methods: Transgenic mice containing the 3.6 kb fragment of the rat collagen type 1 promoter fused to a Topaz-fluorescent protein (3.6 Col1-GFP) and the transgenic mice containing the collagen type 2 promoter fused to a Cyan-fluorescent protein (Col2-GFP) were used to determine their expression in the TMJ. In addition to determine the differentiating fate of the cells expressing 3.6 Col1-GFP, mice carrying the transgene of 3.6 kb fragment of the rat collagen type 1 promoter fused to Cre was cross-bred with ROSA ?-gal mouse line. A minimum of three mice was analyzed for each transgenic line. Results: The mandibular condylar cartilage can be divided into 4 zones (superficial, polymorphic, flattened and hypertrophic). The 3.6 Col1-GFP and Col2-GFP mark two different and distinct populations in the mouse TMJ. The 3.6 Col1-GFP expression is localized in the polymorphic zone, disc, and subchondral bone while the Col 2-GFP expression is localized in the flattened and hypertrophic zones. In addition we found that the 3.6 Col1-expressing cells differentiate into cells which populate both the flattened and hypertrophic zones of the mandibular condylar cartilage. Conclusion: The 3.6 Col1-expressing cells in the TMJ maybe the precursor cells for the flattened and hypertrophic zones and could be a new therapeutic target for the regeneration of the TMJ. This work is supported by American Association of Orthodontists Foundation and NIH grant DE017193 to SW.