METHODS: Potential progenitor cells were isolated from the OMLP using the differential adhesion assay. Clones (>32 cells) were isolated by trypsinsation, passaged and population doubling levels (PDLs) determined. Telomere lengths and telomerase activity were determined using Single Telomere Length Analysis and the Telomere Repeat Amplification Protocol respectively. FACS analysis was performed using an antibody against the stem cell marker, CD105. Expanded cells (Passage 4) were differentiated into chondrocytes using pellet cultures and defined media. Differentiation was confirmed by PCR of chondrogenic markers, histology and immunohistochemistry.
RESULTS: Progenitor cell clones, all expressing high levels of CD105, were successfully isolated from the OMLP. These cells underwent a high level of PDs within a very short time period (6 PD/week). Such rapid cell proliferation was enabled by the presence of extremely long telomeres (> 8 Kb) and the expression of active telomerase within these clones, an enzyme expressed by embryonic stem cells. Pellet culture analysis confirmed that these cells can differentiate down the mesenchymal lineage since they were positive for the chondrogenic markers type II collagen, aggrecan and Sox 9 at both the mRNA and protein levels.
CONCLUSION: This is the first report of the isolation of telomerase positive progenitor cells from the OMLP. On going investigations are elucidating the plasticity of these cells with a view to being able to produce numerous different tissue types for tissue engineering purposes. Importantly, the oral mucosa makes an ideal target from which to harvest progenitor cells and offers a distinct advantage over the skin due to its rapid, scar-free healing phenotype.