Objective: To investigate the mineralization capacity of periodontal ligament stem cells (PDLC) by determining the mRNA expressions of alkaline phosphatase (ALP), osteocalcin (OCN) and matrix extracellular phosphoglycoprotein (MEPE) and to explore the potential of MEPE as a differentiation marker for PDLC, and its possible function in PDLC osteogenic differentiation.
Methods: PDLC were digested and cultured by a solution containing collagenase type I and dispase. PDLC were preceded to osteogenic induction for 7, 14 and 21 days respectively, and the cells before induction served as controls. Mineralization nodules and the expression of OCN in PDLC were investigated by alizarin red and immunohistochemistry respectively. The expressions of ALP, OCN and MEPE mRNA were investigated by quantitative real-time RT-PCR analysis. Statistical analysis was performed to compare the differences of mRNA expression levels among cell samples collected at different time points.
Results: The mRNA expressions of ALP, OCN and MEPE in PDLC before induction were 72, 1.1 and 534 respectively, but increased time-dependently in the induction cultures. The mRNA expressions of ALP, OCN and MEPE were 78, 9.56 and 629.6 on day 7; 290, 133 and 638.3 on day 14; 1108, 925 and 2261.1 on day 21 respectively. The relative mRNA levels of OCN, ALP on day 14 and 21, MEPE on day 21 were significantly higher than control group (P < 0.05).
Conclusions: PDLC showed analogously temporal expression of ALP, OCN and MEPE mRNA while differentiating into cementoblast/osteoblast-like cells in vitro. MEPE may play a regulatory role in PDLC osteogenic differentiation, and may be a potential osteogenic differentiation marker along with ALP and OCN.