Objectives: characterize in vitro cell cultures from adult human periodontal ligament and identify the function of Shh during bone differentiation of the HPLSC. Methods: HPLSC were isolated from human periodontal ligament using antibodies directed against STRO-1. STRO1(+) and STRO1(-) cell populations were characterized through evaluation of bone/cementum markers and components of Shh pathway. To study the function of Shh during the bone/cementum lineage, cells were cultured in osteogenic media with Shh inhibitor cyclopamine (cyc) and therefore alkaline phosphatase activity and calcium deposit were quantified.
Results: HPLSC, identified as STRO1 (+) were characterized by their ability to form colonies and differentiate In the absence of osteogenic media, STRO1(+) cells did not express bone differentiation markers and we confirmed the differentiation potential of STRO-1(+) cells into the bone/cementum, adipose, and neuronal lineages. Cells express components of the Shh pathway and also respond to Shh/Gli pathway. Finally, a lower deposition of calcium in cells treated with Cyc during bone/cementum differentiation was observed, indicating a function of the Shh pathway during the differentiation process in the HPLSC and osteoprogenitors present in the human periodontal ligament.
Conclusions: for the first time we established that Shh influences the bone/cementum differentiation of HPLSC and osteoprogenitors in the adult human periodontal ligament. We propose that Shh should be explored as a novel molecular niche factor to study regenerative models in periodontal tissues.