Osteogenic and osteoclastogenic potential of jaw bone-derived cells-A case study

Though the stem cell properties of tooth-derived periodontal ligament and gingival cells have been widely documented, surprisingly little is known about both the osteogenic and osteoclastogenic differentiation capacities of the more clinically relevant jaw bone-derived cells. These cells could be considered being recruited during bone healing such as after tooth extraction, after placing an implant, or after surgical or traumatic injury. Here, we compared the osteoblast and osteoclastogenesis features of four consecutive bone outgrowths with periodontal ligament and gingiva cells. For osteogenesis assay, cells were cultured in osteogenic medium, whereas in osteoclastogenesis assays, cells were cultured in the presence of human peripheral blood mononuclear cells (PBMCs) as a source of osteoclast precursors. After osteogenic stimulus, all six cell types responded by an increased expression of osteoblast markers RUNX2 and DMP1. Periodontal ligament cells expressed significantly higher levels of RUNX2 compared to all bone outgrowths. Alkaline phosphatase enzyme levels in periodontal ligament cells reached earlier and higher peak expression. Mineral deposits were highest in periodontal ligament, gingiva and the first bone outgrowth. Osteoclastogenesis revealed a stepwise increase of secreted pro-osteoclastogenesis proteins M-CSF, IL-1β, and TNF-α in the last three consecutive bone cultures. OPG mRNA showed the opposite: high expression in periodontal and gingiva cells and the first outgrowth. Osteoclast numbers were similar between the six cultures, both on bone and on plastic. This first study reveals that jaw bone outgrowths contain bone remodelling features that are slightly different from tooth-associated cells.