An osteogenic cell culture system to evaluate the cytocompatibility of osteoset®, a calcium sulfate bone void filler

The purpose of the study was to describe a convenient, reliable and quantitative in vitro assay system to assess the cytocompatibility of a calcium sulfate bone filler on two osteogenic cell lines and primary osteoblasts. The hypothesis was that the bone void filler, OsteoSet® pellets, would not impact adversely on cell proliferation kinetics or osteogenic potential of selected cells. The hypothesis was tested by standard in vitro methodology of placing OsteoSet® pellets either directly in contact with osteogenic cells, or by compartmentalizing within transwell® – clear microporous membrane inserts. Data analyses were accomplished with appropriate post hoc statistics (p 0.05). In the presence of the OsteoSet® pellets, the cell lines exhibited a decrease in cell proliferation at days 4 and 7, independent of either cell type or tissue culture medium. A decrease in the alkaline phosphatase enzyme activity occurred in the osteogenic cell lines maintained for 9 and 16 days in the presence of the OsteoSet® pellets. However, with the exception of the MC3T3E-1 line, no differences were observed with respect to calcium deposition (mineralization) by day 16. Intact human osteocalcin release data for the human-derived OPC1 line and the primary osteoblasts was inconclusive as the OsteoSet® pellets may interact with the osteocalcin secreted into the tissue culture medium. The present studies describe a cell culture system to assess the cytocompatibility of bone-graft substitutes with osteogenic cells by compartmentalizing material from direct cell contact (in transwells®), and additionally, by evaluating direct cell/biomaterial interactions.