OBJECTIVEBy examining arthroplasty interface membrane-derived fibroblasts in vitro, we observed continuous morphological changes in cultured cells similar to the spontaneous differentiation of adult stem cells. This investigation is aimed to study whether the cells possess mesenchymal stem cell-like properties.

METHODSTissue culture, immunohistochemistry and flow cytometry were used to characterize the cultured arthroplasty membrane-derived fibroblasts for their fibroblast and stem cell properties. The plasticity of these cells was also analyzed using osteogenic, adipogenic medium culture and histological techniques.

RESULTSAll the cells in culture expressed vimentin. We found that 0.1% of the cultured interface membrane-derived fibroblasts possessed mesenchymal stem cell markers (SSEA(4)(+)/CD45(-)), 4.5% expressed CD34, and 2.4% were positive for Nanog. These cells did not contain cells positive for such hematopoietic stem cell markers as CD133, Thy-1 or SCF. After exposure to osteogenic differentiation cocktails, calcium deposition was found in many of the arthroplasty membrane-derived fibroblasts, and (24.5-/+5.5)% of the fibroblasts expressed the mineralization precursor enzyme (alkaline phosphatase). When cultured in adipogenic media, (16.0-/+6.5)% of the cells differentiated into lipid droplet- containing adipocytes.

CONCLUSIONA portion of arthroplasty interface membrane-derived fibroblasts express mesenchymal stem cell-related surface antigens. Under certain conditions, these cells can differentiate into osteoblasts or adipocytes, suggesting the properties of mesenchymal stem cells.