CELL SURFACE CHARACTERISATION OF FAT PAD DERIVED STEM CELLS IS NOT AFFECTED BY PASSAGE: IMPLICATIONS FOR ARTICULAR CARTILAGE REPAIR

Abstract

Introduction: Articular cartilage is frequently damaged but only shows a limited capacity for repair. Autologous chondrocytes are being used for the repair of focal articular cartilage defects in the ankle but their use has limitations. The use of undifferentiated progenitor cells from other sources is limited by the fact that these cells loose there stem cell characterisation with passage in culture. The fat pad derived stem cells are a possible alternative that maintain multipotentiality at higher passages. We explore the hypothesis that their cell surface characterisation will resemble that of mesenchymal stem cells and will not alter with passage.

Materials and Methods: Cells were isolated from the human fat pad and expanded in monolayer culture. On confluence, they were harvested by digestion and replated at a ratio of 1:3. Cells from passage 2, 4, 6, 8 and 10 were stained and analysed using flow cytometry for a panel of stem cell surface antibodies.

Results: Fat pad derived cells stained strongly for CD13, 29, 44 and 90 (markers of mesenchymal stem cells). The cells stained poorly for 3G5 (pericyte marker), CD34 and CD56 (marker for haematopoetic lineage), and LNG FR and STRO 1 (markers of bone marrow stem cells). These results suggest that the fat pad cell population has surface expression characteristics of mesenchymal stem cells, but differ from bone marrow derived stem cells. It is also important to note that the expression of these cell-surface markers was maintained up to passage 10.

Conclusion: The consistent pattern of cell surface expression, with little change with passage, shows that the proliferation and expansion of the fat pad stem cell population does not lead to major changes in phenotype of these cells. This can potentially allow a significant increase in number sufficient for clinical applications without loosing their multipotentiality.