Phenotypic and functional properties of dedifferentiated fat cells derived from infrapatellar fat pad

Introduction: Mature adipocyte-derived dedifferentiated fat cells (DFATs) are mesenchymal stem cell (MSC)-like cells with high proliferative ability and multilineage differentiation potential. In this study, we first examined whether DFATs can be prepared from infrapatellar fat pad (IFP) and then compared phenotypic and functional properties of IFP-derived DFATs (IFP-DFATs) with those of subcutaneous adipose tissue (SC)-derived DFATs (SC-DFATs). Methods: Mature adipocytes isolated from IFP and SC in osteoarthritis patients (n = 7) were cultured by ceiling culture method to generate DFATs. Obtained IFP-DFATs and SC-DFATs were subjected to flow cytometric and microarray analysis to compare their immunophenotypes and gene expression profiles. Cell proliferation assay and adipogenic, osteogenic, and chondrogenic differentiation assays were performed to evaluate their functional properties. Results: DFATs could be prepared from IFP and SC with similar efficiency. IFP-DFATs and SC-DFATs exhibited similar immunophenotypes (CD73⁺, CD90⁺, CD105⁺, CD31^-, CD45^-, HLA-DR^-) and tri-lineage (adipogenic, osteogenic, and chondrogenic) differentiation potential, consistent with the minimal criteria for defining MSCs. Microarray analysis revealed that the gene expression profiles in IFP-DFATs were very similar to those in SC-DFATs, although there were certain number of genes that showed different levels of expression. The proliferative activity in IFP-DFATs was significantly (p < 0.05) higher than that in the SC-DFATs. IFP-DFATs showed higher chondrogenic differentiation potential than SC-DFATs in regard to production of soluble galactosaminogalactan and gene expression of type II collagen. Conclusions: IFP-DFATs showed higher cellular proliferative potential and higher chondrogenic differentiation capacity than SC-DFATs. IFP-DFAT cells may be an attractive cell source for chondrogenic regeneration.