Characterization of equine adipose tissue-derived stromal cells: Adipogenic and osteogenic capacity and comparison with bone marrow-derived mesenchymal stromal cells

To characterize equine adipose tissue-derived stromal cell (ASC) frequency and growth characteristics and assess of their adipogenic and osteogenic differentiation potential. In vitro experimental study. Horses (n=5; aged, 9 months to 5 years). Cell doubling characteristics of ASCs harvested from supragluteal subcutaneous adipose tissue were evaluated over 10 passages. Primary, second (P2), and fourth (P4) passage ASCs were induced under appropriate conditions to undergo adipogenesis and osteogenesis. Limit dilution assays were performed on each passage to determine the frequency of colony-forming units with a fibroblastic (CFU-F) phenotype and the frequency of ASC differentiation into the adipocyte (CFU-Ad) and osteoblast (CFU-Ob) phenotype. ASC isolates exhibited an average cell-doubling time of 2.1±0.9 days during the first 10 cell doublings. Approximately 1 in 2.3±0.4 of the total stromal vascular fraction nucleated cells were ASCs, based on the CFU-F assays, and 1 in 3.6±1.3 expressed alkaline phosphatase, an osteogenic marker. Primary ASCs differentiated in response to adipogenic (1 in 4.9±5.4, CFU-Ad) and osteogenic (1 in <2.44, CFU-Ob) inductive conditions and maintained their differentiation potential during subsequent passages (P2 and P4). The frequency, in vitro growth rate, and adipogenic and osteogenic differentiation potential of equine ASCs show some differences to those documented for ASCs in other mammalian species. Adipose tissue is a potential source of adult stem cells for tissue engineering applications in equine veterinary medicine.