Cell-secreted matrices enhance osteogenesis in adipose-derived stem cells undergoing lineage specification

Osteogenic differentiation of mesenchymal stem cells (MSC) is important in the field of bone tissue engineering. The identification of biological factors that influence osteogenesis is vital for developing a broader understanding of how complex microenvironments play a role in differentiation. The aim of this study was to demonstrate that adipose-derived stem cell (ADSC) osteogenesis is enhanced through interaction with extracellular matrices (ECM) secreted by ADSC undergoing osteogenesis. ADSC were obtained from human patients following elective abdominoplasty. Cells were selected for plastic adherence, characterized, and induced to differentiate using osteogenic supplements (OS; dexamethasone, ascorbic acid, and beta-glycerol phosphate). Cells were removed at several time points during osteogenesis and the secreted ECM was isolated. Undifferentiated cells were re-seeded onto the cell secreted ECM's and induced to differentiate with OS. At several time points, cells cultured on ECM's or tissue culture plastic controls (i.e. uncoated surface) were collected and RNA isolated. QPCR and gene array analysis revealed enrichment of osteogenic markers and more rapid progression through osteogenic maturational phases in cells seeded onto ECM secreted at the midpoint in differentiation (ca. 15 days). Our results demonstrate that the cumulative deposition of ECM reaches a critical point at approximately 15 days, before which there appear to be no definitive osteogenic cues from the matrix, and after which, strong drivers of osteogenesis are present. The creation of microenvironments that contain essential morphogenic matrix signals is an important step towards methods of growing and differentiating MSC in a rapid effective manner, particularly for bone-related clinical applications.