Soluble factors from ASCs effectively direct control of chondrogenic fate

Background and objectives: Adipose tissue‐derived stem cells (ASCs) have great potential for regenerative medicine. For molecular understanding of specific functional molecules present in ASCs, we analysed 756 proteins including specific chondrogenic functional factors, using high‐throughput nano reverse‐phase liquid chromatography–electrospray ionization–tandem mass spectrometry. Materials, methods and results: Of these proteins, 33 were identified as chondrogenic factors or proteins including type 2 collagen, biglycan, insulin‐like growth factor‐binding protein and transforming growth factor‐beta 1 (TGF‐β1). ASCs are a possible cell source for cartilage regeneration as they are able to secrete a number of functional cytokines including chondrogenesis‐inducing molecules such as TGF‐β1 and bone morphogenetic protein 4 (BMP4). The chondrogenic phenotype of cultured ASCs was effectively induced by ASC‐culture media (CM) containing BMP4 and TGF‐β1, and maintained after pre‐treatment for 14 days in vitro and subcutaneous implantation in vivo. Chondrogenic differentiation efficiency of cultured ASCs and cultured mouse skin‐derived progenitor cells (SPCs) depended absolutely on ASC CM‐fold concentration. Cell density was also a very important factor for chondrogenic behaviour development during differentiation of ASCs and SPCs. Conclusion: ASC CM‐derived TGF‐β1‐induced chondrogenic differentiation of ASCs resulted in significant reduction in chondrogenic activity after inhibition of the p38 pathway, revealing involvement of this MAPK pathway in TGF‐β1 signalling. On the other hand, TGF‐β1 signalling also led to SMAD activation that could directly increase chondrogenic activity of ASCs.