FKBP5 Regulates the Osteogenesis of Human Adipose-derived Mesenchymal Stem Cells.

Objective: Human adipose-derived stem cells (ASCs) have shown considerable potential for tissue regeneration. FK506 binding protein (FKBP) 5 is a cochaperone of several proteins. The purpose of this work was to explore the function of FKBP5 in ASC osteogenesis.

Methods: Lentivirus infection was used to overexpress or knock down FKBP5 in ASCs. To inhibit FKBP5, SAFit2, a specific inhibitor of FKBP5, was used. Next, the osteogenic capacity of ASCs was evaluated via alkaline phosphatase (ALP) staining, and extracellular calcium precipitation was detected via Alizarin red S staining. The binding proteins of FKBP5 were assessed via proteomics and validated via coimmunoprecipitation experiments.

Results: Following osteogenic induction, FKBP5 expression increased at both the mRNA and protein levels. Interestingly, FKBP5 upregulation by lentivirus infection increased the ability of ASCs to differentiate into osteoblasts, as revealed by ALP staining, while ALP activity also increased. Moreover, increased extracellular calcium precipitation confirmed that FKBP5 overexpression promoted ASC osteogenesis into osteocytes. On the other hand, FKBP5 knockdown or functional suppression with SAFit2 decreased this process. Furthermore, the proteomics and coimmunoprecipitation data demonstrated that FKBP5 bound to a variety of proteins in ASCs. These proteins serve as the molecular chaperone base upon which the osteogenesis-regulating activity of FKBP5 rests.

Conclusion: Our study revealed that FKBP5 enhances the osteogenesis of ASCs, providing a feasible method for clinical bone tissue engineering applications.