A signal-amplification circuit between miR-218 and Wnt/β-catenin signal promotes human adipose tissue-derived stem cells osteogenic differentiation.

Human adipose-derived stem cells (hASCs) have become a highly attractive source of seed cells in bone regenerative. It has become a key issue how to effectively improve osteogenic differentiation of hASCs in the bone tissue engineering. Numerous regulatory pathways dominate osteogenic differentiation of hASCs involve transcriptional factors and signaling molecules. However, how these factors combine with each other to regulate hASCs osteogenic differentiation still remain to be illustrated. The identification of microRNAs will illuminate this and might permit finely tuning the osteogenic differentiation process. Here, we present evidence that miR-218 acts as a positive regulator of hASCs osteogenesis. Real-time PCR shows that miR-218 was up-regulated during osteogenic differentiation. Overexpression of exogenous miR-218 enhanced osteogenic differentiation in vitro, whereas inhibition of miR-218 would suppress osteogenic differentiation. Furthermore, miR-218 directly targeted SFRP2 and DKK2, which is a WNT signaling pathway antagonist, and enhanced Wnt/β-catenin signaling activity. Finally, we found that mimicking Wnt/β-catenin signal strengthened the expression level of miR-218, while blocking the signal attenuated the expression level of miR-218. This feed-forward regulatory circuit provides additional insight into how miRNAs acting as a signal amplifier interact with signal molecules during hASCs osteogenic differentiation. Taken together, we have established a regulatory network with a central role for the miR-218 in hASCs osteogenic differentiation.