WNT3A and the induction of the osteogenic differentiation in adipose tissue derived mesenchymal stem cells.

Adipose tissue derived stem cells (ASCs) can easily be isolated, but the osteogenic differentiation potential is limited. To improve this differentiation potential, more investigations are required about signaling proteins for the induction of the osteogenic differentiation. This study focused on the WNT3A protein, because little is known about the canonical WNT signaling pathway and the osteogenic differentiation of ASCs. The alkaline phosphatase (ALP) activity was measured for the evaluation of the osteogenic differentiation. WNT3A and Dickkopf-related protein 1 (DKK1) were used for the activation and the inhibition of the canonical WNT signaling pathway, respectively. For control we manipulated the bone morphogenetic protein (BMP) pathway in ASCs with BMP2 and NOGGIN (BMP pathway inhibitor). WNT3A stimulated significantly the ALP activity in ASCs, while BMP2, DKK1 and NOGGIN did not induce highly the ALP activity in ASCs. Moreover, an osteogenic differentiation medium with dexamethasone and WNT3A increased the ALP activity, but the gene expression of osteoblast markers and the biomineralization after long-term cultures were not increased. In contrast, ASCs differentiated into adipocyte-like cells in all tested differentiation media. WNT3A did not repress the expression of the adipogenic transcription factor Peroxisome Proliferator-Activated Receptor Gamma (PPARG). In conclusion, WNT3A supports early stages such as the ALP activity, but it does neither improve later stages of the osteogenic differentiation nor it inhibits the genuine adipogenic differentiation of ASCs.