摘要：

Human mesenchymal stem cells (hMSCs) from bone marrow are regarded as putative osteoblast progenitors in vivo and differentiate into osteoblasts in vitro. Positive signaling by the canonical wingless (Wnt) pathway is critical for the differentiation of MSC5 into osteoblasts. In contrast, activation of the peroxisome proliferator-activated receptor-γ (PPARγ)-mediated pathway results in adipogenesis. We therefore compared the effect of glycogen-synthetase-kinase-3β (GSK3β) inhibitors and PPARγ inhibitors on osteogenesis by hMSCs. Both compounds altered the intracellular distribution of βcatenin and GSK3β in a manner consistent with activation of Wnt signaling. With osteogenic supplements, the GSK3β inhibitor 6-bromo-indirubin-3'oxime (BlO) and the PPARγ inhibitor GW9662 (GW) enhanced early osteogenic markers, alkaline phosphatase (ALP), and osteoprotegerin (OPG) by hMSCs and transcriptome analysis demonstrated up-regulation of genes encoding bone-related structural proteins. At higher doses of the inhibitors, ALP levels were attenuated, but dexamethasone-induced biomineralization was accelerated. When hMSCs were pretreated with BlO or GW and implanted into experimentally induced nonself healing calvarial defects, GW treatment substantially increased the capacity of the cells to repair the bone lesion, whereas BlO treatment had no significant effect. Further investigation indicated that unlike GW. BlO induced cell cycle inhibition in vitro. Furthermore, we found that GW treatment significantly reduced expression of chemokines that may exacerbate neutrophiland macrophagemediated cell rejection. These data suggest that use of PPARγ inhibitors during the preparation of hMSCs may enhance the capacity of the cells for osteogenic cytotherapy, whereas adenine analogs such as BlO can adversely affect the viability of hMSC preparations in vitro and in vivo.

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