Pharmaceutical modulation of canonical Wnt signaling in multipotent stromal cells for improved osteoinductive therapy

Abstract

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 MSCs 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 β-catenin and GSK3β in a manner consistent with activation of Wnt signaling. With osteogenic supplements, the GSK3β inhibitor 6-bromo-indirubin-3′-oxime (BIO) 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 BIO 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 BIO treatment had no significant effect. Further investigation indicated that unlike GW, BIO induced cell cycle inhibition in vitro. Furthermore, we found that GW treatment significantly reduced expression of chemokines that may exacerbate neutrophil-and 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 BIO can adversely affect the viability of hMSC preparations in vitro and in vivo.osteogenesis | bone repair | tissue engineering

Autocrine stimulation of osteoblast activity by Wnt5a in response to TNF-α in human mesenchymal stem cells

“…These dose-dependent effects of LiCl and SB216763 also occurred in human SaOS-2 osteoblast-like cells (Fig. 2C), and convincingly, were quite similar to the dose-dependent effects of the GSK3b inhibitor 6-bromoindirubin-3 0 -oxime [33]. Collectively, these data suggest that the canonical Wnt pathway activates TNAP expression and activity in MSCs.…”

Smart Design of Stable Extracellular Matrix Mimetic Hydrogel: Synthesis, Characterization, and In Vitro and In Vivo Evaluation for Tissue Engineering

“…[ 33 ] This effect is due to activation of the transcription factor peroxisome proliferator activated receptor gamma (PPAR γ ), a key regulator of adipogenesis. [ 39 ] Another remarkable fi nding in this experiment was the observation of oriented collagen matrix at the periphery of the tissue, which is relatively rare especially at a site where natural bone does not exist (ectopic site). The anisotropic nature of oriented collagen could be detected as green using polarized light microscope after picrosirius staining.…”

Myeloma plasma cells alter the bone marrow microenvironment by stimulating the proliferation of mesenchymal stromal cells

“…BIO (6-bromoindirubin-3'-oxime) is a GSK3β inhibitor that can increase expression of early osteogenic markers in MSC. 49,50 BIO has been shown to increase bone volume in wild-type mice and may function to decrease MM tumor burden specifically in the context of the bone microenvironment. 51,52 Similarly, purmorphamine, a Hedgehog (Hh) pathway agonist that functions through the receptor Smoothened to enhance osteogenesis of murine-derived MSC 53,54 has been shown to have a pro-osteogenic effect on human-derived MSC.…”