BTL-105 manufacturer BMSCs are potential stem cells with

BMSCs are potential stem BTL-105 manufacturer with the ability to differentiate into osteoblasts or adipocytes depending on the situation (Pittenger et al., 1999). Indeed, several molecules possess a role in regulating the differentiation of BMSCs (D\'Alimonte et al., 2013; Shui et al., 2003; Yang et al., 2012). The Wnt/β-catenin signaling pathway appears to be of particular importance, since its activation promotes BMSCs differentiation into osteoblast cells while suppressing their adipogenic potential (Liu et al., 2009), which is highly similar to the effect of GLP-1 and its analogs. In particular, β-catenin stabilization and induction of its translocation into the nucleus play an important role in promoting BMSC osteogenic differentiation. Furthermore, previous studies suggested that β-catenin may have interactive effects on the cyclic AMP (cAMP) signaling pathway (Hino et al., 2005; Ke et al., 2012). The enhancement of cAMP signaling was reported to facilitate β-catenin signaling in many types of cells (Jiang et al., 2013; Liu and Habener, 2008; Zhang et al., 2014). Therefore, since GLP-1Rs are G-protein-coupled receptors able to induce intracellular cAMP formation and trigger the cAMP-protein kinase A (PKA) signaling pathway when activated (Hayes et al., 2011; Holst, 2007), we hypothesized that Ex-4 might exert its osteoblast activation effect by inducing cAMP and β-catenin signaling in BMSCs.
Results
Discussion The gut-derived hormones, such as serotonin, peptide YY (PYY), and incretins, are now recognized as critical regulators in bone homeostasis (Dicembrini et al., 2012; Wong et al., 2012; Yadav et al., 2008), since they display a negative relationship with osteoblast activity. Therefore, these results provide evidence that the inhibition of the biosynthesis of gut-derived serotonin and PYY could become an effective method to treat low-bone-mass diseases such as osteoporosis. In contrast to the negative regulation of serotonin and PYY on bone homeostasis, our study demonstrated that GLP-1R displayed a positive correlation with osteoblast activity and bone growth. The treatment with the GLP-1R agonist Ex-4 resulted in a significant increase in bone mass in the hindlimb-unloading rats, associated with the increase in osteoblast number and serum level of bone formation biomarkers, with a parallel decrease in the adipocyte number. In addition, the treatment with Ex-4 lowered the increased rates of bone resorption biomarkers (Figure S4). These findings strongly indicated that Ex-4 prevented osteopenia by promoting bone formation and suppressing bone resorption. The effect of Ex-4 in the control of bone resorption is exerted through a calcitonin-dependent pathway (Yamada et al., 2008). However, GLP-1Rs are not present in osteoblasts, so GLP-1 cannot exert a direct effect on them (Bollag et al., 2000; Yamada et al., 2008). Therefore, the anabolic effects of Ex-4 on bone formation that we observed were not a consequence of a direct action on osteoblasts. As it is well known that osteoblasts and adipocytes both differentiate from common mesenchymal precursor cells (Park et al., 2012), we speculated that the changes in the osteoblast and adipocyte numbers might be due to BMSC differentiation preferably to adipocytes rather than osteoblasts, leading to bone formation reduction and consequent osteopenia development, while GLP-1R is expressed in human BMSCs to promote cellular proliferation and prevent the differentiation of human MSCs into adipocytes (Sanz et al., 2010). Thus, we hypothesized that BMSC GLP-1R might play a regulatory role in cell fate, resulting in osteoblast differentiation rather than adipocyte differentiation. To test this hypothesis, we investigated the roles of GLP-1R on BMSC differentiation. BMSC GLP-1R activation by Ex-4 significantly enhanced the expression of osteoblastogenic biomarkers, thus promoting osteoblastic mineralization, and inhibited the induction of adipocyte differentiation biomarkers, thus decreasing endogenous lipoid deposits in cells. GLP-1R silencing or block through its antagonists reduced the effects described above. Taken together, these results suggested that GLP-1R is involved in BMSC differentiation into osteoblasts.