3,5-dicaffeoyl‑epi-quinic acid from Atriplex gmelinii enhances the osteoblast differentiation of bone marrow-derived human mesenchymal stromal cells via WnT/BMP signaling and suppresses adipocyte differentiation via AMPK activation

BackgroundImpaired bone formation is one of the reasons behind osteoporosis. Alterations in the patterns of mesenchymal stromal cell differentiation towards adipocytes instead of osteoblasts contribute to osteoporosis progression. Natural anti-osteoporotic agents are effective and safe alternatives for osteoporosis treatment.PurposeIn this context, 3,5-dicaffeoyl‑epi-quinic acid (DCEQA) which is a derivative of chlorogenic acid with reported bioactivities was studied for its osteogenic differentiation enhancing potential in vitro.MethodsAnti-osteoporotic effects of DCEQA were investigated in human bone marrow-derived mesenchymal stromal cells (hBM-MSCs) which were induced to differentiate into osteoblasts or adipocytes with or without DCEQA treatment. Changes in the osteogenic and adipogenic markers such as ALP activity and lipid accumulation, respectively, were observed along with differentiation-specific activation of mitogen activated protein kinase (MAPK) pathways.ResultsAt 10 μM concentration, DCEQA increased the proliferation of bone marrow-derived human mesenchymal stromal cells (hBM-MSCs) during osteoblast differentiation. The expression of osteogenic markers ALP, osteocalcin, Runx2, BMP2 and Wnt 10a was upregulated by DCEQA treatment. The ALP activity and extracellular mineralization were also increased. DCEQA elevated the phosphorylation levels of p38 and JNK MAPKs as well as the activation of β-catenin and Smad1/5. DCEQA suppressed the lipid accumulation and downregulated expression of adipogenic markers PPARγ, C/EBPα and SREBP1c in adipo-induced hBM-MSCs. DCEQA also decreased the phosphorylation of p38 and ERK MAPKs and stimulated the activation of AMPK in hBM-MSC adipocytes.ConclusionDCEQA was suggested to enhance osteoblast differentiation via stimulating Wnt/BMP signaling. The adipocyte differentiation inhibitory effect of DCEQA was suggested to arise from its ability to increase AMPK phosphorylation. Overall, DCEQA was shown to possess osteogenesis enhancing and adipogenesis inhibitory properties which might facilitate its use against osteoporotic conditions.     

Promotion of osteogenesis through beta-catenin signaling by desferrioxamine

Desferrioxamine, an iron chelator with “hypoxia-mimetic” activity, promotes bone mineralization when used in aluminum-overloaded dialysis patients. However, the effect of desferrioxamine on osteoblastic differentiation from pluripotent mesenchymal stem cells (MSCs) has not been reported. In this study, pluripotent human MSCs and murine mesenchymal C3H10T1/2 cells were simultaneously treated with desferrioxamine and bone morphogenetic protein-2 (BMP2). In BMP2-treated MSCs, desferrioxamine levels of 15 μΜ were found to increase alkaline phosphatase (ALP) activity and calcium deposition, which were the markers of osteoblastic differentiation. These effects of desferrioxamine were accompanied by promoted phosphorylation of glycogen synthase kinase 3β (GSK-3β) and increased β-catenin protein content, a direct GSK-3β substrate. Knockdown of β-catenin by RNA interference eliminates this positive effect of desferrioxamine on ALP activity. Taken together, these data demonstrate that desferrioxamine plays a direct role in the differentiation of mesenchymal stem cells by activating β-catenin signaling cascades.     

Effect of TAK1 on osteogenic differentiation of mesenchymal stem cells by regulating BMP-2 via Wnt/β-catenin and MAPK pathway

Mesenchymal stem cells (MSCs) have the ability to differentiate into osteoblasts and chondrocytes. In vitro osteogenic differentiation is critical but the molecular mechanism has yet to be further clarified. The role of TGF-β activated kinase 1 (TAK1) in MSCs osteogenesis differentiation has not been reported. By adding si-TAK1 and rhTAK1, the osteogenic differentiation of MSCs was measured. Expression levels of the osteoblastic marker genes during osteogenic differentiation of MSCs were checked. As well as molecules involved in BMP and Wnt/β-catenin signaling pathways. The phosphorylation of p38 and JNK was also checked. TAK1 is essential for mineralization of MSCs at low concentration, but excessive rhTAK1 inhibits mineralization of MSCs. It up regulates the expression levels of bone sialoprotein (BSP), osteocalcin (OSC), Alkaline phosphatase (ALP), and RUNX2 during osteogenic differentiation of MSCs. It can also promote TGF-β/BMP-2 gene expression and β-catenin expression, and down regulate GSK-3β expression. Meanwhile, TAK1 promotes the phosphorylation of p38 and JNK. Additionally, TAK1 up regulates the expression of BMP-2 at all concentration under the inhibition of p38 and JNK. Our results suggested that TAK1 is essential in MSCs osteogenesis differentiation, and functions as a double-edged sword, probably through regulation of β-catenin and p38/JNK.     

Bone morphogenetic protein-7 (OP1) and transforming growth factor-beta1 modulate 1,25(OH)2-vitamin D3-induced differentiation of human osteoblasts

Bone morphogenetic proteins (BMPs) and transforming growth factor-beta (TGFbeta) are potent regulators of osteoblast differentiation and proliferation, processes that are crucial in bone remodeling. BMPs and TGFbeta act in concert with other local factors and hormones, among them 1,25(OH)2-vitamin D3 and insulin. Here we show that BMP7 inhibits 1,25(OH)2-vitamin D3-induced differentiation of human osteoblasts, whereas TGFbeta1 stimulates it, as assessed by assays for alkaline phosphatase (ALP) induction, matrix mineralization, and morphology changes. BMP7 or TGFbeta1 alone affects the differentiation of human osteoblasts. Similar results were obtained in assays for ALP induction using conditionally immortalized human osteoblasts (hFOB) and primary osteoblasts obtained from trabecular bone of the femoral head after hip replacement surgery. BMP7 stimulation led to a decrease of 1,25(OH)2-vitamin D3-induced binding of nuclear proteins to a vitamin D response element, as shown by electrophoretic mobility shift assay. Our results suggest that 1,25(OH)2-vitamin D3 modulates in opposite ways the effects of BMP7 and TGFbeta1 on osteoblast differentiation.     

A low dose of daidzein acts as an ERbeta-selective agonist in trabecular osteoblasts of young female piglets

The role of estrogens and estrogen-like molecules, including isoflavones, in regulating bone cell activities is essential in understanding the etiology and treatment of post-menopausal osteoporosis. Although estrogen replacement (HRT) has been the main therapy used to prevent and treat osteoporosis, there are concerns about its safety. Isoflavones have attracted attention to their potential roles in osteoporosis prevention and treatment. We have compared the effects of the isoflavone daidzein (1 nM), which has no effect on tyrosine kinases, and 17beta-estradiol (1 nM) on the development and function of cultured osteoblasts isolated from long bones of young female piglets. Daidzein increased ALP activity, osteocalcin secretion, and mineralization, while E2 increased only ALP activity. The content of ERbeta and osteoprotegerin secretion by control cells gradually increased during osteoblast differentiation, whereas the ERalpha and RANK-L content decreased. Daidzein enhanced only the nuclear ERbeta whereas estradiol increased both ERalpha and ERbeta. Daidzein and estradiol increased osteoprotegerin and RANK-L secretion. Daidzein had a more pronounced effect than did estradiol. Daidzein and estradiol increased the membrane content of RANK-L and the nuclear content of runx2/Cbfa1. Daidzein enhanced the nuclear content of progesterone and vitamin D receptors but not as much as did estradiol. All the effects of daidzein were blocked by ICI 182,780. We conclude that a low concentration of daidzein may exert its anti-resorptive action by increasing the activity of porcine mature osteoblasts via ERbeta, by regulating runx2/Cbfa1 production, and by stimulating the secretion of key proteins involved in osteoclastogenesis, such as osteoprotegerin and RANK-ligand.     

Oversulfated chondroitin sulfate-E binds to BMP-4 and enhances osteoblast differentiation

Small leucine-rich proteoglycans, such as biglycan, and their side chain sulfated glycosaminoglycans (GAGs), have been suggested to be involved in bone formation and mineralization processes. The present study was designed to investigate whether chondroitin sulfate (CS), one of the GAG, and its oversulfated structures coupled with bone morphogenetic protein-4 (BMP-4) alter the differentiation and subsequent mineralization of MC3T3-E1 osteoblastic cells. CS-E, one of the oversulfated CS structure, enhanced cell growth, alkaline phosphatase (ALP) activity, collagen deposition, and mineralization whereas heparin enhanced only ALP activity and mineralization. As well as CS-E, CS-H, and CPS also enhanced the mineralization of the cells. CS-E enhanced the mineralization of the cells by interacting with protein in the conditioned medium. CS-E induced mineralization was significantly inhibited by an antibody against BMP-4. The addition of exogenous BMP-4 further increased the capacity of CS-E to enhance mineralization. Fluorescence correlation spectroscopy method using fluoresceinamine-labeled GAG revealed that the oversulfated GAGs have a high affinity for BMP-4. The disaccharide analysis of the cells indicated that MC3T3-E1 cells are capable of producing oversulfated structures of CS by themselves. The lack of CS from the cells after chondroitinase treatment resulted in the inhibition of mineralization. These results in the present study indicate that oversulfated CS, which possesses 4,6-disulfates in N-acetyl-galactosamine, binds to BMP-4 and promotes osteoblast differentiation and subsequent mineralization.     

Sonic hedgehog is involved in osteoblast differentiation by cooperating with BMP-2

The roles of Sonic hedgehog (Shh) and Bone morphogenetic protein-2 (Bmp-2) in osteoblast differentiation were investigated using in vitro cell systems. Recombinant amino-terminal portion of SHH (rSHH-N) dose dependently stimulated ALP activity in C3H10T1/2 and MC3T3-E1 cells. rSHH-N induced expression of Osteocalcin mRNA in C3H10T1/2 cells. A soluble form of the receptor for type IA BMP receptor antagonized rSHH-N-induced ALP activity in C3H10T1/2 and MC3T3-E1 cells, indicating that BMPs are involved in SHH-induced osteoblast differentiation. Simultaneous supplement with rSHH-N and BMP-2 synergistically induced ALP activity and expression of Osteocalcin mRNA in C3H10T1/2 cells. Pretreatment with rSHH-N for 6 h enhanced the response to BMP-2 by increasing ALP activity in C3H10T1/2 and MC3T3-E1 cells. Stimulatory effects of rSHH-N and additive effects with rSHH-N and BMP-2 on ALP activity were also observed in mouse primary osteoblastic cells. Transplantation of BMP-2 (1 microg) into muscle of mice induced formation of ectopic bone, whereas transplantation of r-SHH-N (1-5 microg) failed to generate it. These results indicate that Shh plays important roles in osteoblast differentiation by cooperating with BMP.     

Preactivation of β-catenin in osteoblasts improves the osteoanabolic effect of PTH in type 1 diabetic mice

Type 1 diabetes (T1D) is correlated with osteopenia primarily due to low bone formation. Parathyroid hormone (PTH) is a known anabolic agent for bone, the anabolic effects of which are partially mediated through the Wnt/β-catenin signaling pathway. In the present study, we first determined the utility of intermittent PTH treatment in a streptozotocin-induced T1D mouse model. It was shown that the PTH-induced anabolic effects on bone mass and bone formation were attenuated in T1D mice compared with nondiabetic mice. Further, PTH treatment failed to activate β-catenin signaling in osteoblasts of T1D mice and was unable to improve osteoblast proliferation and differentiation. Next, the Col1–3.2 kb-CreERTM; β-cateninfx(ex3) mice were used to conditionally activate β-catenin in osteoblasts by injecting tamoxifen, and we addressed whether or not preactivation of β-catenin boosted the anabolic action of PTH on T1D-related bone loss. The results demonstrated that pretreatment with activation of osteoblastic β-catenin followed by PTH treatment outperformed PTH or β-catenin activation monotherapy and led to greatly improved bone structure, bone mass, and bone strength in this preclinical model of T1DM. Further analysis demonstrated that osteoblast proliferation and differentiation, as well as osteoprogenitors in the marrow, were all improved in the combination treatment group. These findings indicated a clear advantage of developing β-catenin as a target to improve the efficacy of PTH in the treatment of T1D-related osteopenia.     

The Effect and Osteoblast Signaling Response of Trace Silicon Doping Hydroxyapatite

It is commonly accepted that silicon-doped hydroxyapatite (HAp) can achieve good repair effects for both spinal fusion and bone defect filling. However, the underlying mechanism by which silicon aids such beneficial effects is still not fully understood. Herein, we report on silicon-doped hydroxyapatites with excellent biocompatibility to osteoblast cells and suggest the signaling pathway involved. Non-doped HAp and trace Si-doped HAp (Si/HAp) with Si concentration close to and higher than natural bones were synthesized (i.e., 32, 260, and 2000 ppm Si). The composition, crystal lattice vibration pattern, and morphology of these samples are characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR), and SEM, respectively. Positive biological activities of these Si-doped HAp materials were demonstrated through a cytotoxicity study and with the MTT and alkaline phosphatase (ALP) activity assays. The Si-doped samples were not toxic to MC3T3-E1 cells. Indeed, osteoblast proliferation measurement illustrated that 2000 ppm Si-doped HAp increased osteoblast proliferation by about 1.6 times compared to non-doped HAp. The ALP assay also proves that the trace Si doping has the function to enhance cell proliferation and differentiation. The ALP assay showed that Si doping also enhanced cell differentiation. QRT-PCR results revealed that Si-doped HAp enhanced osteogenic differentiation of osteoblast cells by upregulating genes such as MAPK3, Fzd1, Wnt1, Lrp6, and BMP2. In conclusion, Si-doped HAp promotes osteoblast proliferation and differentiation by activating the Wnt/β-catenin and MAPK signaling pathways. This work could provide useful information of the beneficial effects of silicon in human bones and provide clues as to the molecular mechanism of the promotive effect of Si-doped HAp biomaterials.     

Cissus quadrangularis extract enhances biomineralization through up-regulation of MAPK-dependent alkaline phosphatase activity in osteoblasts

Cissus quadrangularis Linn. has been implicated as therapeutic agent for enhancing bone healing. Though its osteogenic activity has been suggested, the underlying mechanism still remains unclear. In the present study, the effects of ethanol extract of C. quadrangularis (CQ-E) on osteoblast differentiation and function were analyzed using murine osteoblastic cells. The results indicated that mRNA expressions of osteoblast-related genes were not affected by the CQ-E treatment. However, alkaline phosphatase (ALP) activity and the extent of mineralized nodules were significantly increased in treated cells compared with controls. The addition of an extracellular regulated kinase 1/2 inhibitor, a Jun N-terminal kinase 1/2/3 inhibitor and a p38 mitogen-activated protein kinase (MAPK) inhibitor resulted in significantly decreased ALP activity, preferentially by p38 MAPK inhibitor. These results suggested that CQ-E may regulate osteoblastic activity by enhancing ALP activity and mineralization process, and the increased ALP activity effect of CQ-E is likely mediated by MAPK-dependent pathway.