Rapamycin could increase the effects of melatonin against age-dependent bone loss

Osthole accelerates osteoporotic fracture healing by inducing the osteogenesis-angiogenesis coupling of BMSCs via the Wnt/β-catenin pathway

Osthole, a natural coumarin derivative, has been shown to have multiple pharmacological activities. However, its effect on osteoporotic fracture has not yet been examined. This research was designed to explore the unknown role and potential mechanism of osthole on osteoporotic fracture healing. We first evaluated the osteogenic and angiogenic abilities of osthole. Then angiogenesis-related assays were conducted to investigate the relationship between osteogenesis and angiogenesis, and further explore its molecular mechanism. After that, we established osteoporotic fracture model in ovariectomy-induced osteoporosis rats and treated the rats with osthole or placebo. Radiography, histomorphometry, histology, and sequential fluorescent labeling were used to evaluate the effect of osthole on osteoporotic fracture healing. In vitro research revealed that osthole promoted osteogenesis and up-regulated the expression of angiogenic-related markers. Further research found that osthole couldn't facilitate the angiogenesis of human umbilical vein endothelial cells in a direct manner, but it possessed the ability to induce the osteogenesis-angiogenesis coupling of bone marrow mesenchymal stem cells (BMSCs). Mechanistically, this was conducted through activating the Wnt/β-catenin pathway. Subsequently, using ovariectomy-induced osteoporosis tibia fracture rat model, we observed that osthole facilitated bone formation and CD31hiEMCNhi type H-positive capillary formation. Sequential fluorescent labeling confirmed that osthole could effectively accelerate bone formation in the fractured region. The data above indicated that osthole could accelerate osteoporotic fracture healing by inducing the osteogenesis-angiogenesis coupling of BMSCs via the Wnt/β-catenin pathway, which implied that osthole may be a potential drug for treating osteoporosis fracture.

Icariin accelerates bone regeneration by inducing osteogenesis-angiogenesis coupling in rats with type 1 diabetes mellitus

BACKGROUND

Icariin (ICA), a natural flavonoid compound monomer, has multiple pharmacological activities. However, its effect on bone defect in the context of type 1 diabetes mellitus (T1DM) has not yet been examined.

AIM

To explore the role and potential mechanism of ICA on bone defect in the context of T1DM.

METHODS

The effects of ICA on osteogenesis and angiogenesis were evaluated by alkaline phosphatase staining, alizarin red S staining, quantitative real-time polymerase chain reaction, Western blot, and immunofluorescence. Angiogenesis-related assays were conducted to investigate the relationship between osteogenesis and angiogenesis. A bone defect model was established in T1DM rats. The model rats were then treated with ICA or placebo and micron-scale computed tomography, histomorphometry, histology, and sequential fluorescent labeling were used to evaluate the effect of ICA on bone formation in the defect area.

RESULTS

ICA promoted bone marrow mesenchymal stem cell (BMSC) proliferation and osteogenic differentiation. The ICA treated-BMSCs showed higher expression levels of osteogenesis-related markers (alkaline phosphatase and osteocalcin) and angiogenesis-related markers (vascular endothelial growth factor A and platelet endothelial cell adhesion molecule 1) compared to the untreated group. ICA was also found to induce osteogenesis-angiogenesis coupling of BMSCs. In the bone defect model T1DM rats, ICA facilitated bone formation and CD31hiEMCNhi type H-positive capillary formation. Lastly, ICA effectively accelerated the rate of bone formation in the defect area.

CONCLUSION

ICA was able to accelerate bone regeneration in a T1DM rat model by inducing osteogenesis-angiogenesis coupling of BMSCs.

The role of melatonin in the development of postmenopausal osteoporosis

Melatonin is an important endogenous hormone that modulates homeostasis in the microenvironment. Recent studies have indicated that serum melatonin levels are closely associated with the occurrence and development of osteoporosis in postmenopausal women. Exogenous melatonin could also improve bone mass and increase skeletal strength. To determine the underlying mechanisms of melatonin in the prevention and treatment of postmenopausal osteoporosis, we performed this review to analyze the role of melatonin in bone metabolism according to its physiological functions. Serum melatonin is related to bone mass, the measurement of which is a potential method for the diagnosis of osteoporosis. Melatonin has a direct effect on bone remodeling by promoting osteogenesis and suppressing osteoclastogenesis. Melatonin also regulates the biological rhythm of bone tissue, which benefits its osteogenic effect. Additionally, melatonin participates in the modulation of the bone microenvironment. Melatonin attenuates the damage induced by oxidative stress and inflammation on osteoblasts and prevents osteolysis from reactive oxygen species and inflammatory factors. As an alternative drug for osteoporosis, melatonin can improve the gut ecology, remodel microbiota composition, regulate substance absorption and maintain metabolic balance, all of which are beneficial to the health of bone structure. In conclusion, our review systematically demonstrates the effects of melatonin on bone metabolism. Based on the evidence in this review, melatonin will play a more important role in the diagnosis, prevention and treatment of postmenopausal osteoporosis.

The role of melatonin in bone regeneration: A review of involved signaling pathways

Increasing bone resorption followed by decreasing bone mineralization are hallmarks of bone degeneration, which mostly occurs in the elderly population and post-menopausal women. The use of mesenchymal stem cells (MSCs) has raised many promises in the field of bone regeneration due to their high osteoblastic differentiation capacity and easy availability from abundant sources. A variety of compounds, including growth factors, cytokines, and other internal factors, have been combined with MSCs to increase their osteoblastic differentiation capacity. One of these factors is melatonin, whose possible regulatory role in bone metabolism and formation has recently been suggested by many studies. Melatonin also is a potential signaling molecule and can affect many of the signaling pathways involved in MSCs osteoblastic differentiation, such as activation of PI3K/AKT, BMP/Smad, MAPK, NFkB, Nrf2/HO-1, Wnt, SIRT/SOD, PERK/ATF4. Furthermore, melatonin in combination with other components such as strontium, vitamin D3, and vitamin K2 has a synergistic effect on bone microstructure and improves bone mineral density (BMD). In this review article, we aim to summarize the regulatory mechanisms of melatonin in osteoblastic differentiation of MSCs and underling involved signaling pathways as well as the clinical potential of using melatonin in bone degenerative disorders.

Assessment of the Therapeutic Potential of Melatonin for the Treatment of Osteoporosis Through a Narrative Review of Its Signaling and Preclinical and Clinical Studies

Melatonin is a bioamine produced primarily in the pineal gland, although peripheral sites, including the gut, may also be its minor source. Melatonin regulates various functions, including circadian rhythm, reproduction, temperature regulation, immune system, cardiovascular system, energy metabolism, and bone metabolism. Studies on cultured bone cells, preclinical disease models of bone loss, and clinical trials suggest favorable modulation of bone metabolism by melatonin. This narrative review gives a comprehensive account of the current understanding of melatonin at the cell/molecular to the systems levels. Melatonin predominantly acts through its cognate receptors, of which melatonin receptor 2 (MT2R) is expressed in mesenchymal stem cells (MSCs), osteoblasts (bone-forming), and osteoclasts (bone-resorbing). Melatonin favors the osteoblastic fate of MSCs, stimulates osteoblast survival and differentiation, and inhibits osteoclastogenic differentiation of hematopoietic stem cells. Produced from osteoblastic cells, osteoprotegerin (OPG) and receptor activator of nuclear factor kappa B ligand (RANKL) critically regulate osteoclastogenesis and melatonin by suppressing the osteoclastogenic RANKL, and upregulating the anti-osteoclastogenic OPG exerts a strong anti-resorptive effect. Although the anti-inflammatory role of melatonin favors osteogenic function and antagonizes the osteoclastogenic function with the participation of SIRT signaling, various miRNAs also mediate the effects of the hormone on bone cells. In rodent models of osteoporosis, melatonin has been unequivocally shown to have an anti-osteoporotic effect. Several clinical trials indicate the bone mass conserving effect of melatonin in aging/postmenopausal osteoporosis. This review aims to determine the possibility of melatonin as a novel class of anti-osteoporosis therapy through the critical assessment of the available literature.

Targeting Sirt1, AMPK, Nrf2, CK2, and Soluble Guanylate Cyclase with Nutraceuticals: A Practical Strategy for Preserving Bone Mass

There is a vast pre-clinical literature suggesting that certain nutraceuticals have the potential to aid the preservation of bone mass in the context of estrogen withdrawal, glucocorticoid treatment, chronic inflammation, or aging. In an effort to bring some logical clarity to these findings, the signaling pathways regulating osteoblast, osteocyte, and osteoclast induction, activity, and survival are briefly reviewed in the present study. The focus is placed on the following factors: the mechanisms that induce and activate the RUNX2 transcription factor, a key driver of osteoblast differentiation and function; the promotion of autophagy and prevention of apoptosis in osteoblasts/osteoclasts; and the induction and activation of NFATc1, which promotes the expression of many proteins required for osteoclast-mediated osteolysis. This analysis suggests that the activation of sirtuin 1 (Sirt1), AMP-activated protein kinase (AMPK), the Nrf2 transcription factor, and soluble guanylate cyclase (sGC) can be expected to aid the maintenance of bone mass, whereas the inhibition of the serine kinase CK2 should also be protective in this regard. Fortuitously, nutraceuticals are available to address each of these targets. Sirt1 activation can be promoted with ferulic acid, N1-methylnicotinamide, melatonin, nicotinamide riboside, glucosamine, and thymoquinone. Berberine, such as the drug metformin, is a clinically useful activator of AMPK. Many agents, including lipoic acid, melatonin, thymoquinone, astaxanthin, and crucifera-derived sulforaphane, can promote Nrf2 activity. Pharmacological doses of biotin can directly stimulate sGC. Additionally, certain flavonols, notably quercetin, can inhibit CK2 in high nanomolar concentrations that may be clinically relevant. Many, though not all, of these agents have shown favorable effects on bone density and structure in rodent models of bone loss. Complex nutraceutical regimens providing a selection of these nutraceuticals in clinically meaningful doses may have an important potential for preserving bone health. Concurrent supplementation with taurine, N-acetylcysteine, vitamins D and K2, and minerals, including magnesium, zinc, and manganese, plus a diet naturally high in potassium, may also be helpful in this regard.

Melatonin Accelerates Osteoporotic Bone Defect Repair by Promoting Osteogenesis-Angiogenesis Coupling

Previous studies have revealed that melatonin could play a role in anti-osteoporosis and promoting osteogenesis. However, the effects of melatonin treatment on osteoporotic bone defect and the mechanism underlying the effects of melatonin on angiogenesis are still unclear. Our study was aimed to investigate the potential effects of melatonin on angiogenesis and osteoporotic bone defect. Bone marrow mesenchymal stem cells (BMSCs) were isolated from the femur and tibia of rats. The BMSC osteogenic ability was assessed using alkaline phosphatase (ALP) staining, alizarin red S staining, qRT-PCR, western blot, and immunofluorescence. BMSC-mediated angiogenic potentials were determined using qRT-PCR, western blot, enzyme-linked immunosorbent assay, immunofluorescence, scratch wound assay, transwell migration assay, and tube formation assay. Ovariectomized (OVX) rats with tibia defect were used to establish an osteoporotic bone defect model and then treated with melatonin. The effects of melatonin treatment on osteoporotic bone defect in OVX rats were analyzed using micro-CT, histology, sequential fluorescent labeling, and biomechanical test. Our study showed that melatonin promoted both osteogenesis and angiogenesis in vitro. BMSCs treated with melatonin indicated higher expression levels of osteogenesis-related markers [ALP, osteocalcin (OCN), runt-related transcription factor 2, and osterix] and angiogenesis-related markers [vascular endothelial growth factor (VEGF), angiopoietin-2, and angiopoietin-4] compared to the untreated group. Significantly, melatonin was not able to facilitate human umbilical vein endothelial cell angiogenesis directly, but it possessed the ability to promote BMSC-mediated angiogenesis by upregulating the VEGF levels. In addition, we further found that melatonin treatment increased bone mineralization and formation around the tibia defect in OVX rats compared with the control group. Immunohistochemical staining indicated higher expression levels of osteogenesis-related marker (OCN) and angiogenesis-related markers (VEGF and CD31) in the melatonin-treated OVX rats. Then, it showed that melatonin treatment also increased the bone strength of tibia defect in OVX rats, with increased ultimate load and stiffness, as performed by three-point bending test. In conclusion, our study demonstrated that melatonin could promote BMSC-mediated angiogenesis and promote osteogenesis-angiogenesis coupling. We further found that melatonin could accelerate osteoporotic bone repair by promoting osteogenesis and angiogenesis in OVX rats. These findings may provide evidence for the potential application of melatonin in osteoporotic bone defect.

Simvastatin reverses the harmful effects of high fat diet on titanium rod osseointegration in ovariectomized rats

INTRODUCTION

The objectives of the present study were to determine whether simvastatin (SIM) could reverse the harmful effects on titanium rod osseointegration in ovariectomized rats fed high-fat diet (HFD).

MATERIALS AND METHODS

Ovariectomized female Sprague-Dawley rats were randomly allocated to three groups and received SIM treatment plus HFD for 12 weeks. We then evaluated the microstructure parameters, histological parameters, biomechanical parameters, bone turnover, and blood lipid level.

RESULTS

After 12 weeks of treatment, SIM can significantly improve bone formation around the titanium rod and osseointegration including higher values of maximum push-out force, bone area ratio (BAR), bone-to-implant contact (BIC), bone mineral density (BMD), bone volume (BV/TV), trabecular number (Tb.N), trabecular thickness (Tb.Th), mean connective density (Conn.D) when compared with the HFD group. In addition, system administration of SIM showed positive effects on collagen type 1 cross-linked C-telopeptide (CTX-1), procollagen I N-terminal propeptide (PINP), total cholesterol (TC), triglycerides (TGL), low-density lipoprotein (LDL) cholesterol and high-density lipoprotein (HDL) cholesterol. Compared with the HFD group, lower values of CTX-1, P1NP, TC, TGL and LDL were observed in the SIM+HFD group (P < 0.05).

CONCLUSION

Our findings revealed that HFD may have an adverse effect on osseointegration in osteoporotic conditions, and the harmful effect of HFD on osseointegration could be reversed by SIM.

Melatonin Inhibits Osteoclastogenesis and Osteolytic Bone Metastasis: Implications for Osteoporosis

Osteoblasts and osteoclasts are major cellular components in the bone microenvironment and they play a key role in the bone turnover cycle. Many risk factors interfere with this cycle and contribute to bone-wasting diseases that progressively destroy bone and markedly reduce quality of life. Melatonin (N-acetyl-5-methoxy-tryptamine) has demonstrated intriguing therapeutic potential in the bone microenvironment, with reported effects that include the regulation of bone metabolism, acceleration of osteoblastogenesis, inhibition of osteoclastogenesis and the induction of apoptosis in mature osteoclasts, as well as the suppression of osteolytic bone metastasis. This review aims to shed light on molecular and clinical evidence that points to possibilities of melatonin for the treatment of both osteoporosis and osteolytic bone metastasis. It appears that the therapeutic qualities of melatonin supplementation may enable existing antiresorptive osteoporotic drugs to treat osteolytic metastasis.

Intermittent administration sodium valproate has a protective effect on bone health in ovariectomized rats

The present work was aimed to evaluate the effect of different administration modes of sodium valproate (VPA) on bone strength, bone mass and bone mineral density in ovariectomized (OVX) rats and further investigation of the possible mechanism. 60 female SD rats were randomly divided into 4 groups: Sham group (Sham, n = 15), OVX group (OVX, n = 15), OVX rats received intermittent VPA treatment group (IVPA, n = 15) and OVX rats received daily VPA treatment group (EVPA, n = 15). After 12 weeks of treatment, the rats were sacrificed, and serum and femur samples were harvested. DEXA, Micro-CT, history, biomechanical testing, biochemical index and western blot analysis were used to observe the therapeutic effect and explore the possible mechanism. Micro-CT and DEXA analysis of bones revealed better BMD and higher BV/TV, Tb. Th, Tb. N, Conn. D and lower Tb. Sp at femoral metaphysis evaluated in IVPA when compared with OVX and EVPA group (P < 0.05). Histological, fluorescent analysis and biological strength revealed more trabecular bone and higher relative mineral apposition rate, maximal load, elastic modulus and energy at break with evaluated in IVPA when compared with OVX and EVPA group (P < 0.05). The levels of P1NP, estrogen, CTX, TRAP-5b and RANKL of the IVPA group showed a significant increase when compared with the OVX and EVPA group (P < 0.05). We confirm adverse effects on protein expressions including Notch1, Jagged1, HEY1, Wnt 1, β-catenin and RUNX2 following daily VPA treatment in OVX female rats. Our current study demonstrated that intermittent administration of sodium valproate has a protective effect on bone health in OVX rats and these effects may be achieved by activating Notch/Wnt/β-catenin/RUNX2 signal axis.

Effects of Melatonin on Osteogenic Differentiation of Bone Marrow Mesenchymal Stem Cells in Inflammatory Environment by Regulating Mammalian Target of Rapamycin/Phosphatidylinositol 3-Kinase/Protein Kinase B Signaling

Human bone marrow mesenchymal stem cells (BMSCs) differentiation into special cell types is affected by inflammation. Melatonin has various effects such as anti-oxidation and immune regulation. However, melatonin’s effect on BMSCs osteogenic differentiation during inflammation has not been elucidated. Rat BMSCs were isolated and assigned into control group, inflammation group (1 μg/ml lipopolysaccharide, LPS) and melatonin group (100 μM melatonin was added to LPSstimulated BMSCs cells) followed by analysis of BMSCs proliferation by MTT assay, Caspase 3 and ALP activity, expression of Runx2 and OP by Real time PCR, ROS content and SOD activity, TNF-α and IL-1β secretion by ELISA and mTOR/PI3K/AKT signaling protein level by Western blot. LPS action on BMSCs significantly inhibits BMSCs proliferation, promotes Caspase 3 activity, inhibits ALP activity, decreases Runx2 and OP expression and SOD activity, increases ROS content and TNF-α and IL-1β secretion as well as reduced mTOR and p-PI3K level (P <0.05). Melatonin addition significantly reversed the above changes (P <0.05). Melatonin can regulate oxidative stress, inhibit inflammation, and promote BMSCs proliferation and osteogenic differentiation in inflammatory environment by activating mTOR/PI3K/AKT signaling pathway.

Moderate SMFs attenuate bone loss in mice by promoting directional osteogenic differentiation of BMSCs

Background

Osteoporosis is a common metabolic bone disease without effective treatment. Bone marrow-derived mesenchymal stem cells (BMSCs) have the potential to differentiate into multiple cell types. Increased adipogenic differentiation or reduced osteogenic differentiation of BMSCs might lead to osteoporosis. Whether static magnetic fields (SMFs) might influence the adipo-osteogenic differentiation balance of BMSCs remains unknown.

Methods

The effects of SMFs on lineage differentiation of BMSCs and development of osteoporosis were determined by various biochemical (RT-PCR and Western blot), morphological (staining and optical microscopy), and micro-CT assays. Bioinformatics analysis was also used to explore the signaling pathways.

Results

In this study, we found that SMFs (0.2–0.6 T) inhibited the adipogenic differentiation of BMSCs but promoted their osteoblastic differentiation in an intensity-dependent manner. Whole genomic RNA-seq and bioinformatics analysis revealed that SMF (0.6 T) decreased the PPARγ-mediated gene expression but increased the RUNX2-mediated gene transcription in BMSCs. Moreover, SMFs markedly alleviated bone mass loss induced by either dexamethasone or all-trans retinoic acid in mice.

Conclusions

Taken together, our results suggested that SMF-based magnetotherapy might serve as an adjunctive therapeutic option for patients with osteoporosis.

Supplementary information

Supplementary information accompanies this paper at 10.1186/s13287-020-02004-y.