Bone morphogenetic protein 2 promotes osteogenesis of bone marrow stromal cells in type 2 diabetic rats via the Wnt signaling pathway

Wnt signaling pathways in biology and disease: mechanisms and therapeutic advances

The Wnt signaling pathway is critically involved in orchestrating cellular functions such as proliferation, migration, survival, and cell fate determination during development. Given its pivotal role in cellular communication, aberrant Wnt signaling has been extensively linked to the pathogenesis of various diseases. This review offers an in-depth analysis of the Wnt pathway, detailing its signal transduction mechanisms and principal components. Furthermore, the complex network of interactions between Wnt cascades and other key signaling pathways, such as Notch, Hedgehog, TGF-β, FGF, and NF-κB, is explored. Genetic mutations affecting the Wnt pathway play a pivotal role in disease progression, with particular emphasis on Wnt signaling's involvement in cancer stem cell biology and the tumor microenvironment. Additionally, this review underscores the diverse mechanisms through which Wnt signaling contributes to diseases such as cardiovascular conditions, neurodegenerative disorders, metabolic syndromes, autoimmune diseases, and cancer. Finally, a comprehensive overview of the therapeutic progress targeting Wnt signaling was given, and the latest progress in disease treatment targeting key components of the Wnt signaling pathway was summarized in detail, including Wnt ligands/receptors, β-catenin destruction complexes, and β-catenin/TCF transcription complexes. The development of small molecule inhibitors, monoclonal antibodies, and combination therapy strategies was emphasized, while the current potential therapeutic challenges were summarized. This aims to enhance the current understanding of this key pathway.

Enriched H3K27Me3 on BMP4 suppresses the osteoblastic differentiation potential of BMSCs in diabetes mellitus

Diabetes mellitus has been widely acknowledged to have a negative effect on the osteoblastic differentiation of bone marrow-derived mesenchymal stem cells (BMSCs). However, the underlying epigenetic mechanisms associated with this process remain to be elucidated. The goal of the present study was to investigate the effect of diabetes mellitus on the osteoblastic differentiation of BMSCs and assess the role of histone methylation in the observed phenomena. The osteoblastic differentiation ability of BMSCs was shown to be decreased in diabetes mellitus, as indicated by alkaline phosphatase activity and the mRNA levels of osteoblast-related genes. Furthermore, diabetes mellitus caused an increased expression of the histone methylase EZH2 and the levels of H3K27Me3 and decreased the expression of the histone demethylase KDM6B, as demonstrated by qRT-PCR and western blotting. Furthermore, immunofluorescence staining suggested that both EZH2 and H3K27Me3 were primarily localized in the nucleus. In addition, chromatin immunoprecipitation assays indicated an increased presence of H3K27Me3 on the promoter region of the BMP4 gene. In summary, in the present study, we demonstrated that the osteoblastic differentiation of BMSCs is dramatically reduced in diabetes mellitus. In addition, upregulation of EZH2 expression and downregulation of KDM6B expression may not be enough to eliminate transcriptional repression mediated by H3K27Me3 on the promoter region of the BMP4 gene during the osteoblastic differentiation of BMSCs in diabetes mellitus.

Development of gelatin-methacryloyl composite carriers for bone morphogenetic Protein-2 delivery: A potential strategy for spinal fusion

To reduce the risk of nonunion after spinal fusion surgery, the in situ transplantation of bone marrow mesenchymal stem cells (BMSCs) induced toward osteogenic differentiation by bone morphogenetic protein-2 (BMP2) has been proven effective. However, the current biological agents used for transplantation have limitations, such as a short half-life and low bioavailability. To address this, our study utilized a safe and effective gelatin-methacryloyl (GelMA) as a carrier for BMP2. In vitro, experiments were conducted to observe the ability of this composite vehicle to induce osteogenic differentiation of BMSCs. The results showed that the GelMA hydrogel, with its critical properties and controlled release performance of BMP2, exhibited a slow release of BMP2 over 30 days. Moreover, the GelMA hydrogel not only enhanced the proliferation activity of BMSCs but also significantly promoted their osteogenic differentiation ability, surpassing the BMP2 effects. To investigate the potential of the GelMA-BMP2 composite vehicle, a rabbit model was employed to explore its ability to induce in situ intervertebral fusion by BMSCs. Transplantation experiments in rabbits demonstrated the effective induction of intervertebral bone fusion by the GelMA-BMP2-BMSC composite vehicle. In conclusion, the GelMA-BMP2-BMSC composite vehicle shows promising prospects in preclinical translational therapy for spinal intervertebral fusion. It addresses the limitations of current biological agents and offers a controlled release of BMP2, enhancing the proliferation and osteogenic differentiation of BMSCs.

Recent progress in bone-repair strategies in diabetic conditions

Bone regeneration following trauma, tumor resection, infection, or congenital disease is challenging. Diabetes mellitus (DM) is a metabolic disease characterized by hyperglycemia. It can result in complications affecting multiple systems including the musculoskeletal system. The increased number of diabetes-related fractures poses a great challenge to clinical specialties, particularly orthopedics and dentistry. Various pathological factors underlying DM may directly impair the process of bone regeneration, leading to delayed or even non-union of fractures. This review summarizes the mechanisms by which DM hampers bone regeneration, including immune abnormalities, inflammation, reactive oxygen species (ROS) accumulation, vascular system damage, insulin/insulin-like growth factor (IGF) deficiency, hyperglycemia, and the production of advanced glycation end products (AGEs). Based on published data, it also summarizes bone repair strategies in diabetic conditions, which include immune regulation, inhibition of inflammation, reduction of oxidative stress, promotion of angiogenesis, restoration of stem cell mobilization, and promotion of osteogenic differentiation, in addition to the challenges and future prospects of such approaches.

Schizophyllan promotes osteogenic differentiation of human adipose tissue-derived mesenchymal stem cells in vitro

BACKGROUND

Bioactive polysaccharides are a promising way for bone disease prevention with high efficiency. Schizophyllan (SPG) is a polysaccharide derived from a species of fungus with anticancer, antitumor, and anti-inflammatory effects. In the present study, for the first time, the cell proliferation, osteogenic markers, mineral deposition, and osteogenic gene expression of human adipose tissue-derived mesenchymal stem cells (hADMSCs) grown on SPG were evaluated by in vitro assays.

METHODS AND RESULTS

The cytotoxicity of SPG was measured using the MTT assay and acridine orange staining. Differentiation of hADMSCs was assessed using alkaline phosphatase (ALP) activity test, cellular calcium content assay, and mineralized matrix staining. To this end, Alizarin red S, von Kossa staining, and the expression of bone-specific markers, including ALP, Runx2, and osteonectin, were used by real-time RT-PCR over a 2-week period. According to the results, SPG at 10 µg/ml concentration was determined as the optimal dosage for differentiation studies. The results of osteogenic differentiation tests showed that compared to the control groups in vitro, SPG enhanced the osteogenic markers and mineralization as well as upregulation of the expression of bone specific genes in differentiated hADMSCs during differentiation.

CONCLUSIONS

The results revealed that SPG could be applied as effective factor for osteogenic differentiation in the future. The current study provides insights into the hADMSC-based treatment and introduces promising therapeutic material for individuals who suffer from bone defects and injuries.

Vanadium-Doped Mesoporous Bioactive Glass Promotes Osteogenic Differentiation of rBMSCs via the WNT/β-Catenin Signaling Pathway

Pentavalent vanadium [V(V)] has been studied as bioactive ions to improve the bone defect repair; however, its osteogenic promotion mechanism is still not fully understood so far. In this study, a V-doped mesoporous bioactive glass (V-MBG) was prepared, and its effects on osteogenic differentiation of rat bone marrow mesenchymal stem cells (rBMSCs) and potential signaling pathways were investigated. The physicochemical characterization revealed that the incorporation of V slightly reduced the specific surface area and increased the mesoporous pore size, and the abundant mesopores of V-MBG were beneficial to the sustained dissolution of V(V) ions as well as calcium, silicon, and phosphorus ions. Cell proliferation results indicated that the high dilution ratio (>16) V-MBG extract markedly promoted the proliferation of rBMSCs compared with the control group and the same dilution ratio MBG extract. Compared with the same dilution ratio MBG extract, diluted V-MBG extracts markedly promoted the secretion of alkaline phosphatase (ALP) and osteocalcin (OCN) protein at day 7 but insignificantly stimulated the runt-related transcription factor 2 (RUNX2) and vascular endothelial growth factor (VEGF) protein synthesis. In depth, the diluted V-MBG extracts remarkably up-regulated the expression of WNT/β-catenin pathway direct target genes, including WNT3a, β-catenin, and AXIN2 genes in contrast to the same dilution ratio MBG extracts, suggesting that the released V(V) ions might promote osteogenic differentiation of rBMSCs via the WNT/β-catenin signaling pathway.

Enamel matrix derivative expedites osteogenic differentiation of BMSCs via Wnt/β-catenin pathway in high glucose microenvironment

INTRODUCTION

The influence of enamel matrix derivative (EMD) on proliferation and osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) was explored in high glucose (HG) microenvironment with interaction of Wnt/β-catenin pathway.

MATERIALS AND METHODS

Extraction of BMSCs from Sprague-Dawley rats, culture, and identification were manifested. The cells were treated with different concentration of EMD in HG to figure out the most available concentration for proliferation and osteogenic differentiation. Then, observation of cell growth curve and cell cycle changes, and detection of Osterix, runt-related transcription factor 2 (Runx2), COL-I, early osteogenic indexes, Calcium salt deposition, and β-catenin protein in Wnt/β-catenin pathway were assured. After adding Wnt/β-catenin pathway inhibitor (XAV-939) in the cells with osteogenesis induction, detection of binding of β-catenin to Osterix was clarified.

RESULTS

Via identification BMSCs cultured in vitro was qualified. Different concentrations of EMD could accelerate cell proliferation in HG and osteogenesis induction, and 75 μg/mL EMD had the best effect. The HG augmented BMSCs proliferation and the propidium iodide index of flow cytometry cycle was elevated in HG, which were strengthened via the EMD. After BMSCs' osteogenesis induction, Osterix, Runx2, CoL-1, early osteogenic indexes, and calcium salt deposition were reduced, but elevated via EMD. β-Catenin was the lowest in the HG, but elevated after EMD. After addition of XAV-939, reduction of β-catenin and the downstream (Osterix and Runx2) were manifested. Detection of binding protein bands was in β-catenin and Osterix of the HG after EMD treatment.

CONCLUSION

EMD may facilitate the osteogenic differentiation of BMSCs via activating the Wnt/β-catenin pathway in HG.

Fluoride induces hypomethylation of BMP2 and activates osteoblasts through the Wnt/β-catenin signaling pathway

BACKGROUND

Skeletal fluorosis has become a public health issue in recent years as its serious impact on patients' life expectancy. Bone morphogenetic protein 2 (BMP2) plays a key role in promoting osteogenesis. However, the mechanism of BMP2-Wnt/β-catenin axis in skeletal fluorosis needs further exploration.

METHODS

The RT-qPCR and western blot assay were carried out to examine the mRNA and protein levels. Cell viability was measured by MTT assay. A commercial ALP assay kit was used to detect ALP activities. Alizarin Red staining was performed to measure the formation of mineralized nodules. Methylation-specific PCR (MSP) was performed to measure the methylation level of BMP2.

RESULTS

Fluoride promoted the expression of osteogenic marker genes (OPN, OCN, OSX and RUNX2) and induced the proliferation and differentiation of MC3T3-E1 cells. Fluoride induced hypomethylation and high expression of BMP2. Furthermore, knockdown of BMP2 reversed the promoting effect of fluoride on osteogenic differentiation of MC3T3-E1. The expression of β-catenin, glycogen synthase kinase 3β (GSK3β), wingless/integrated 3α (Wnt3α), low-density lipoprotein receptor-related protein 5 (LRP5) and dishevelled 1 (Dv1) were increased in osteoblasts treated with fluoride, however, knockdown of BMP2 reversed this phenomenon. Simultaneous knockdown of BMP2 and β-catenin significantly inhibited the differentiation of osteoblasts induced by fluoride.

CONCLUSION

Fluoride contributed to proliferation and differentiation of osteoblasts through BMP2-Wnt/β-catenin axis, providing a feasible theoretical basis for the treatment of skeletal fluorosis.

Effects of Coculture Fibroblasts and Vascular Endothelial Cells on Proliferation and Osteogenesis of Adipose Stem Cells

Background

The development of tissue engineering provides a new method for the clinical treatment of bone defects, but the problems of slow formation and slow vascularization of tissue engineered bone have always existed. Studies have shown that the combined culture system of vascular endothelial cells and adipose stem cells is superior to single cell in repairing bone defects. With the excellent proliferation ability, secretion of synthetic collagen and a variety of regulatory factors and fibroblasts can differentiate into osteoblasts and have the potential to be excellent seed cells involved in tissue engineering bone construction.

Objective

To investigate the effects of combined culture of fibroblasts, vascular endothelial cells, and adipose stem cells on proliferation and osteogenic differentiation of adipose stem cells.

Methods

The cells were divided into 4 groups: adipose stem cell group, adipose stem cell+vascular endothelial cell coculture group, adipose stem cell+fibroblast coculture group, and adipose stem cell+vascular endothelial cell+fibroblast coculture group. The morphological changes of the cells were observed under an inverted microscope. After 1, 3, 5, 7, and 9 days of coculture, the proliferation of adipose stem cells in each group was detected by a CCK-8 method and the growth curve was plotted. Adipose stem cells in each group were stained with alizarin red and alkaline phosphatase at days 7, 14, 21, and 28. At the third week of coculture, Western blot was used to detect the expression level of bone morphogenetic protein 2 of adipose stem cells in each group. Results and Conclusions. (1) After 14 days of culture, some cells in the adipose stem cell+vascular endothelial cell+fibroblast coculture group fused into clumps and distributed in nests, while the adipose stem cells in the adipose stem cell group had a single cell morphology and no cell clusters were observed. (2) The cell growth curves were basically the same in each group, and the absorbance value increased gradually. The absorbance value of the adipocyte+vascular endothelial cell+fibroblast coculture group was the highest, followed by the adipocyte+fibroblast coculture group and then the adipocyte+fibroblast coculture group. (3) Alizarin red staining showed negative reaction in each group on the 7th day, and a small number of red positive cells gradually appeared in each group as time went on. On the 28th day, red positive cells were found in all groups, and most of them were in the coculture group of adipose stem cells+vascular endothelial cells+fibroblasts, showing red focal. The coculture group of adipose stem cells+vascular endothelial cells and adipose stem cells+fibroblasts was less, and the adipose stem cell group was the least. On day 28 of alkaline phosphatase staining, cells in each group had red positive particles, and the adipose stem cell+vascular endothelial cell+fibroblast coculture group and adipose stem cell+fibroblast coculture group had the most, followed by the adipose stem cell+vascular endothelial cell coculture group and then the adipose stem cell group. (4) Bone morphogenetic protein 2 was expressed in all groups, especially in adipose stem cell+fibroblast coculture group and adipose stem cell+vascular endothelial cell+ fibroblast coculture group. (5) Fibroblast could promote adipose stem cell osteogenic differentiation better than vascular endothelial cells, but the proliferation effect was not as good as vascular endothelial cells. The coculture system of fibroblast combined with vascular endothelial cells and adipose stem cells promoted the proliferation of adipose stem cells and the rapid and efficient differentiation of adipose stem cells into osteoblasts.

Marantodes pumilum (blume) Kuntze (Kacip Fatimah) leaves aqueous extract prevents downregulation of Wnt/β-catenin pathway and upregulation of apoptosis in osteoblasts of estrogen-deficient, diabetes-induced rats

ETHNOPHARMACOLOGICAL RELEVANCE

Marantodes pumilum (Blume) Kuntze has been claimed to be beneficial in protecting the bone against loss in post-menopausal women. In view of increased incidence of diabetes mellitus (DM) in post-menopausal period, M. pumilum ability to overcome the detrimental effect of estrogen-deficiency and DM on the bones were identified.

AIM OF THE STUDY

To identify the mechanisms underlying protective effect of MPLA on the bone in estrogen-deficient, diabetic condition.

METHODS

Adult female, estrogen-deficient, diabetic rats (225 ± 10 g) were divided into untreated group and treated with M. pumilum leaf aqueous extract (MPLA) (50 mg/kg/day and 100 mg/kg/day) and estrogen for 28 days (n = 6 per group). Fasting blood glucose (FBG) levels were weekly monitored and at the end of treatment, rats were sacrificed and femur bones were harvested. Bone collagen distribution was observed by Masson's trichome staining. Levels of bone osteoblastogenesis, apoptosis and proliferative markers were evaluated by Realtime PCR, Western blotting, immunofluorescence and immunohistochemistry.

RESULTS

MPLA treatment was able to ameliorate the increased in FBG levels in estrogen deficient, diabetic rats. In these rats, decreased bone collagen content, expression level of osteoblastogenesis markers (Wnt3a, β-catenin, Frizzled, Dvl and LRP-5) and proliferative markers (PCNA and c-Myc) and increased expression of anti-osteoblastogenesis marker (Gsk-3β) and apoptosis markers (Caspase-3, Caspase-9 and Bax) but not Bcl-2 were ameliorated. Effects of 100 mg/kg/day MPLA were greater than estrogen.

CONCLUSION

MPLA was able to protect against bone loss, thus making it a promising agent for the treatment of osteoporosis in women with estrogen deficient, diabetic condition.

Alendronate Alleviated Femoral Head Necrosis and Upregulated BMP2/EIF2AK3/EIF2A/ATF4 Pathway in Liquid Nitrogen Treated Rats

Background

Osteonecrosis of the femoral head (ONFH) seriously affects the quality of life and labor ability of patients. It is urgent and vital to find the methods for necrosis clinical treatment.

Objective

This study aims to study the potential protective effects of Alendronate in the early stage of femur head necrosis.

Methods

Ten clinal ONFH tissue samples were employed. H&E staining was employed for the observation of the pathological characteristics of ONFH. The rat model (n=12) was established by the treatment of liquid nitrogen and then treated with Alendronate. The protein expression of BMP2, EIF2AK3, EIF2A and ATF4 were detected via Western blotting and IHC.

Results

Fibrin and necrotizing granulation tissue were observed in ONFH tissues with lymphocytes and plasma cells infiltrating in the necrotic area, exhibiting the inflammatory muscle with abnormal shape and color. In the Model group, the BMP2 and ATF4 were mainly distributed in the cell boundaries. The relative protein expression of BMP2, EIF2AK3, EIF2A, ATF4 was decreased in the Model group, compared to the NC group, which was partially recovered by the Alendronate application.

Conclusion

Alendronate application partially reversed the suppression of expression of BMP2, EIF2AK3, EIF2A, ATF4 caused by liquid nitrogen. Alendronate could be a promising strategy of curing ONFH via targeting BMP2/EIF2AK3/EIF2A/ATF4 pathway.

The synergistic promotion of osseointegration by nanostructure design and silicon substitution of hydroxyapatite coatings in a diabetic model

Accumulating evidence indicates much higher failure rates for biomedical titanium implants in diabetic patients. This phenomenon is attributed to impaired osteoblastic function, suppressed angiogenesis capacity, and abnormal osteoclast activation in diabetic patients. Our previous study demonstrated that titanium implants coated with highly crystalline nanostructured hydroxyapatite (nHA) promoted the osteogenic differentiation of bone marrow stromal cells (BMSCs) and bone-implant osseointegration under healthy conditions. Furthermore, recent studies showed that silicon-substituted biomaterials exhibited excellent osteogenesis and angiogenesis performance while repressing osteoclastogenesis. Hence, we proposed that a combination of nanostructural modification and Si substitution might produce synergetic effects to mitigate the impaired osseointegration of bone implants under diabetes mellitus (DM) conditions. To confirm this hypothesis, titanium implants coated with highly crystalline Si-substituted nHA (Si-nHA) were successfully fabricated via atmospheric plasma spraying combined with hydrothermal treatment. An in vitro study demonstrated that compared to the original HA coating, the nHA coating improved osteogenic and angiogenic differentiation and altered the OPG/RANKL ratio of DM-BMSCs. In addition, the Si-nHA coating further enhanced cell proliferation, improved osteogenic and angiogenic differentiation, and repressed osteoclastogenesis in DM-BMSCs. An in vivo study confirmed that the titanium implants coated with nHA or Si-nHA effectively promoted bone formation and bone-implant osseointegration in a diabetic rabbit model, with the Si-nHA coating exhibiting the best stimulatory effect. Collectively, the results suggest that the nanostructured topography and Si substitution act synergistically to ameliorate the poor bone regeneration and osseointegration associated with DM. Thus, the results provide a promising coating method for dental and orthopedic applications under diabetic conditions.

Bone morphogenetic protein 2-enhanced osteogenic differentiation of stem cell spheres by regulation of Runx2 expression

Bone morphogenetic protein 2 (BMP-2) is a growth factor that is used to induce osteogenic differentiation in stem cells. The present study assessed the effects of BMP-2 on stem cell spheroid morphology, viability and osteogenic differentiation. Stem cell spheres were constructed and treated with BMP-2 at predetermined concentrations (0-100 ng/ml) using concave microwells. Cell viability was qualitatively and quantitatively analyzed via microscopy and a water-soluble tetrazolium salt assay kit, respectively. Alkaline phosphatase activity was assessed and an anthraquinone dye for calcium deposit evaluation was performed to determine osteogenic differentiation. The expressions of (runt-related transcription factor 2) and collagen 1 were also determined via quantitative PCR. Spherical shapes were formed using concave microwells on day 1, which were maintained up to day 21. On day 1, the relative cell viability of 0, 10 and 100 ng/ml BMP-2 treated cells was 100.0±1.9, 97.3±4.4 and 101.3±2.6%, respectively. Significantly higher values for alkaline phosphatase activity were determined in the 100 ng/ml treated group when compared with the control group. Additionally, Runx2 mRNA levels were significantly higher in the 100 ng/ml BMP-2 group compared with the control group, as determined via quantitative PCR. The results of the present study indicated that BMP-2 enhanced the differentiation of stem cell spheres, which was demonstrated by increased alkaline phosphatase activity and Runx2 expression.

Prospect of circular RNA in osteogenesis: A novel orchestrator of signaling pathways

Circular RNAs (circRNAs) were initially regarded as by-products of aberrant splicing. But now, there are substantial evidence on their various roles in the regulation of genes during the development of organs and diseases. Consistent with these breakthroughs, it is experiencing rapid growth that circRNAs function as the important checkpoints during the osteogenesis. Therefore, characterizing the roles of circRNAs is useful and critical to better understanding the process of osteogenic differentiation, which could provide new avenues for the diagnosis and treatment of bone diseases, such as bone defects and osteoporosis. In this review, we presented a map of the interaction between circRNAs and the molecules of signaling pathways associated with osteogenesis, summarized the current knowledge of the biological functions of circRNAs during the osteogenic differentiation, figured out the limits of existing research works, and provided a novel look on the diagnostic and therapeutic methods of bone diseases based on circRNAs.

miR-381 modulates human bone mesenchymal stromal cells (BMSCs) osteogenesis via suppressing Wnt signaling pathway during atrophic nonunion development

The osteogenic differentiation of human bone mesenchymal stromal cells (BMSCs) has been considered as a central issue in fracture healing. Wnt signaling could promote BMSC osteogenic differentiation through inhibiting PPARγ. During atrophic nonunion, Wnt signaling-related factors, WNT5A and FZD3 proteins, were significantly reduced, along with downregulation of Runx2, ALP, and Collagen I and upregulation of PPARγ. Here, we performed a microarray analysis to identify differentially expressed miRNAs in atrophic nonunion tissues that were associated with Wnt signaling through targeting related factors. Of upregulated miRNAs, miR-381 overexpression could significantly inhibit the osteogenic differentiation in primary human BMSCs while increase in PPARγ protein level. Through binding to the 3'UTR of WNT5A and FZD3, miR-381 modulated the osteogenic differentiation via regulating β-catenin nucleus translocation. Moreover, PPARγ, an essential transcription factor inhibiting osteogenic differentiation, could bind to the promoter region of miR-381 to activate its expression. Taken together, PPARγ-induced miR-381 upregulation inhibits the osteogenic differentiation in human BMSCs through miR-381 downstream targets, WNT5A and FZD3, and β-catenin nucleus translocation in Wnt signaling. The in vivo study also proved that inhibition of miR-381 promoted the fracture healing. Our finding may provide a novel direction for atrophic nonunion treatment.

Effect of recombinant human bone morphogenetic protein delivered by chitosan microspheres on ectopic osteogenesis in rats

In the present study, the effect of recombinant human bone morphogenetic protein-2 (rhBMP-2) delivered by chitosan (CS) microspheres on ectopic osteogenesis was investigated in a rat model. rhBMP-2-loaded CS microspheres and blank CS microspheres were prepared. A total of 24 male Sprague Dawley rats were divided into 4 groups with 6 rats in each group: The CS/rhBMP-2 group, the rhBMP-2 group, in which rhBMP-2 was directly implanted (rhBMP-2 dose in either group, 1 mg), the CS blank group and the control group. X-ray was performed at 4 weeks after ectopic osteogenesis surgery and micro-computed tomography (CT) examination was scheduled at 1, 2, 3 and 4 weeks after the surgery to determine ectopic osteogenesis in the different groups. Histological analysis, and determination of alkaline phosphatase (ALP) activity and calcium content were also performed. The mean diameter of the osteoid tissues was 1.1±0.3 cm (range, 0.8-1.4 cm) in the CS/rhBMP-2 group, which was significantly bigger than that in the rhBMP-2 group (0.3±0.1 cm; range, 0.1-0.4 cm) at 4 weeks after the surgery. X-ray analysis and micro-CT scan indicated that the area of high-density tissues and the radionuclide intensity, as well as bone volume in the 3-dimensional reconstruction were greatest in the CS/rhBMP-2 group, followed by those in the rhBMP-2 group. All parameters, including bone mineral density, tissue mineral density, tissue mineral content and bone volume fraction, were significantly higher in the CS/rhBMP-2 group at 3 and 4 weeks after the surgery, compared with those in the rhBMP-2 group. The histological analysis, ALP activity analysis and determination of calcium content revealed that the CS/rhBMP-2 system had the greatest ability to induce osteoblast differentiation. In conclusion, the CS/rhBMP-2 microsphere delivery system significantly enhanced the induction and promotion effects of rhBMP-2 regarding ectopic osteogenesis. The present study enhances the basic data available for future application of the CS/rhBMP-2 microspheres delivery system and provides a deeper understanding of the role of BMP-2 in bone regeneration.

Polydatin promotes the osteogenic differentiation of human bone mesenchymal stem cells by activating the BMP2-Wnt/β-catenin signaling pathway

Steroid-induced osteonecrosis of the femoral head (SONFH) is a refractory disease induced by glucocorticoids. Marrow mesenchymal stem cells (MSCs) differentiate into multiple bone matrix cells and have been used as cell-based therapies to treat ONFH. However, the osteogenesis of MSCs isolated from patients with SONFH is significantly decreased. Polydatin has been widely used in traditional Chinese remedies due to its multiple pharmacological actions. As shown in our previous study, Polydatin protects from oxidative stress and promotes BMSC migration. However, little is known about its role in BMSC (Bone marrow mesenchymal stem cells) osteogenesis; therefore, we further investigated the effect and mechanism of Polydatin in hBMSC osteogenesis. The ability of Polydatin to promote the proliferation and osteogenic differentiation of hBMSCs was determined using the MTT assay, ALP staining and the ALP activity assay. Next, qPCR and western blotting were performed to measure the levels of genes and proteins related to the osteogenesis of hBMSCs. Then, the effect of Polydatin on the nuclear translocation of β-catenin was determined using immunofluorescence staining. Polydatin (30 μM) markedly enhanced the proliferation of hBMSCs and alkaline phosphatase (ALP) activity. Additionally, it also significantly upregulated the expression of osteogenic genes (Runx2, osteopontin, DLX5, osteocalcin, collagen type I and BMP2) and components of the Wnt signaling pathway (β-catenin, Lef1, TCF7, c-jun, c-myc and cyclin D). These osteogenesis-potentiating effects of Polydatin were blocked by Noggin, an inhibitor of the BMP pathway, and DKK1, an inhibitor of the Wnt/β-catenin pathway. However, DKK1 did not affect Polydatin-induced BMP2 expression. Based on our results, Polydatin promotes the proliferation and osteogenic differentiation of hBMSCs through the BMP2-Wnt/β-catenin signaling pathway.

Aqueous Extract of Mori Folium Exerts Bone Protective Effect Through Regulation of Calcium and Redox Homeostasis via PTH/VDR/CaBP and AGEs/RAGE/Nox4/NF-κB Signaling in Diabetic Rats

Purpose: The present study is aimed to explore whether the aqueous extract of Mori Folium (MF) exhibits bone protective effect by regulating calcium and redox homeostasis in diabetic rats, and to identify the signaling pathways involved in this process. Methods: Diabetic rats were established using high-sugar and high-fat diet and streptozotocin (STZ) (30 mg/kg for 3 consecutive days). The serum levels of osteocalcin (OC), insulin-like growth factor-1 (IGF-1), tartrate-resistant acid phosphatase (TRAP), phosphorus (P), calcium (Ca), 1,25-dihydroxyvitamin D3 [1,25(OH)2D3], parathormone (PTH), advanced glycation end products (AGEs), superoxide dismutase (SOD), and malondialdehyde (MDA), total antioxidant capacity (TAC), 8-hydroxy-2'-deoxyguanosine (8-OH-dG), and interleukin 6 (IL-6) were determined by ELISA or biochemical assays. Histopathological alterations in the femurs were evaluated by the stainings of hematoxylin-eosin (H&E) and alizarin red S. In addition, femoral strength was detected by a three-point bending assay, bone microstructure was detected with micro-computer tomography. Bone material properties were examined by Fourier-transform infrared spectroscopy. Furthermore, the expressions of IGF-1, runt-related transcription factor 2 (Runx2), osteoprotegerin (OPG), receptor activator of nuclear factor kappa-B ligand (RANKL), cathepsin K, AGEs, receptor of advanced glycation end products (RAGE), NADPH oxidase 4 (Nox4), and nuclear factor kappa-B (NF-κB) in the femurs and tibias, and the alterations in the levels of calcium-binding protein-28k (CaBP-28k), transient receptor potential V6 (TRPV6), and vitamin D receptor (VDR) in the kidneys and duodenums were determined by western blot and immunohistochemical analysis. Results: Treatment of diabetic rats with MF aqueous extract induces an increase in the levels of OC and IGF-1 as well as a decrease in TRAP level in serum. MF treatment also upregulates the expression of OPG, downregulates the expressions of AGEs, RAGE, Nox4, NF-κB, and RANKL, which leads to improve bone microstructure and strength exhibited by an increase in cortical area ratio, cortical thickness, and trabecular area ratio as well as ultimate load, elastic modulus, and bending stress in the femurs and tibias of diabetic rats. In addition, MF aqueous extract preserves bone material properties by decreasing the ratio of fatty acid/collagen and increasing the ratio of mineral/matrix in the femurs of diabetic rats. Moreover, MF treatment increases the levels of P, Ca, and 1,25(OH)2D3, and decreases the level of PTH in the serum, as well as upregulates the expressions of TRPV6 and VDR in the duodenums and CaBP-28k in the kidneys of diabetic rats. Additionally, MF has ability of rebuilding redox homeostasis and eliminating inflammatory stress by increasing the levels of SOD and TAC as well as decreasing the levels of IL-6, AGEs, MDA, and 8-OH-dG. Conclusions: MF treatment may improve bone quality through maintenance of calcium homeostasis via regulating the PTH/VDR/CaBP signaling, and elimination of oxidative stress via regulating the AGEs/RAGE/Nox4/NF-κB signaling. These results may suggest the potential of MF in preventing the development of diabetic osteoporosis.

Enhancement of osteogenesis of rabbit bone marrow derived mesenchymal stem cells by transfection of human BMP-2 and EGFP recombinant adenovirus via Wnt signaling pathway

Bone marrow mesenchymal stem cells (BMSCs) are considered the most important seed cells in bone tissue engineering. The present study aimed to investigate the potential of rabbit BMSCs in osteogenesis after the transfection of human BMP-2 and EGFP recombinant adenovirus. Rabbit BMSCs were isolated and the surface stem cell makers, including CD29, CD44 and CD45 were detected by flow cytometry. The expression of BMP-2 mRNA and protein in BMSCs were detected by reverse transcription-quantitative polymerase chain reaction and western blot analysis, respectively. After an induction with osteogenic medium, the alkaline phosphatase (ALK) activity at 7 days, the type I collagen at 14 days, and the calcium nodules at 21 days were performed using an ALK activity kit, immunohistochemical staining and alizarin red S staining, respectively. The expression levels of proteins related to the Wnt signaling pathway were detected by western blot analysis. The positive rates of CD29, CD44 and CD45 were 62.92±1.99, 93.55±0.99 and 0.21±0.12%. The expression of BMP-2 mRNA and protein was significantly upregulated in Ad-BMP-2/EGFP transfected BMSCs. Furthermore, Ad-BMP-2/EGFP induced ALP activity, promoted the production of type I collagen and calcium nodule formation in rabbit BMSCs. The levels of β-catenin, cyclin D1, Runx2 and c-myc were upregulated in Ad-hBMP-2/EGFP transfected BMSCs, while the level of GSK3β was significantly decreased. Results also indicated that the overexpression of BMP-2 by Ad-hBMP-2/EGFP enhanced the osteogenic differentiation ability of cultured rabbit BMSCs via stimulating the Wnt signaling pathway with the accumulation of β-catenin and suppression of GSK3β. The Ad-hBMP-2/EGFP transfected rabbit BMSCs are expected to be a good seed cell in bone tissue engineering.

MicroRNA-539 promotes osteoblast proliferation and differentiation and osteoclast apoptosis through the AXNA-dependent Wnt signaling pathway in osteoporotic rats

This study aims to explore the effects of miR-539 on osteoblast proliferation and differentiation and osteoclast apoptosis in a rat model of osteoporosis, and its mechanism involving the regulation of the AXIN1-mediated wingless-Int (Wnt) signaling pathway. A rat model of osteoporosis was successfully established by ovariectomy. With osteoblasts and osteoclasts of rats not receiving ovariectomy in the sham group as control, those of osteoporotic rats were treated with miR-539 inhibitor, miR-539 mimic, and AXIN1 shRNA. The expression of miR-53, AXIN1, the Wnt pathway related-genes, apoptosis related-genes, and osteogenic markers were measured by RT-qPCR and Western blot analysis, respectively. Alkaline phosphatase (ALP) activity in osteoblast and tartrate-resistant acid phosphatase (TRAP) activity in osteoclasts were determined after cell transfection. Osteoblast and osteoclast viability was assayed by CCK-8 assay. Cell cycle and apoptosis of osteoblasts and osteoclasts were detected by flow cytometry. Lastly, alizarin red S staining was used to detect mineralized nodules of osteoblasts. Firstly, we determined that miR-539 was down-regulated in osteoblast and osteoclast of osteoporotic rats and AXIN1 was negatively regulated by miR-539. Additionally, overexpression of miR-539 increased the expressions of β-catenin, LEF1, c-myc, cyclin D1, RUNX2, BGP, BMP-2 in osteoblast as well as β-catenin, RhoA, caspase-3, and Bcl-2 in osteoclasts. Finally, overexpression of miR-539 elevated ALP activity, proliferation, and mineralized nodules in osteoblast and osteoclast apoptosis, with reduced TRAP activity in osteoclasts. Our results demonstrate that miR-539 promotes osteoblast proliferation and differentiation as well as osteoclast apoptosis through the AXIN1-dependent Wnt signaling pathway in osteoporotic rats.

IL-17A Inhibits Osteogenic Differentiation of Bone Mesenchymal Stem Cells via Wnt Signaling Pathway

Background

Interleukin-17A (IL-17A) is not only an important modulator of inflammatory reactions, but also affects bone metabolism, which is involved in osteogenic differentiation of stem cells. However, the role and mechanism of IL-17A in osteogenic differentiation of bone mesenchymal stem cells (BMSCs) are not fully understood. In this study, we investigated the role and mechanism of IL-17A in osteogenic differentiation of BMSCs.

Material/Methods

The osteogenic differentiation of BMSCs was induced by osteoblast-induction medium with IL-17A or without IL-17A. The osteogenic differentiation of BMSCs was confirmed by the alkaline phosphatase and alizarin red staining. The lentiviral plasmid was used to construct the sFRP1-shRNA expression vector. The associated osteogenic differentiation marks (RUNX2, ALP, OPN), Wnt signaling pathway inhibitor (sFRP1), and modulators of Wnt signaling pathway (Wnt3, Wnt6) were detected by qRT-PCR and Western blot method.

Results

The results showed that the addition of IL-17A inhibited osteogenic differentiation of BMSCs. IL-17A induced up-regulated expression of sFRP1 and down-regulated expression of Wnt3 and Wnt6 in BMSCs. In addition, sFRP1-shRNA abolished the inhibition effect of IL-17A in osteogenic differentiation of BMSCs and induced up-regulated expression of Wnt3 and Wnt6 in the Wnt signaling pathway in BMSCs.

Conclusions

Our findings show that IL-17A inhibits osteogenic differentiation of bone mesenchymal stem cells via the Wnt signaling pathway.

Differential circRNA expression profiles during the BMP2-induced osteogenic differentiation of MC3T3-E1 cells

OBJECTIVE

Recent studies have indicated that circular RNAs (circRNAs) might play important roles in various diseases. However, little is known about the functions of circRNAs in the skeletal system, and the role of circRNAs in the mechanism by which bone morphogenetic protein 2 (BMP2) promotes bone differentiation remains unknown. Here, we performed RNA-seq to analyze differential expression of circRNA during different osteoblast differentiation stages and investigated the relevant mechanisms.

MATERIALS AND METHODS

Alkaline phosphatase (ALP) staining and activity were performed to assess osteogenic differentiation in MC3T3-E1 cells. The expression of osteogenic markers in MC3T3-E1 cells and the differential expression levels of circRNAs were measured and validated by qRT-PCR. Osteogenic marker proteins were measured by western blot. RNA-seq was performed to detect differential expression of circRNAs during the osteogenic differentiation of MC3T3-E1 cells induced by BMP2. Gene ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) and PANTHER pathway analyses were performed to predict the functions of differentially expressed circRNAs and potentially co-expressed target genes. The microRNA (miRNA) targets of the circRNAs and circRNA-miRNA interactions were predicted by miRanda. The circRNA-miRNA co-expression network was constructed based on the correlation analysis between the differentially expressed circRNAs and miRNAs. A graph of the circRNA-miRNA network was created using Cytoscape 3.01.

RESULTS

The Cell Counting Kit 8 (CCK-8) assay showed that BMP2 promoted the proliferation of osteoblasts in vitro. Both the intracellular ALP content and activity were increased in BMP2-treated MC3T3-E1 cells. In addition, the mRNA and protein levels of the osteoblastic markers ALP, Sp7 transcription factor (SP7) and runt-related transcription factor 2 (RUNX2) were substantially up-regulated. In the present study, 158 circRNAs were differentially expressed by a fold-change ≥2.0, P<0.05 and false discovery rate <0.05. Among these, 74 circRNAs were up-regulated, while 84 circRNAs were down-regulated. In addition, the expression levels of circRNA.5846, circRNA.19142 and circRNA.10042 were significantly increased in the BMP2 group. Furthermore, by analyzing the target mRNAs of miR-7067-5p using GO and PANTHER pathway analyses, circ19142 and circ5846 were found to be not only strongly associated with the biological process of the positive regulation of developmental processes but also related to the fibroblast growth factor, epidermal growth factor, platelet-derived growth factor and Wnt signaling pathways, which are involved in cell growth and differentiation.

CONCLUSION

The present study identified circ19142 and circ5846 as being associated with osteoblast differentiation and BMP2 may induce osteogenic differentiation through a circ19142/circ5846-targeted miRNA-mRNA axis.