Exosome Secreted from Mesenchymal Stem Cells (MSCs) of Osteoporosis Inhibits the Osteogenic Differentiation

This study analyze the effect of exosome secreted from MSCs on osteogenic differentiation in OP rats. The exosome was obtained from cultivated MSCs isolated from OP rats with ultracentrifugation. OP rats were treated with exosome secreted from MSCs of normal rats, exosome secreted from MSCs of OP rats and exosome secreted from MSCs of OP rats with overexpression of ALP followed by analysis of the osteogenic differentiation, the expression of ALP, Bglap and Runx2 and the targeted correlation between miR-351 and ALP. The MSCs in normal rats and OP rats were able to adhere to wall. There was elongated. The level of miR-351 in OP rats was significantly higher than normal rats. The Runx2 expression and ALP activity in rats treated with exosome secreted from MSCs of OP rats was declined significantly compared to that from MSCs of normal rats. ALP was a target gene of miR-351. In conclusion, the exosome secreted from MSCs of OP rats inhibits the osteogenic differentiation possibly through restraining miR-351-ALP.

miRNA-126 Inhibits Osteogenic Differentiation of Rat Bone Marrow Mesenchymal Stem Cells (BMSCs)

This study was to determine whether microRNA (miRNA)-126 regulates osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs). Rat BMSCs were extracted and stimulated for osteogenic differentiation. Functional experiments were conducted to assess miR-126’s impact on BMSCs differentiation. Western blot and RT-qPCR determined miR-126 expression. ALP activity detection and alizarin red staining detection were also performed. After osteogenic differentiation of BMSCs, miR-126 expression was gradually decreased over time. Overexpression of miR-26 decreased ALP activity, Notch signaling activity as well as declined Runx2 expression and calcium Salt nodules after treatment. Importantly, we found that Smad4 serves as a target of miR-126 while upregulation of the miRNA was accompanied with the decreased Smad4 protein expression without affecting the Smad4 mRNA level. In conclusion, miR-126 restrains osteogenic differentiation through inhibition of SMAD4 signaling, providing a novel insight into the mechanism.

Calycosin-7-O-β-Glucoside Isolated from Astragalus membranaceus Promotes Osteogenesis and Mineralization in Human Mesenchymal Stem Cells

Stem cells have received attention in various diseases, such as inflammatory, cancer, and bone diseases. Mesenchymal stem cells (MSCs) are multipotent stem cells that are critical for forming and repairing bone tissues. Herein, we isolated calycosin-7-O-β-glucoside (Caly) from the roots of Astragalus membranaceus, which is one of the most famous medicinal herbs, and investigated the osteogenic activities of Caly in MSCs. Caly did not affect cytotoxicity against MSCs, whereas Caly enhanced cell migration during the osteogenesis of MSCs. Caly increased the expression and enzymatic activities of ALP and the formation of mineralized nodules during the osteogenesis of MSCs. The osteogenesis and bone-forming activities of Caly are mediated by bone morphogenetic protein 2 (BMP2), phospho-Smad1/5/8, Wnt3a, phospho-GSK3β, and phospho-AKT, inducing the expression of runt-related transcription factor 2 (RUNX2). In addition, Caly-mediated osteogenesis and RUNX2 expression were attenuated by noggin and wortmannin. Moreover, the effects were validated in pre-osteoblasts committed to the osteoblast lineages from MSCs. Overall, our results provide novel evidence that Caly stimulates osteoblast lineage commitment of MSCs by triggering RUNX2 expression, suggesting Caly as a potential anabolic drug to prevent bone diseases.

Effect of Sirtuin1 (Sirt1) on Bone Marrow Mesenchymal Stem Cells (BMSCs) Osteogenesis/Adipogenesis via β-Catenin/The Transcription Factor T Cell Factor 1 (TCF1)/Runt-Related Transcription Factor 2 (RUNX2)

Bone marrow mesenchymal stem cells (BMSCs) have self-renewal potential. Sirt1 regulates cell differentiation and apoptosis. However, Sirt1’s effect on BMSCs osteogenic/adipogenic differentiation has not been fully elucidated. SD rats were randomly divided into Osteoporosis (OP) group and sham operation group. OP rat BMSCs were isolated and assigned into control group, NC group and Sirt1 siRNA group followed by analysis of Sirt1 level by Real-time PCR, cell proliferation by MTT assay, expression of OC, OPN and FABP4 level by real time PCR, and β-Catenin/TCF1/Runx2 protein expression by Western blot. In OP group, Sirt1 expression was significantly increased and BMSCs proliferation was decreased along with reduced OC and OPN mRNA expression, increased FABP4 expression and reduced β-Catenin/TCF1/Runx2 expression compared with sham operation group (P < 0.05). In Sirt1 siRNA group, Sirt1 expression was significantly reduced, BMSCs proliferation was increased, OC and OPN mRNA expression was increased, FABP4 expression was decreased, and β-Catenin/TCF1/Runx2 expression was increased compared to OP group (P < 0.05). Sirt1 is increased in osteoporosis. Down-regulating Sirt1 in osteoporotic BMSCs can regulate β-Catenin/TCF1/Runx2 signaling and promote BMSCs osteogenic differentiation and inhibit adipogenic differentiation.

Activation of transcriptional factor ZBTB16 expression during osteogenic differentiation of mesenchymal stem cells

Aim. Calcified aortic valve stenosis is the third leading cause of cardiovascular disease. The mechanisms underlying this process remain unclear, however, it is known that they are largely similar to the formation of bone tissue during embryonic development, as well as in the postnatal period during regeneration. There is evidence for the involvement of Zinc Finger and BTB Domain Containing 16 (ZBTB16) in skeletal development. At the same time, a number of studies carried out on different types of cell cultures indicate a contradictory and ambiguous effect of ZBTB16 on RUNX2 expression. Thus, the aim of this study was to investigate the dynamic variability of ZBTB16 expression, as well as its role in aortic valve calcification.Methods. The study used different types of mesenchymal cells cultures - aortic valve interstitial cells, umbilical cord mesenchymal stem cells, ligament stem cells and dental pulp stem cells. Changes in ZBTB16 and RUNX2 expression levels under the influence of osteogenic stimuli, as well as during exogenous activation of ZBTB16, were analyzed using real-time PCR. Expression levels of some osteogenic markers - BMP2,4, COL1A1, IBSP, DLX2, PDK4 - were analyzed in the interstitial cells of the aortic valve.Results. The results of the study indicate that a significant increase in the expression of ZBTB16 is observed during the induction of osteogenic differentiation of various cell cultures - interstitial cells of the aortic valve, mesenchymal stem cells of the umbilical cord, stem cells of the ligaments and dental pulp. Apparently, the processes of osteogenic differentiation of aortic valve interstitial cells, in the presence of dexamethasone in cultivation medium, are provided through RUNX2-dependent signaling for the further activation of osteogenic markers.Conclusion. The study of modulation of cellular signals by ZBTB16, when activating or suppressing the work of a transcriptional factor, in the future may bring us closer to the ability to enhance the regenerative abilities of bone tissue cells or, conversely, prevent calcification of the aortic valve tissues.

HDAC6 inactivates Runx2 promoter to block osteogenesis of bone marrow stromal cells in age-related bone loss of mice

Background Senile osteoporosis can cause bone fragility and increased risk for fractures and has been one of the most prevalent and severe diseases affecting the elderly population worldwidely. The underlying mechanisms are currently intensive areas of investigation. In age-related bone loss, decreased bone formation overweighs increased bone resorption. The molecular mechanisms underlying defective bone formation in age-related bone loss are not completely understood. In particular, the specific role of histone acetylation in age-related bone loss has not been examined thoroughly. Methods We employed 6- and 18-month-old mice to investigate the mechanisms of defective bone formation in age-related bone loss. Bone marrow stromal cells (BMSCs) were induced to undergo in vitro osteogenic differentiation. Chromatin immunoprecipitation (ChIP) was used to investigate the binding of histone deacetylases (HDACs) on Runx2 promoter in BMSCs. Luciferase reporter and transient transfection assay were employed to study Runx2 gene expression modulation by HDAC and androgen receptor (AR). siRNA and HDAC6 inhibitor, Tubastatin A, were used to inhibit HDAC6 in vitro. And systemic administration of Tubastatin A was used to block HDAC6 in vivo. Results Age-related trabecular bone loss was observed in 18-month-old mice compared with 6-month-old mice. In vitro osteogenic differentiation potential of BMSCs from 18-month-old mice was weaker than 6-month-old mice, in which there was Runx2 expression inactivation in BMSCs of 18-month-old mice compared with 6-month-old mice, which was attributable to HDAC6-mediated histone hypoacetylation in Runx2 promoter. There was competitive binding of HDAC6 and AR on Runx2 promoter to modulate Runx2 expression in BMSCs. More importantly, through siRNA- or specific inhibitor-mediated HDAC6 inhibition, we could activate Runx2 expression, rescue in vitro osteogenesis potential of BMSCs, and alleviate in vivo age-related bone loss of mice. Conclusion HDAC6 accumulation and histone hypoacetylation on Runx2 promoter contributed to the attenuation of in vitro osteogenic differentiation potential of BMSCs from aged mice. Through HDAC6 inhibition, we could activate Runx2 expression and osteogenic differentiation potential of BMSCs from aged mice and alleviate the age-related bone loss of aged mice. Our study will benefit not only for understanding the age-related bone loss, but also for finding new therapies to treat senile osteoporosis.

Biological Characteristics and Odontogenic Differentiation Effects of Calcium Silicate-Based Pulp Capping Materials

We compared calcium silicate-based pulp capping materials to conventional calcium hydroxide in terms of their biological properties and potential effects on odontogenic differentiation in human dental pulp stem cells (hDPSCs). We cultured hDPSCs on disks (7-mm diameter, 4-mm high) of ProRoot MTA (Dentsply Tulsa Dental Specialties), Biodentine (Septodont), TheraCal LC (Bisco), or Dycal (Dentsply Tulsa Dental Specialties). Cell viability was assessed with cell counting (CCK) and scanning electron microscopy (SEM). Odontogenic activity was assessed by measuring alkaline phosphatase (ALP) activity and gene expression (quantitative real-time PCR). CCK assays showed that Dycal reduced cell viability compared to the other materials (p < 0.05). SEM showed low and absent cell attachment on TheraCal LC and Dycal disks, respectively. hDPSCs exposed to TheraCal LC and Dycal showed higher ALP activity on day 6 than the control group (p < 0.05). The day-9 Runx2 expression was higher in the ProRoot MTA and TheraCal LC groups than in the control group (p < 0.05). On day 14, the ProRoot MTA group showed the highest dentin sialophosphoprotein levels (not significant; p > 0.05). In conclusion, various pulp capping materials, except Dycal, exhibited biological properties favorable to hDPSC viability. ProRoot MTA and TheraCal LC promoted higher Runx2 expression than Biodentine. Future studies should explore the odontogenic potential of pulp capping materials.