TGFβ-induced factor homeobox 2 blocks osteoblastic differentiation through targeting pSmad3/HDAC4/H4ac/Runx2 axis

Acetylation of H3K18 activated by p300 promotes osteogenesis in human adipose-derived mesenchymal stem cells

Human adipose-derived mesenchymal stem cells (hAD-MSCs) have garnered significant interest as a viable alternative source of stem cells for applications in bone tissue engineering due to their high and ease availability. At present, the limited studies on potential epigenetic regulatory mechanism in hAD-MSCs greatly hinders its clinical application in bone repair. Histone acetylation has been identified as a critical regulator of the osteogenic differentiation of mesenchymal stem cells (MSCs), with increased levels of histone acetylation sites frequently correlating with enhanced osteogenic differentiation. However, their specific roles in MSCs osteogenesis remain unclear. In this study, we observed a significant up-regulation of H3K18 acetylation (H3K18ac) during the osteogenic induction of hAD-MSCs. This modification was notably enriched in the promoter regions of genes associated with osteogenesis, thereby facilitating osteogenic differentiation. Furthermore, the treatment of histone acetyltransferases p300 inhibitor A-485 in hAD-MSCs resulted in a reduction of H3K18 acetylation levels during the osteogenic differentiation, which corresponded with a diminished osteoblast phenotype and function. These results indicated that p300-mediated acetylation of H3K18 enhances the osteogenic differentiation of hAD-MSCs. It provides a novel insight into understanding the mechanism of osteogenic differentiation of hAD-MSCs and promoting its application in bone tissue engineering.

LMK-235 suppresses osteoclastogenesis and promotes osteoblastogenesis by inhibiting HDAC4

Osteoblasts and osteoclasts play an important role in maintaining the structural integrity of bone tissue, in which osteoclasts degrade bone structure and osteoblasts restore bone tissue. The imbalance of osteoblast and osteoclast function can lead to many bone-related diseases, such as osteoporosis and inflammatory osteolysis. The drug that can both promote bone formation and inhibit bone loss will be able to treat those diseases. In this study, it was found that LMK-235, an selective HDAC4/5 inhibitor, inhibited the differentiation and maturation of osteoclasts by regulating NF-κB and p-Smad2/3 signaling pathways via inhibition of HDAC4. At the same time, we found that LMK-235 promoted osteoblast mineralization by upregulating Runx2 expression via inhibition of HDAC4. In vivo, LMK-235 was able to alleviate lipopolysaccharide (LPS)-induced calvarial osteolysis and promote the repair of bone defects. Taken together, LMK-235 suppresses osteoclast differentiation and promotes osteoblast formation by inhibiting HDAC4. This may provide a valuable treatment for bone diseases caused by abnormal osteoclast bone resorption and osteoblast bone regeneration.

Pluronic F127 hydrogel-loaded extracellular vesicles from adipose-derived mesenchymal stem cells promote tracheal cartilage regeneration via SCNN1B delivery

Extracellular vesicles (EVs) derived from adipose-derived mesenchymal stem cells (AMSC-EVs) have been highlighted as a cell-free therapy due to their regenerative capability to enhance tissue and organ regeneration. Herein, we aimed to examine the mechanism of PF127-hydrogel@AMSC-EVs in promoting tracheal cartilage defect repair. Based on bioinformatics methods, SCNN1B was identified as a key gene for the osteogenic differentiation of AMSCs induced by AMSC-EVs. EVs were isolated from rat AMSCs and then loaded onto thermo-sensitive PF-127 hydrogel to develop PF127-hydrogel@AMSC-EVs. It was established that PF127-hydrogel@AMSC-EVs could effectively deliver SCNN1B into AMSCs, where SCNN1B promoted AMSC osteogenic differentiation. The promotive effect was evidenced by enhanced ALP activity, extracellular matrix mineralization, and expression of s-glycosaminoglycan, RUNX2, OCN, collagen II, PERK, and ATF4. Furthermore, the in vivo experiments revealed that PF127-hydrogel@AMSC-SCNN1B-EVs stimulated tracheal cartilage regeneration in rats through PERK/ATF4 signaling axis activation. Therefore, PF127-hydrogel@AMSC-SCNN1B-EVs may be a novel cell-free biomaterial to facilitate tracheal cartilage regeneration and cartilage injury repair.

Superoxide dismutase 2 scavenges ROS to promote osteogenic differentiation of human periodontal ligament stem cells by regulating Smad3 in alveolar bone-defective rats

BACKGROUND

Osteogenic differentiation of human periodontal ligament stem cells (hPDLSCs) is an essential event in alveolar bone regeneration. Oxidative stress may be the main inhibiting factor of hPDLSC osteogenesis. Superoxide dismutase 2 (SOD2) is a key antioxidant enzyme, but its effect on hPDLSC osteogenic differentiation is unclear.

METHODS

Several surface markers were detected by flow cytometry, and the differentiation potential of hPDLSCs was validated by alkaline phosphatase (ALP), Alizarin Red S, and Oil Red O staining. Osteogenic indicators of hPDLSCs were detected by real-time quantitative polymerase chain reaction (RT-qPCR), Western blotting, and ALP staining. Furthermore, alveolar bone defect rat models were analyzed through micro-CT, hematoxylin and eosin, and Masson staining. The intracellular reactive oxygen species (ROS) level was evaluated by a ROS assay kit. Finally, the expression of SOD2, Smad3, and p-Smad3 in hPDLSCs was detected by RT-qPCR and Western blotting (WB).

RESULTS

SOD2 positively regulated the gene and protein expressions of ALP, BMP6, and RUNX2 in hPDLSCs (p < 0.05). Ideal bone formation and continuous cortical bone were obtained by transplanting LV-SOD2 hPDLSCs (lentivirus vector for overexpressing SOD2 in hPDLSCs) in vivo. Exogenous H2O2 downregulated osteogenic indicators (ALP, BMP6, RUNX2) in hPDLSCs (p < 0.05); this was reversed by overexpression of SOD2. WB results showed that the Smad3 and p-Smad3 signaling pathways participated in the osteogenic process of SOD2 in hPDLSCs.

CONCLUSION

SOD2 positively regulated hPDLSC osteogenic differentiation in vitro and in vivo. Mechanistically, SOD2 promotes hPDLSC osteogenic differentiation by regulating the phosphorylation of Smad3 to scavenge ROS. This work provides a theoretical basis for the treatment of alveolar bone regeneration.

Association between circHIPK3/miR-378a-3p/HDAC4 axis and osteoporotic fractures: A comprehensive investigation

BACKGROUND

Osteoporotic fractures (OFs) are a significant public health issue, which can lead to pain and impaired mobility. The underlying mechanisms of OFs remain unclear, but recent studies have suggested that the circRNA-miRNA-mRNA pathway may play a crucial role.

PURPOSE

This study aimed to investigate the potential involvement of the circHIPK3/miR-378a-3p/HDAC4 pathway in the pathogenesis of OFs.

METHODS

We collected tissue and serum samples from 10 patients with OFs and 10 healthy controls. The expression levels of circHIPK3, miR-378a-3p, and HDAC4 were measured by qPCR and WB. Additionally, we quantified the serum levels of bone metabolism-related indicators (ALP, OC, TRAP, OCIF, ODF) using ELISA.

RESULTS

Our results revealed significant upregulation of circHIPK3 and HDAC4 in both tissue and serum samples from OF patients compared with controls. Simultaneously, we detected a lower expression level of miR-378a-3p in OF tissues and serum than that in the control group. Furthermore, the serum levels of bone metabolism-related indicators ALP, TRAP, OCIF, and ODF were significantly higher in OF patients than in the control group. Interestingly, the serum level of OCIF was lower in OF patients than in the control group.

CONCLUSION

Our study provides important evidence for the involvement of the circHIPK3/miR-378a-3p/HDAC4 pathway in the pathogenesis of OFs. The upregulation of circHIPK3 and HDAC4 and downregulation of miR-378a-3p observed in OF patients suggests their potential regulatory effects on bone metabolism. Meanwhile, abnormal expression of serum bone metabolism-related indicators may contribute to the development of OFs by disrupting the balance of bone remodeling.

Strontium Regulates the Proliferation and Differentiation of Isolated Primary Bovine Chondrocytes via the TGFβ/SMAD Pathway

The present study evaluated the effects of strontium (Sr) on proliferation and differentiation of chondrocytes isolated from dairy cows, and whether Sr exerts its effects via transforming growth factor β (TGFβ) signaling. The chondrocytes were isolated from patellar cartilage from newborn Holstein bull calves (n = 3, 1 day old, 38.0 ± 2.8 kg, fasting) within 15 min after euthanasia, and treated with different concentrations of Sr (0, 0.1, 1, and 10 μg/ml, as SrCl₂·6H₂O). After pretreatment with or without activin receptor-like kinase 5 (ALK5) inhibitor (10 μM SB-505124) for 4 h, chondrocytes were incubated with Sr for another 4 h. Overall effects of Sr were evaluated relative to NaCl as the control. In contrast, the 1 μg/ml Sr-treated group served as the control to determine effects of preincubating with SB-505124. Western blot and qRT-PCR were used for measuring expression of proliferation-, differentiation-, and TGFβ1-responsive factors. Data were analyzed using one-way ANOVA in GraphPad Prism 7.0. Incubation with all doses of Sr increased TGFβ1/ALK5-induced SMAD3 phosphorylation, and at 10 μg/ml it inhibited ALK1-induced SMAD1/5/9 phosphorylation. Expression of mRNA and protein of the proliferation-responsive factors type Ⅱ Collagen α1 (COL2A1) and aggrecan (ACAN) was induced by Sr at 1 μg/ml. In contrast, Sr at 10 μg/ml inhibited the expression of differentiation-responsive factors type Ⅹ Collagen α1 (COL10A1) and secreted phosphoprotein 1 (SPP1), and at 1 μg/ml it had the same effect on alkaline phosphatase (ALPL) mRNA and protein levels. Cells were stained with PI/RNase Staining buffer to assess cell cycle activity using flow-cytometry. Incubation with Sr at 1 and 10 μg/ml induced an increase in the number of cells in the S-phase, leading to an increase in the proliferation index. Incubation with SB-505124 inhibited phosphorylation of SMAD3. Abundance of ACAN and COL2A1 mRNA and protein was lower when cells were pre-incubated with SB-505124. Overall, data indicated that Sr promotes proliferation and inhibits differentiation of primary chondrocytes by directing TGFβ1 signaling towards SMAD3 phosphorylation rather than SMAD1/5/9 phosphorylation. Whether these effects occur in vivo remains to be determined and could impact future application of Sr as an experimental tool in livestock.

MACF1 promotes osteoblast differentiation by sequestering repressors in cytoplasm

Osteoblast differentiation leading to bone formation requires a coordinated transcriptional program. Osteoblastic cells with low level of microtubule actin crosslinking factor 1 (MACF1) show reduced osteoblast differentiation ability, however, the comprehensive mechanism of MACF1's action remains unexplored. In the current study, we found that MACF1 knockdown suppressed osteoblast differentiation by altering the transcriptome dynamics. We further identified two MACF1-interacted proteins, cyclin-dependent kinase 12 (CDK12) and MYST/Esa1-associated factor 6 (MEAF6), and two MACF1-interacted transcription factors (TFs), transcription factor 12 (TCF12) and E2F transcription factor 6 (E2F6), which repress osteoblast differentiation by altering the expression of osteogenic TFs and genes. Moreover, we found that MACF1 regulated cytoplasmic-nuclear localization of itself, TCF12 and E2F6 in a concentration-dependent manner. MACF1 oppositely regulates the expression of TCF12 and transcription factor 7 (TCF7), two TFs that drive osteoblast differentiation to opposite directions. This study reveals that MACF1, a cytoskeletal protein, acts as a sponge for repressors of osteoblast differentiation to promote osteoblast differentiation and contributes to a novel mechanistic insight of osteoblast differentiation and transcription dynamics.

Circular RNA circANAPC2 mediates the impairment of endochondral ossification by miR-874-3p/SMAD3 signalling pathway in idiopathic short stature

Idiopathic short stature (ISS) is a main reason for low height among children. Its exact aetiology remains unclear. Recent findings have suggested that the aberrant expression of circRNAs in peripheral blood samples is associated with many diseases. However, to date, the role of aberrant circRNA expression in mediating ISS pathogenesis remains largely unknown. The up-regulated circANAPC2 was identified by circRNA microarray analysis and RT-qPCR. Overexpression of circANAPC2 inhibited the proliferation of human chondrocytes, and cell cycle was arrested in G1 phase. The expressions of collagen type X, RUNX2, OCN and OPN were significantly down-regulated following circANAPC2 overexpression. Moreover, Von Kossa staining intensity and alkaline phosphatase activity were also decreased. Luciferase reporter assay results showed that circANAPC2 could be targeted by miR-874-3p. CircANAPC2 overexpression in human chondrocytes inhibits the expression of miR-874-3p. The co-localization of circANAPC2 and miR-874-3p was confirmed in both human chondrocytes and murine femoral growth plates via in situ hybridization. The rescue experiment demonstrated that the high expression of miR-874-3p overexpression antagonized the suppression of endochondral ossification, hypertrophy and chondrocyte growth caused by circANAPC2 overexpression. A high-throughput screening of mRNA expression and RT-qPCR verified SMAD3 demonstrated the highest different expressions following overcircANAPC2. Luciferase reporter assay results indicated that miR-874-3p could be targeted by Smad3, thus down-regulating the expression of Smad3. Subsequent rescue experiments of SMAD3 further confirmed that circANAPC2 suppresses endochondral ossification, hypertrophy and chondrocyte growth through miR-874-3p/Smad3 axis. The present study provides evidence that circANAPC2 can serve as a promising target for ISS treatment.

MicroRNA-197-3p Inhibits the Osteogenic Differentiation in Osteoporosis by Down-Regulating KLF 10

Background

Studies have shown that microRNA (miRNA) regulates gene expression of osteoporosis (OS). It is known that miR-197-3p is abnormally expressed in osteoporosis. This study is to investigate the mechanism of miR-197-3p in regulating osteoblast differentiation.

Methods

Rats were ovariectomized to establish an animal model of postmenopausal osteoporosis. The expression of miR-197-3p and KLF10 was detected in ovariectomized rat models. Primary osteoblasts and MC3T-E1 cells were divided into the control group, miR-197-3p inhibitor group, NC inhibitor group and miR-197-3p inhibitor + si-KLF10 group. The expression of miR-197-3p and Kruppel-like factor 10 (KLF10) was detected by qRT-PCR and Western blot. The relationship between miR-197-3p and KLF10 was analyzed by bioinformatics and luciferase reporter assay. Cell viability was evaluated by MTT assay. The ALP activity measurement and mineralization analysis were performed.

Results

The expression of miR-197-3p was significantly raised in ovariectomized osteoporosis rats. During the differentiation of osteoblasts, the expression of miR-197-3p was significantly decreased, while the expression of KLF10 was significantly raised in primary osteoblasts and MC3E3T1 cells. The expression of RUNX2, ALP, OCN and OSX in miR-197-3p inhibitor group and MC3T3-E1 group was significantly raised, and the cell survival rate and mineralized nodule were raised as well. KLF10 may be the downstream target gene of miR-197-3p. After co-transfection of miR-197-3p inhibitor and si-klf10, ALP, Runx2, OCN and OSX mRNA, cell survival rate and mineralized nodule were significantly decreased in primary osteoblasts and MC3T3-E1 cells.

Conclusion

MiR-197-3p Inhibition promoted osteoblast differentiation and reduced OS by up-regulating KLF10.

Symphytum officinale augments osteogenesis in human bone marrow-derived mesenchymal stem cells in vitro as they differentiate into osteoblasts

ETHNOPHARMACOLOGICAL RELEVANCE

Mesenchymal stem cells (MSCs) are multipotent stem cells possessing regenerative potential. Symphytum officinale (SO) is a medicinal plant and in homoeopathic literature, believed to accelerate bone healing.

AIM OF THE STUDY

This study aimed to determine if homoeopathic doses of SO could augment osteogenesis in MSCs as they differentiate into osteoblasts in vitro.

MATERIALS AND METHODS

Bone marrow samples were obtained from patients who underwent bone grafting procedures (n = 15). MSCs were isolated, expanded and characterized by flow cytometry (CD90, CD105). Cytotoxicity of SO was evaluated by MTT assay. Osteogenic differentiation was induced in MSCs with β-glycerophosphate, ascorbic acid and dexamethasone over 2 weeks. Different homoeopathic doses of SO (MT, 3C, 6C, 12C and 30C) were added to the basic differentiation medium (BDM) and efficiency of MSCs differentiating into osteoblasts were measured by evaluating expression of Osteocalcin using flow cytometry, and alkaline phosphatase activity using ELISA. Gene expression analyses for osteoblast markers (Runx-2, Osteopontin and Osteocalcin) were evaluated in differentiated osteoblasts using qPCR.

RESULTS

Flow cytometry (CD90, CD105) detected MSCs isolated from bone marrow (93-98%). MTT assay showed that the selected doses of SO did not induce any cytotoxicity in MSCs (24 hours). The efficiency of osteogenic differentiation (2 weeks) for different doses of Symphytum officinale was determined by flow cytometry (n = 10) for osteoblast marker, Osteocalcin, and most doses of Symphytum officinale enhanced osteogenesis. Interestingly, gene expression analysis for Runx-2 (n = 10), Osteopontin (n = 10), Osteocalcin (n = 10) and alkaline phosphatase activity (n = 8) also showed increased osteogenesis with the addition of Symphytum officinale to BDM, specially mother tincture.

CONCLUSIONS

Our findings suggest that homoeopathic dose (specially mother tincture) of Symphytum officinale has the potential to enhance osteogenesis.