Development and Comparative Study of a Mouse Model of Airway Inflammation and Remodeling Induced by Exosomes Derived from Bone Marrow Mesenchymal Stem Cells.

We developed a model of inflammation and airway remodeling in C57 mice provoked by exosomes derived from bone marrow mesenchymal stem cells infected by respiratory syncytial virus (RSV). The mean size of control and infected exosomes in vitro were 167.9 and 118.5 nm, respectively. After induction of modeled pathology, the severity of airway inflammation and its remodeling were analyzed by histopathological methods. In addition, the blood levels of inflammatory factors IL-10, IL-17, transforming growth factor-ß (TGF-ß), and TNFα were assayed; in the lung tissues, the expression levels of MMP-2, MMP-9, α-smooth muscle actin (α-SMA), and TGF-ß were measured. In the developed model, the effects of RSV-induced and non-induced exosomes were compared with those of inactivated and non-inactivated RSV. Intranasal administration of RSV-induced exosomes decreased the levels of serum inflammatory factors IL-10 and IL-17 and increased the expression of serum proinflammatory cytokine TNFα. Increased levels of MMP-2, MMP-9, and α-SMA, enhanced expression of TGF-ß in the lung tissue, and pathological staining of the lung tissues indicated infiltration with inflammatory cells and luminal constriction. Thus, RSV-induced exosomes can provoke airway inflammation and remodeling in mice similar to RSV, while non-induced exosomes cannot produce such alterations.

Hypoxic preconditioning-engineered bone marrow mesenchymal stem cell-derived exosomes promote muscle satellite cell activation and skeletal muscle regeneration via the miR-210-3p/KLF7 mechanism.

Sarcopenia is a gradual and widespread decline in muscle mass and function in skeletal muscle, leading to significant implications for individuals and society. Currently, there is a lack of effective treatment methods for sarcopenia. Muscle satellite cells(SCs) play a crucial role in the occurrence and development of sarcopenia, and their proliferation and differentiation abilities are closely related to the progression of disease. This study evaluated the effects of exosomes derived from hypoxic preconditioning bone marrow mesenchymal stem cells (BMSCs) on the proliferation of SCs and skeletal muscle regeneration. We found that the capacity for the proliferation and differentiation of SCs in elderly rats was notably diminished, leading us to create a sarcopenia model in elderly rats. By separating and extracting exosomes from BMSCs treated with normoxic (N-Exos) and hypoxic (H-Exos) conditions, in vivo and in vitro studies showed that both N-Exos and H-Exos can regulate the proliferation and differentiation of SCs in elderly rats, and promote skeletal muscle regeneration and functional recovery. The beneficial effects of H-Exos were also more significant than those of the N-Exos group. In vitro studies demonstrated that H-Exos could influence the expression of the KLF7 gene and protein in SCs by delivering miR-210-3P. This, in turn, impacted the phosphorylation of the PI3K/AKT signaling pathway and contributed to the function of SCs. H-Exos stimulated SCs and promoted skeletal muscle regeneration during sarcopenia by delivering miR-210-3P to target the KLF7/PI3K/AKT signaling pathway. This may serve as a possible treatment option for sarcopenia.

CB1 Promotes Osteogenic Differentiation Potential of Periodontal Ligament Stem Cells by Enhancing Mitochondrial Transfer of Bone Marrow Mesenchymal Stem Cells.

OBJECTIVE: To reveal the role and mechanism of cannabinoid receptor 1 (CB1) and mitochondria in promoting osteogenic differentiation of periodontal ligament stem cells (PDLSCs) in the inflammatory microenvironment. METHODS: Bidirectional mitochondrial transfer was performed in bone mesenchymal stem cells (BMSCs) and PDLSCs. Laser confocal microscopy and quantitative flow cytometry were used to observe the mitochondrial transfer and quantitative mitochondrial transfer efficiency. Realtime reverse transcription polymerase chain reaction (RT-PCR) was employed to detect gene expression. Alkaline phosphatase (ALP) activity, alizarin red staining (ARS) and quantitative calcium ion analysis were used to evaluate the degree of osteogenic differentiation of PDLSCs. RESULTS: Bidirectional mitochondrial transfer was observed between BMSCs and PDLSCs. The indirect co-culture system could simulate intercellular mitochondrial transfer. Compared with the conditioned medium (CM) for BMSCs, that for HA-CB1 BMSCs could significantly enhance the mineralisation ability of PDLSCs. The mineralisation ability of PDLSCs could not be enhanced after removing the mitochondria in CM for HA-CB1 BMSCs. The expression level of HO-1, PGC-1α, NRF-1, ND1 and HK2 was significantly increased in HA-CB1 BMSCs. CONCLUSION: CM for HA-CB1 BMSCs could significantly enhance the damaged osteogenic differentiation ability of PDLSCs in the inflammatory microenvironment, and the mitochondria of CM played an important role. CB1 was related to the activation of the HO-1/PGC-1α/NRF-1 mitochondrial biogenesis pathway, and significantly increased the mitochondrial content in BMSCs.

Evaluating potential of H'mong chicken bone marrow-derived mesenchymal stem cells at different ages for primordial germ cells' feeder layer.

Primordial germ cells (PGCs) have potential applications in genetic conservation, vaccination, tissue repair therapies, and genetic research. Chicken bone marrow-derived mesenchymal stem cells (cbMSCs) is a good candidate for co-culture with PGCs. However, there is no consensus on the optimal age of donors. In this study, we aimed to compare specific parameters of H'Mong cbMSCs obtained from day 14th and 19th embryos, and day 3rd newborns. Isolated cbMSCs showed characteristics of MSCs. Cells had fibroblast-like morphology, plastic-adherent, expressed specific markers of MSCs and multilineage differentiation potential. The growth rate of cells from day 19th embryos was higher than from other ages. Moreover, cells expressed markers of pluripotency such as Nanog, PouV, Sox2, CVH, DAZL, and KIT, known for their role in maintaining stem cell self-renewal and pluripotency. As feeder cells, cbMSCs from three different ages promoted proliferation of H'Mong PGCs during co-culture. These results suggested that cbMSCs from different ages can be used for co-culture H'Mong PGCs which were further used for genetic preservation of H'Mong chicken or gene editing research.

Comparative investigation of exosome extraction from rat bone marrow mesenchymal stem cells using three different methodologies.

Exosomes have been identified as crucial mediators in numerous physiological and pathological processes, emerging as a focal point of scientific inquiry. This study aims to compare three methods for isolating exosomes from rat bone marrow mesenchymal stem cells: ultracentrifugation (UC), ultrafast separation system (EXODUS), and commercial precipitation kit (EXO-kit). First, the investigation compared exosomal morphology, particle size distribution, and expression of marker proteins. Subsequently, the RNA content, protein concentration, and purity of exosomes were evaluated. Finally, the impact of these exosomes on cellular metabolic viability and migration capacity was assessed. Results indicated that exosomes exhibited spherical or elliptical membrane structures, and most of the exosomes extracted by the three methods were in the range of 30to 200 nm. UC-extracted exosomes demonstrated the least impurities and clearest background, followed by EXODUS-extracted exosomes, and lastly EXO-kit-extracted exosomes. The EXO-kit-extracted exosomes yielded the highest RNA and protein content, whereas those isolated through UC exhibited superior purity. Furthermore, exosomes extracted from EXODUS and EXO-kit methods effectively enhanced the metabolic viability and migratory ability of osteoblast precursor cells compared to UC-extracted exosomes. In conclusion, each of the three methodologies presents advantages and limitations. Therefore, the selection of an appropriate exosome extraction technique should be based on specific experimental objectives and requirements.

Bone marrow mesenchymal stem cells with PTBP1 knockdown protect against cerebral ischemia-reperfusion injury by inhibiting ferroptosis via the JNK/P38 pathway in rats.

Over the years, the neuroprotective potential of bone marrow mesenchymal stem cells (BMSCs) in acute ischemic stroke has attracted significant attention. However, BMSCs face challenges like short metabolic cycles and low survival rates post-transplant. Polypyrimidine tract-binding protein 1 (PTBP1) is an immunomodulatory RNA-binding protein that regulates the cell cycle and increases cell viability. This study investigated the protective effects and underlying mechanism of PTBP1 knockdown in BMSCs (PTBP1KD-BMSCs) following ischemia-reperfusion injury (IRI) in neurons. BMSCs were isolated from Sprague-Dawley rat femurs and characterized through flow cytometry and differentiation induction. PTBP1 knockdown inhibited BMSCs proliferation. Co-culture with PTBP1KD-BMSCs decreased reactive oxygen species (ROS) and malondialdehyde (MDA) levels, while increasing glutathione (GSH) production in oxygen and glucose deprivation/reperfusion-induced PC12 cells. Transcriptome sequencing analysis of PC12 cells suggested that the protective effect of PTBP1KD-BMSCs against injury may involve ferroptosis. Furthermore, western blotting showed upregulation of glutathione synthetase (GSS), glutathione peroxidase 4 (GPX4), and solute carrier family 7 member 11 (SLC7A11) in PTBP1KD-BMSCs, known negative regulators of ferroptosis. Moreover, PTBP1KD-BMSCs inhibited p38MAPK and JNK activation. In addition, PTBP1KD-BMSCs transplantation into middle cerebral artery occlusion/reperfusion (MCAO/R) rats reduced cerebral infarction volume and improved neurological function. Immunofluorescence analysis confirmed the upregulation of GSS expression in neurons of the ischemic cortex, while immunohistochemistry indicated a downregulation of p-P38. These result suggest that PTBP1KD-BMSCs can alleviate neuronal IRI by reducing oxidative stress, inhibiting ferroptosis, and modulating the MAPK pathway, providing a theoretical basis for potential treatment strategies for cerebral IRI.

LINC01133 promotes the osteogenic differentiation of bone marrow mesenchymal stem cells by upregulating CTNNB1 by acting as a sponge for miR-214-3p.

BACKGROUND: Osteoporosis results from decreased bone mass and disturbed bone structure. Human bone marrow mesenchymal stem cells (hBMSCs) demonstrate robust osteogenic differentiation, a critical process for bone formation. This research was designed to examine the functions of LINC01133 in osteogenic differentiation. METHODS: Differentially expressed lncRNAs affecting osteogenic differentiation in hBMSCs were identified from the GEO database. A total of 74 osteoporosis patients and 70 controls were enrolled. hBMSCs were stimulated to undergo osteogenic differentiation using an osteogenic differentiation medium (OM). RT-qPCR was performed to evaluate LINC01133 levels and osteogenesis-related genes such as osteocalcin, osteopontin, and RUNX2. An alkaline phosphates (ALP) activity assay was conducted to assess osteogenic differentiation. Cell apoptosis was detected using flow cytometry. Dual luciferase reporter assay and RIP assay were employed to investigate the association between miR-214-3p and LINC01133 or CTNNB1. Loss or gain of function assays were conducted to elucidate the impact of LINC01133 and miR-214-3p on osteogenic differentiation of hBMSCs. RESULTS: LINC01133 and CTNNB1 expression decreased in osteoporotic patients but increased in OM-cultured hBMSCs, whereas miR-214-3p showed an opposite trend. Depletion of LINC01133 suppressed the expression of genes associated with bone formation and ALP activity triggered by OM in hBMSCs, leading to increased cell apoptosis. Nevertheless, this suppression was partially counteracted by the reduced miR-214-3p levels. Mechanistically, LINC01133 and CTNNB1 were identified as direct targets of miR-214-3p. CONCLUSIONS: Our study highlights the role of LINC01133 in positively regulating CTNNB1 expression by inhibiting miR-214-3p, thereby promoting osteogenic differentiation of BMSCs. These findings may provide valuable insights into bone regeneration in osteoporosis.

Self-assembled peptide hydrogel loaded with functional peptide Dentonin accelerates vascularized bone tissue regeneration in critical-size bone defects.

Regeneration of oral craniofacial bone defects is a complex process, and reconstruction of large bone defects without the use of exogenous cells or bioactive substances remains a major challenge. Hydrogels are highly hydrophilic polymer networks with the potential to promote bone tissue regeneration. In this study, functional peptide Dentonin was loaded onto self-assembled peptide hydrogels (RAD) to constitute functionally self-assembling peptide RAD/Dentonin hydrogel scaffolds with a view that RAD/Dentonin hydrogel could facilitate vascularized bone regeneration in critical-size calvarial defects. The functionalized peptide RAD/Dentonin forms highly ordered ß-sheet supramolecular structures via non-covalent interactions like hydrogen bonding, ultimately assembling into nano-fiber network. RAD/Dentonin hydrogels exhibited desirable porosity and swelling properties, and appropriate biodegradability. RAD/Dentonin hydrogel supported the adhesion, proliferation and three-dimensional migration of bone marrow mesenchymal stem cells (BMSCs) and has the potential to induce differentiation of BMSCs towards osteogenesis through activation of the Wnt/ß-catenin pathway. Moreover, RAD/Dentonin hydrogel modulated paracrine secretion of BMSCs and increased the migration, tube formation and angiogenic gene expression of human umbilical vein endothelial cells (HUVECs), which boosted the angiogenic capacity of HUVECs. In vivo, RAD/Dentonin hydrogel significantly strengthened vascularized bone formation in rat calvarial defect. Taken together, these results indicated that the functionalized self-assembling peptide RAD/Dentonin hydrogel effectively enhance osteogenic differentiation of BMSCs, indirectly induce angiogenic effects in HUVECs, and facilitate vascularized bone regeneration in vivo. Thus, it is a promising bioactive material for oral and maxillofacial regeneration.

Bone marrow mesenchymal stem cells in treatment of peripheral nerve injury.

Peripheral nerve injury (PNI) is a common neurological disorder and complete functional recovery is difficult to achieve. In recent years, bone marrow mesenchymal stem cells (BMSCs) have emerged as ideal seed cells for PNI treatment due to their strong differentiation potential and autologous transplantation ability. This review aims to summarize the molecular mechanisms by which BMSCs mediate nerve repair in PNI. The key mechanisms discussed include the differentiation of BMSCs into multiple types of nerve cells to promote repair of nerve injury. BMSCs also create a microenvironment suitable for neuronal survival and regeneration through the secretion of neurotrophic factors, extracellular matrix molecules, and adhesion molecules. Additionally, BMSCs release pro-angiogenic factors to promote the formation of new blood vessels. They modulate cytokine expression and regulate macrophage polarization, leading to immunomodulation. Furthermore, BMSCs synthesize and release proteins related to myelin sheath formation and axonal regeneration, thereby promoting neuronal repair and regeneration. Moreover, this review explores methods of applying BMSCs in PNI treatment, including direct cell transplantation into the injured neural tissue, implantation of BMSCs into nerve conduits providing support, and the application of genetically modified BMSCs, among others. These findings confirm the potential of BMSCs in treating PNI. However, with the development of this field, it is crucial to address issues related to BMSC therapy, including establishing standards for extracting, identifying, and cultivating BMSCs, as well as selecting application methods for BMSCs in PNI such as direct transplantation, tissue engineering, and genetic engineering. Addressing these issues will help translate current preclinical research results into clinical practice, providing new and effective treatment strategies for patients with PNI.

Bmi-1 Epigenetically Orchestrates Osteogenic and Adipogenic Differentiation of Bone Marrow Mesenchymal Stem Cells to Delay Bone Aging.

With the increase in the aging population, senile osteoporosis (SOP) has become a major global public health concern. Here, it is found that Prx1 and Bmi-1 co-localized in trabecular bone, bone marrow cavity, endosteum, and periosteum. Prx1-driven Bmi-1 knockout in bone-marrow mesenchymal stem cells (BMSCs) reduced bone mass and increased bone marrow adiposity by inhibiting osteoblastic bone formation, promoting osteoclastic bone resorption, downregulating the proliferation and osteogenic differentiation of BMSCs, and upregulating the adipogenic differentiation of BMSCs. However, Prx1-driven Bmi-1 overexpression showed a contrasting phenotype to Prx1-driven Bmi-1 knockout in BMSCs. Regarding mechanism, Bmi-1-RING1B bound to DNMT3A and promoted its ubiquitination and inhibited DNA methylation of Runx2 at the region from 45047012 to 45047313 bp, thus promoting the osteogenic differentiation of BMSCs. Moreover, Bmi-1-EZH2 repressed the transcription of Cebpa by promoting H3K27 trimethylation at the promoter region -1605 to -1596 bp, thus inhibiting the adipogenic differentiation of BMSCs. It is also found that Prx1-driven Bmi-1 overexpression rescued the SOP induced by Prx1-driven Bmi-1 knockout in BMSCs. Thus, Bmi-1 functioned as a hub protein in the epigenetic regulation of BMSCs differentiation to delay bone aging. The Prx1-driven Bmi-1 overexpression in BMSCs can be used as an approach for the translational therapy of SOP.

Bone marrow-derived mesenchymal stem cell-derived exosome-loaded miR-129-5p targets high-mobility group box 1 attenuates neurological-impairment after diabetic cerebral hemorrhage.

BACKGROUND: Diabetic intracerebral hemorrhage (ICH) is a serious complication of diabetes. The role and mechanism of bone marrow mesenchymal stem cell (BMSC)-derived exosomes (BMSC-exo) in neuroinflammation post-ICH in patients with diabetes are unknown. In this study, we investigated the regulation of BMSC-exo on hyperglycemia-induced neuroinflammation. AIM: To study the mechanism of BMSC-exo on nerve function damage after diabetes complicated with cerebral hemorrhage. METHODS: BMSC-exo were isolated from mouse BMSC media. This was followed by transfection with microRNA-129-5p (miR-129-5p). BMSC-exo or miR-129-5p-overexpressing BMSC-exo were intravitreally injected into a diabetes mouse model with ICH for in vivo analyses and were cocultured with high glucose-affected BV2 cells for in vitro analyses. The dual luciferase test and RNA immunoprecipitation test verified the targeted binding relationship between miR-129-5p and high-mobility group box 1 (HMGB1). Quantitative polymerase chain reaction, western blotting, and enzyme-linked immunosorbent assay were conducted to assess the levels of some inflammation factors, such as HMGB1, interleukin 6, interleukin 1ß, toll-like receptor 4, and tumor necrosis factor α. Brain water content, neural function deficit score, and Evans blue were used to measure the neural function of mice. RESULTS: Our findings indicated that BMSC-exo can promote neuroinflammation and functional recovery. MicroRNA chip analysis of BMSC-exo identified miR-129-5p as the specific microRNA with a protective role in neuroinflammation. Overexpression of miR-129-5p in BMSC-exo reduced the inflammatory response and neurological impairment in comorbid diabetes and ICH cases. Furthermore, we found that miR-129-5p had a targeted binding relationship with HMGB1 mRNA. CONCLUSION: We demonstrated that BMSC-exo can reduce the inflammatory response after ICH with diabetes, thereby improving the neurological function of the brain.

Enhanced osteogenic differentiation in 3D hydrogel scaffold via macrophage mitochondrial transfer.

To assess the efficacy of a novel 3D biomimetic hydrogel scaffold with immunomodulatory properties in promoting fracture healing. Immunomodulatory scaffolds were used in cell experiments, osteotomy mice treatment, and single-cell transcriptomic sequencing. In vitro, fluorescence tracing examined macrophage mitochondrial transfer and osteogenic differentiation of bone marrow-derived mesenchymal stem cells (BMSCs). Scaffold efficacy was assessed through alkaline phosphatase (ALP), Alizarin Red S (ARS) staining, and in vivo experiments. The scaffold demonstrated excellent biocompatibility and antioxidant-immune regulation. Single-cell sequencing revealed a shift in macrophage distribution towards the M2 phenotype. In vitro experiments showed that macrophage mitochondria promoted BMSCs' osteogenic differentiation. In vivo experiments confirmed accelerated fracture healing. The GAD/Ag-pIO scaffold enhances osteogenic differentiation and fracture healing through immunomodulation and promotion of macrophage mitochondrial transfer.

Dimethyl Fumarate Preconditioning can Reinforce the Therapeutic Potential of Bone Marrow Mesenchymal Stem Cells through Trophic Factor Profile Enhancement.

Background: Numerous studies have confirmed the therapeutic efficacy of bone marrow-derived mesenchymal stem cells (BM-MSCs) in addressing neurologic disorders. To date, several preconditioning strategies have been designed to improve the therapeutic potential of these stem cells. This study was designed to evaluate the preconditioning effect of dimethyl fumarate (DMF) on the expression of main trophic factors in human BM-MSCs. Materials and Methods: Initially, the identity of stem cells was confirmed through the evaluation of surface markers and their capacity for osteogenic and adipogenic differentiation using flow cytometry and differentiation assay, respectively. Subsequently, stem cells were subjected to different concentrations of DMF for 72 hours and their viability was defined by MTT assay. Following 72-hour preconditioning period with 10 µM DMF, gene expression was assessed by quantitative RT-PCR. Results: Our findings demonstrated that the isolated stem cells expressed cardinal MSC surface markers and exhibited osteogenic and adipogenic differentiation potential. MTT results confirmed that 10 µM DMF was an optimal dose for maintaining cell viability. Preconditioning of stem cells with DMF significantly upregulated the expression of BDNF, NGF, and NT-3. Despite a slight increase in transcript level of GDNF and VEGF after DMF preconditioning, this difference was not statistically significant. Conclusions: Our findings suggest that DMF preconditioning can enhance the expression of major neurotrophic factors in human BM-MSCs. Given the curative potential of both BM-MSCs and DMF in various neurological disease models and preconditioning outcomes, their combined use may synergistically enhance their neuroprotective properties.

miR-18a-5p promotes osteogenic differentiation of BMSC by inhibiting Notch2.

Postmenopausal osteoporosis (PMOP) is a metabolic disorder characterized by the loss of bone density, which increases the risk of developing complications such as fractures. A pivotal factor contributing to the onset of PMOP is the diminished osteogenic differentiation capacity of bone marrow mesenchymal stem cells (BMSCs). MicroRNAs (miRNAs) play a substantial role in this process; however, their specific impact on regulating BMSCs osteogenesis remains unclear. Studies have evidenced a reduced expression of miR-18a-5p in PMOP, and concomitantly, our observations indicate an augmented expression of miR-18a-5p during the osteogenic differentiation of BMSCs. This investigation seeks to elucidate the regulatory influence of miR-18a-5p on BMSC osteogenic differentiation and the underlying mechanisms. In vitro experiments demonstrated that the overexpression of miR-18a-5p facilitated the osteogenic differentiation of BMSCs, while the downregulation of miR-18a-5p yielded converse outcomes. Mechanistically, We employed bioinformatics techniques to screen out the target gene Notch2 of miR-18a-5p. Subsequently, dual-luciferase reporter gene assays and rescue experiments substantiated that miR-18a-5p promotes BMSC osteogenic differentiation by suppressing Notch2. Finally, miR-18a-5p was overexpressed via adenovirus injection into the femoral bone marrow cavity, with results demonstrating its capability to enhance osteogenic differentiation and alleviate PMOP symptoms. Our findings disclose that miR-18a-5p fosters osteogenic differentiation of BMSC by inhibiting Notch2, thereby offering novel targets and strategies for PMOP treatment.

Bone Marrow Mesenchymal Stem Cells-Derived Extracellular Vesicle miR-208a-3p Alleviating Spinal Cord Injury via Regulating the Biological Function of Spinal Cord Neurons.

We aim to explore the potential mechanism of bone marrow mesenchymal stem cells-derived extracellular vesicles (BMSCs-Exo) in improving spinal cord injury (SCI). Thirty male 12-week specific pathogen-free (SPF) Sprague-Dawley (SD) rats were used to construct SCI model in vivo. Ten male 12-week SPF SD rats were used to extract BMSCs. The Basso, Beattie, Bresnahan (BBB) score was used to evaluate the motor function of rats. Real-time fluorescence quantitative PCR (RT-PCR), western blot (WB), and double luciferase assay were used to explore the regulation between rno-miR-208a-3p and Cdkn1a (p21) in BMSCs. Primary spinal cord neurons were treated with lipopolysaccharide (100 ng/mL) for 30 min to mimic SCI in vitro. Compared with the model group (14 scores), BMSCs-Exo increased BBB score (19 scores) in SCI rats. Compared with the sham group, Cdkn1a was upregulated, whereas rno-miR-208a-3p was downregulated in the model group. However, compared with the model group, Cdkn1a was downregulated, whereas rno-miR-208a-3p was upregulated in the BMSCs-Exo group. In addition, rno-miR-208a-3p inhibited the expression of Cdkn1a via direct binding way. BMSCs-Exo-rno-miR-208a-3p promoted the proliferation of primary spinal neurons via inhibiting apoptosis in vitro. Moreover, BMSCs-Exo-rno-miR-208a-3p promoted cyclin D1, CDK6, and Bcl-2 and inhibited Bax expression in a cell model of SCI. In conclusion, BMSCs-Exo-carried rno-miR-208a-3p significantly protects rats from SCI via regulating the Cdkn1a pathway.

Annexin A family: A new perspective on the regulation of bone metabolism.

Osteoblast-mediated bone formation and osteoclast-mediated bone resorption are critical processes in bone metabolism. Annexin A, a calcium-phospholipid binding protein, regulates the proliferation and differentiation of bone cells, including bone marrow mesenchymal stem cells, osteoblasts, and osteoclasts, and has gradually become a marker gene for the diagnosis of osteoporosis. As calcium channel proteins, the annexin A family members are closely associated with mechanical stress, which can target annexins A1, A5, and A6 to promote bone cell differentiation. Despite the significant clinical potential of annexin A family members in bone metabolism, few studies have reported on these mechanisms. Therefore, based on a review of relevant literature, this article elaborates on the specific functions and possible mechanisms of annexin A family members in bone metabolism to provide new ideas for their application in the prevention and treatment of bone diseases, such as osteoporosis.

miR-203-3p promotes senescence of mouse bone marrow mesenchymal stem cells via downregulation of Pbk.

The senescence of bone marrow mesenchymal stem cells (BMSCs) contributes to the development of degenerative skeletal conditions. To date, the molecular mechanism resulting in BMSC senescence has not been fully understood. In this study, we identified a small non-coding RNA, miR-203-3p, the expression of which was elevated in BMSCs from aged mice. On the other hand, overexpression of miR-203-3p in BMSCs from young mice reduced cell growth and enhanced their senescence. Mechanistically, PDZ-linked kinase (PBK) is predicted to be the target of miR-203-3p. The binding of miR-203-3p to Pbk mRNA could decrease its expression, which in turn inhibited the ubiquitination-mediated degradation of p53. Furthermore, the intravitreal injection of miR-203-3p-inhibitor into the bone marrow cavity of aged mice attenuated BMSC senescence and osteoporosis in aged mice. Collectively, these findings suggest that targeting miR-203-3p to delay BMSC senescence could be a potential therapeutic strategy to alleviate age-related osteoporosis.

Bioinformatics analysis and validation of RNA methylation-related genes in osteogenic and adipogenic differentiation of rat bone marrow mesenchymal stem cells.

BACKGROUND: The regulatory mechanisms of RNA methylation during the processes of osteogenic and adipogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) have yet to be fully understood. The objective of our study was to analyze and validate the contribution of RNA methylation regulators to the mechanisms underlying the osteogenic and adipogenic differentiation of rat BMSCs. METHODS: We downloaded the GSE186026 from the Gene Expression Omnibus (GEO). Differentially expressed genes (DEGs) were screened using the DESeq2 package in R software (version 3.6.3). A total of 50 RNA methylation genes obtained from literature review and summary were intersected with the previous DEGs to obtain RNA methylation genes, which have different expressions (RM-DEGs). Gene Ontology (GO) analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis were utilized to reveal the functional enrichment. Quantitative real-time polymerase chain reaction (qRT-PCR) was performed to validate RM-DEGs. Protein-protein interaction network (PPI) analysis and visual analysis were performed using STRING and Cytoscape. RM-DEGs regulatory network was constructed to analyze the top 10 hub genes. The relationship between RM-DEGs, some enriched GO and pathways was also been analyzed. The miRNAs and RM-DEGs regulatory networks were established by using miRWalk and TargetScan. RESULTS: As part of our research, we detected varying levels of expression for m6A regulators Mettl3 and Rbm15, as well as m7G regulators Mettl1 and Wdr4, in relation to osteogenic differentiation, along with m6A regulator Fmr1 in adipogenic differentiation. The protein-protein interaction (PPI) networks were constructed for 49 differentially expressed genes (DEGs) related to RNA methylation during the process of osteogenic differentiation, and 13 DEGs for adipogenic differentiation. Moreover, top10 hub genes were calculated. In osteogenic differentiation, Mettl3 regulated the Wnt pathway and Hippo pathway by regulating Smad3, Rbm15 regulated the Notch pathway by Notch1, Mettl1 regulated the PI3K-Akt pathway by Gnb4. In adipogenic differentiation, Fmr1 regulated the PI3K-Akt pathway by Egfr. M6A methylation sites of Smad3, Notch1 and Gnb4 were predicted, and the results showed that all three genes were possibly methylated by m6A, and more than 9 sites per gene were possibly methylated. Finally, we constructed the regulatory networks of Mettl3, Rbm15, Mettl1, and Wdr4 and 109 miRNAs in osteogenic differentiation, Fmr1 and 118 miRNAs in adipogenic differentiation. CONCLUSIONS: Mettl3(m6A), Rbm15(m6A), Wdr4 and Mettl1(m7G) were differentially expressed in osteogenic differentiation, while Fmr1(m6A) was differentially expressed in adipogenic differentiation. These findings offered potential candidates for further research on the involvement of RNA methylation in the osteogenic and adipogenic differentiation of BMSCs.

AMPK, a hub for the microenvironmental regulation of bone homeostasis and diseases.

AMP-activated protein kinase (AMPK), a crucial regulatory kinase, monitors energy levels, conserving ATP and boosting synthesis in low-nutrition, low-energy states. Its sensitivity links microenvironmental changes to cellular responses. As the primary support structure and endocrine organ, the maintenance, and repair of bones are closely associated with the microenvironment. While a series of studies have explored the effects of specific microenvironments on bone, there is lack of angles to comprehensively evaluate the interactions between microenvironment and bone cells, especially for bone marrow mesenchymal stem cells (BMMSCs) which mediate the differentiation of osteogenic lineage. It is noteworthy that accumulating evidence has indicated that AMPK may serve as a hub between BMMSCs and microenvironment factors, thus providing a new perspective for us to understand the biology and pathophysiology of stem cells and bone. In this review, we emphasize AMPK's pivotal role in bone microenvironment modulation via ATP, inflammation, reactive oxygen species (ROS), calcium, and glucose, particularly in BMMSCs. We further explore the use of AMPK-activating drugs in the context of osteoarthritis and osteoporosis. Moreover, building upon the foundation of AMPK, we elucidate a viewpoint that facilitates a comprehensive understanding of the dynamic relationship between the microenvironment and bone homeostasis, offering valuable insights for prospective investigations into stem cell biology and the treatment of bone diseases.

Repair of spinal cord injury by bone marrow mesenchymal stem cell-derived exosomes: a systematic review and meta-analysis based on rat models.

Objective: This study aims to systematically evaluate the efficacy of bone marrow mesenchymal stem cell-derived exosomes (BMSCs-Exo) in improving spinal cord injury (SCI) to mitigate the risk of translational discrepancies from animal experiments to clinical applications. Methods: We conducted a comprehensive literature search up to March 2024 using PubMed, Embase, Web of Science, and Scopus databases. Two researchers independently screened the literature, extracted data, and assessed the quality of the studies. Data analysis was performed using STATA16 software. Results: A total of 30 studies were included. The results indicated that BMSCs-Exo significantly improved the BBB score in SCI rats (WMD = 3.47, 95% CI [3.31, 3.63]), inhibited the expression of the pro-inflammatory cytokine TNF-α (SMD = -3.12, 95% CI [-3.57, -2.67]), and promoted the expression of anti-inflammatory cytokines IL-10 (SMD = 2.76, 95% CI [1.88, 3.63]) and TGF-ß (SMD = 3.89, 95% CI [3.02, 4.76]). Additionally, BMSCs-Exo significantly reduced apoptosis levels (SMD = -4.52, 95% CI [-5.14, -3.89]), promoted the expression of axonal regeneration markers NeuN cells/field (SMD = 3.54, 95% CI [2.65, 4.42]), NF200 (SMD = 4.88, 95% CI [3.70, 6.05]), and the number of Nissl bodies (SMD = 1.89, 95% CI [1.13, 2.65]), and decreased the expression of astrogliosis marker GFAP (SMD = -5.15, 95% CI [-6.47, -3.82]). The heterogeneity among studies was primarily due to variations in BMSCs-Exo transplantation doses, with efficacy increasing with higher doses. Conclusion: BMSCs-Exo significantly improved motor function in SCI rats by modulating inflammatory responses, reducing apoptosis, inhibiting astrogliosis, and promoting axonal regeneration. However, the presence of selection, performance, and detection biases in current animal experiments may undermine the quality of evidence in this study.