Search Results (254)

Background and Objectives: Peripheral cytopenia occurs in approximately 2% of the population; however, in up to 0.9%, no cause is identified by conventional tests. Next-Generation Sequencing (NGS) detects somatic variants consistent with clonal hematopoiesis (CH). We aimed to determine the prevalence of CH and pre-myelodysplastic syndrome (pre-MDS) using a 51-gene panel with histopathological assessment. Materials and Methods: Bone marrow samples from 96 consecutive patients evaluated for cytopenia were retrospectively analyzed for genetic alterations. Results: In the overall cohort (n = 96), the median follow-up was 8.1 months (range, 1–20). A total of 37 (39%) out of 96 patients were diagnosed with idiopathic cytopenia of undetermined significance (ICUS), 9 (9%) with clonal cytopenia of undetermined significance (CCUS), 9 (9%) with clonal cytopenia and monocytosis of undetermined significance (CCMUS), 34 (36%) with myelodysplastic syndrome (MDS), and 7 (7%) with myelodysplastic/myeloproliferative neoplasm (MDS/MPN). Among 41 patients in whom no cytogenetic abnormalities were detected by fluorescence in situ hybridization (FISH), somatic variants were identified by NGS. In CCUS, 88% of patients had a single variant, most commonly ASXL1 (44%), followed by TET2 (22%). In CCMUS, ASXL1 and DNMT3A (each 25%) were the most frequent variants. The mean variant allele frequency (VAF) was higher in MDS (33.4%) than in CCUS/CCMUS (13.6%). In MDS patients aged 60 years and older, a higher number of variants were found compared to patients aged less than 60 years (p = 0.028). RUNX1 variants (n = 8) were associated with leukopenia (p = 0.012). Patients with SRSF2 variants (n = 4) had significantly poorer progression-free survival (p = 0.001). EZH2 and SETBP1 variants were associated with inferior overall survival (p = 0.04 and p = 0.019, respectively). In MDS patients (n = 34), thrombocytopenia (plt < 100.000) was associated with shorter PFS (p = 0.005). Conclusions: Given that pre-MDS conditions are considered predictors of hematologic malignancies, conventional diagnostic workup may be insufficient to accurately identify these entities, whereas NGS provides significant additional diagnostic value. Full article

Objectives: Pilose antler protein extract (PAE) was investigated for its therapeutic efficacy against ovariectomy (OVX)-induced osteoporosis and its underlying molecular mechanism. Methods: An OVX rat model was established to evaluate the effects of PAE on bone microarchitecture, histopathological changes, and bone metabolism-related parameters. Bone structure was assessed using Micro-CT and histological analysis, and biochemical and bone turnover markers were quantified. In vitro, Mouse calvarial pre-osteoblast subclone 14 (MC3T3-E1) Subclone 14 cells were used to examine the effects of PAE on cell viability, proliferation, osteogenic differentiation, and osteogenesis-related protein expression. Results: High-dose PAE markedly improved trabecular bone microarchitecture in OVX rats, as reflected by increased bone surface area and bone volume fraction and reduced trabecular separation. PAE significantly enhanced bone calcium content and elevated serum Bone Morphogenetic Protein 2 (BMP-2) and Procollagen Type I N-Terminal Propeptide (PINP) levels, while decreasing serum Alkaline Phosphatase (ALP) activity and C-Terminal Telopeptide of Type I Collagen (CTX-I) levels, indicating a shift toward bone formation. Mechanistically, PAE activated the Wnt-3a/β-Catenin signaling pathway in bone tissue and MC3T3-E1 cells, as evidenced by increased expression of Wnt-3a and β-Catenin proteins. In vitro experiments further demonstrated that PAE promoted MC3T3-E1 cell proliferation and upregulated osteogenic markers, i.e., Runt-related transcription factor 2 (RUNX2) and Osteocalcin (OCN). Conclusions: Collectively, these findings suggest that PAE exerts pronounced anti-osteoporotic effects and is associated with activation of the Wnt/β-Catenin signaling pathway. Full article

Osteoporosis is a major global health challenge, particularly among aging populations, underscoring the need for safe and effective nutritional interventions. Probiotics and their metabolites have emerged as promising candidates for modulating bone health via the gut-bone axis. In this study, we investigated the effects of a cell-free culture supernatant (CFS) from the food-grade bacterium Limosilactobacillus fermentum GBE18 on the proliferation, differentiation, and mineralization of MC3T3-E1 pre-osteoblasts. GBE18 CFS exhibited no cytotoxicity at concentrations ranging from 1% to 4% (v/v). Notably, 2% (v/v) CFS significantly enhanced alkaline phosphatase (ALP) activity and extracellular matrix mineralization (p < 0.05). Transcriptomic profiling revealed that differentially expressed genes were enriched in osteoblast-related processes and two key signaling pathways: Wnt/β-catenin and PI3K/Akt. Subsequent qRT-PCR and Western blot analyses confirmed the upregulation of critical regulators (Rspo2, Pdpk1, Malat1) and demonstrated coordinated activation of Akt phosphorylation, β-catenin stabilization, and Runx2 protein expression. Our findings indicate that GBE18 CFS promotes osteogenic differentiation through coordinated modulation of the PI3K/Akt and Wnt/β-catenin pathways. Consequently, this study provides mechanistic evidence supporting the potential application of L. fermentum GBE18-derived metabolites as functional food ingredients or dietary interventions for bone health and osteoporosis management. Full article

Background/Objectives: There is a lack of cohesion in integrating current knowledge on the genetic and environmental etiology of dental impaction. The primary aim of this article is to review the current literature to identify candidate genes involved in the pathogenesis of dental impaction. Methods: A scoping review was conducted following PRISMA-ScR guidelines to identify and organize the available body of evidence. Relevant literature was searched in MEDLINE (via PubMed), Scopus, and Web of Science, with the final search conducted on 03 January 2026. Eligibility criteria included case–control, cohort, cross-sectional observational, and case report studies in humans. Selected studies focused on syndromic and non-syndromic variants, inheritance patterns, and genetic analyses. Risk of bias was assessed using the Joanna Briggs Institute (JBI) Critical Appraisal Checklists and AMSTAR 2. Results: Only 18 studies met the eligibility criteria. Most articles were case reports and retrospective observational studies, revealing a multifaceted genetic landscape underlying dental impaction, with mutations affecting transcription factors and signaling pathways critical for odontogenesis, particularly RUNX2, FGFR1, MSX1, PAX9, and AXIN2. Overall, the included studies showed moderate methodological quality. Conclusions: Current evidence does not clearly support specific genes as causal factors in dental impaction, but instead suggests a complex, likely polygenic susceptibility that modulates the anatomical threshold for tooth eruption. This review highlights RUNX2, FGFR1, MSX1, PAX9, and AXIN2, as well as emerging candidates involved in eruption and bone remodeling pathways. Future progress depends on standardized phenotyping, large replicated cohorts, and functional studies linking genetic variation to dental follicle-mediated eruptive remodeling. Full article

Mechanobiology plays a pivotal role in skeletal development and bone remodeling. Mechanical signals such as matrix stiffness, fluid shear stress, and hydrostatic pressure activate the Runt-related transcription factor 2 (RUNX2) bone-specific transcription factor through pathways including the mitogen-activated protein kinase (MAPK) signaling cascade and yes-associated protein (YAP)/transcriptional co-activator with PDZ-binding motif (TAZ) effectors. RUNX2 itself affects chromatin remodeling and nuclear architecture via Lamin A/C and Nesprin 1, thereby directing osteogenic differentiation. Thus, RUNX2 acts both as a mechanosensor and mechanoregulator, whereas RUNX2’s mechanosensitivity has been leveraged as a target to achieve bone regeneration. Notably, post-translational modifications and epigenetic alterations can orchestrate this regulation, integrating metabolic and circadian signals. However, due to RUNX2’s nuclear localization, its targeting remains a challenging issue. To this end, indirect targeting, through mammalian/mechanistic target of rapamycin complex 1 (mTORC1) or microRNAs (miRNAs), offers new strategies to employ biomechanics in an attempt to intervene with bone diseases driven by mechanical cues or degeneration, and ultimately repair and regenerate the damaged tissues. Herein we critically elaborate upon molecular aspects of RUNX2 regulation towards exploitation at the clinical level. Full article

Calcium phosphate cements (CPCs) and biomaterials, such as mesoporous bioactive glass (MBG), are critical for bone tissue engineering. This study aimed to 3D-print CPC scaffolds modified with MBG to enhance their osteogenic potential and regenerative ability. MBG powder was synthesized and characterized using transmission electron microscopy (TEM), X-ray diffraction (XRD), and nitrogen adsorption–desorption techniques. A commercial CPC ink (hydroxyapatite/α-tricalcium phosphate) was mixed with 5% MBG (w/w; CPC/MBG), and, after rheological assessment, the mixture was used to obtain scaffolds via 3D printing. These scaffolds were then tested for chemical, morphological, and mechanical properties, as well as ion release analysis. Unmodified CPC 3D-printed scaffolds served as controls. Biological experiments, including cell viability, DNA content, cell adhesion/spreading, and osteogenic gene expression, were performed by seeding alveolar bone-derived mesenchymal stem cells onto the scaffolds. Statistics were performed using Student’s t-test and ANOVA with post hoc tests (α = 5%). MBG characterization showed a typical mesoporous structure with aligned microchannels and an amorphous structure. Both formulations released calcium and phosphate ions; however, CPC/MBG also released silicon. Cell viability, adhesion/spreading, and DNA content were significantly greater in CPC/MBG scaffolds compared to CPC (p < 0.05) after 3 and 7 days of culture. Furthermore, CPC/MBG supported increased expression of key osteogenic genes, including collagen (COL1A1), osteocalcin (OCN), and Runt-related transcription factor 2 (RUNX2), after 14 days (p < 0.05). The combination of CPC ink with MBG particles effectively enhances the biocompatibility and osteogenic potential of the scaffold, making it an innovative bioceramic ink formulation for 3D printing personalized scaffolds for bone regeneration. Full article

Periodontitis is a prevalent chronic inflammatory disease that leads to the progressive destruction of periodontal tissues and remains the primary cause of tooth loss worldwide. Despite advances in regenerative approaches—including stem cell therapy, scaffold-based tissue engineering, and guided tissue regeneration—the complete and functional restoration of the periodontal ligament remains a major clinical challenge. Stem-cell-based therapies and advanced biomaterials have emerged as promising strategies in regenerative medicine, offering potential for restoring periodontal structure and function. Among cells, periodontal-ligament-derived stem cells (PDLSCs) show exceptional regenerative potential due to their ability to differentiate into cementoblasts, osteoblasts, and other cell types essential for periodontal repair. In recent years, a variety of biomaterials with distinct specifications and properties have been utilized to repair periodontal damage. In addition to the inherent properties of biomaterials, the morphology and structural characteristics of these materials as bioequivalents for periodontal regeneration are also critical considerations. Furthermore, recent studies emphasize that mechanical stimulation plays a considerable role in directing stem cell differentiation, gene expression, matrix organization, and modulating inflammatory responses in periodontal regeneration. Canonical parameter ranges for systematic analysis indicate that cyclic stretch strain of 1–20% at 0.1–0.5 Hz (6–30 cycles/min) typically increases the expression of osteogenic markers (RUNX2, ALP, OCN) and matrix components (Col1) in PDLSCs. Conversely, higher values (>15%) often bias the response toward inflammatory pathways (IL-6, PGE2). Static compression above 2 g/cm² consistently stimulates the secretion of pro-inflammatory cytokines (IL-6, IL-8) and alters the RANKL/OPG balance in favor of osteoclastogenesis. Significant heterogeneity in response across studies will be analyzed by examining key methodological variables, including specific loading regimens (duration, frequency patterns) and culture conditions (e.g., serum/osteogenic supplements), which critically modulate mechanotransduction outcomes. This review summarizes current progress in periodontal regenerative medicine, emphasizing cellular and biomaterial considerations, as well as biofabrication techniques, with a particular focus on the influence of mechanical forces on PDLSCs. We discuss cellular responses to mechanical stimuli, including changes in gene expression, cytoskeletal organization, proliferation, and differentiation. Combining biological knowledge with advances in bioprinting and the study of mechanobiology, we finally discuss promising opportunities for improving periodontal regeneration that can be applied in the future in clinical practice. Full article

Desmosomal junctions provide structural stability supporting concerted cardiomyocyte contractility. Previously, we demonstrated that a deficiency in the desmosomal transmembrane cadherin desmoglein 2 (Dsg2) reduces desmosome formation and disrupts cardiac morphogenesis, leading to excessive endothelial-to-hematopoietic cell transformation and embryonic lethality. It remained unclear whether this phenotype was specifically driven by Dsg2-deficiency or was a broader consequence of impaired desmosome adhesion. To address this question, we generated Pkp2^mt/mt mouse embryos lacking the desmosomal plaque protein Pkp2, which resulted in loss of desmosome formation. Despite the absence of cardiac wall rupture, Pkp2^mt/mt and some Pkp2^wt/mt presented accumulations of Ter-119⁺ blood cells and RUNX1⁺/CD44⁺ hematopoietic stem cells in the pericardial space. Remarkably, in Pkp2^mt/mt hearts, the epicardium was detached from the myocardium, contained rounded cells expressing the hematopoietic stem cell marker RUNX1, and showed altered intermediate filament expression. These findings suggest a potential trans-differentiation of the epicardial cells into hematopoietic cells. In conclusion, deficiencies in both Dsg2 and Pkp2 promote hematopoiesis in the developing murine heart but target different cell types, i.e., endothelial cells, which lack desmosomes, or desmosome-containing epicardial cells. Our results provide evidence for the involvement of Pkp2 in epicardial morphogenesis and remodeling. Full article

Background: Pediatric acute myeloid leukemia (pAML) is the second most common type of childhood leukemia, behind acute lymphoblastic leukemia. High-throughput technologies have enabled the identification of increasing molecular alterations linked to AML prognosis, revealing genomic heterogeneity among individual patients and providing clinically valuable diagnostic and prognostic information. This study systematically analyzed the correlation between high-frequency mutated genes and prognosis in pAML by performing whole-transcriptome sequencing (WTS) of bone marrow samples from newly diagnosed AML children in Southwest China and mapping their genetic profiles. Methods: pAML patients treated at the Department of Hematology and Oncology, Children’s Hospital of Chongqing Medical University, from January 2015 to October 2024, were enrolled, and WTS was performed. The study described the frequency, pathogenicity classification, and risk stratification of mutation genes and fusion genes, and constructed a genetic landscape. For high-frequency pAML mutations, the impact on early induction remission rate (CR) and long-term event-free survival (EFS) was evaluated. Results: A total of 134 pediatric AML patients from Southwest China were included, with a male-to-female ratio of 74:60 and a median diagnosis age of 5.96 years. Based on pathogenicity classification using WTS, fusion genes were categorized into level 1, level 2, and level 3 genes, as well as mutation genes. The study identified five fusion genes of level 1, the most frequent being RUNX1::RUNX1T1 (32/134, 23.88%), KMT2A rearrangements (29/134, 21.64%), and CBFB::MYH11 (13/134, 9.7%). Sixteen mutation genes of level 1 were detected, seven of which recurred in over 5% of patients, including NRAS (31/134, 23.13%), FLT3 (25/134, 18.66%), KIT (24/134, 17.91%), CEBPA (14/134, 10.45%), WT1 (13/134, 9.7%), KRAS (11/134, 8.2%), and PTPN11 (7/134, 5.22%). Sex-based analysis revealed that PTPN11 mutations were significantly more frequent in males (9.45% vs. 0%, p = 0.023), as were KIT mutations (24.32% vs. 10.00%, p = 0.044). Risk-stratified analysis showed that WT1 mutations (14.13% vs. 0%, p = 0.031) and FLT3-ITD mutations (13.19% vs. 0%, p = 0.042) were enriched in intermediate- and high-risk groups, whereas CEBPA (25.64% vs. 5.43%, p = 0.012), KIT (35.90% vs. 10.87%, p = 0.003), and KIT-E8 (20.51% vs. 1.10%, p < 0.001) mutations were more prevalent in low-risk groups. Prognostic analysis indicated that PTPN11 and KIT mutations did not affect CR or EFS across sexes, nor did WT1, CEBPA, or KIT mutations influence outcomes by risk stratification. However, FLT3-ITD-positive patients had significantly lower CRs (χ² value = 11.965, p = 0.007), although EFS differences were nonsignificant. In contrast, WT1 mutations were associated with inferior EFS compared to wild-type (p = 0.036). Furthermore, the univariate and multivariate Cox regression revealed consistent results with the above findings, indicating that WT1 mutation was an independent adverse prognostic factor for EFS (HR = 2.400, 95% CI: 1.101–5.233, p = 0.028). The results of univariate and multivariate logistic regression analyses also confirmed that FLT3-ITD mutation was an independent predictor of initial treatment response in our cohort (OR = 10.699, 95% CI: 2.108–54.302, p = 0.004). Conclusions: This study delineated the genetic landscape of pAML in Southwest China and explored the prognostic value of gene fusions and mutations in early and long-term outcomes. These findings provide a foundation for understanding the genetic heterogeneity of pAML and offer evidence for the development of precision medicine approaches. Full article

(1) Background: Zirconia (ZrO₂) is increasingly used in dental implantology due to its biocompatibility and favorable mechanical and biological properties. While subtractive and stereolithographic additive manufacturing techniques are well established, the application of Fused Filament Fabrication (FFF) for zirconia-based dental implants remains largely unexplored. (2) Methods: Cylindrical ZrO₂ specimens were fabricated using three different manufacturing techniques: milling (MIL), Digital Light Processing (DLP), and FFF. Surface topography was analyzed via white-light interferometry. Human fetal osteoblasts (hFOBs 1.19) were cultured on the specimens to evaluate cell adhesion after 4 and 24 h, proliferation for 4 days, cell surface coverage after 4 and 24 h, and osteogenic gene expression (RUNX2, ALPL, and BGLAP) after 24 h, 48 h, 7 days, and 14 days. (3) Results: The FFF samples exhibited significantly higher surface roughness than the MIL and DLP specimens. After 24 h, enhanced cell adhesion and the highest proliferation rates were observed on FFF surfaces. At 14 days, gene expression analysis revealed elevated expression of BGLAP on FFF surfaces, suggesting advanced osteogenic differentiation compared to MIL and DLP. (4) Conclusions: The inherent surface roughness of FFF-printed zirconia appears to promote osteogenic activity without additional surface treatment. These findings suggest that FFF may constitute a viable manufacturing method for the fabrication of customized zirconia components in dental implantology, warranting further investigations, particularly regarding their mechanical performance. Full article

Reparative tertiary dentinogenesis requires the recruitment and odontogenic differentiation of dental pulp stem cells (DPSCs). Extracellular vesicles (EVs) as bioactive molecules have gained attention in regenerative medicine for their ability to mediate tissue repair through intercellular communication, influencing cell recruitment, proliferation, and differentiation. This study aimed to evaluate the effects of EVs on DPSC homing and odontogenic differentiation for dentin regeneration. DPSC-derived EVs were cultured in either growth (EV-G) or odontogenic differentiation (EV-O) conditions and isolated using a modified precipitation method. EVs were characterized by nanoparticle tracking analysis, scanning electron microscopy, antibody array, and cellular uptake assay. Treatment with 5 × 10⁸ EVs/mL significantly enhanced DPSC chemotaxis and proliferation compared with a no-treatment control and a lower dosage of EV (5 × 10⁷ EVs/mL). Gene expression and biochemical analyses revealed that EV-O up-regulated odontogenic markers including collagen type 1A1 (COL1A1), runt-related transcription factor 2 (RUNX2), and alkaline phosphatase (ALP). EV-O enhanced dentin regeneration by approximately 55% over vehicle controls in a rabbit partial dentinotomy/pulpotomy model. We identified key microRNAs (miR-21-5p, miR-221-3p, and miR-708-3p) in EV-O involved in cell homing and odontogenesis. In conclusion, our EV-based cell homing and odontogenic differentiation strategy has significant therapeutic potential for dentin regeneration. Full article

High-altitude pulmonary edema (HAPE) is a severe condition associated with high-altitude environments, and its molecular mechanism has not been fully elucidated. This study systematically analyzed the DNA methylation status of HAPE patients and healthy controls using reduced-representation bisulfite sequencing (RRBS) and 850K DNA methylation chips, identifying key differentially methylated regions (DMRs). Targeted bisulfite sequencing (TBS) revealed significant abnormalities in DMRs of five genes, azurocidin 1 (AZU1), growth factor receptor bound protein 7 (GRB7), mannose receptor C-type 2 (MRC2), RUNX family transcription factor 3 (RUNX3), and septin 9 (SEPT9). The abnormal expression of AZU1 was validated using peripheral blood leukocytes from HAPE patients and normal controls, as well as rat lung tissue, indicating its potential importance in the pathogenesis of HAPE. To further validate the function of AZU1, we conducted experimental studies using a hypobaric hypoxia injury model in Human Umbilical Vein Endothelial Cells (HUVEC). The results showed that AZU1 was significantly upregulated under hypobaric hypoxia. Knocking down AZU1 mitigates the reduction in HUVEC proliferation, angiogenesis, and oxidative stress damage induced by acute hypobaric hypoxia. AZU1 induces cellular oxidative stress via the p38/mitogen-activated protein kinase (p38/MAPK) signaling pathway. This study is the first to elucidate the mechanism of AZU1 in HAPE via the p38/MAPK pathway, offering novel insights into the molecular pathology of HAPE and laying a foundation for future diagnostic and therapeutic strategies. Full article

Mechanical stresses affect a variety of cellular events in relation to the frequency, magnitude, and duration of the stimuli applied. Embryonic stem cell (ESC)-derived embryoid bodies (EBs) are pluripotent stem cell aggregates and comprise all somatic cells. Numerous studies have highlighted the effects of mechanosignals on stem cells, whereas their impact on EBs has been barely investigated. Here, we examined how cyclic tensile stress affects the behavior of EBs to differentiate into mineralized osteocytes by applying 2% elongation at 0.5 Hz frequency for 1 h once or 1 h every other day for 5 or 14 days in osteogenic medium. EBs that expressed undifferentiated markers, Oct4 and Sox2, were differentiated into mineralized cells, along with the accumulation of runt-related transcription factor 2 (RUNX2) and β-catenin in osteogenic medium. The application of tensile force inhibited EB’ mineralization via the downregulation of bone sialoprotein, osteocalcin, osterix, and RUNX2. While the transfection with si-β-catenin did not affect the osteogenic potency of EBs at a significant level, treatment with 10 μM of PD98059, but not of SP600125 or SB203580, diminished the mineralization of EBs and the expression of RUNX2 and RUNX2-regulated osteoblastic genes. The level of phosphorylated extracellular signal-regulated kinase-1 (p-ERK1) rather than p-ERK2 was more apparently diminished in tension-applied EBs. The transfection with si-ERK1, but not with si-ERK2, suppressed the mineralization of osteogenic medium-supplied EBs and the expression of osteoblast-specific genes. Collectively, this study demonstrates that tensile stress inhibits osteogenic potency of EBs by downregulating ERK1-mediated signaling and osteogenic gene expression. Full article

Mechanical stress is known to be a pivotal risk factor in the development of OA. However, the involvement of repetitive compressive loading in mitochondrial dysfunction in chondrocytes remains unclear. The aim of this study was to investigate whether physiologic levels of repetitive mechanical force affect the regulation of energy metabolism and activities of mitochondrial function regulators, sirtuin 1 and nicotinamide adenine dinucleotide (NAD) in chondrocytes, and to clarify any correlation with chondrocyte catabolic activity. Repetitive physiological mechanical stress was applied in a 3D chondrocyte-collagen scaffold construct, and the 3D cultured tissues were collected at different time points by collagenase treatment to collect cellular proteins. Changes in chondrocyte activity (cell proliferation, MMP-13 production), energy metabolism regulator levels (sirtuin 1), mitochondrial function (ATP production, NAD level), and the expression level of the osteogenic and hypertrophic chondrogenic transcription factor, runt-related transcription factor 2 (Runx2), were measured. Treatment with repetitive compressive loading resulted in no significant change in the cell viability of chondrocytes. In the repetitive mechanical loading group, there were statistically significant increases in MMP-13 production and expression of both sirtuin 1 and Runx2 in chondrocytes relative to the non-loading control group. Furthermore, ATP production and NAD activity in mitochondria decreased in the repetitive mechanical loading group. Our present study reveals that in chondrocytes, repetitive compressive loading accelerated sirtuin activation, which requires and consumes NAD within mitochondria, leading to a decrease of NAD and ultimately in reduced mitochondrial ATP production. Additionally, since sirtuin 1 is known to positively regulate Runx2 activity in chondrocytes, the activation of sirtuin 1 by repetitive load stimulation may induce an increase in the expression of Runx2, which promotes the expression of MMP-13, and subsequently enhances MMP-13 production. Our findings indicate that repetitive compression loading-mediated mitochondrial dysfunction plays a pivotal role in the progression of OA, primarily by driving the downregulation of ATP production and promoting the expression of the matrix-degrading enzyme MMP-13. Full article

Background and Objectives: Aging-related bone loss still lacks interventions. As bone marrow-derived mesenchymal stem cells (BMSCs) undergo aging, R-loop-induced DNA replication stress impairs the osteogenic ability of BMSCs. High-mobility group A-2 (Hmga2) acts as a DNA-binding protein, and the understanding of its underlying mechanisms is crucial for developing effective preventive and therapeutic strategies. Materials and Methods: Aging mice were used as the experimental model, and mouse BMSCs were isolated from their femurs. Hmga2 was achieved through specific gene delivery methods. R-loop formation was detected using dot blotting, chromatin immunoprecipitation (ChIP), and DNA–RNA immunoprecipitation (DRIP) assays. Osteogenic differentiation was evaluated. Results: R-loops were highly accumulated in aging BMSCs. Notably, the key regulator Hmga2 reversed the accumulation of R-loops in aging BMSCs. Hmga2 overexpression significantly decreased the senescence and improved the osteogenic differentiation of aging mBMSCs. Mechanistically, R-loop-forming sequence (RLFS) regions were confirmed in key osteogenesis-related genes, including runt-related transcription factor 2 (Runx2). Hmga2 bound to the RLFS region of Runx2 and promoted its expression by reducing the R-loop level. More, Hmga2 treatment delivered via the AAV system effectively decreased bone loss in aging mice and increased the serum bone turnover biomarkers and collagen remodeling. Conclusions: Our study demonstrates that Hmga2 acts as an activator of aging BMSCs, significantly promoting their osteogenic ability by eliminating the aging-induced DNA replication stress caused by R-loops. Our findings provide new insights into the mechanisms of aging-related bone loss, suggesting that Hmga2 may be a new strategy for alleviating the bone loss phenotype in aging individuals. Full article