Impaired Bone Formation Research Articles

GelMA Hydrogels Integrated With aptamer CH6-Functionalized Tetrahedral DNA Nanostructures for Osteoporotic Mandibular Regeneration.

Osteoporotic bone regeneration is challenging due to impaired bone formation. Tetrahedral DNA nanostructures (TDN), promising nucleic acid nanomaterials, have garnered attention for their potential in osteoporotic mandibular regeneration owing to their ability to enhance cellular activity and promote osteogenic differentiation. Osteoblasts play a critical role in bone regeneration; however, intracellular delivery of TDN into osteoblasts remains difficult. In this study, a novel osteoblast-targeted CH6 aptamer-functionalized TDN (TDN-CH6) is aimed to develop for osteoporotic mandibular regeneration. This results demonstrated that TDN-CH6 exhibits superior osteoblast specificity and efficient recruitment to bone fracture sites. Furthermore, TDN-CH6 significantly enhances cellular activity and osteogenic differentiation compared to TDN alone. Notably, Gelatin Methacryloyl (GelMA) hydrogels incorporating TDN and TDN-CH6 shows improved biological performance and are favorable for osteoporotic mandibular regeneration, suggesting that this platform represents a promising strategy for addressing complex bone defects.

Vitamin E Improves Cellular and Structural Bone Histomorphometry in an Alcohol-Induced Osteoporosis Rat Model.

Background: Alcohol-induced osteoporosis is a significant health concern, impairing bone formation and enhancing resorption, thereby weakening skeletal integrity. This study examines the effects of palm vitamin E on bone histomorphometry in a male rat model of alcohol-induced osteoporosis. Methods: Three-month-old Sprague-Dawley rats were randomized into seven groups, with one baseline control group (BC) and six experimental groups undergoing a two-phase treatment. In the first month, the control group received normal saline, while experimental groups received intraperitoneal alcohol (3 g/kg) three times weekly. For the subsequent two months, alcohol treatment continued in one group (A), while others received olive oil (C), saline (AN), alpha-tocopherol (AA), or palm vitamin E (AE) orally. Results: Femur histomorphometric analysis post-sacrifice showed that alcohol exposure significantly decreased osteoblastic activity and impaired bone microarchitecture, evidenced by reduced Ob.S/BS, OS/BS, OV/BV, Tb.Th, BV/TV, and Tb.N, alongside increased Oc.S/BS, ES/BS, and Tb.Sp. Both alpha-tocopherol and palm vitamin E improved bone parameters, with palm vitamin E showing superior efficacy except in OV/BV. Conclusions: These findings suggest that palm vitamin E may offer a therapeutic benefit for mitigating alcohol-induced bone damage.

Integrative in-silico and in-vitro analysis of taurine and vitamin B12 in modulating PPARγ and Wnt signaling in hyperhomocysteinemia-induced osteoporosis

Peroxisome proliferator-activated receptor-γ (PPARγ) is a critical regulator of adipogenesis and bone metabolism, playing complex roles in osteoporosis. This study investigates the effects of taurine and homocysteine on PPARγ, focusing on their roles in osteoclastogenesis and bone health. In-silico analyses, including molecular docking and molecular dynamic simulations, revealed that both taurine and homocysteine bind competitively to the PPARγ ligand-binding domain, exhibiting distinctive antagonistic modes, including destabilization of PPARγ’s key helices H3, H4/5, H11, and H12. In-vitro experiments further supported these results, demonstrating that taurine protects against oxidative damage, enhances bone mineralization, and reduces the expression levels of PPARγ, while also downregulating negative regulators of the Wnt signaling pathway, such as SOST and DKK1. Homocysteine, on the other hand, was observed to increase the expression of these regulators and impair bone formation. Vitamin B12 was included in the study due to its known role in mitigating hyperhomocysteinemia, a condition linked to impaired bone health and reduced taurine levels. While vitamin B12 alone demonstrated some beneficial effects, it did not achieve the same level of efficacy as taurine. However, a combination of taurine and vitamin B12 showed greater efficacy in ameliorating hyperhomocysteinemia-induced osteoporosis. Overall, this study highlights taurine’s therapeutic potential in counteracting the adverse effects of hyperhomocysteinemia on bone health and underscores the need for further research into taurine’s mechanisms in osteoporosis treatment.Graphical abstract

SNPs in GPCR Genes and Impaired Osteogenic Potency in Osteoporotic Patient Lines-Based Study.

G-protein-coupled receptors (GPCRs) have emerged as critical regulators of bone development and remodeling. In this study, we aimed to identify specific GPCR mutations in osteoporotic patients via next-generation sequencing (NGS). We performed NGS sequencing of six genomic DNA samples taken from osteoporotic patients and two genomic DNA samples from healthy donors. Next, we searched for single-nucleotide polymorphisms (SNPs) in GPCR genes that are associated with osteoporosis. For three osteoporotic patients and one healthy donor, bone biopsies were used to generate patient-specific mesenchymal stem cell (MSC) lines, and their ability to undergo osteodifferentiation was analyzed. We found that MSCs derived from osteoporotic patients have a different response to osteoinductive factors and impaired osteogenic differentiation using qPCR and histochemical staining assays. The NGS analysis revealed specific combinations of SNPs in GPCR genes in these patients, where SNPs in ADRB2 (rs1042713), GIPR (rs1800437), CNR2 (rs2501431, rs3003336), and WLS (rs3762371) were associated with impaired osteogenic differentiation capacity. By integrating NGS data with functional assessments of patient-specific cell lines, we linked GPCR mutations to impaired bone formation, providing a foundation for developing personalized therapeutic strategies. SNP analysis is recognized as a proactive approach to osteoporosis management, enabling earlier interventions and targeted preventive measures for individuals at risk. Furthermore, SNP analysis contributes to the development of robust, holistic risk prediction models that enhance the accuracy of risk assessments across the population. This integration of genetic data into public health strategies facilitates healthcare initiatives. This approach could guide treatment decisions tailored to the patient's genetic profile and provide a foundation for developing personalized therapeutic strategies.

Rejuvenating aged osteoprogenitors for bone repair

Aging is marked by a decline in tissue regeneration, posing significant challenges to an increasingly older population. Here, we investigate age-related impairments in calvarial bone healing and introduce a novel two-part rejuvenation strategy to restore youthful repair. We demonstrate that aging negatively impacts the calvarial bone structure and its osteogenic tissues, diminishing osteoprogenitor number and function and severely impairing bone formation. Notably, increasing osteogenic cell numbers locally fails to rescue repair in aged mice, identifying the presence of intrinsic cellular deficits. Our strategy combines Wnt-mediated osteoprogenitor expansion with intermittent fasting, which leads to a striking restoration of youthful levels of bone healing. We find that intermittent fasting improves osteoprogenitor function, benefits that can be recapitulated by modulating NAD+-dependent pathways or the gut microbiota, underscoring the multifaceted nature of this intervention. Mechanistically, we identify mitochondrial dysfunction as a key component in age-related decline in osteoprogenitor function and show that both cyclical nutrient deprivation and Nicotinamide mononucleotide rejuvenate mitochondrial health, enhancing osteogenesis. These findings offer a promising therapeutic avenue for restoring youthful bone repair in aged individuals, with potential implications for rejuvenating other tissues.

Rejuvenating aged osteoprogenitors for bone repair.

Aging is marked by a decline in tissue regeneration, posing significant challenges to an increasingly older population. Here, we investigate age-related impairments in calvarial bone healing and introduce a novel two-part rejuvenation strategy to restore youthful repair. We demonstrate that aging negatively impacts the calvarial bone structure and its osteogenic tissues, diminishing osteoprogenitor number and function and severely impairing bone formation. Notably, increasing osteogenic cell numbers locally fails to rescue repair in aged mice, identifying the presence of intrinsic cellular deficits. Our strategy combines Wnt-mediated osteoprogenitor expansion with intermittent fasting, which leads to a striking restoration of youthful levels of bone healing. We find that intermittent fasting improves osteoprogenitor function, benefits that can be recapitulated by modulating NAD+-dependent pathways or the gut microbiota, underscoring the multifaceted nature of this intervention. Mechanistically, we identify mitochondrial dysfunction as a key component in age-related decline in osteoprogenitor function and show that both cyclical nutrient deprivation and Nicotinamide mononucleotide rejuvenate mitochondrial health, enhancing osteogenesis. These findings offer a promising therapeutic avenue for restoring youthful bone repair in aged individuals, with potential implications for rejuvenating other tissues.

Osteogenesis imperfecta: shifting paradigms in pathophysiology and care in children.

The formation of functional bone requires a delicate interplay between osteogenesis and osteolysis. Disturbances in this subtle balance result in an increased risk for fractures. Besides its mechanical function, bone tissue represents a key player in the regulation of calcium homeostasis. Impaired bone formation results in bone fragility, which is especially pronounced in osteogenesis imperfecta (OI). This rare genetic disorder is characterized by frequent fractures as well as extraskeletal manifestations. The current classification of OI includes 23 distinct types. In recent years, several new mutations in different genes have been identified, although the exact pathomechanisms leading to the clinical presentation of OI often remain unclear. While bisphosphonates are still the standard of care, novel therapeutic approaches are emerging. Especially, targeted antibody therapies, originally developed for osteoporosis, are increasingly being investigated in children with OI and represent a promising approach to alleviate the consequences of impaired osteogenesis and improve quality of life in OI patients. This review aims to provide insight into the pathophysiology of OI and the consequences of distinct disease-causing mutations affecting the regulation of bone homeostasis. In this context, we describe the four most recently identified OI-causing genes and provide an update on current approaches for diagnosis and treatment.

Integrin β2 regulates titanium particle‑induced inflammation in macrophages: In vitro aseptic loosening model.

Aseptic loosening is a major complication of joint replacement surgery, characterized by periprosthetic osteolysis and chronic inflammation at the bone‑implant interface. Cells release chemokines, cytokines and other pro‑inflammatory substances that perpetuate inflammation reactions, while other particle‑stimulated macrophages promote osteoclastic bone resorption and impair bone formation. The present study investigated integrin and inflammatory cytokine expression patterns in RAW 264.7 cells treated with titanium (Ti) particles to elucidate the role of integrins in Ti particle‑mediated inflammatory osteolysis. Assessment was performed by reverse transcription‑quantitative PCR, western blotting, confocal immunofluorescence, flow cytometry and enzyme‑linked immunosorbent assays. Cell migration was evaluated by wound healing assay. It was found that Ti particles significantly induced integrin expression in RAW 264.7 cells, including upregulation of integrins β2 (CD18), aL (CD11a), aM (CD11b) and aX (CD11c). Ti particles also enhanced the expression of Toll‑like receptors (TLRs; TLR1, TLR2, TLR3 and TLR4) and triggered the release of inflammatory cytokines such as tumor necrosis factor α, interleukin (IL)‑1β, IL‑8 and IL‑12. Proteomics showed higher expression and activity levels of TLR2 and TLR4, along with their downstream signaling adaptors myeloid differentiation primary response protein 88 (MyD88) and Mal/TIR‑domain‑containing adapter protein (TIRAP), following Ti treatment. Additionally, Ti treatment significantly enhanced the migration rate of RAW 264.7 cells. The present findings indicated that Ti particles regulate the inflammatory response of RAW 264.7 cells in an in vitro aseptic loosening model by activating the TLR/TIRAP/MyD88 signaling pathway.

Single-cell transcriptomic resolution of osteogenesis during craniofacial morphogenesis

Craniofacial morphogenesis depends on complex cell fate decisions during the differentiation of post-migratory cranial neural crest cells. Molecular mechanisms of cell differentiation of mesenchymal cells to developing bones, cartilage, teeth, tongue, and other craniofacial tissues are still poorly understood. We performed single-cell transcriptomic analysis of craniofacial mesenchymal cells derived from cranial NCCs in mouse embryo. Using FACS sorting of Wnt1-Cre2 progeny, we carefully mapped the cell heterogeneity in the craniofacial region during the initial stages of cartilage and bone formation. Transcriptomic data and in vivo validations identified molecular determinants of major cell populations involved in the development of lower and upper jaw, teeth, tongue, dermis, or periocular mesenchyme. Single-cell transcriptomic analysis of Meis2-deficient mice revealed critical gene expression differences, including increased osteogenic and cell adhesion markers. This leads to affected mesenchymal cell differentiation and increased ossification, resulting in impaired bone, cartilage, and tongue formation.

Loss of Hdac4 in osteoprogenitors impairs postnatal trabecular and cortical bone formation, resulting in a dwarfism and osteopenia phenotype in mice

HDAC4 is a class II histone deacetylation protein with a well-characterized role in chondrocyte differentiation and skeletal development, and dysregulated expression or haploinsufficiency of Hdac4 leads to skeletal formation and malformation disorders. The early lethality of hdac4 ablation mice hindered further investigation of its role in postnatal bone growth and development. Therefore, this study aims to investigate the significant role of Hdac4 in postnatal endochondral bone development using two mouse models with conditional deletion of Hdac4 in Sp7-expressing osteoprogenitors or chondrocytes and monitored postnatal bone development. The phenotype of Acan-CreERT2; Hdac4fl/fl mice largely resembled that of conventional Hdac4-/- mice. But phenotypic characterizations of mice with Hdac4 inactivation in Sp7-expressing osteoprogenitors (Sp7-Cre; Hdac4fl/fl) showed dwarfism with body and limb shortening and remarkable skeletal defects. Micro-computed tomography analysis of tibias further demonstrated that loss of Hdac4 expression impaired bone formation and microarchitecture, mainly characterized by dysplasia of trabecular and cortical bone in young mice. Our in vivo and in vitro data support a crucial role for Hdac4 in regulating osteoblast proliferation and differentiation, bone matrix protein production, angiogenesis, and ultimately trabecular and cortical bone formation. Moreover, RNA-seq analysis implicated Hdac4 in the regulation of key genes and pathways necessary to affect the accumulation of extracellular matrix, biological processes related to signal transduction, and skeletal growth. Collectively, our data show that postnatal expression of Hdac4 in Sp7-expressing osteoprogenitors provides essential regulatory oversight of endochondral bone formation, bone morphology, and homeostasis.

Metabolic rewiring during bone development underlies tRNA m7G-associated primordial dwarfism.

Translation of mRNA to protein is tightly regulated by transfer RNAs (tRNAs), which are subject to various chemical modifications that maintain structure, stability, and function. Deficiency of tRNA N7-methylguanosine (m7G) modification in patients causes a type of primordial dwarfism, but the underlying mechanism remains unknown. Here we report that the loss of m7G rewires cellular metabolism, leading to the pathogenesis of primordial dwarfism. Conditional deletion of the catalytic enzyme Mettl1 or missense mutation of the scaffold protein Wdr4 severely impaired endochondral bone formation and bone mass accrual. Mechanistically, Mettl1 knockout decreased abundance of m7G-modified tRNAs and inhibited translation of mRNAs relating to cytoskeleton and Rho GTPase signaling. Meanwhile, Mettl1 knockout enhanced cellular energy metabolism despite incompetent proliferation and osteogenic commitment. Further exploration revealed that impairment of Rho GTPase signaling upregulated the level of branched-chain amino acid transaminase 1 (BCAT1) that rewired cell metabolism and restricted intracellular α-ketoglutarate (αKG). Supplementation of αKG ameliorated the skeletal defect of Mettl1-deficient mice. In addition to the selective translation of metabolism-related mRNAs, we further revealed that Mettl1 knockout globally regulated translation via integrated stress response (ISR) and mammalian target of rapamycin complex 1 (mTORC1) signaling. Restoring translation by targeting either ISR or mTORC1 aggravated bone defects of Mettl1-deficient mice. Overall, our study unveils a critical role of m7G tRNA modification in bone development by regulation of cellular metabolism and indicates suspension of translation initiation as a quality control mechanism in response to tRNA dysregulation.

Differences in Bone Metabolism between Children with Prader-Willi Syndrome during Growth Hormone Treatment and Healthy Subjects: A Pilot Study.

Despite therapy with growth hormone (GH) in children with Prader-Willi syndrome (PWS), low bone mineral density and various orthopedic deformities have been observed often. Therefore, this study aimed to analyze bone markers, with an emphasis on vitamin K-dependent proteins (VKDPs), in normal-weight children with PWS undergoing GH therapy and a low-energy dietary intervention. Twenty-four children with PWS and 30 healthy children of the same age were included. Serum concentrations of bone alkaline phosphatase (BALP), osteocalcin (OC), carboxylated-OC (Gla-OC), undercarboxylated-OC (Glu-OC), periostin, osteopontin, osteoprotegerin (OPG), sclerostin, C-terminal telopeptide of type I collagen (CTX-I), and insulin-like growth factor-I (IGF-I) were determined using immunoenzymatic methods. OC levels and the OC/CTX-I ratios were lower in children with PWS than in healthy children (p = 0.011, p = 0.006, respectively). Glu-OC concentrations were lower (p = 0.002), but Gla-OC and periostin concentrations were higher in patients with PWS compared with the controls (p = 0.005, p < 0.001, respectively). The relationships between IGF-I and OC (p = 0.013), Gla-OC (p = 0.042), and the OC/CTX-I ratio (p = 0.017) were significant after adjusting for age in children with PWS. Bone turnover disorders in children with PWS may result from impaired bone formation due to the lower concentrations of OC and the OC/CTX-I ratio. The altered profile of OC forms with elevated periostin concentrations may indicate more intensive carboxylation processes of VKDPs in these patients. The detailed relationships between the GH/IGF-I axis and bone metabolism markers, particularly VKDPs, in children with PWS requires further research.

Analysis of PANoptosis-related ceRNA network reveals lncRNA MIR17HG involved in osteogenic differentiation inhibition impaired by tumor necrosis factor-α

BackgroundInflammatory cytokines such as Interleukin 1β(IL1β), IL6,Tumor Necrosis Factor-α (TNF-α) can inhibit osteoblast differentiation and induce osteoblast apoptosis. PANoptosis, a newly identified type of programmed cell death (PCD), may be influenced by long noncoding RNA (lncRNAs) which play important roles in regulating inflammation. However, the potential role of lncRNAs in inflammation and PANoptosis during osteogenic differentiation remains unclear. This study aimed to investigate the regulatory functions of lncRNAs in inflammation and apoptosis during osteogenic differentiation.Methods and resultsHigh-throughput sequencing was used to identify differentially expressed genes involved in osteoblast differentiation under inflammatory conditions. Two lncRNAs associated with inflammation and PANoptosis during osteogenic differentiation were identified from sequencing data and Gene Expression Omnibus (GEO) databases. Their functionalities were analyzed using diverse bioinformatics methodologies, resulting in the construction of the lncRNA-miRNA-mRNA network. Among these, lncRNA (MIR17HG) showed a high correlation with PANoptosis. Bibliometric methods were employed to collect literature data on PANoptosis, and its components were inferred. PCR and Western Blotting experiments confirmed that lncRNA MIR17HG is related to PANoptosis in osteoblasts during inflammation.ConclusionsOur data suggest that TNF-α-induced inhibition of osteogenic differentiation and PANoptosis in MC3T3-E1 osteoblasts is associated with MIR17HG. These findings highlight the critical role of MIR17HG in the interplay between inflammation, PANoptosis, and osteogenic differentiation, suggesting potential therapeutic targets for conditions involving impaired bone formation and inflammatory responses.

Indoxyl Sulfate Inhibits Osteogenesis in Bone Marrow Mesenchymal Stem Cells through the AhR/Hes1 Pathway.

Uremic toxins cause bone disorders in patients with chronic kidney disease (CKD). These disorders are characterized by low turnover osteodystrophy and impaired bone formation in the early stages of CKD. Evidence indicates that the aryl hydrocarbon receptor (AhR) mediates signals that suppress early osteogenic differentiation in bone marrow mesenchymal stem cells (BMSCs). However, whether the AhR mediates the effects of indoxyl sulfate (IS), a uremic toxin, on BMSC osteogenesis remains unclear. We investigated whether IS affects osteogenesis through the AhR/Hes1 pathway. Expression levels of osteogenesis genes (Runx2, Bmp2, Alp, and Oc), AhR, and Hes1 were measured in mouse BMSCs (D1 cells). At concentrations of 2-50 μM, IS significantly reduced mineralization, particularly in the early stages of BMSC osteogenesis. Furthermore, IS significantly downregulated the expression of Runx2, Bmp2, Oc, and Alp. Notably, this downregulation could be prevented using an AhR antagonist and through Ahr knockdown. Mechanistically, IS induced the expression of Hes1 through AhR signaling, thereby suppressing the transcription of Runx2 and Bmp2. Our findings suggest that IS inhibits early osteogenesis of BMSCs through the AhR/Hes1 pathway, thus suppressing the transcription of Runx2 and Bmp2. Our findings may guide new therapeutic strategies against CKD-related bone disorders.

P-628 The role of Anti-Müllerian Hormone (AMH) on human osteoblast differentiation

Abstract Study question May AMH, an ovarian hormone belonging to the Transforming Growth Factor β superfamily (TGF-β), represent a possible candidate for use as a bone anabolic factor? Summary answer Our findings provided interesting clues on the stimulatory effects of AMH on mature osteoblasts expressing its specific receptor, the Anti-Müllerian Hormone Type-2 receptor (AMHRII). What is known already Impaired bone formation is a principal pathogenetic mechanism mediating bone fragility in osteoporosis. Several growth factors capable of inducing bone matrix apposition by increasing the number of osteoblast precursor cells or promoting the function of mature osteoblasts have been identified, including members of the TGF-β superfamily such as BMPs. However, their clinical use is limited due to their pleiotropic extraskeletal effects. Anti-Müllerian Hormone (AMH) is a member of the TGF-β superfamily whose role in bone tissues has never been investigated. To date, AMH functions and the expression of its specific receptor are mainly limited to the reproductive organs. Study design, size, duration We performed in vitro studies on Human Osteoblasts (HOb) to evaluate the expression and the functionality of AMH receptor type-2 and investigate the effects of recombinant AMH (rhAMH) exposure on osteogenic gene expression and osteoblast functions. Participants/materials, setting, methods RT-PCR, real-time PCR and Western blotting analyses were performed in Hob cells cultured both in the presence and in the absence of 100 ng/mL rhAMH to evaluate the effect of AMH exposure on osteoblast differentiation. Alizarin red staining was performed after 14 days of treatment with 100 ng/mL rhAMH to assess the mineralized nodule formation. Main results and the role of chance Our study revealed the presence of a strong mRNA and protein expression of AMHRII in HOb cells, thus indicating that osteoblasts may represent a specific target for exogenous AMH treatment. We also observed that rhAMH exposure increased SMAD 1/5 protein levels, demonstrating that the binding of AMHRII by AMH was able to activate the SMAD-mediated AMH signalling pathway. Interestingly, we also observed that AMH treatment upregulates mRNA levels of crucial osteoblastic transcription factors such as RUNX2 and OSX and extracellular matrix proteins including OPN and OC. Consistently, the prolonged exposure to AMH also promoted matrix mineralization in HOb cells, as demonstrated by both increased ALP gene expression and the greater amount of mineralized nodules observed in AMH-treated osteoblasts compared to untreated controls. Limitations, reasons for caution The study was conducted only in HOb cells. Additional functional studies are needed to investigate the action mechanism of AMH in the other bone cells to understand the mechanisms by which AMH may influence bone homeostasis and pave the way for subsequent in vivo studies. Wider implications of the findings This study may have translation value in opening the perspective that AMH may be an effective candidate to counteract bone loss in osteoporotic patients by developing a new therapy selectively targeting osteoblast with minimal off-target effect. Trial registration number Not Applicable

METTL3 Modulates Ctsk+ Lineage Supporting Cranial Osteogenesis via Hedgehog

N6-methyladenosine (m6A) modification, a eukaryotic messenger RNA modification catalyzed by methyltransferase-like 3 (METTL3), plays a pivotal role in stem cell fate determination. Calvarial bone development and maintenance are orchestrated by the cranial sutures. Cathepsin K (CTSK)–positive calvarial stem cells (CSCs) contribute to mice calvarial ossification. However, the role of m6A modification in regulating Ctsk+ lineage cells during calvarial development remains elusive. Here, we showed that METTL3 was colocalized with cranial nonosteoclastic Ctsk+ lineage cells, which were also associated with GLI1 expression. During neonatal development, depletion of Mettl3 in the Ctsk+ lineage cells delayed suture formation and decreased mineralization. During adulthood maintenance, loss of Mettl3 in the Ctsk+ lineage cells impaired calvarial bone formation, which was featured by the increased bone porosity, enhanced bone marrow cavity, and decreased number of osteocytes with the less-developed cellular outline. The analysis of methylated RNA immunoprecipitation sequencing and RNA sequencing data indicated that loss of METTL3 reduced Hedgehog (Hh) signaling pathway. Restoration of Hh signaling pathway by crossing Sufufl/+ alleles or by local administration of SAG21 partially rescued the abnormity. Our data indicate that METTL3 modulates Ctsk+ lineage cells supporting calvarial bone formation by regulating the Hh signaling pathway, providing new insights for clinical treatment of skull vault osseous diseases.

Osteochondroprogenitor cells and neutrophils expressing p21 and senescence markers modulate fracture repair.

Cells expressing features of senescence, including upregulation of p21 and p16, appear transiently following tissue injury, yet the properties of these cells or how they contrast with age-induced senescent cells remains unclear. Here, we used skeletal injury as a model and identified the rapid appearance following fracture of p21+ cells expressing senescence markers, mainly as osteochondroprogenitors (OCHs) and neutrophils. Targeted genetic clearance of p21+ cells suppressed senescence-associated signatures within the fracture callus and accelerated fracture healing. By contrast, p21+ cell clearance did not alter bone loss due to aging; conversely, p16+ cell clearance, known to alleviate skeletal aging, did not affect fracture healing. Following fracture, p21+ neutrophils were enriched in signaling pathways known to induce paracrine stromal senescence, while p21+ OCHs were highly enriched in senescence-associated secretory phenotype factors known to impair bone formation. Further analysis revealed an injury-specific stem cell-like OCH subset that was p21+ and highly inflammatory, with a similar inflammatory mesenchymal population (fibro-adipogenic progenitors) evident following muscle injury. Thus, intercommunicating senescent-like neutrophils and mesenchymal progenitor cells were key regulators of tissue repair in bone and potentially across tissues. Moreover, our findings established contextual roles of p21+ versus p16+ senescent/senescent-like cells that may be leveraged for therapeutic opportunities.

Astaxanthin-mediated Nrf2 activation ameliorates glucocorticoid-induced oxidative stress and mitochondrial dysfunction and impaired bone formation of glucocorticoid-induced osteonecrosis of the femoral head in rats

BackgroundOsteonecrosis of the femoral head caused by glucocorticoids (GIONFH) is a significant issue resulting from prolonged or excessive clinical glucocorticoid use. Astaxanthin, an orange-red carotenoid present in marine organisms, has been the focus of this study to explore its impact and mechanism on osteoblast apoptosis induced by dexamethasone (Dex) and GIONFH.MethodsIn this experiment, bioinformatic prediction, molecular docking and dynamics simulation, cytotoxicity assay, osteogenic differentiation, qRT-PCR analysis, terminal uridine nickend labeling (TUNEL) assay, determination of intracellular ROS, mitochondrial function assay, immunofluorescence, GIONFH rat model construction, micro-computed tomography (micro-CT) scans were performed.ResultsOur research demonstrated that a low dose of astaxanthin was non-toxic to healthy osteoblasts and restored the osteogenic function of Dex-treated osteoblasts by reducing oxidative stress, mitochondrial dysfunction, and apoptosis. Furthermore, astaxanthin rescued the dysfunction in poor bone quality, bone metabolism and angiogenesis of GIONFH rats. The mechanism behind this involves astaxanthin counteracting Dex-induced osteogenic damage by activating the Nrf2 pathway.ConclusionAstaxanthin shields osteoblasts from glucocorticoid-induced oxidative stress and mitochondrial dysfunction via Nrf2 pathway activation, making it a potential therapeutic agent for GIONFH treatment.

Investigating Novel Therapeutic Approaches for Idiopathic Short Stature: Targeting siRNA and Growth Hormone Delivery to the Growth Plate Using Exosome Nanoparticles.

Idiopathic short stature (ISS) is a common childhood condition with largely unknown underlying causes. Recent research highlights the role of circulating exosomes in the pathogenesis of various disorders, but their connection to ISS remains unexplored. In the experiments, human chondrocytes are cocultured with plasma exosomes from ISS patients, leading to impaired chondrocyte growth and bone formation. Elevated levels of a specific long non-coding RNA (lncRNA), ISSRL, are identified as a distinguishing factor in ISS, boasting high specificity and sensitivity. Silencing ISSRL in ISS plasma exosomes reverses the inhibition of chondrocyte proliferation and bone formation. Conversely, overexpression of ISSRL in chondrocytes impedes their growth and bone formation, revealing its mechanism of action through the miR-877-3p/GZMB axis. Subsequently, exosomes (CT-Exo-siISSRL-oeGH) with precise cartilage-targeting abilities are engineered, loaded with customized siRNA for ISSRL and growth hormone. This innovative approach offers a therapeutic strategy to address ISS by rectifying abnormal non-coding RNA expression in growth plate cartilage and delivering growth hormone with precision to promote bone growth. This research provides valuable insights into ISS diagnosis and treatment, highlighting the potential of engineered exosomes.

Nerve growth factor receptor limits inflammation to promote remodeling and repair of osteoarthritic joints

Osteoarthritis (OA) is a painful, incurable disease affecting over 500 million people. Recent clinical trials of the nerve growth factor (NGF) inhibitors in OA patients have suggested adverse effects of NGF inhibition on joint structure. Here we report that nerve growth factor receptor (NGFR) is upregulated in skeletal cells during OA and plays an essential role in the remodeling and repair of osteoarthritic joints. Specifically, NGFR is expressed in osteochondral cells but not in skeletal progenitor cells and induced by TNFα to attenuate NF-κB activation, maintaining proper BMP-SMAD1 signaling and suppressing RANKL expression in mice. NGFR deficiency hyper-activates NF-κB in murine osteoarthritic joints, which impairs bone formation and enhances bone resorption as exemplified by a reduction in subchondral bone and osteophytes. In human OA cartilage, NGFR is also negatively associated with NF-κB activation. Together, this study suggests a role of NGFR in limiting inflammation for repair of diseased skeletal tissues.