Search Results (541)

Microtia–atresia is a rare craniofacial malformation primarily affecting the first and second pharyngeal arches, leading to the deformity of the auricle and atresia of the external ear canal. Its etiology is heterogenous and largely unknown, including both genetic and environmental factors. The HOXA4 gene has been identified as potentially pathogenetic for microtia–atresia in three twin families. A hoxa4a mosaic knockdown zebrafish model was constructed using CRISPR/Cas9. hoxa4a was expressed in the mandible during early development in zebrafish, while the F0 mosaic knockdowns exhibited craniofacial malformations with abnormal chondrocyte morphologies. Specifically, hoxa4a knockdown reduced cranial neural crest cell proliferation while increasing apoptosis, markedly downregulating chondrogenic markers sox9a and col2a1a. Consequently, pharyngeal arch chondrocytes exhibited disorganized arrangement and morphological abnormalities, resulting in mandibular hypoplasia. Our findings provide important insights into the role of hoxa4a in zebrafish mandibular development and the pathology of microtia–atresia caused by HOXA4 gene mutations in humans. Full article

The progressive decline in immune function during aging, termed immunosenescence, is increasingly recognized as a critical driver of skeletal fragility and impaired bone regeneration. This age-associated phenomenon—driven by thymic involution, inflammaging, and the accumulation of senescent immune cells—disrupts bone homeostasis primarily through the establishment of a pro-inflammatory milieu, wherein senescence-associated secretory phenotype (SASP) factors directly reprogram the function and fate of mesenchymal stem cells, osteoblasts, osteoclasts, and chondrocytes. Clinically, this immune-driven disruption of the bone microenvironment manifests across a spectrum of age-related skeletal disorders—including osteoporosis and osteoarthritis as prototypes of systemic and local bone loss, respectively, as well as delayed fracture healing, intervertebral disc degeneration, and periodontitis as paradigms of impaired regenerative and defensive responses. Despite advances in osteoimmunology revealing bidirectional immune-bone interactions, the mechanistic links between senescent immune cells and bone pathophysiology remain incompletely defined, presenting a significant barrier to therapeutic innovation. Herein, we synthesize current evidence to elucidate how immunosenescence, through the dysfunction of both innate and adaptive immunity, progressively dismantles bone homeostasis. We critically evaluate current challenges in dissecting the relative contributions of immunological memory accumulation versus fundamental aging processes to skeletal decline. We identify key knowledge gaps and propose strategic research directions, including longitudinal human immunophenotyping studies and innovative organoid-immune aging models. Such approaches hold the potential to transform the therapeutic landscape of age-related skeletal diseases by enabling precision interventions that target specific immunosenescence pathways to rejuvenate the aging skeleton. Full article

Most high-tech drugs and tissue engineering products based on human chondrocytes currently available on the market are aimed at restoring traumatic damage to cartilage tissue. However, in the presence of inflammation, their regenerative potential is significantly reduced, which limits their use in patients with osteoarthritis—one of the most common degenerative and inflammatory joint pathologies. The central element of the pathogenesis of osteoarthritis is inflammation—not classical acute inflammation, but rather chronic low-grade inflammation, primarily mediated by mechanisms of the innate immune response. Therefore, a key challenge is to enhance the anti-inflammatory effectiveness of cell-based drugs to broaden their indications to include degenerative diseases such as osteoarthritis and arthrosis. In recent years, cell-based drugs using stem cells, including mesenchymal stem cells (MSCs), hematopoietic stem cells (HSCs), and stromal vascular fraction (SVF) cells, have been actively studied. Despite their confirmed safety in inflammatory processes, meta-analyses of clinical trials show limited effectiveness in improving symptoms and MRI data in the treatment of osteoarthritis. A promising direction appears to be the development of combined cell-based drugs that combine MSCs with M2-polarized macrophages; however, data on their clinical effectiveness are still insufficient. This review explores key cellular effectors of inflammation and its molecular mechanisms, potential strategies for creating tissue engineering products that possess not only regenerative but also pronounced anti-inflammatory effects. The development of such products will expand their application in the treatment of inflammatory-degenerative joint diseases. Full article

Shear stress is a significant consideration in 3D bioprinting systems, with implications for cell viability and behaviour. This study hypothesised that relevant levels of shear stress would be generated during the process of 3D bioprinting human nasoseptal chondrocytes in a nanocellulose alginate bioink, with implications for cell viability and chondrogenic gene expression. Through a combined approach of in silico modelling and in vitro testing, we assessed chondrocyte viability and gene expression immediately within the first 72 h post-printing. Cell viability was determined using live–dead, alamarBlue and lactate dehydrogenase assays immediately and 24 h post-printing compared to cell-only and unprinted cell–biomaterial controls. Gene expression analysis of Type 2 collagen, SOX9, aggrecan and alkaline phosphatase gene expression was performed 4 h and 72 h post-printing. Computational fluid dynamics predicted a shear stress of 292 Pa and maximum fluid velocity of 19 mm/s during the bioprinting process. No statistically significant cell death or cell lysis was detected between groups immediately post-printing; however, statistically significant chondrocyte cell death was observed at 24 h in the printed group (p = 0.047). Moreover, the bioprinting process evoked a transient initial rise in both chondrogenic (SOX9, aggrecan) and osteogenic gene expression (ALP) with a marked suppression in type 2 collagen expression at 72 h (0.05, p = 0.0005), indicating biological effects evoked by shear stress during printing. This study highlights the importance of optimising the bioprinting process to facilitate low shear stress conditions for durable cartilage tissue engineering. Full article

Hyaluronic acid (HA) is widely used in medical, cosmetic, and nutraceutical applications, yet the systemic fate of orally administered HA, particularly non-animal forms, remains poorly characterised. This study investigates the stability, absorption, metabolism, and biological effects of a novel fungal-derived HA extracted from Tremella fuciformis using a sequential in vitro multi-barrier model simulating human physiological compartments, including gastric, intestinal, hepatic, renal, chondrocyte, and keratinocyte environments. Across the gastrointestinal stages, fungal-derived HA demonstrated high structural stability, maintained molecular weight, and exerted superior antioxidant and anti-inflammatory activity compared with sodium hyaluronate. It efficiently crossed the intestinal barrier without increasing hyaluronidase activity, indicating protection from premature enzymatic degradation. In hepatic cells, fungal-derived HA exhibited reduced intracellular uptake and greater extracellular persistence, suggesting lower first-pass metabolism and suggesting improved persistence under in vitro conditions. At peripheral targets, it increased the cluster of differentiation 44 (CD44) expression and HA internalisation in chondrocytes and keratinocytes, supporting anti-inflammatory and pro-regenerative effects. Renal assessments revealed minimal excretion and no cytotoxicity, supporting potential systemic availability. Overall, these results provide the first integrated in vitro evidence describing the absorption, distribution, metabolism, and excretion process of fungal-derived HA. This supports the conclusion that this form of HA is stable, biocompatible, and bioactive with therapeutic potential for joint and skin health, as suggested by the in vitro models. Full article

Background/Objectives: SETD2 is a dual-function methyltransferase important for methylation of histone H3 at lysine 36 and α-tubulin in spindle microtubules. Genetic inactivation of SETD2 during oncogenesis drives loss of H3K36me3, genomic instability, and cancer progression. This study asked if disruption of genomic stability was a canonical feature of SETD2 inactivation via different pathways. Methods: We evaluated the impact of EPZ-719, a pharmacologic SETD2 inhibitor, and an H3.3K36M mutant histone (“oncohistone”) that binds and sequesters SETD2, on methylation activity and genomic stability in human cell lines. SETD2 activity was measured using in vitro methylation assays, H3K36me3 loss confirmed by Western analysis, and mitotic defects, specifically micronuclei and chromatin bridges, quantified with cytogenetic analysis. Results: EPZ-719 caused a dose- and time-dependent reduction in SETD2 activity on both histone and tubulin substrates, accompanied by significant increases in chromatin bridges and micronuclei in retinal pigmented epithelial (RPE-1) and 786-O ccRCC cells. Similarly, oncohistone expression markedly decreased SETD2 function, as determined by H3K36me3 levels, and induced comparable mitotic defects in 786-O cells, and aneuploidy in two chondrocyte cell lines expressing the H3.3K36M oncohistone. Combining EPZ-719 with H3.3K36M expression did not exacerbate mitotic defects beyond either oncohistone or pharmacologic inhibition alone, consistent with inhibition of SETD2 as their shared underlying mechanism of action. Conclusions: Pharmacologic inhibition and oncohistone-mediated sequestration of SETD2 converge on the induction of mitotic defects, underscoring SETD2’s essential role in maintaining genomic stability. Identification of loss of genomic stability as a canonical feature of SETD2 inactivation points to a potential therapeutic liability associated with targeting SETD2 in cancers where it is overexpressed and reveals a mechanism that could contribute to the progression of cancers expressing oncohistone mutations. Full article

Type II collagen (CII), the major structural protein in the cartilage extracellular matrix, is a promising biomaterial for scaffold design in cartilage tissue engineering. In this study, high-purity CII was successfully extracted from bovine cartilage, an abundant by-product of cattle slaughter, and its amino acid composition, triple-helical conformation, and thermal stability were verified. CII was subsequently combined with silk fibroin (SF) and chitosan (CS) to fabricate three-dimensional (3D) porous scaffolds via freeze-drying. The pore structure, porosity, swelling behavior, mechanical properties and in vitro degradation characteristics were systematically evaluated. Scaffolds with favorable structural integrity, mechanical performance, and degradation rates were further evaluated biologically using human primary chondrocytes. All CII-based composite scaffolds supported chondrocyte growth and promoted early extracellular matrix deposition. Notably, the scaffold with a CII:SF:CS ratio of 7:3:1 showed the highest GAG/DNA content, accompanied by upregulated gene expression related to the cartilage phenotype (COL2A1, ACAN, and SOX9) and reduced expression of the dedifferentiation marker COL1A1, indicating improved phenotype maintenance. Overall, within the tested range, CII70 (CII:SF:CS = 7:3:1) represents a practical compromise between scaffold stability and in vitro chondrocyte-related outcomes, providing a basis for selecting CII/SF/CS formulations for cartilage tissue engineering. Full article

Knee osteoarthritis (KOA) is a chronic degenerative joint disorder driven largely by persistent inflammation and progressive cartilage damage. Naringin, a bioactive flavonoid abundant in citrus fruits, has shown potential anti-inflammatory effects; however, its molecular mechanisms in KOA remain unclear. In this study, an integrated approach combining network pharmacology, molecular docking, molecular dynamics (MD) simulations, and in vitro experiments was employed to investigate the anti-inflammatory effects of naringin in KOA. Network pharmacology analysis identified 59 potential KOA-related targets of naringin, among which TNF, PTGS2, TP53, CASP3, and PPARG were recognized as core targets. Functional enrichment indicated these targets were primarily associated with inflammation- and apoptosis-related pathways, especially the TNF and IL-17 signaling pathways. Molecular docking and MD simulations revealed strong binding affinity and stable interactions between naringin and the key inflammatory mediators TNF-α and PTGS2. In an IL-1β-stimulated C28/I2 human chondrocyte model, naringin dose-dependently improved cell viability and significantly suppressed TNF-α and PTGS2 expression at both mRNA and protein levels. These findings provide mechanistic evidence that naringin alleviates KOA-associated chondrocyte inflammation by modulating key inflammatory mediators, supporting its potential as an anti-inflammatory therapeutic candidate for KOA. Full article

Glucocorticoids are widely applied intra-articularly to alleviate inflammation and pain in osteoarthritis (OA). However, repeated administration and high local concentrations can lead to crystal deposition on the cartilage surface, contributing to chondrocyte damage and extracellular matrix (ECM) degradation, potentially accelerating OA progression. Calcium-dependent mechanosensors play a critical role in mediating catabolic responses in chondrocytes, but it remains unclear whether glucocorticoids affect chondrocyte mechanosensitivity or biomechanical properties. This in vitro study examined the dose-dependent effects of triamcinolone acetonide (TA) on chondrocyte biomechanics and mechanosensitivity. Primary human chondrocytes (N = 23) were cultured for one week with TA (2 µM–2 mM) or control medium. Cytoskeletal organization was visualized by F-actin staining (N = 6), and cellular elasticity (N = 5) was quantified via atomic force microscopy (AFM). Mechanotransduction was analyzed by Ca²⁺ imaging (Fluo-4 AM) upon AFM-based indentation (500 nN). Expression of matrix-related and mechanosensitive genes (N = 9) was assessed by qPCR. TA exposure induced a concentration-dependent reorganization of the F-actin cytoskeleton, pronounced at 0.2 mM, accompanied by a significant increase in the elastic modulus (p < 0.001). TA further augmented Ca²⁺ fluorescence intensity under basal conditions and during mechanical stimulation. Blocking cationic mechanosensitive channels with GsMtx4 (N = 3) markedly reduced the TA-evoked Ca²⁺ influx (p < 0.0001). Significant reduction in MMP1 was observed on the transcriptional level (N = 9) after TA-treatment (p < 0.05). In summary, TA enhances chondrocyte stiffness through cytoskeletal condensation and amplifies Ca²⁺-dependent mechanotransduction but reduces MMP1 expression, indicating a dual biomechanical response of chondrocytes to OA under exposure of potent corticosteroid. Full article

Joint acidosis is increasingly recognized as an important determinant of cellular behavior in osteoarthritis (OA). Declines in extracellular pH (pHe) occur across cartilage, meniscus, synovium, and subchondral bone, where they influence inflammation, matrix turnover, and pain. Among proton-sensing G protein-coupled receptors, GPR68 responds to the acidic pH range characteristic of human OA joints. The receptor is activated between pH 6.8 and 7.0, couples to Gq/PLC-MAPK, cAMP-CREB, G12/13-RhoA-ROCK signaling pathways, and is expressed most prominently in articular cartilage, with additional expression reported in synovium, bone, vasculature, and some neuronal populations. These pathways regulate transcriptional programs relevant to cartilage stress responses, inflammation, and matrix turnover. GPR68 expression is increased in human OA cartilage and aligns with regions of active matrix turnover. We previously reported that pharmacologic activation of GPR68 suppresses IL1β-induced MMP13 expression in human chondrocytes under acidic conditions, indicating that increased GPR68 expression may represent a microenvironment-responsive, potentially adaptive signaling response rather than a driver of cartilage degeneration. Evidence from intestinal, stromal, and vascular models demonstrates that GPR68 integrates pH changes with inflammatory and mechanical cues, providing mechanistic context, although these effects have not been directly established in most joint tissues. Small-molecule modulators, including the positive allosteric agonist Ogerin and the inhibitor Ogremorphin, illustrate the tractability of GPR68 as a drug target, although no GPR68-directed therapies have yet been evaluated in preclinical models of OA. Collectively, current data support GPR68 as a functionally relevant proton sensor within the acidic OA joint microenvironment. Full article

Osteoarthritis (OA) is a degenerative joint disease characterized by progressive cartilage loss, extracellular matrix degradation, chondrocyte apoptosis, and elevated inflammatory mediators. Chondrocytes respond to IL-1β and other inflammatory signals by secreting cytokines and activating transcriptional pathways that perpetuate inflammation. Because current therapies do not prevent OA progression, bioactive compounds with cytoprotective and immunomodulatory activity are of considerable interest. Lonomia obliqua bristle extract (LOCBE) and its recombinant proteins rLOPAP and rLOSAC exhibit cytoprotective, proliferative, and antioxidant effects in mammalian cells, as well as the ability to influence cytoskeletal dynamics. Given the importance of Rac-1, RhoA, Rab9, and β-catenin in chondrocyte function and cartilage homeostasis, we evaluated LOCBE, rLOPAP, and rLOSAC in human chondrocytes stimulated or not with IL-1β. LOCBE and rLOPAP induced IL-6 and IL-8 secretion, although at lower levels than IL-1β. LOCBE exerts a cytoprotective effect in IL-1β-treated chondrocytes and reduces β-catenin, RhoA, and Rab9 expression without affecting NF-κB p65 translocation. rLOPAP increased mitochondrial activity, cytokine secretion, Rab9 expression, and membrane-associated β-catenin, and under inflammatory conditions, enhanced Rac-1 levels. In contrast, rLOSAC did not induce inflammatory cytokines and decreased RhoA and Rac-1 expression while increasing membrane-associated β-catenin. These findings suggest that L. obliqua extract and its derived-proteins rLOPAP and rLOSAC modulate cytoskeletal regulatory pathways and inflammatory responses in chondrocytes, supporting their potential as therapeutic leads for targeting mechanisms relevant to OA progression. Full article

Human umbilical cord-derived mesenchymal stem cells (hUC-MSCs) possess the potential for chondrogenic differentiation, offering a promising alternative source for cartilage regeneration. To address the limited availability and expansion capacity of autologous chondrocytes, we investigated the effect of co-overexpression of Sox9, TGFβ1, and type II collagen (Col II) on the chondrogenic differentiation of hUC-MSCs using both 2D and 3D pellet culture systems. Following transfection, the cells exhibited a chondrocyte-like morphology and a marked downregulation of the stemness marker Stro-1. After 21 days in a 3D pellet culture system, the cells formed cartilage-like tissue characterized by the strong expression of chondrocyte-specific genes (Sox9, TGFβ1, Col II, Aggrecan) along with the significant secretion of sulfated glycosaminoglycans (sGaGs). These effects were attributed to enhanced cell–cell contact and extracellular matrix interactions promoted by the 3D environment. Our findings suggest that genetically modified hUC-MSCs cultured in a 3D pellet system represent a robust in vitro model for cartilage regeneration, with potential applications in transplantation and drug toxicity screening. Full article

Osteoarthritis (OA) is the most common multifactorial joint disease characterized by progressive cartilage degradation and impaired tissue repair. Osteochondral defects represent a major clinical challenge within OA, as damage to cartilage and underlying bone can initiate degenerative changes and contribute to joint deterioration. The Wnt/β-catenin signaling pathway plays an important role in OA pathogenesis, and its dysregulation contributes to chondrocyte catabolism and cartilage loss. NOTUM, an extracellular Wnt inhibitor, has emerged as a potential therapeutic modulator capable of restoring signaling balance and promoting cartilage homeostasis. This study aimed to evaluate the efficacy of NOTUM compared with hyaluronic acid (HA), human adipose-derived mesenchymal stromal cells (hAd-MSCs), and Colchicine in a rabbit osteochondral defect model relevant to osteoarthritis. Twenty-seven New Zealand White rabbits underwent standardized femoral condyle injury and received single-dose treatments. Serum levels of cartilage biomarkers—Procollagen Type IIA N-terminal Propeptide (PIIANP) and Cartilage Oligomeric Matrix Protein (COMP)—were measured by ELISA at 4, 6, and 8 weeks post-surgery, and histological repair at week 12 was assessed using the modified O’Driscoll scoring system. NOTUM treatment significantly increased PIIANP and decreased COMP levels compared with HA, indicating enhanced cartilage synthesis and reduced degradation. Histological scores confirmed superior surface morphology and tissue composition in NOTUM-treated joints. These findings suggest that NOTUM performs a protective and regenerative effect through Wnt/β-catenin modulation, supporting the conclusion that it enhances osteochondral defect repair and motivating further studies of NOTUM as an OA therapy. Full article

Background: Osteoarthritis (OA) is a prevalent degenerative joint disease often causing functional disability. Current therapies provide only temporary relief and can cause adverse effects that frequently result in pain and disability. Current pharmacological options offer only temporary symptom relief and may cause adverse effects. Piper sarmentosum (PS), a plant traditionally used for its medicinal properties, has demonstrated antioxidant and anti-inflammatory activities that may counteract OA-related degeneration. This study provides preliminary insight into the therapeutic potential of PS aqueous extract in human OA chondrocytes. Methods: Compounds in the PS aqueous extract were profiled using liquid chromatography–tandem mass spectrometry (LC-MS/MS). Primary human OA chondrocytes (HOCs) were treated with 0.5, 2, and 4 µg/mL of PS aqueous extract for 72 h. Key OA-related parameters were assessed, including anabolic markers (sulfated glycosaminoglycan (sGAG), collagen type II (COL II), aggrecan core protein (ACP), SRY-box transcription factor 9 (SOX9)), catabolic markers (matrix metalloproteinase (MMP) 1, MMP13, cyclooxygenase 2 (COX2)), oxidative stress (nitric oxide (NO) production, inducible NO synthase (iNOS) expression), and inflammatory responses (interleukin (IL) 6). Gene expression was quantified using qPCR, and protein levels were evaluated using the colorimetric method, immunocytochemistry, and Western blot. Results: A total of 101 compounds were identified in the extract, including vitexin, pterostilbene, and glutathione—bioactives known for antioxidant, anti-inflammatory, and chondroprotective functions. PS-treated chondrocytes maintain healthy polygonal morphology. PS aqueous extract significantly enhanced anabolic gene expression (COL2A1, ACP, SOX9) and sGAG production, while concurrently suppressing COX2 expression and NO synthesis. Additionally, PS aqueous extract reduced COX2 and iNOS protein levels, indicating inhibition of the NO signaling pathway. Catabolic activity was attenuated, and inflammatory responses were partially reduced. Conclusions: PS aqueous extract exhibits promising chondroprotective, antioxidant, and anti-inflammatory effects in human OA chondrocytes, largely through the suppression of NO-mediated catabolic signaling. The presence of multiple bioactive compounds supports its mechanistic potential. These findings highlight PS aqueous extract as a potential therapeutic candidate for OA management. Further ex vivo and in vivo studies are warranted to validate its efficacy and clarify its mechanism in joint-tissue environments. Full article

Osteoarthritis (OA) is a progressive joint disorder affecting over 250 million people globally and is characterized by chronic pain and disability. Among its key pathogenic mechanisms are mitochondrial dysfunction and elevated reactive oxygen species (ROS), often triggered by inflammatory mediators such as lipopolysaccharide (LPS). This study evaluates the protective effects of curcumin on mitochondrial function, autophagy, and apoptosis in an in vitro model of OA. Human bone marrow-derived mesenchymal stem cells (BMSCs) were differentiated into chondrocytes using MesenCult™-ACF medium. Differentiation was confirmed by histological staining for Type II Collagen, Alcian Blue, and Toluidine Blue. LPS was used to induce an OA-like inflammatory response. Mitochondrial membrane potential (ΔΨm) was assessed using Rhodamine 123 staining. Autophagy and apoptosis were evaluated using Acridine orange and propidium iodide staining, respectively. Western blotting was performed to analyze the expression of pro-caspase-3, Bcl-2, Beclin-1, LC3-I/II, and GAPDH. LPS significantly impaired mitochondrial function, limited autophagy, and enhanced apoptotic signaling (reduced pro-caspase-3). Curcumin (25 µM and 100 µM) restored ΔΨm, increased Beclin-1 and LC3-II, and maintained pro-caspase-3 expression, with Bcl-2 showing a non-monotonic response (higher at 25 µM than at 100 µM). Curcumin exerted cytoprotective effects in inflamed chondrocytes by stabilizing ΔΨm, promoting autophagy, and attenuating apoptotic activation, supporting its multi-target therapeutic potential in OA. Full article