Cartilage Of Mice Research Articles

Effect Of XBP1 Deficiency In Cartilage On The Regulatory Network Of LncRNA/circRNA-miRNA-mRNA.

X-box binding protein 1(XBP1) is a critical component for unfolded protein response (UPR) in ER stress. According to previous studies performed with different XBP1-deficient mice, the XBP1 gene affects mouse cartilage development and causes other related diseases. However, how the complete transcriptome, including mRNA and ncRNAs, affects the function of cartilage and other tissues when XBP1 is deficient in chondrocytes is unclear. In this study, we aimed to screen the differentially expressed (DE) mRNAs, circRNAs, lncRNAs and miRNAs in XBP1 cartilage-specific knockout (CKO) mice using high throughput sequencing and construct the circRNA-miRNA-mRNA and lncRNA-miRNA-mRNA regulatory networks. DE LncRNAs (DE-LncRNAs), circRNAs (DE-circRNAs), miRNAs (DE-miRNAs), and mRNAs [differentially expressed genes (DEGs)] between the cartilage tissue of XBP1 CKO mice and controls were identified, including 441 DE-LncRNAs, 15 DE-circRNAs, 6 DE-miRNAs, and 477 DEGs. Further, 253,235 lncRNA-miRNA-mRNA networks and 1,822 circRNA-miRNA-mRNA networks were constructed based on the correlation between lncRNAs/circRNAs, miRNAs, mRNAs. The whole transcriptome analysis revealed that XBP1 deficiency in cartilage affects the function of cartilage and other different tissues, as well as associated diseases. Overall, our findings may provide potential biomarkers and mechanisms for the diagnosis and treatment of cartilage and other related diseases.

Role of Ciliary Protein Intraflagellar Transport Protein 88 in the Regulation of Cartilage Thickness and Osteoarthritis Development in Mice.

Mechanical and biologic cues drive cellular signaling in cartilage development, health, and disease. Primary cilia proteins, which are implicated in the transduction of biologic and physiochemical signals, control cartilage formation during skeletal development. This study was undertaken to assess the influence of the ciliary protein intraflagellar transport protein 88 (IFT88) on postnatal cartilage from mice with conditional knockout of the Ift88 gene (Ift88-KO). Ift88fl/fl and aggrecanCreERT2 mice were crossed to create a strain of cartilage-specific Ift88-KO mice (aggrecanCreERT2 ;Ift88fl/fl ). In these Ift88-KO mice and Ift88fl/fl control mice, tibial articular cartilage thickness was assessed by histomorphometry, and the integrity of the cartilage was assessed using Osteoarthritis Research Society International (OARSI) damage scores, from adolescence through adulthood. In situ mechanisms of cartilage damage were investigated in the microdissected cartilage sections using immunohistochemistry, RNAScope analysis, and quantitative polymerase chain reaction. Osteoarthritis (OA) was induced in aggrecanCreERT2 ;Ift88fl/fl mice and Ift88fl/fl control mice using surgical destabilization of the medial meniscus (DMM). Following tamoxifen injection and DMM surgery, the mice were given free access to exercise on a wheel. Deletion of Ift88 resulted in progressive reduction in the thickness of the medial tibial cartilage in adolescent mice, as well as marked atrophy of the cartilage in mice during adulthood. In aggrecanCreERT2 ;Ift88fl/fl mice at age 34 weeks, the median thickness of the medial tibial cartilage was 89.42 μm (95% confidence interval [95% CI] 84.00-93.49), whereas in Ift88fl/fl controls at the same age, the median cartilage thickness was 104.00 μm (95% CI 100.30-110.50; P < 0.0001). At all time points, the median thickness of the calcified cartilage was reduced. In some mice, atrophy of the medial tibial cartilage was associated with complete, spontaneous degradation of the cartilage. Following DMM, aggrecanCreERT2 ;Ift88fl/fl mice were found to have increased OARSI scores of cartilage damage. In articular cartilage from maturing mice, atrophy was not associated with obvious increases in aggrecanase-mediated destruction or chondrocyte hypertrophy. Of the 44 candidate genes analyzed, only Tcf7l2 expression levels correlated with Ift88 expression levels in the microdissected cartilage. However, RNAScope analysis revealed that increased hedgehog (Hh) signaling (as indicated by increased expression of Gli1) was associated with the reductions in Ift88 expression in the tibial cartilage from Ift88-deficient mice. Wheel exercise restored both the articular cartilage thickness and levels of Hh signaling in these mice. Our results in a mouse model of OA demonstrate that IFT88 performs a chondroprotective role in articular cartilage by controlling the calcification of cartilage via maintenance of a threshold of Hh signaling during physiologic loading.

Tert-butylhydroquinone attenuates osteoarthritis by protecting chondrocytes and inhibiting macrophage polarization.

AimsTert-butylhydroquinone (tBHQ) has been identified as an inhibitor of oxidative stress-induced injury and apoptosis in human neural stem cells. However, the role of tBHQ in osteoarthritis (OA) is unclear. This study was carried out to investigate the role of tBHQ in OA.MethodsOA animal model was induced by destabilization of the medial meniscus (DMM). Different concentrations of tBHQ (25 and 50 mg/kg) were intraperitoneally injected in ten-week-old female mice. Chondrocytes were isolated from articular cartilage of mice and treated with 5 ng/ml lipopolysaccharide (LPS) or 10 ng/ml interleukin 1 beta (IL-1β) for 24 hours, and then treated with different concentrations of tBHQ (10, 20, and 40 μM) for 12 hours. The expression levels of malondialdehyde (MDA) and superoxide dismutase (SOD) in blood were measured. The expression levels of interleukin 6 (IL-6), IL-1β, and tumour necrosis factor alpha (TNF-α) leptin in plasma were measured using enzyme-linked immunoabsorbent assay (ELISA) kits. The expression of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) and mitogen-activated protein kinase (MAPK) signalling pathway proteins, and macrophage repolarization-related markers, were detected by western blot.ResultsTert-butylhydroquinone significantly attenuated cartilage destruction in DMM-induced mice in vivo. It demonstrated clear evidence of inhibiting IL-1β-induced chondrocyte apoptosis, inflammation, and differentiation defect in vitro. Meanwhile, tBHQ inhibited LPS-induced activation of NF-κB and MAPK signalling pathways, and also inhibited LPS-induced reactive oxygen species production and macrophages repolarization in vitro.ConclusionTaken together, tBHQ might be a potential therapeutic strategy for protecting against OA development.Cite this article: Bone Joint Res 2021;10(11):704–713.

Non-invasive monitoring of arthritis treatment response via targeting of tyrosine-phosphorylated annexin A2 in chondrocytes

BackgroundThe development and optimization of therapies for rheumatoid arthritis (RA) is currently hindered by a lack of methods for early non-invasive monitoring of treatment response. Annexin A2, an inflammation-associated protein whose presence and phosphorylation levels are upregulated in RA, represents a potential molecular target for tracking RA treatment response.MethodsLS301, a near-infrared dye-peptide conjugate that selectively targets tyrosine 23-phosphorylated annexin A2 (pANXA2), was evaluated for its utility in monitoring disease progression, remission, and early response to drug treatment in mouse models of RA by fluorescence imaging. The intraarticular distribution and localization of LS301 relative to pANXA2 was determined by histological and immunohistochemical methods.ResultsIn mouse models of spontaneous and serum transfer-induced inflammatory arthritis, intravenously administered LS301 showed selective accumulation in regions of joint pathology including paws, ankles, and knees with positive correlation between fluorescent signal and disease severity by clinical scoring. Whole-body near-infrared imaging with LS301 allowed tracking of spontaneous disease remission and the therapeutic response after dexamethasone treatment. Histological analysis showed preferential accumulation of LS301 within the chondrocytes and articular cartilage in arthritic mice, and colocalization was observed between LS301 and pANXA2 in the joint tissue.ConclusionsWe demonstrate that fluorescence imaging with LS301 can be used to monitor the progression, remission, and early response to drug treatment in mouse models of RA. Given the ease of detecting LS301 with portable optical imaging devices, the agent may become a useful early treatment response reporter for arthritis diagnosis and drug evaluation.

Pharmacological characterization of GLPG1972/S201086, a potent and selective small-molecule inhibitor of ADAMTS5

A disintegrin and metalloproteinase with thrombospondin motifs 5 (ADAMTS5) is a key enzyme in degradation of cartilage in osteoarthritis (OA). We report the pharmacological characterization of GLPG1972/S201086, a new, potent and selective small-molecule ADAMTS5 inhibitor. Potency and selectivity of GLPG1972/S201086 for ADAMTS5 were determined using fluorescently labeled peptide substrates. Inhibitory effects of GLPG1972/S201086 on interleukin-1α-stimulated glycosaminoglycan release in mouse femoral head cartilage explants and on interleukin-1β-stimulated release of an ADAMTS5-derived aggrecan neoepitope (quantified with ELISA) in human articular cartilage explants were determined. In the destabilization of the medial meniscus (DMM) mouse and menisectomized (MNX) rat models, effects of oral GLPG1972/S201086 on relevant OA histological and histomorphometric parameters were evaluated. GLPG1972/S201086 inhibited human and rat ADAMTS5 (IC50±SD: 19±2nM and <23±1nM, respectively), with 8-fold selectivity over ADAMTS4, and 60->5,000-fold selectivity over other related proteases in humans. GLPG1972/S201086 dose-dependently inhibited cytokine-stimulated aggrenolysis in mouse and human cartilage explants (100% at 20μM and 10μM, respectively). In DMM mice, GLPG1972/S201086 (30-120mg/kg b.i.d) vs vehicle reduced femorotibial cartilage proteoglycan loss (23-37%), cartilage structural damage (23-39%) and subchondral bone sclerosis (21-36%). In MNX rats, GLPG1972/S201086 (10-50mg/kg b.i.d) vs vehicle reduced cartilage damage (OARSI score reduction, 6-23%), and decreased proteoglycan loss (∼27%) and subchondral bone sclerosis (77-110%). GLPG1972/S201086 is a potent, selective and orally available ADAMTS5 inhibitor, demonstrating significant protective efficacy on both cartilage and subchondral bone in two relevant in vivo preclinical OA models.

Cartilage tissue miR-214-3p regulates the TrkB/ShcB pathway paracrine VEGF to promote endothelial cell migration and angiogenesis.

This study was designed to explore the mechanisms through which chondrocytes regulated endothelial cell migration and angiogenesis in osteoarthritis (OA). The expressions of related genes of OA were detected by Western blot and real-time quantitative PCR. Chondrocytes were co-cultured with endothelial cells, and migration as well as angiogenesis rates, and vascular endothelial growth factor (VEGF) secretion of the cells were detected. The relationship between miRNA and TrkB were analyzed by bioinformatics analysis, RNA immunoprecipitation and dual-luciferase assays. The effects of miRNA on the histopathology of the OA mice were determined. The expressions of NGF, TrkA, TrkB, and ShcB were increased significantly in OA patients. IL-1β promoted the expressions of TrkA, TrkB, and ShcB in chondrocytes and inhibited the expressions of chondrogenic differentiation markers, but shTrkB partially reversed IL-1β-mediated chondrogenic differentiation. Overexpression of TrkB promoted cell migration, angiogenesis, and VEGF levels, while silencing ShcB reversed the regulation of TrkB. Moreover, chondrocytes miR-214-3p regulated endothelial cell migration and angiogenesis by targeting TrkB paracrine VEGF to activate PI3K/Akt pathway proteins. In addition, overexpressed miR-214-3p improved collagenase-induced cartilage and synovial damage in OA mice. The activation of TrkB/ShcB signaling pathway paracrine VEGF is mediated by miR-214-3p in chondrocytes and it regulates endothelial cell migration and angiogenesis in the development of OA.

Age-dependent changes in protein incorporation into collagen-rich tissues of mice by in vivo pulsed SILAC labelling.

Collagen-rich tissues have poor reparative capacity that predisposes to common age-related disorders such as osteoporosis and osteoarthritis. We used in vivo pulsed SILAC labelling to quantify new protein incorporation into cartilage, bone, and skin of mice across the healthy life course. We report dynamic turnover of the matrisome, the proteins of the extracellular matrix, in bone and cartilage during skeletal maturation, which was markedly reduced after skeletal maturity. Comparing young adult with older adult mice, new protein incorporation was reduced in all tissues. STRING clustering revealed changes in epigenetic modulators across all tissues, a decline in chondroprotective growth factors such as FGF2 and TGFβ in cartilage, and clusters indicating mitochondrial dysregulation and reduced collagen synthesis in bone. Several pathways were implicated in age-related disease. Fewer changes were observed for skin. This methodology provides dynamic protein data at a tissue level, uncovering age-related molecular changes that may predispose to disease.

Asporin regulated by miR-26b-5p mediates chondrocyte senescence and exacerbates osteoarthritis progression via TGF-β1/Smad2 pathway.

This study aimed to investigate the role and mechanism of asporin in modulating chondrocyte senescence in OA pathology. Asporin and senescence-related hallmark expression were examined in human and experimental OA mouse cartilage samples. Twelve-week-old male C57 mice were administered with recombinant protein (rm-asporin)- or asporin-siRNA-expressing lentiviruses via intra-articular injection once a week after destabilization of the medial meniscus (DMM) surgery to induce OA. Cartilage damage was measured using the Osteoarthritis Research Society International score. Senescence-associated β-galactosidase (SA-β-Gal) staining, γH2AX, p21 and p16INK4a were analysed by immunofluorescence staining and western blot to assess the specific role of asporin in chondrocyte senescence. The TGF-β1-Smad2 signalling pathway and miR-26b-5p were further evaluated to explore the mechanism of asporin in OA. Asporin was upregulated in articular chondrocytes of OA patients and DMM mice and accompanied by accumulation of senescent cells. Asporin overexpression exaggerated OA progression, whereas silencing asporin restored chondrocyte homeostasis and deferred chondrocyte senescence, leading to markedly attenuated DMM-induced OA. Cellular and molecular analyses showed that asporin can be inhibited by miR-26b-5p, which was significantly downregulated in OA cartilage, leading to exacerbation of experimental OA partially through inhibition of TGF-β1-Smad2 signalling in chondrocytes. Our findings indicate that asporin plays an essential role in chondrocyte senescence and OA pathogenesis. Upregulated by miR-26b-5p, asporin inhibits the TGF-β1-Smad2 pathway to accelerate chondrocyte senescence and exacerbate cartilage degeneration. Targeting the miR-26b-5p-asporin-Smad2 axis may serve as a practical therapeutic strategy to delay chondrocyte senescence and OA development.

Articular cartilage regeneration by activated skeletal stem cells

Osteoarthritis (OA) is a degenerative disease resulting in irreversible, progressive destruction of articular cartilage1. The etiology of OA is complex and involves a variety of factors, including genetic predisposition, acute injury and chronic inflammation2–4. Here we investigate the ability of resident skeletal stem-cell (SSC) populations to regenerate cartilage in relation to age, a possible contributor to the development of osteoarthritis5–7. We demonstrate that aging is associated with progressive loss of SSCs and diminished chondrogenesis in the joints of both mice and humans. However, a local expansion of SSCs could still be triggered in the chondral surface of adult limb joints in mice by stimulating a regenerative response using microfracture (MF) surgery. Although MF-activated SSCs tended to form fibrous tissues, localized co-delivery of BMP2 and soluble VEGFR1 (sVEGFR1), a VEGF receptor antagonist, in a hydrogel skewed differentiation of MF-activated SSCs toward articular cartilage. These data indicate that following MF, a resident stem-cell population can be induced to generate cartilage for treatment of localized chondral disease in OA. Endogenous skeletal stem cells are recruited to form cartilage in mice when stimulated by microfracture surgery together with localized delivery of growth factors, pointing to a new approach for treating cartilage defects.

Role of osteoclast differentiation in the occurrence of osteoarthritis of temporomandibular joint.

This study aimed to explore the role of osteoclast differentiation in the occurrence of temporomandibular joint osteoarthritis (TMJOA). A mouse TMJOA model was constructed. Micro-CT was used to observe the changes in condylar bone during the development of TMJOA. Hematoxylin-eosin (HE) staining was used to observe the histological structure changes of the condyle of TMJOA mice. Tartrate resistant acid phosphatase (TRAP) staining was used to observe the presence of osteoclasts in TMJOA joint tissue. The synovial fluid of patients with TMJ-OA was collected to determine the effect on osteoclast differentiation. Micro-CT revealed that the condyle of the TMJOA group had the most obvious damage in the second and third weeks, and the shape of the condyles also changed in a beak-like manner. HE staining showed that the condyle cartilage and subchondral bone structure of TMJOA mice were disordered in the second week. TRAP tissue staining showed that the number of osteoclasts of the TMJOA group obviously increased in the second week. Results of cell experiments showed that the number of osteoclast differentiation significantly increased after stimulation of synovial fluid from TMJOA patients, and the cell volume increased. TMJOA animal models and TMJOA patient synovial cell experiments could induce osteoclast differentiation, indicating that osteoclast differentiation plays an important role in TMJOA occurrence.

The protective mechanism of SIRT1 on cartilage through regulation of LEF-1

BackgroundOsteoarthritis (OA) is a chronic degenerative disease that suppresses middle-aged and older people worldwide. Silent information regulator 1(SIRT-1) is associated with several age-related diseases, such as cardiovascular diseases, neurodegenerative diseases and tumors, etc. The protective role of SIRT-1 in bone and joint diseases has become increasingly well known.ObjectiveTo explore the relationship between SIRT-1 and its related factors in OA.MethodsFresh tibial plateau specimens were collected from 30 patients with knee OA who underwent total knee arthroplasty. According to the results of Safranin O Fast Green Staining, hematoxylin–eosin staining and the OARSI grade developed by the International Association for the Study of Osteoarthropathy, the specimens were divided into the mild group, moderate group and severe group, and the damage of cartilage was evaluated. SIRT-1 protein levels in cartilage samples were analyzed by immunohistochemistry. Then, take 60 8-week-old female C57BL/6 J mice and apply the Destabilization of the medial meniscus (DMM) to induce OA. Mice were randomly divided into normal group (sham), model group (model), and post-modeling drug administration group (srt), and each group was further divided into 2 weeks after modeling (2 W) and 8 weeks after modeling (8 W) according to the time after surgery. The degenerative degree of a knee joint in mouse knee cartilage samples was evaluated using Safranin O Fast Green Staining and OARSI grade. Immunohistochemical techniques assessed the protein levels of SIRT-1, β-catenin, LEF-1, MMP-13 and Collagen II in cartilage samples. The protein levels of β-catenin, LEF-1 and MMP-13 in the samples were assessed by the immunohistofluorescence technique. The mRNA expression of SIRT-1 and LEF-1 in mouse cartilage samples was evaluated by real-time quantitative polymerase chain reaction (qPCR).ResultsIn the human cartilage samples, according to the results of Safranin O Fast Green Staining, compared with the mild group, the moderate group and the severe group showed damage cartilage layer structure, the number of chondrocytes decreased, the cell hypertrophic, the cartilage surface discontinuous, and the OARSI grade increased. The severe group had severe cartilage injury and the highest OARSI grade. In the mice cartilage samples, according to immunohistochemical analysis, the protein levels of β-catenin, LEF-1 and MMP-13 in cartilage specimens of model 2 W and model 8 W groups were significantly increased than the sham 2 W and sham 8 W groups. The protein levels of SIRT-1 and Collagen II were significantly decreased (P < 0.05), the results of srt 2 W and srt 8 W groups were between the sham group and the model group. According to immunofluorescence analysis, the protein levels of β-catenin, LEF-1 and MMP-13 in model 2 W and model 8 W groups were significantly increased than sham 2 W and sham 8 W groups. The results of srt 2w and srt 8w groups were between the sham group and the model group. According to the real-time qPCR results: Compared with sham 2 W and sham 8 W groups, the mRNA expression of SIRT-1 in model 2 W and model 8 W groups was significantly decreased, while the mRNA expression of LEF-1 was significantly increased. In contrast, the results of srt 2 W and srt 8 W groups were between the sham group and the model group.ConclusionSRT-1720, as a specific activator of SIRT-1, does increase the protein level of SIRT-1. SIRT-1 may play a protective role in cartilage by regulating the expression of LEF-1 and related inflammatory factors in OA.

Involvement of Transient Receptor Potential Vanilloid Channel 2 in the Induction of Lubricin and Suppression of Ectopic Endochondral Ossification in Mouse ArticularCartilage.

Transient receptor potential vanilloid channel 2 (TRPV2) is a Ca2+ -permeable channel and plays a role in mediating intracellular Ca2+ current via mechanical stimuli. This study was undertaken to examine the expression and role of TRPV2 in adult articular cartilage and the development of osteoarthritis (OA). We examined TRPV2 expression in mouse and human articular cartilage. We analyzed the development of OA in Col2a1-CreERt2 ;Trpv2fl/fl mice and Trpv2fl/fl littermates in the resection of the medial meniscus and medial collateral ligament model (n = 5 each), the destabilization of the medial meniscus model (n = 5 each), and the aging mouse model (n = 8-9 each). We examined marker protein expression in these joints, Ca2+ influx by mechanical stimuli, and downstream pathways in vitro. TRPV2 was expressed in mouse and human articular cartilage and ectopic ossification lesions. In all mouse models of OA examined, Col2a1-CreERt2 ;Trpv2fl/fl mice were observed to have enhanced degradation of articular cartilage accompanied by decreased expression of lubricin/Prg4, and marked formation of periarticular ectopic ossification. Mechanical stress-induced Ca2+ influx was decreased by Trpv2 knockout (KO). Prg4 induction by fluid-flow shear stress was diminished in Trpv2-KO mouse chondrocytes, and this was mediated by the Ca2+ /calmodulin-dependent protein kinase kinase-cyclic AMP response element binding protein axis. Hypertrophic differentiation was enhanced in Trpv2-KO mouse chondrocytes. Increased activity of calcineurin and nuclear translocation of nuclear factor in activated T cells 1 induced by fluid-flow shear stress or TRP agonist treatment was reversed by Trpv2 knockout. Our findings demonstrate regulation of articular cartilage by TRPV2 through Prg4 induction and suppression of ectopic ossification.

Expression of VEGF-A Signaling Pathway in Cartilage of ACLT-induced Osteoarthritis Mouse Model

BackgroundAnterior cruciate ligament transection surgery (ACLT)-induced OA model was often used to investigate the molecular mechanism of knee osteoarthritis (KOA). Researches have shown that vascular endothelial growth factor (VEGF) played an important role in OA. The present study aimed to investigate the pathological changes after ACLT surgery and reveal the expression characteristics of the VEGF-A/VEGFR2 signaling pathway in this model.MethodsModerate KOA model was established by ACLT, and 1, 2, 4, 8, and 12 weeks after surgery, hematoxylin-eosin (HE) and Safranin-O(S-O) staining were used to detect the pathological changes in mouse knee cartilage, and the matrix biomarkers A Disintegrin and Metalloproteinase with Thrombospondin Motifs 5(ADAMTS5), Collagen II (COL-II) were detected using immunohistochemistry (IHC), CD31 was detected by immunofluorescence (IF) to show the vascular invasion in cartilage, and proteins expression of VEGF-A pathway were detected by Western blot (WB). Meanwhile, the inflammatory biomarkers cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) in cartilage were detected by WB.ResultsACLT surgery can lead to degeneration of cartilage in mice, and the characteristics of the lesion were time-dependent. The ADAMTS5-positive cells increased while COL-II decreased in OA cartilage with time, and new blood vessels labeled by CD31 can be seen from 1 week in OA cartilage, and increased in 8 and 12 weeks. The expression of VEGF-A, VEGFR2, COX-2, and iNOS were higher than control groups, which were basically consistent with the degree of osteoarthritis.ConclusionsThe degenerative degree of articular cartilage was time-dependent; angiogenesis and inflammation were important pathological changes of cartilage in KOA. The expression of the VEGF-A/VEGFR2 signaling pathway was basically correlated with the degree of KOA.

Self-assembled hyaluronic acid nanoparticles for osteoarthritis treatment

Although osteoarthritis (OA) is the most prevalent degenerative joint disease, there is no effective disease-modifying therapy. We report an empty self-assembled hyaluronic acid nanoparticle (HA-NP) as a potential therapeutic agent for OA treatment. In mouse primary articular chondrocytes, HA-NPs blocked the receptor-mediated cellular uptake of free low-molecular-weight HA, and the cellular uptake of HA-NPs increased by ectopic expression of CD44, using an adenoviral delivery system (Ad-Cd44). HA-NP showed in vitro resistance to digestion with hyaluronidase and in vivo long-term retention ability in knee joint, compared with free high-molecular-weight (HMW) HA. CD44 expression increased in the damaged articular cartilage of patients and mice with OA. Ad-Cd44 infection and IL-1β treatment induced in vitro phenotypes of OA by enhancing catabolic gene expression in primary articular chondrocytes, and these effects were attenuated by HA-NP, but not HMW HA. Both Cd44 deficiency and intra-articular injection of HA-NP protected joint cartilage against OA development in the OA mouse model. NF-κB was found to mediate CD44-induced catabolic factor expression and HA-NP inhibited CD44-induced NF-κB activation in chondrocytes. Our results identify an empty HA-NP as a potential therapeutic agent targeting CD44 for OA treatment, and the CD44-NF-κB-catabolic gene axis as an underlying mechanism of destructive cartilage disorders.

Immune-Inflammatory Responses of an Acellular Cartilage Matrix Biomimetic Scaffold in a Xenotransplantation Goat Model for Cartilage Tissue Engineering.

The rapid development of tissue engineering and regenerative medicine has introduced a new strategy for ear reconstruction, successfully regenerating human-ear-shaped cartilage and achieving the first clinical breakthrough using a polyglycolic acid/polylactic acid (PGA/PLA) scaffold. However, its clinical repair varies greatly among individuals, and the quality of regenerated cartilage is unstable, which seriously limits further clinical application. Acellular cartilage matrix (ACM), with a cartilage-specific microenvironment, good biocompatibility, and potential to promote cell proliferation, has been used to regenerate homogeneous ear-shaped cartilage in immunocompromised nude mice. However, there is no evidence on whether ACM will regenerate homogeneous cartilage tissue in large animals or has the potential for clinical transformation. In this study, xenogeneic ACM assisted with gelatin (GT) with or without autologous chondrocytes was implanted subcutaneously into goats to establish a xenotransplantation model and compared with a PGA/PLA scaffold to evaluate the immune-inflammatory response and quality of regenerated cartilage. The results confirmed the superiority of the ACM/GT, which has the potential capacity to promote cell proliferation and cartilage formation. Although there is a slight immune-inflammatory response in large animals, it does not affect the quality of the regenerated cartilage and forms homogeneous and mature cartilage. The current study provides detailed insights into the immune-inflammatory response of the xenogeneic ACM/GT and also provides scientific evidence for future clinical application of ACM/GT in cartilage tissue engineering.

An automated technique for double staining of bone and cartilage in fetal mouse skeletal specimens using alizarin red S and Alcian blue

ABSTRACT Automated methods exist for double staining bone and cartilage in fetal rat, rabbit and mice using alizarin red S and Alcian blue. None of the published methods produce consistently stained bone and cartilage in mouse fetuses. Consequently, we modified an automated staining method for use with mouse fetuses. Methanol replaced 95% industrial denatured alcohol, and 5% glacial acetic acid was used instead of 20%. We describe here our new protocol, which has been used successfully to stain specimens for regulatory prenatal developmental toxicity studies.

Long‐term effect of bilateral anterior elevation of occlusion on the temporomandibular joints

Incisors tubed prosthesis with bilateral anterior elevation (BAE) relation had been reported to stimulate the proliferative response in the mandibular condylar cartilage of mice, thus the prosthetic occlusion elevation had been proposed to treat cartilage degeneration. Currently, we aimed to detect the long-term effect of BAE on temporomandibular joints (TMJs). Twelve 6-week-old female mice were assigned to age-matched control and BAE groups (n=6). Micro-CT images and the macro- and micro-morphology of the mandibular condyles were analyzed at 29weeks. Compared with the age-matched controls, in BAE group, there were loss of subchondral cortical bone and heavy loss of the subchondral trabecular bone at the superior sites of the TMJ condyles, but hyperostosis at the inferior sites as revealed by micro-CT images and histological slices. In BAE group, cartilage thickness and matrix area were increased with upregulated expression of type II, type X collagen, and Ki67, but the expression of cleaved caspase-3 was downregulated (all, p<0.05). In addition to cartilage thickening, long-term BAE induces loss of the subchondral cortical bone and heavy loss of the underneath subchondral trabecular bone, but hyperostosis further underneath. Using BAE as a treatment remains double-edged.

Spaceflight and hind limb unloading induces an arthritic phenotype in knee articular cartilage and menisci of rodents

Reduced knee weight-bearing from prescription or sedentary lifestyles are associated with cartilage degradation; effects on the meniscus are unclear. Rodents exposed to spaceflight or hind limb unloading (HLU) represent unique opportunities to evaluate this question. This study evaluated arthritic changes in the medial knee compartment that bears the highest loads across the knee after actual and simulated spaceflight, and recovery with subsequent full weight-bearing. Cartilage and meniscal degradation in mice were measured via microCT, histology, and proteomics and/or biochemically after: (1) ~ 35 days on the International Space Station (ISS); (2) 13-days aboard the Space Shuttle Atlantis; or (3) 30 days of HLU, followed by a 49-day weight-bearing readaptation with/without exercise. Cartilage degradation post-ISS and HLU occurred at similar spatial locations, the tibial-femoral cartilage-cartilage contact point, with meniscal volume decline. Cartilage and meniscal glycosaminoglycan content were decreased in unloaded mice, with elevated catabolic enzymes (e.g., matrix metalloproteinases), and elevated oxidative stress and catabolic molecular pathway responses in menisci. After the 13-day Shuttle flight, meniscal degradation was observed. During readaptation, recovery of cartilage volume and thickness occurred with exercise. Reduced weight-bearing from either spaceflight or HLU induced an arthritic phenotype in cartilage and menisci, and exercise promoted recovery.

A requirement for STAT3 in limb development

The Interleukin-6/STAT3 (IL-6/STAT3) signaling pathway is essential for proper immune response to invading pathogens and viral infections. Moreover, STAT3 has high implications as a therapeutic target for rheumatoid and osteoarthritis. Recent literature has found that the IL-6/STAT3 signaling pathway plays an imperative role in the development of cartilage and bone. However, the direct role and the downstream effectors of STAT3 signaling during cartilage formation remains elusive. Through the use of cleared skeletal preparations, and histology, conditional loss of STAT3 in mouse cartilage, via the Col2-Cre driver, show that STAT3 is essential for proper limb growth plate formation. Furthermore, loss of STAT3 results in spontaneous bone fractures of the humerus. Interestingly, these severe fractures are rapidly repaired, underscoring an untapped mechanism for regeneration in musculoskeletal tissue. Moreover, conditional loss of STAT3 in limb mesenchyme, via the Prx1-Cre driver was generated. Loss of STAT3 in mesoderm show contortion phenotypes in the humerus. The stronger limb phenotype of Prx1Cre;Stat3fxfx compared to Col2Cre;Stat3fxfx mice indicates that Stat3 may exert effects at multiple stages of endochondral bone formation. Future experiments elucidating the downstream effectors of STAT3 mediated pathways will reveal the mechanisms by which STAT3 modulates different processes in limb development.

Diabetes Promotes Mild Osteoarthritis in The Streptozotocin‐ Induced Diabetic Mouse Model

Osteoarthritis (OA) is a degenerative joint disease that affects millions of people worldwide. In the United States alone OA affects more than 30 million adults. Several risk factors for OA are well studied, still, there are no therapies to prevent OA. Diabetes mellitus has emerged as a possible risk factor for OA. However, the current literature shows inconsistent results and most of these studies do not address the molecular changes associated with this effect. In addition, most of these studies do not account for changes in body mass index, a well-known risk factor for OA. In the present study, we first aimed to determine if diabetes is indeed a risk factor for OA, independently of body mass index. Next, we examined diabetes-related molecular changes in the mouse cartilage knee joints that could contribute to OA. We hypothesized that diabetes would promote OA. Sixteen weeks old streptozotocin-induced diabetic male mice were assessed for OA and molecular changes in the knee cartilage joint. Cartilage degeneration measurements of the knee joint show a mild OA phenotype in the diabetic group, characterized by proteoglycan loss, when compared to the control group, suggesting that diabetes can moderately promote OA. However, diabetes does not intensify post-traumatic osteoarthritis induced by a non-invasive tibial compression injury model. Changes in cartilage knee joint gene expression by RNA sequencing (RNAseq) identified 519 up regulated genes and 645 down regulated genes differentially regulated between diabetic and non-diabetic animals. This includes known regulators of cartilage and bone remodeling genes such as Col11a2, Col27a1, Mmp28, Adam33, Bglap, Ctsk and Acp5. Our findings suggest that diabetes can be a risk factor for OA, and we identified differential expression of genes that might contribute to the enhanced OA phenotype observed in the diabetic group. This study provides the first account of cartilage knee joint gene expression changes related to diabetes and the risk of OA. Understanding the relationship between diabetes and OA and the molecular changes associated with this can lead to the development of new therapeutic strategies.