Maintenance Of Cartilage Research Articles

Exogenous Application of Proteoglycan to the Cell Surface Microenvironment Facilitates to Chondrogenic Differentiation and Maintenance.

Osteoarthritis (OA), a disease that greatly impacts quality of life, has increasing worldwide prevalence as the population ages. However, its pathogenic mechanisms have not been fully elucidated and current therapeutic treatment strategies are inadequate. In recent years, abnormal endochondral ossification in articular cartilage has received attention as a pathophysiological mechanism in OA. Cartilage is composed of abundant extracellular matrix components, which are involved in tissue maintenance and regeneration, but how these factors affect endochondral ossification is not clear. Here, we show that the application of aggrecan-type proteoglycan from salmon nasal cartilage (sPG) exhibited marked proliferative capacity through receptor tyrosine kinases in chondroprogenitor cells, and also exhibited differentiation and three-dimensional structure formation via phosphorylation of Insulin-like Growth Factor-1 Receptor and Growth Differentiation Factor 5 expression. Furthermore, sPG inhibited calcification via expression of Runx2 and Col10 (factors related to induction of calcification), while increasing Mgp, a mineralization inhibitory factor. As a result of analyzing the localization of sPG applied to the cells, it was localized on the surface of the cell membrane. In this study, we found that sPG, as a biomaterial, could regulate cell proliferation, differentiation and calcification inhibition by acting on the cell surface microenvironment. Therefore, sPG may be the foundation for a novel therapeutic approach for cartilage maintenance and for improved symptoms in OA.

CCN3 (NOV) Drives Degradative Changes in Aging Articular Cartilage.

Aging is a major risk factor of osteoarthritis, which is characterized by the degeneration of articular cartilage. CCN3, a member of the CCN family, is expressed in cartilage and has various physiological functions during chondrocyte development, differentiation, and regeneration. Here, we examine the role of CCN3 in cartilage maintenance. During aging, the expression of Ccn3 mRNA in mouse primary chondrocytes from knee cartilage increased and showed a positive correlation with p21 and p53 mRNA. Increased accumulation of CCN3 protein was confirmed. To analyze the effects of CCN3 in vitro, either primary cultured human articular chondrocytes or rat chondrosarcoma cell line (RCS) were used. Artificial senescence induced by H2O2 caused a dose-dependent increase in Ccn3 gene and CCN3 protein expression, along with enhanced expression of p21 and p53 mRNA and proteins, as well as SA-β gal activity. Overexpression of CCN3 also enhanced p21 promoter activity via p53. Accordingly, the addition of recombinant CCN3 protein to the culture increased the expression of p21 and p53 mRNAs. We have produced cartilage-specific CCN3-overexpressing transgenic mice, and found degradative changes in knee joints within two months. Inflammatory gene expression was found even in the rib chondrocytes of three-month-old transgenic mice. Similar results were observed in human knee articular chondrocytes from patients at both mRNA and protein levels. These results indicate that CCN3 is a new senescence marker of chondrocytes, and the overexpression of CCN3 in cartilage may in part promote chondrocyte senescence, leading to the degeneration of articular cartilage through the induction of p53 and p21.

Hybrid Three-Dimensional-Printed Ear Tissue Scaffold With Autologous Cartilage Mitigates Soft Tissue Complications.

To analyze the use of highly translatable three-dimensional (3D)-printed auricular scaffolds with and without novel cartilage tissue inserts in a rodent model. Preclinical rodent animal model. This prospective study assessed a single-stage 3D-printed auricular bioscaffold with or without porcine cartilage tissue inserts in an athymic rodent model. Digital Imaging and Communications in Medicine computed tomography images of a human auricle were segmented to create an external anatomic envelope filled with orthogonally interconnected spherical pores. Scaffolds with and without tissue inset sites were 3D printed by laser sintering bioresorbable polycaprolactone, then implanted subcutaneously in five rats for each group. Ten athymic rats were studied to a goal of 24 weeks postoperatively. Precise anatomic similarity and scaffold integrity were maintained in both scaffold conditions throughout experimentation with grossly visible tissue ingrowth and angiogenesis upon explantation. Cartilage-seeded scaffolds had relatively lower rates of nonsurgical site complications compared to unseeded scaffolds with relatively increased surgical site ulceration, though neither met statistical significance. Histology revealed robust soft tissue infiltration and vascularization in both seeded and unseeded scaffolds, and demonstrated impressive maintenance of viable cartilage in cartilage-seeded scaffolds. Radiology confirmed soft tissue infiltration in all scaffolds, and biomechanical modeling suggested amelioration of stress in scaffolds implanted with cartilage. A hybrid approach incorporating cartilage insets into 3D-printed bioscaffolds suggests enhanced clinical and histological outcomes. These data demonstrate the potential to integrate point-of-care tissue engineering techniques into 3D printing to generate alternatives to current reconstructive surgery techniques and avoid the demands of traditional tissue engineering. NA Laryngoscope, 131:1008-1015, 2021.

Circadian Rhythm Protein Bmal1 Modulates Cartilage Gene Expression in Temporomandibular Joint Osteoarthritis via the MAPK/ERK Pathway.

The purpose of this study was to elucidate the role of the circadian gene Bmal1 in human cartilage and its crosstalk with the MAPK/ERK signaling pathway in temporomandibular joint osteoarthritis (TMJ-OA). We verified the periodical variation of the circadian gene Bmal1 and then established a modified multiple platform method (MMPM) to induce circadian rhythm disturbance leading to TMJ-OA. IL-6, p-ERK, and Bmal1 mRNA and protein expression levels were assessed by real-time RT-PCR and immunohistochemistry. Chondrocytes were treated with an ERK inhibitor (U0126), siRNA and plasmid targeting Bmal1 under IL-6 simulation; then, the cells were subjected to Western blotting to analyze the relationship between Bmal1 and the MAPK/ERK pathway. We found that sleep rhythm disturbance can downregulate the circadian gene BMAL-1 and improve phosphorylated ERK (p-ERK) and IL-6 levels. Furthermore, Bmal1 siRNA transfection was sufficient to improve the p-ERK level and aggravate OA-like gene expression changes under IL-6 stimulation. Bmal1 overexpression relieved the alterations induced by IL-6, which was consistent with the effect of U0126 (an ERK inhibitor). However, we also found that BMAL1 upregulation can decrease ERK phosphorylation, whereas ERK downregulation did not change BMAL1 expression. Collectively, this study provides new insight into the regulatory mechanism that links chondrocyte BMAL1 to cartilage maintenance and repair in TMJ-OA via the MAPK/ERK pathway and suggests that circadian rhythm disruption is a risk factor for TMJ-OA.

Dentin Sialophosphoprotein Deletion Leads to Femoral Head Cartilage Attenuation and Subchondral Bone Ill-mineralization.

Dentin sialophosphoprotein (DSPP), which expresses and synthesizes in odontoblasts of dental pulp, is a critical protein for normal teeth mineralization. Originally, DSPP was identified as a dentin-specific protein. In 2010, DSPP was also found in femoral head cartilage, and it is still unclear what roles DSPP play in femoral head cartilage formation, growth, and maintenance. To reveal biological functions of DSPP in the femoral head cartilage, we examined Dspp null mice compared with wild-type (WT) mice to observe DSPP expression as well as localization in WT mice and to uncover differences of femoral head cartilage, bone morphology, and structure between these two kinds of mice. Expression data demonstrated that DSPP had heterogeneous fragments, expressed in each layer of femoral head cartilage and subchondral bone of WT mice. Dspp null mice exhibited a significant reduction in the thickness of femoral head cartilage, with decreases in the amount of proliferating cartilage cells and increases in apoptotic cells. In addition, the subchondral bone mineralization decreased, and the expressions of vessel markers (vascular endothelial growth factor [VEGF] and CD31), osteoblast markers (Osterix and dentin matrix protein 1 [DMP1]), osteocyte marker (sclerostin [SOST]), and osteoclast marker (tartrate-resistant acid phosphatase [TRAP]) were remarkably altered. These indicate that DSPP deletion can affect the proliferation of cartilage cells in the femoral head cartilage and endochondral ossification in subchondral bone. Our data clearly demonstrate that DSPP plays essential roles in the femoral head cartilage growth and maintenance and subchondral biomineralization.

Genetic Insights of Primary knee osteoarthritis

Introduction:Knee Osteoarthritis (KOA) is charecterised by focal loss of joint articular cartilage, osteophyte formation and sub chondral bone remodelling. Common clinical symptoms include pain, stiffness, limitation of the joint movement and swelling. OA is the most common joint disease worldwide and the knee is the common site involved. Classical risk factors of OA include age, gender, weight, joint injury, trauma. However, family history/Hereditary component is the one of the crucial factors. knee OA is a complex disease with environmental and genetic factors associated with its development and progression.Hypotheses:It is classified as primary when no discernible cause is evident and secondary when a triggering factor is apparent. However primary OA possesses significant genetic component. Despite the fact that OA is a late onset advanced age disease the increasing incidence of OA individuals below the age of 55 years and the fact that the several members of the same family are affected suggest a genetic predisposition. Hence, there is a need to identify molecular biomarkers associated with primary early knee osteoarthritisMethods:Several Genome wide association studies and candidate gene studies have identified genetic variants involved in the pathogenesis of OA like VDR, MMP, TGF, GDF5, COL11A1 and VEGF. Currently, the majority of genetic association studies on disease risk focused on identifying the individual’s effect on single nucleotide polymorphisms (SNPs).Results:In the present study, ten gene polymorphisms were studied in Indian population. They are COL21, CRTL1, CRTM, ACE, VDR, GDF5, COG5, CYBA, SREBP2 and TGFβ1 genes which were selected based on their role in cartilage maintenance and bone remodelling.This is the first study in India which looked at the gene polymorphisms. Altogether 100 clinically diagnosed and radiologically confirmed early primary knee OA (KOA) cases and 100 controls with no musculoskeletal diseases, were recruited and molecular analysis was performed by routine PCR - RFLP techniques.Results indicated that COL21, CRTL1, ACE, GDF5, COG5, CYBA, SREBP2 and TGFβ1gene polymorphisms showed an association with the disease where as CRTM and VDR lack of association.Conclusion:These gene polymorphisms can be used as molecular biomarkers for identifying the individuals who are at risk of developing the disease ( primary knee osteoarthritis) and these molecular genotypes helps us in planning tailored treatment and management. It also help us to identify individuals who are at risk of developing knee osteoarthritis and preventive measures can be planned accordingly. To the best of our knowledge this is the first study in India which assessed these ten gene polymorphisms with primary early knee osteoarthritis.

Hypoxic induction of CCN2 mRNA through p38 MAP kinase activation in the human chondrosarcoma‐derived cell line, HCS‐2/8

AbstractCCN2/CTGF (cellular communication network factor 2/connective tissue growth factor) plays critical roles in cartilage development, maintenance, and regeneration. Hypoxia‐induced expression of CCN2 mRNA is regulated post‐transcriptionally in the human chondrosarcoma‐derived cell line, HCS‐2/8. In the present study, the hypoxia‐induced increase in CCN2 mRNA expression was assessed with quantitative real‐time PCR in HCS‐2/8 cells in the presence of inhibitors of mitogen‐activated protein kinases (MAPKs). Subsequently, the stability of CCN2 mRNA in hypoxia was evaluated with mRNA degradation assays in the presence or absence of the selective p38 MAPK inhibitor, SB203580. We detected phosphorylation of p38 MAPK by immunoblot analysis within 30 minutes in hypoxia, and we observed ~twofold higher CCN2 mRNA levels in hypoxia compared to normoxia. Blockade of p38 MAPK activation with 10 µmol/L SB203580 abolished this CCN2 induction. Furthermore, we found that inhibition of p38 MAPK suppressed the elongation of CCN2 mRNA half‐life in hypoxia. Taken together, these findings suggest that the molecular mechanism, by which CCN2 mRNA expression is increased in hypoxia, induces the activation of p38 MAPK leading to the post‐transcriptional regulation of the stability of CCN2 mRNA.

Properties of Cartilage-Subchondral Bone Junctions: A Narrative Review with Specific Focus on the Growth Plate.

The purpose of this narrative review is to summarize what is currently known about the structural, chemical, and mechanical properties of cartilage-bone interfaces, which provide tissue integrity across a bimaterial interface of 2 very different structural materials. Maintaining these mechanical interfaces is a key factor for normal bone growth and articular cartilage function and maintenance. A comprehensive search was conducted using Google Scholar and PubMed/Medline with a specific focus on the growth plate cartilage-subchondral bone interface. All original articles, reviews in journals, and book chapters were considered. Following a review of the overall structural and functional characteristics of the physis, the literature on histological studies of both articular and growth plate chondro-osseous junctions is briefly reviewed. Next the literature on biochemical properties of these interfaces is reviewed, specifically the literature on elemental analyses across the cartilage-subchondral bone junctions. The literature on biomechanical studies of these junctions at the articular and physeal interfaces is also reviewed and compared. Unlike the interface between articular cartilage and bone, growth plate cartilage has 2 chondro-osseous junctions. The reserve zone of the mature growth plate is intimately connected to a plate of subchondral bone on the epiphyseal side. This interface resembles that between the subchondral bone and articular cartilage, although much less is known about its makeup and formation. There is a notably paucity of information available on the structural and mechanical properties of reserve zone-subchondral epiphyseal bone interface. This review reveals that further studies are needed on the microstructural and mechanical properties of chondro-osseous junction with the reserve zone.

The role of SIRT1 in BMP2-induced chondrogenic differentiation and cartilage maintenance under oxidative stress.

Articular cartilage defects are common in the clinic but difficult to treat. Exploring the chondrogenic molecular mechanisms of mesenchymal stem cells (MSCs) is of great theoretical interest and industrial significance. Bone morphogenetic protein 2 (BMP2) is a key factor that induces cartilage differentiation and can induce stem cell chondrogenic differentiation. However, the oxidative stress in the microenvironment during cartilage injury and degeneration inhibits cartilage regeneration and homeostasis. Silent mating type information regulator 2 homolog-1 (SIRT1) is an important histone deacetylase that regulates proliferation, differentiation, aging, and inflammation processes; moreover, it is an essential factor for chondrogenesis. The specific mechanism of SIRT1 in cartilage differentiation and homeostasis is still unclear. First, we investigated whether SIRT1 could coordinate BMP2-induced chondrogenic differentiation. Second, we investigated the protective effect of SIRT1 on BMP2-induced MSCs under oxidative stress. The results showed that SIRT1 could promote BMP2-induced chondrogenic differentiation of MSCs, and reduce the apoptosis and decomposition of extracellular matrix under oxidative stress. In summary, these results suggested that SIRT1 plays an important coordination role in BMP2-induced chondrogenic differentiation of stem cells and cartilage maintenance under oxidative stress, establishing the experimental basis for exploring the use of SIRT1 in cartilage defect repair.

Stiffness Matters: Fine-Tuned Hydrogel Elasticity Alters Chondrogenic Redifferentiation.

Biomechanical cues such as shear stress, stretching, compression, and matrix elasticity are vital in the establishment of next generation physiological in vitro tissue models. Matrix elasticity, for instance, is known to guide stem cell differentiation, influence healing processes and modulate extracellular matrix (ECM) deposition needed for tissue development and maintenance. To better understand the biomechanical effect of matrix elasticity on the formation of articular cartilage analogs in vitro, this study aims at assessing the redifferentiation capacity of primary human chondrocytes in three different hydrogel matrices of predefined matrix elasticities. The hydrogel elasticities were chosen to represent a broad spectrum of tissue stiffness ranging from very soft tissues with a Young’s modulus of 1 kPa up to elasticities of 30 kPa, representative of the perichondral-space. In addition, the interplay of matrix elasticity and transforming growth factor beta-3 (TGF-β3) on the redifferentiation of primary human articular chondrocytes was studied by analyzing both qualitative (viability, morphology, histology) and quantitative (RT-qPCR, sGAG, DNA) parameters, crucial to the chondrotypic phenotype. Results show that fibrin hydrogels of 30 kPa Young’s modulus best guide chondrocyte redifferentiation resulting in a native-like morphology as well as induces the synthesis of physiologic ECM constituents such as glycosaminoglycans (sGAG) and collagen type II. This comprehensive study sheds light onto the mechanobiological impact of matrix elasticity on formation and maintenance of articular cartilage and thus represents a major step toward meeting the need for advanced in vitro tissue models to study both re- and degeneration of articular cartilage.

High synovial fluid resistin levels are associated with radiographic severity in female patients with knee osteoarthritis

Purpose: Osteoarthritis (OA) is one of the ten disabling diseases affecting predominantly women worldwide. Resistin is an adipocytokine which has been related with inflammation and insulin resistance. Although the resistin level of knee OA patients comparing to healthy controls has been investigated in previous studies, there were limited data regarding the association between synovial fluid resistin levels and severity of knee OA. We examined the relationship between the synovial fluid resistin level and radiographic severity in female knee OA patients. We also investigated the association between the synovial resistin and those of factors involved in inflammation and cartilage maintenance. Methods: Thirty five female patients with primary knee OA grade 1∼4 Kellgren Lawrence (KL) score were included in this study. Patients with traumatic OA or all systemic autoimmune diseases were excluded. The patients were divided into two groups according to radiographic severity (Group I: KL score 1∼2, Group II: KL score 3∼4). Synovial levels of resistin, Interlukin (IL)-6, matrix metalloproteinase (MMP)-1, MMP-3 were measured by enzyme-linked immunosorbent assay. Results: The patients had a mean age of 69.7 ± 5.5 years and mean body mass index (BMI) was 27.5 ± 3.3 (kg/m2). There were 13 and 21 patients in group I and group II, respectively. Mean age and BMI were not significantly different between two groups. Synovial resistin level was significantly higher in group II compared to group I (p = 0.028) (Figure). However the synovial levels of IL-6, MMP-1 and MMP-3 showed no difference between the two groups. Synovial resistin level tend to be positively correlated with synovial IL-6 level, but did not showed statistical significance (r=0.053, p = 0.076). Conclusions: The result showed that resistin is produced within knee OA joints, and it is associated with the radiographic severity in female knee OA patients. This finding proposed a specific role of resistin in the pathogenesis of OA and as a target for disease modifying osteoarthritis drugs.

The ciliary protein intraflagellar transport 88 is required for the maturation, homeostasis and mechanoadaptation of articular cartilage

Purpose: The development, maturation and maintenance of articular cartilage depends on the integration of external cues, such as mechanics, with intrinsic cell signalling programmes, such as hedgehog (Hh) signalling. Aberrant mechanics and the post-natal activation of Hh signalling have both been associated with the development of murine and human OA. It remains to be fully elucidated how chondrocytes transduce and integrate these cues in vivo. Chondrocytes assemble a primary cilium, a microtubule-based organelle with a devoted trafficking machinery, IntraFlagellar Transport or IFT.

Characterization of the pathophysiological processes of osteoarthritis using RNA sequencing data of subchondral bone

Purpose: Osteoarthritis (OA) has a considerable genetic component and genetic research has resulted in many insights into underlying disease pathways. Most recent large-scale genomic association studies have identified TGFA , MGP, CHADL as compelling genes involved in the aetiology of OA. The functions of these genes confirm that deviations in both cartilage and bone maintenance processes are major pathways underlying OA pathology in humans. Moreover, follow-up studies have shown that risk SNPs frequently modulate pathology due to altering transcription of the genes in cis both in bone and cartilage. Nonetheless, follow up study of these genes towards underlying biological mechanisms, preclinical studies on target discovery and eventually drug testing have thus far focused on gene expression profiling in articular cartilage. The aim of the current study was to characterize interactive pathophysiological processes of subchondral bone and articular cartilage in human osteoarthritis (OA) in large human cohort RNA sequencing. Methods: We performed RNA sequencing on macroscopically preserved and lesioned OA subchondral bone of patients that underwent a joint replacement surgery due to OA (N=24 pairs; 6 hips, 18 knees, RAAK-study). Unsupervised hierarchical clustering and differential expression analysis were performed on the data. Gene enrichment was performed using the online tool DAVID. Moreover, we compared the differentially expressed genes identified here to our previously reported differentially expressed genes in OA articular cartilage. Results: Upon performing cluster analysis we identified two clusters; one representing hips and the other representing knees. Due to the low hip sample size, differential expression analysis was performed on knee samples only. As shown in Figure 1, we identified 1757 significantly differentially expressed genes between lesioned and preserved subchondral bone. The most significantly downregulated gene was FRZB (FC=0.48, FDR=3.07x10-12), encoding the frizzled receptor protein and is a well-known cartilage OA gene. The most significantly upregulated gene was CNTNAP2 (FC=2.90, FDR=3.38x10-6), encoding the contactin-associated protein-like 2 protein (CASPR2). Among the 1757 differentially expressed genes, 102 genes showed an absolute foldchange of 2 or higher. The highest upregulated gene was STMN2 (FC=23.0, FDR=1.8x10-4), encoding stathmin 2, while the most downregulated gene was CHRDL2 (FC=0.09, FDR=4.13x10-6), encoding chordin-like protein 2 and is also known to be involved in OA in cartilage. Enrichment of the differentially expressed genes resulted in significant enrichment of GO-terms regarding the extracellular matrix. To investigate whether the subchondral bone and the articular cartilage show similarities in the OA pathophysiological processes, we compared the results presented here with our previously reported results on differentially expressed genes in OA articular cartilage. As a result, we identified 398 genes that were differentially expressed in both tissues, of which 361 showed similar directions of effect, including the genes IL11, encoding Interleukin 11, and CHADL, encoding Chondroadherin-Like Protein. Conclusions: To our knowledge, we are the first to report on the differential expression pattern of OA subchondral bone using RNA sequencing on a large sample size while integrating these with differential expression patterns of cartilage of the same individuals. By performing cluster analysis on our RNA sequencing data, we identified two clusters representing hips and knees, respectively. These clusters indicate distinct OA pathophysiological processes in the subchondral bone between the two joint sites, which was not previously seen with similar analyses of the cartilage. Among the most consistently differentially expressed genes with OA pathophysiology in bone and cartilage are IL11, and CHADL. Notably, these genes were recently found in large GWA studies on OA indicating also their causal involvement in the OA pathophysiology. Moreover, IL11 was recognized as being targeted by FDA approved drugs. As such, we advocate that IL11 could be an attractive potential drug for OA patients with a therapeutic effect both in cartilage and subchondral.

Balancing the regulatory role between TGF-β and BMP sub pathways in articular cartilage may offer promising for treating osteoarthritis

Purpose: Transforming growth factor-β (TGF-β) signaling has a diverse set of effects on cellular processes. Several genes involved in this pathway were found to be associated with OA, but how the pathway adversely modulates joint tissues is unclear. While published data from in vitro or animal models provide clues to understanding mechanisms of cartilage maintenance, data directly from human OA patients are still sparse. We therefore undertook this study to examine how genes involved in TGF-β signaling were expressed in normal and OA-affected cartilage obtained from patients, and how they were correlated to the targeted gene expressions.

Hypoxia-inducible factor-1 alpha maintains mouse articular cartilage through suppression of NF-\u03baB signaling

HIF-1α, an essential transcription factor under hypoxic condition, is indispensable for chondrocytes during skeletal development but its expression and roles in articular chondrocytes are yet to be revealed. We examined HIF-1α protein expression and the hypoxic condition during mouse osteoarthritis (OA) development using state of the art hypoxic probes and found that its expression decreased as OA progressed, coinciding with the change in hypoxic conditions in articular cartilage. Gain- and loss-of-function of HIF-1α in cell culture experiments showed that HIF-1α suppressed catabolic genes such as Mmp13 and Hif2a. We confirmed these anticatabolic effects by measuring glycosaminoglycan release from wild type and conditional knock-out mice femoral heads cultured ex vivo. We went on to surgically induce OA in mice with chondrocyte-specific deletion of Hif1a and found that the development of OA was exacerbated. Increased expression of catabolic factors and activation of NF-κB signalling was clearly evident in the knock-out mice. By microarray analysis, C1qtnf3 was identified as a downstream molecule of HIF-1α, and experiments showed it exerted anti-catabolic effects through suppression of NF-κB. We conclude that HIF-1α has an anti-catabolic function in the maintenance of articular cartilage through suppression of NF-κB signalling.

Bionic composite hydrogel with a hybrid covalent/noncovalent network promoting phenotypic maintenance of hyaline cartilage.

The injectable composite hydrogel based on collagen and hyaluronic acid provided a bionic three-dimensional microenvironment and mimetic natural extracellular matrix (ECM) for the growth of cells in vivo and has been widely researched and developed for cartilage tissue engineering. Here, a novel injectable bionic hydrogel with hybrid covalent/noncovalent network derived from covalent conjugation of HA-SH and noncovalent supramolecular self-assembly of BPAA-AFF-OH short peptide was fabricated to overcome the collagen immunogenicity of animal origin and effectively maintain its biological function. Moreover, through optimizing the network structure and polymer composition, the bionic HS5FFAB5 hydrogel presented a reliable mechanical strength which depended on the highly integrated fiber structure between HA-SH and FFAB-AFF-OH molecules. The results in vitro and in vivo proved that HA-SH could provide a fundamental frame structure, while the supramolecular hydrogels could reinforce this structure via hydrogen bonds and hydrophilic/hydrophobic interactions, and endow bionic hydrogels with more abundant cell adhesion sites. The bionic composite hydrogel could improve the cell adhesion and proliferation when compared to HA-SH hydrogel, and enhanced chondrogenic related gene expression and matrix secretion by three-dimensional co-cultured in vitro and subcutaneous implantation in vivo, which further promoted phenotypic maintenance of hyaline cartilage. This bionic hydrogel with a hybrid covalent/noncovalent network is supposed to have potential application prospects in cartilage regeneration.

Damage control articular surgery: Maintaining chondrocyte health and minimising iatrogenic injury

Articular cartilage has limited intrinsic regenerative potential. The maintenance of healthy articular cartilage is essential to prevent joint degeneration and the morbidity associated with arthritis. In this review, we outline the structure and function of healthy articular cartilage. We summarise some of the recent literature outlining the influence of surgical factors on chondrocyte health. These factors include mechanical injury from instrumentation and drilling, drying, and the influence of irrigation fluids, antimicrobial solutions and local anaesthetics. We demonstrate that there is scope for improving cartilage viability at the time of surgery if simple chondroprotective measures are routinely adopted.

Collagen Organization Within the Cartilage of Trpv4-/- Mice Studied with Two-Photon Microscopy and Polarized Second Harmonic Generation.

The polymodal channel TRPV4 has been shown to regulate development and maintenance of cartilage. Here we investigate whether TRPV4 activity regulates the early deposition and structure of collagen matrix in the femoral head cartilage by comparing the 3D morphology and the sub-micrometer organization of the collagen matrix between wild type and Trpv4 -/- mice pups four to five days old. Two-photon microscopy can be used to conduct label-free imaging of cartilage, as collagen generates a second harmonic signal (second harmonic generation [SHG]) under pulsed infrared excitation. In one set of measurements, we use circularly polarized laser light to reconstruct the 3D morphology of the femoral head cartilage and to measure the tissue thickness. Second, by rotating the direction of the linearly polarized light and using polarized SHG detection, we investigate the sub-micrometer orientation of collagen fibers in the cartilage. At this developmental stage, we cannot detect statistically significant differences between the two mice strains, although a tendency toward a more random orientation of collagen fibers and a higher thickness of the whole cartilage seems to characterize the Trpv4 -/- mice. We discuss possible reasons for these observations. © 2019 The Authors. Cytometry Part A published by Wiley Periodicals, Inc. on behalf of International Society for Advancement of Cytometry.

Identification of GDF5 gene polymorphism of bull-calves of the Kalmyk breed

The study covers bull-calves of the Kalmyk breed (n=182) aged 12-14 months. It considers the impact of polymorphism of the growth differentiation factor 5 (T586C in exon 1) ensuring development, maintenance and restoration of bones and cartilage on body parameters, body weight and musculoskeletal diseases. The frequency of occurrence of TT alleles in selection made 48.9%, TC – 46.7 and CC – 4.4%, χ2 test – 4.94. Bull-calves with CC genotype surpassed their analogues with TT and TC genotypes in terms of growth intensity and body measurements. The analysis of non-contagious musculoskeletal diseases (arthritides, bursitides, arthrobursitides) since birth until the 12th month of age revealed diseases among 17 heads (19.1%) with TT genotype, 9 heads (10.6%) with TC genotype and absence of diseases with CC genotype. There is a need for further study with increasing the group of animals with C homozygous genotype.

TGFβ/BMP Signaling Pathway in Cartilage Homeostasis.

Cartilage homeostasis is governed by articular chondrocytes via their ability to modulate extracellular matrix production and degradation. In turn, chondrocyte activity is regulated by growth factors such as those of the transforming growth factor β (TGFβ) family. Members of this family include the TGFβs, bone morphogenetic proteins (BMPs), and growth and differentiation factors (GDFs). Signaling by this protein family uniquely activates SMAD-dependent signaling and transcription but also activates SMAD-independent signaling via MAPKs such as ERK and TAK1. This review will address the pivotal role of the TGFβ family in cartilage biology by listing several TGFβ family members and describing their signaling and importance for cartilage maintenance. In addition, it is discussed how (pathological) processes such as aging, mechanical stress, and inflammation contribute to altered TGFβ family signaling, leading to disturbed cartilage metabolism and disease.