SETD7 mediates the vascular invasion in articular cartilage and chondrocytes apoptosis in osteoarthriis

Interaction Between YTH Domain-Containing Family Protein 2 and SET Domain-Containing Lysine Methyltransferase 7 Suppresses Autophagy in Osteoarthritis Chondrocytes, Exacerbating Cartilage Damage

BACKGROUND AND OBJECTIVE

Osteoarthritis (OA) is characterized by progressive cartilage degeneration mediated by various molecular pathways, including inflammatory and autophagic processes. SET domain-containing lysine methyltransferase 7 (SETD7), a methyltransferase, has been implicated in OA pathology. This study investigates the expression pattern of SETD7 in OA and its role in promoting interleukin-1 beta (IL-1β)-induced chondrocyte injury through modulation of autophagy and inflammation.

METHODS

The expression of SETD7 in cartilage tissues from OA patients and healthy controls was quantified using quantitative reverse transcription PCR and Western blot analysis. Small interfering RNA targeting SETD7 (si-SETD7) was transfected into human articular chondrocytes (HACs) treated with IL-1β to examine its impact on cellular viability, apoptosis, inflammatory responses, and autophagy. Functional assays including Cell Counting Kit-8, flow cytometry, enzyme-linked immunosorbent assay, and commercial kits were employed to assess biochemical changes. Interaction between YTH N6-methyladenosine RNA binding protein 2 (YTHDF2) and SETD7 was explored using RNA immunoprecipitation and co-immunoprecipitation assays.

RESULTS

SETD7 was overexpressed in OA cartilage compared with controls and increased further upon IL-1β treatment. Knockdown of SETD7 in IL-1β-treated HACs improved cellular viability, decreased apoptosis, and reversed the adverse effects on lactate dehydrogenase release and inflammatory markers (tumor necrosis factor-alpha and interleukin-6) while enhancing antioxidant enzymes (catalase, malondialdehyde, and superoxide dismutase). Additionally, autophagy was restored, as evidenced by changes in the levels of autophagy related 5, Beclin1, and sequestosome 1. Interfering with autophagy using chloroquine negated the protective effects of SETD7 knockdown. Furthermore, YTHDF2 was found to stabilize SETD7 mRNA, influencing its expression and enhancing IL-1β-induced chondrocyte injury.

CONCLUSION

SETD7 plays a critical role in the pathogenesis of OA by modulating chondrocyte survival, apoptosis, inflammation, and autophagy. The interaction between YTHDF2 and SETD7 exacerbates chondrocyte injury under inflammatory conditions, highlighting potential therapeutic targets for OA treatment. The YTHDF2/SETD7 axis offers a novel insight into the molecular mechanisms governing cartilage degeneration in OA.

Morphology of the sternoclavicular joint and its microanatomical changes in response to osteoarthritic degeneration

Although the sternoclavicular joint shares structural similarities with the knee and hip joints as a diarthrodial joint, its biomechanics differ significantly due to its non-weight-bearing nature. Nevertheless, it is subject to considerable loading, leading to increased susceptibility to osteoarthritis, a prevalent condition characterized by the degeneration of the joint's articular surfaces and fibrocartilaginous intra-articular disc. The osteoarthritic degeneration of the fibrocartilaginous and cartilaginous surfaces of the sternoclavicular joint has been investigated, considering multiple factors. These include cell count, collagen alignment, surface fibrillation, cyst formation, and glycosaminoglycan content, with the findings deemed significant. However, current treatments for osteoarthritis of the sternoclavicular joint tend to focus on symptom management rather than active prevention of disease progression. Therefore, a detailed understanding of the anatomy, biomechanics, and morphological changes of the sternoclavicular joint during all stages of the osteoarthritic disease is essential for effective management to allow for maximum patient outcomes. This review explores the current literature on the anatomy of the sternoclavicular joint, starting with its structure and comparison to surrounding joints, biomechanics, and morphology, before considering the microanatomical changes that occur due to osteoarthritic degeneration. Early identification of osteoarthritic changes within this joint can enhance treatment and management outcomes before advancing joint degeneration, improving the quality of life for those affected.

Activating UCHL1 through the CRISPR activation system promotes cartilage differentiation mediated by HIF-1α/SOX9

Developing strategies to enhance cartilage differentiation in mesenchymal stem cells and preserve the extracellular matrix is crucial for successful cartilage tissue reconstruction. Hypoxia-inducible factor-1α (HIF-1α) plays a pivotal role in maintaining the extracellular matrix and chondrocyte phenotype, thus serving as a key regulator in chondral tissue engineering strategies. Recent studies have shown that Ubiquitin C-terminal hydrolase L1 (UCHL1) is involved in the deubiquitylation of HIF-1α. However, the regulatory role of UCHL1 in chondrogenic differentiation has not been investigated. In the present study, we initially validated the promotive effect of UCHL1 expression on chondrogenesis in adipose-derived stem cells (ADSCs). Subsequently, a hybrid baculovirus system was designed and employed to utilize three CRISPR activation (CRISPRa) systems, employing dead Cas9 (dCas9) from three distinct bacterial sources to target UCHL1. Then UCHL1 and HIF-1α inhibitor and siRNA targeting SRY-box transcription factor 9 (SOX9) were used to block UCHL1, HIF-1α and SOX9, respectively. Cartilage differentiation and chondrogenesis were measured by qRT-PCR, immunofluorescence and histological staining. We observed that the CRISPRa system derived from Staphylococcus aureus exhibited superior efficiency in activating UCHL1 compared to the commonly used the CRISPRa system derived from Streptococcus pyogenes. Furthermore, the duration of activation was extended by utilizing the Cre/loxP-based hybrid baculovirus. Moreover, our findings show that UCHL1 enhances SOX9 expression by regulating the stability and localization of HIF-1α, which promotes cartilage production in ADSCs. These findings suggest that activating UCHL1 using the CRISPRa system holds significant potential for applications in cartilage regeneration.

MiR-29a-3p mediates phosphatase and tensin homolog and inhibits osteoarthritis progression

Despite substantial progress in clinical trials of osteoarthritis (OA) gene therapy, the prevalence of OA is still on the rise. MiRNAs have a potential biomarker and therapeutic target for OA. OA cartilage and chondrosarcoma cells were studied to determine the role of miR-29a-3p and PTEN. OA cartilage and human chondrosarcoma cells (SW1353) were obtained. miR-29a-3p and PTEN signature expression was determined by RT-qPCR. The binding relationship between miR-29a-3p and PTEN was investigated by dual-luciferase reporter gene and western blot assay. TUNEL, immunohistochemistry, CCK-8, and flow cytometry were utilized to determine the proliferation and apoptosis of SW1353 cells. This study indicated downregulation of miR-29a-3p expression and upregulation of PTEN expression in human OA primary chondrocytes or OA tissue samples, compared with the normal cartilage cells or tissues. PTEN expression was negatively correlated with miR-29a-3p expression, and miR-29a-3p targeted PTEN mechanistically. miR-29a-3p reduced SW1353 cell activity and proliferation and promoted cell apoptosis. However, the aforementioned effects could be reversed by downregulating PTEN. miR-29a-3p can stimulate chondrocyte proliferation and inhibit apoptosis by inhibiting PTEN expression.

UCHL1 alleviates apoptosis in chondrocytes via upregulation of HIF‑1α‑mediated mitophagy

Stem cell‑based tissue engineering has shown significant potential for rapid restoration of injured cartilage tissues. Stem cells frequently undergo apoptosis because of the prevalence of oxidative stress and inflammation in the microenvironment at the sites of injury. Our previous study demonstrated that stabilization of hypoxia‑inducible factor 1α (HIF‑1α) is key to resisting apoptosis in chondrocytes. Recently, it was reported that Ubiquitin C‑terminal hydrolase L1 (UCHL1) can stabilize HIF‑1α by abrogating the ubiquitination process. However, the effect of UCHL1 on apoptosis in chondrocytes remains unclear. Herein, adipose‑derived stem cells were differentiated into chondrocytes. Next, the CRISPR activation (CRISPRa) system, LDN‑57444 (LDM; a specific inhibitor for UCHL1), KC7F2 (a specific inhibitor for HIF‑1α), and 3‑methyladenine (a specific inhibitor for mitophagy) were used to activate or block UCHL1, HIF‑1α, and mitophagy. Mitophagy, apoptosis, and mitochondrial function in chondrocytes were detected using immunofluorescence, TUNEL staining, and flow cytometry. Moreover, the oxygen consumption rate of chondrocytes was measured using the Seahorse XF 96 Extracellular Flux Analyzer. UCHL1 expression was increased in hypoxia, which in turn regulated mitophagy and apoptosis in the chondrocytes. Further studies revealed that UCHL1 mediated hypoxia‑regulated mitophagy in the chondrocytes. The CRISPRa module was utilized to activate UCHL1 effectively for 7 days; endogenous activation of UCHL1 accelerated mitophagy, inhibited apoptosis, and maintained mitochondrial function in the chondrocytes, which was mediated by HIF‑1α. Taken together, UCHL1 could block apoptosis in chondrocytes via upregulation of HIF‑1α-mediated mitophagy and maintain mitochondrial function. These results indicate the potential of UCHL1 activation using the CRISPRa system for the regeneration of cartilage tissue.

The Effect of JAK Inhibitor Tofacitinib on Chondrocyte Autophagy

Osteoarthritis (OA) is a multifactorial disease of the whole joint that has a complex pathogenesis. There is currently no cure for OA. Tofacitinib is a broad JAK inhibitor that can have an anti-inflammatory effect. The objective of this study was to investigate the effect of tofacitinib on the cartilage extracellular matrix in OA and determine whether tofacitinib exerts a protective effect by inhibiting the JAK1/STAT3 signaling pathway and upregulating autophagy in chondrocytes. We investigated the expression profile of OA in vitro by exposing SW1353 cells to interleukin-1β (IL-1β), and induced OA in vivo using the modified Hulth method in rats. We found that IL-1β promoted the expression of OA-related matrix metalloproteinases (MMP3 and MMP13), reduced the expression of collagen II, reduced the expression of beclin1 and LC3-II/I, and promoted the accumulation of p62 in SW1353 cells. Tofacitinib attenuated IL-1β-stimulated changes in MMPs and collagen II and restored autophagy. In IL-1β-stimulated SW1353 cells, the JAK1/STAT3 signaling pathway was activated. Tofacitinib inhibited the IL-1β-stimulated expression of p-JAK1 and p-STAT3 and prevented translocation of p-STAT3 to the nucleus. In the rat model of OA, tofacitinib reduced articular cartilage degeneration by delaying cartilage extracellular matrix degradation and increasing chondrocyte autophagy. Our study demonstrates that chondrocyte autophagy was impaired in experimental models of OA. Tofacitinib reduced the inflammatory response and restored the damaged autophagic flux in OA.

Nanoparticles of Cerium-Doped Zeolitic Imidazolate Framework-8 Promote Soft Tissue Integration by Reprogramming the Metabolic Pathways of Macrophages

Soft tissue integration around the abutment of implants is the basis of long-term retention of implants. Macrophages are an important component involved in the repair of soft tissue due to their crucial role in improving the biological structure of connective tissues by regulating the fiber synthesis, adhesion, and contraction of gingival fibroblasts. Recent studies have illustrated that cerium-doped zeolitic imidazolate framework-8 (Ce@ZIF-8) nanoparticles (NPs) can attenuate periodontitis via both antibacterial and anti-inflammatory effects. However, the effect of Ce@ZIF-8 NPs on soft tissue integration around the abutment is unknown. Herein, we first prepared Ce@ZIF-8 NPs by a one-pot synthesis. Then, we probed the regulatory effect of Ce@ZIF-8 NPs on macrophage polarization, and further experiments were performed to study the changes of fiber synthesis as well as adhesion and contraction of fibroblasts in the M2 macrophage environment stimulated by Ce@ZIF-8 NPs. Strikingly, Ce@ZIF-8 NPs can be internalized by M1 macrophages through macropinocytosis and caveolae-mediated endocytosis in addition to phagocytosis. By catalyzing hydrogen peroxide to produce oxygen, the mitochondrial function was remedied, while hypoxia inducible factor-1α was restrained. Then, macrophages were shifted from the M1 to M2 phenotype via this metabolic reprogramming pathway, provoking soft tissue integration. These results provide innovative insights into facilitating soft tissue integration around implants.

Autophagy and apoptosis: regulatory factors of chondrocyte phenotype transition in osteoarthritis

Osteoarthritis (OA) is the main pathogenic factor in diseases that cause joint deformities. As the main manifestation of the progress of OA, cartilage degradation has been closely associated with the degeneration of chondrocytes, which is induced by inflammatory factors and other trauma factors. Autophagy and apoptosis are the main mechanisms for cells to maintain homeostasis and play crucial roles in OA. Under the influence of external environmental factors (such as aging and injury), the metabolism of cells can be altered, which may affect the extent of autophagy and apoptosis. With the progression of OA, these changes can alter the cell phenotypes, and the cells of different phenotypes display distinct differences in morphology and function. In this review, we have summarized the alteration in cell metabolism, autophagy, and the extent of apoptosis during OA progression and its effects on the cell phenotypes to provide new ideas for further research on the mechanisms of phenotypic transition and therapeutic strategies so as to reverse the cell phenotypes.

The Effect of the JAK-inhibitor Tofacitinib on Chondrocyte Autophagy in Osteoarthritis.. [DOI: 10.21203/rs.3.rs-2670470/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

Osteoarthritis (OA) is a multifactorial disease of the whole joint that has a complex pathogenesis. There is currently no cure for OA. Tofacitinib is a broad JAK inhibitor that can have an anti-inflammatory effect. The objective of this study was to investigate the effect of tofacitinib on the cartilage extracellular matrix in OA and determine whether tofacitinib exerts a protective effect by inhibiting the JAK1/STAT3 signaling pathway and upregulating autophagy in chondrocytes. We established an vitro OA model by exposing SW1353 cells to interleukin-1β (IL-1β) and induced OA in rats using the modified Hulth method. We found that IL-1β promoted the expression of OA-related matrix metalloproteinases (MMP-3 and MMP-13), reduced the expression of collagen II, reduced the expression of beclin1 and LC3-II/I, and promoted the accumulation of p62 in SW1353 cells. Tofacitinib attenuated IL-1β-stimulated changes in MMPs and collagen II and restored chondrocyte autophagy. In IL-1β-stimulated SW1353 cells, the JAK1/STAT3 signaling pathway was activated. Tofacitinib inhibited the IL-1β-stimulated expression of p-JAK1 and p-STAT3 and prevented translocation of p-STAT3 to the nucleus. In the rat model of OA, tofacitinib reduced articular cartilage degeneration by delaying cartilage extracellular matrix degradation and increasing chondrocyte autophagy. Our study demonstrates that chondrocyte autophagy was impaired in experimental models of OA. Tofacitinib reduced the inflammatory response and restored the damaged autophagic flux in OA.

Mechanism of HIFs in osteoarthritis

Osteoarthritis (OA) is a common disabling disease which has a high incidence rate in the elderly. Studies have found that many factors are involved in the pathogenesis of OA. Hypoxia-inducible factors (HIFs) are core regulators that induce hypoxia genes, repair the cellular oxygen environment, and play an important role in the treatment of OA. For example, HIF-1α can maintain the stability of the articular cartilage matrix, HIF-2α is able to cause chondrocyte apoptosis and intensify in-flammatory response, and HIF-3α may be the target gene of HIF-1α and HIF-2α, thereby playing a negative regulatory role. This review examines the mechanism of HIFs in cartilage extracellular matrix degradation, apoptosis, inflammatory reaction, autophagy and then further expounds on the roles of HIFs in OA, consequently providing theoretical support for the pathogenesis of OA and a new target for OA treatment.

Freeze-casting osteochondral scaffolds: The presence of a nutrient-permeable film between the bone and cartilage defect reduces cartilage regeneration

Microfracture treatment that is basically relied on stem cells and growth factors in bone marrow has achieved a certain progress for cartilage repair in clinic. Nevertheless, the neocartilage generated from the microfracture strategy is limited endogenous regeneration and prone to fibrosis due to the influences of cell inflammation and vascular infiltration. To explore the crucial factor for articular cartilage remodeling, here we design a trilaminar osteochondral scaffold with a selective permeable film in middle isolation layer which can prevent stem cells, immune cells, and blood vessels in the bone marrow from invading into the cartilage layer, but allow the nutrients and cytokines to penetrate. Our findings show that the trilaminar scaffold exhibits a good biocompatibility and inflammatory regulation, but the osteochondral repair is far less effective than the control of double-layer scaffold without isolation layer. These results demonstrate that it is not adequate to rely only on nutrients and cytokines to promote reconstruction of articular cartilage, and the various cells in bone marrow are indispensable. Consequently, the current study illustrates that cell infiltration involving stem cells, immune cells and other cells from bone marrow plays a crucial role in articular cartilage remodeling based on the integrated scaffold strategy. STATEMENT OF SIGNIFICANCE: Clinical microfracture treatment plays a certain role on the restoration of injured cartilage, but the regenerative cartilage is prone to be fibrocartilage due to the modulation of bone marrow cells. Herein, we design a trilaminar osteochondral scaffold with a selective permeable film in middle isolation layer. This specific film made of dense electrospun nanofiber can prevent bone marrow cells from invading into the cartilage layer, but allow the nutrients and cytokines to penetrate. Our conclusion is that the cartilage remodeling will be extremely inhibited when the bone marrow cells are blocking. Owing to the diverse cells in bone marrow, we will further explore the influence of each cell type on cartilage repair in our continuous future work.

Treatment outcomes of injectable thermosensitive hydrogel containing bevacizumab in intervertebral disc degeneration

Intervertebral disc (IVD) degeneration (IDD) is a common musculoskeletal disease and its treatment remains a clinical challenge. It is characterised by reduced cell numbers and degeneration of the extracellular matrix (ECM). Nucleus pulposus (NP) cells play a crucial role in this process. The purpose of this study is to explore the role of bevacizumab, a vascular endothelial growth factor (VEGF) inhibitor, in the treatment of IDD through local drug delivery. High expression of VEGF was observed in degenerating human and rat IVDs. We demonstrated that MMP3 expression was decreased and COL II synthesis was promoted, when VEGF expression was inhibited by bevacizumab, thereby improving the degree of disc degeneration. Thus, these findings provide strong evidence that inhibition of VEGF expression by local delivery of bevacizumab is safe and effective in ameliorating disc degeneration in rats. The injectable thermosensitive PLGA-PEG-PLGA hydrogels loaded with bevacizumab is a potential therapeutic option for disc degeneration.

The Epigenetic Regulation of Nonhistone Proteins by SETD7: New Targets in Cancer

Epigenetic modifications are essential mechanism by which to ensure cell homeostasis. One such modification is lysine methylation of nonhistone proteins by SETD7, a mono-methyltransferase containing SET domains. SETD7 methylates over 30 proteins and is thus involved in various classical pathways. As such, SETD7 has been implicated in both the basic functions of normal tissues but also in several pathologies, such as cancers. In this review, we summarize the current knowledge of SETD7 substrates, especially transcriptional-related proteins and enzymes, and their putative roles upon SETD7-mediated methylation. We focus on the role of SETD7 in cancers, and speculate on the possible points of intervention and areas for future research.

Inhibition of SET domain-containing (lysine methyltransferase) 7 alleviates cognitive impairment through suppressing the activation of NOD-like receptor protein 3 inflammasome in isoflurane-induced aged mice

BACKGROUND

As a common postoperative complication to elderly patients, postoperative cognitive dysfunction (POCD) is a central nervous system complication, often taking place after anesthesia and surgery. (Su(var)3-9, enhancer-of-zeste, and trithorax) domain-containing protein 7 (SETD7) plays important roles in metabolic-related diseases, viral infections, tumor formation, and some inflammatory reactions. However, the role and mechanism of SETD7 in POCD have not been previously studied.

METHODS

RT-PCR and Western blot were performed to evaluate the efficiency of knockdown of SETD7. The pathological changes of hippocampal neurons in isoflurane-anesthetized mice were detected by HE staining, and the Morris water maze experiment was performed to evaluate the learning and memory abilities of mice. The effect of SETD7 on the hippocampus in isoflurane-induced aged mice was examined by Western blot and TUNEL assay. Then ELISA assay was applied to determine the expression of some inflammatory cytokines, followed by the detection of expression of NOD-like receptor protein 3 (NLRP3) inflammasome through Western blot.

RESULTS

The data of this research revealed that SETD7 knockdown improved cognitive impairment in isoflurane-anesthetized mice, ameliorated cell pyroptosis, inhibited the release of inflammatory cytokines, and suppressed the activation of NLRP3 inflammasome in the hippocampus in isoflurane-induced aged mice.

CONCLUSION

Collectively, these results provided evidence that the inhibition of SETD7 could alleviate neuroinflammation, pyroptosis, and cognitive impairment by suppressing the activation of the NLRP3 inflammasome in isoflurane-induced aged mice.

The essential anti-angiogenic strategies in cartilage engineering and osteoarthritic cartilage repair

In the cartilage matrix, complex interactions occur between angiogenic and anti-angiogenic components, growth factors, and environmental stressors to maintain a proper cartilage phenotype that allows for effective load bearing and force distribution. However, as seen in both degenerative disease and tissue engineering, cartilage can lose its vascular resistance. This vascularization then leads to matrix breakdown, chondrocyte apoptosis, and ossification. Research has shown that articular cartilage inflammation leads to compromised joint function and decreased clinical potential for regeneration. Unfortunately, few articles comprehensively summarize what we have learned from previous investigations. In this review, we summarize our current understanding of the factors that stabilize chondrocytes to prevent terminal differentiation and applications of these factors to rescue the cartilage phenotype during cartilage engineering and osteoarthritis treatment. Inhibiting vascularization will allow for enhanced phenotypic stability so that we are able to develop more stable implants for cartilage repair and regeneration.

The Releasate of Avascular Cartilage Demonstrates Inherent Pro-Angiogenic Properties In Vitro and In Vivo

OBJECTIVE

Cartilage is avascular and numerous studies have identified the presence of single anti- and pro-angiogenic factors in cartilage. To better understand the maintenance hyaline cartilage, we assessed the angiogenic potential of complete cartilage releasate with functional assays in vitro and in vivo.

DESIGN

We evaluated the gene expression profile of angiogenesis-related factors in healthy adult human articular cartilage with a transcriptome-wide analysis generated by next-generation RNAseq. The effect on angiogenesis of the releasate of cartilage tissue was assessed with a chick chorioallantoic membrane (CAM) assay as well as human umbilical vein endothelial cell (HUVEC) migration and proliferation assays using conditioned media generated from tissue-engineered cartilage derived from human articular and nasal septum chondrocytes as well as explants from bovine articular cartilage and human nasal septum. Experiments were done with triplicate samples of cartilage from 3 different donors.

RESULTS

RNAseq data of 3 healthy human articular cartilage donors revealed that the majority of known angiogenesis-related factors expressed in healthy adult articular cartilage are pro-angiogenic. The releasate from generated cartilage as well as from tissue explants, demonstrated at least a 3.1-fold increase in HUVEC proliferation and migration indicating a pro-angiogenic effect of cartilage. Finally, the CAM assay demonstrated that cartilage explants can indeed attract vessels; however, their ingrowth was not observed.

CONCLUSION

Using multiple approaches, we show that cartilage releasate has an inherent pro-angiogenic capacity. It remains vessel free due to anti-invasive properties associated with the tissue itself.

SET8, a novel regulator to ameliorate vascular calcification via activating PI3K/Akt mediated anti-apoptotic effects

Previous studies have shown that the apoptosis of vascular smooth muscle cells (VSMCs) underlies the mechanism of pathological calcification in patients with chronic kidney disease (CKD). SET domain-containing protein 8 (SET8) is an efficient protein that modulates apoptosis in hepatocellular carcinoma cells, esophageal squamous cells, and neuronal cells by regulating pathological processes, such as cell cycle progression and transcription regulation. However, whether SET8 is involved in high phosphorus-induced vascular calcification by mediating apoptosis remains unclear. Here, we report that SET8 is located both in the nucleus and cytoplasm and is significantly downregulated in calcification models. SET8 deficiency promoted apoptosis of VSMCs, as indicated by the increased Bax/Bcl-2 and cleaved caspase-3/total caspase-3 ratios. Mechanistically, the PI3K/Akt pathway was mediated by SET8, and inhibition of the PI3K/Akt signaling pathway by administering LY294002 or transfecting the Akt phosphorylation-inactivated mutation plasmid increased apoptosis and calcification. Akt phosphorylation constitutively activated mutations can reduce the apoptosis and calcification of VSMCs. Furthermore, exogenous overexpression of SET8 reversed the effect of PI3K/Akt inhibition on VSMC apoptosis and calcification. In summary, our research suggests that SET8 overexpression ameliorates high phosphorus-induced calcification of VSMCs by activating PI3K/Akt mediated anti-apoptotic effects.

SETD7 regulates chondrocyte differentiation and glycolysis via the Hippo signaling pathway and HIF‑1α

Chondrocytes are well adapted to hypoxia and produce more functional extracellular matrix in low oxygen environments in vitro. In our previous study, methyltransferase SET domain containing (SETD)7 regulated chondrocyte activity in hypoxic conditions. However, the precise association between SETD7 and chondrocyte differentiation under low oxygen partial pressure remains unclear. The association between SETD7 and chondrocyte differentiation was studied by silencing SETD7 in chondrocytes in vitro. The results showed that the silencing of SETD7 in ATDC5 cells inhibited the Hippo signaling pathway, decreased Yes-associated protein (YAP) phosphorylation and increased the levels of YAP and hypoxia inducible factor-1α (HIF-1α) in the nucleus. YAP combined with HIF-1α to form a complex that promoted the expression of genes involved in chondrogenic differentiation and the glycolytic pathway. Thus, SETD7 inhibited chondrocyte differentiation and glycolysis via the Hippo signaling pathway. The present study demonstrated that SETD7 was a potential molecular target that maintained the chondrocyte phenotype during cartilage tissue engineering and cartilage-associated disease.