Wwp2 maintains cartilage homeostasis through regulation of Adamts5

Pectolinarigenin targeting FGFR3 alleviates osteoarthritis progression by regulating the NF-κB/NLRP3 inflammasome pyroptotic pathway

OBJECTIVE

Osteoarthritis (OA) is a chronic degenerative disease characterized by cartilage degeneration, involving inflammation, pyroptosis, and degeneration of the extracellular matrix (ECM). Pectolinarigenin (PEC) is a natural flavonoid with antioxidant, anti-inflammatory and anti-tumor properties. This study aims to explore the potential of PEC in ameliorating OA progression and its underlying mechanisms.

METHODS

Chondrocytes were exposed to 10 ng/mL IL-1β to simulate OA-like changes. The effect of PEC on IL-1β-treated chondrocytes was assessed using ELISA, western blot, and immunofluorescence. The mRNA sequencing (mRNA-seq) was employed to explore the possible targets of PEC in delaying OA progression. The OA mouse model was induced through anterior cruciate ligament transection (ACLT) and divided into sham, ACLT, ACLT+5 mg/kg PEC, and ACLT+10 mg/kg PEC groups. Micro-computed tomography and histological analysis were conducted to confirm the beneficial effects of PEC on OA in vivo.

RESULTS

PEC mitigated chondrocyte pyroptosis, as evidenced by reduced levels of pyroptosis-related proteins. Additionally, PEC attenuated IL-1β-mediated chondrocyte ECM degradation and inflammation. Mechanistically, mRNA-seq showed that FGFR3 was a downstream target of PEC. FGFR3 silencing reversed the beneficial effects of PEC on IL-1β-exposed chondrocytes. PEC exerted anti-pyroptotic, anti-ECM degradative, and anti-inflammatory effects through upregulating FGFR3 to inhibit the NF-κB/NLRP3 pyroptosis-related pathway. Consistently, in vivo experiments demonstrated the chondroprotective effects of PEC in OA mice.

CONCLUSION

PEC alleviate OA progression by FGFR3/NF-κB/NLRP3 pathway mediated chondrocyte pyroptosis, ECM degradation and inflammation, suggesting the potential of PEC as a therapeutic agent for OA.

Effects of the oral administration of glycosaminoglycans with or without native type II collagen on the articular cartilage transcriptome in an osteoarthritic-induced rabbit model

BACKGROUND

In a previous study, the 84-day administration of glycosaminoglycans (GAGs), with or without native collagen type II (NC), in an osteoarthritis (OA)-induced rabbit model slowed down OA progression, improved several micro- and macroscopic parameters and magnetic resonance imaging (MRI) biomarkers in cartilage, and increased hyaluronic acid levels in synovial fluid. To elucidate the potential underlying mechanisms, a transcriptomics approach was conducted using medial femoral condyle and trochlea samples.

RESULTS

The administration of chondroitin sulfate (CS), glucosamine hydrochloride (GlHCl), and hyaluronic acid (HA), with (CGH-NC) or without (CGH) NC, strongly modulated several genes involved in chondrocyte extracellular matrix (ECM) remodeling and homeostasis when compared to non-treated rabbits (CTR group). Notably, both treatments shared the main mechanism of action, which was related to ECM modulation through the down-regulation of genes encoding proteolytic enzymes, such as ADAM metallopeptidase with thrombospondin type 1 motif, 9 (Adamts9), and the overexpression of genes with a relevant role in the synthesis of ECM components, such as aggrecan (Acan) in both CGH-NC and CGH groups, and fibronectin 1 (Fn1) and collagen type II, alpha 1 (Col2A1) in the CGH group. Furthermore, there was a significant modulation at the gene expression level of the mTOR signaling pathway, which is associated with the regulation of the synthesis of ECM proteolytic enzymes, only in CGH-NC-supplemented rabbits. This modulation could account for the better outcomes concerning the microscopic and macroscopic evaluations reported in these animals.

CONCLUSIONS

In conclusion, the expression of key genes involved in chondrocyte ECM remodeling and homeostasis was significantly modulated in rabbits in response to both CGH and CGH-NC treatments, which would partly explain the mechanisms by which these therapies exert beneficial effects against OA.

Suppression of YAP Ameliorates Cartilage Degeneration in Ankle Osteoarthritis via Modulation of the Wnt/β-Catenin Signaling Pathway

Ankle osteoarthritis is a relatively understudied condition and the molecular mechanisms involved in its development are not well understood. This investigation aimed to explore the role and underlying molecular mechanisms of Yes-associated protein (YAP) in rat ankle osteoarthritis. The results demonstrated that YAP expression levels were abnormally increased in the ankle osteoarthritis cartilage model. In addition, knockdown of YAP expression was shown to hinder the imbalance in ECM metabolism induced by IL-1β in chondrocytes, as demonstrated by the regulation of matrix metalloproteinase (MMP)-3, MMP-9, and MMP-13, a disintegrin, metalloprotease with thrombospondin motifs, aggrecan, and collagen II expression. Additional studies revealed that downregulation of YAP expression markedly inhibited the overexpression of β-catenin stimulated by IL-1β. Furthermore, inhibition of the Wnt/β-catenin signaling pathway reversed the ECM metabolism imbalance caused by YAP overexpression in chondrocytes. It is important to note that the YAP-specific inhibitor verteporfin (VP) significantly delayed the progression of ankle osteoarthritis. In conclusion, the findings highlighted the crucial role of YAP as a regulator in modulating the progression of ankle osteoarthritis via the Wnt/β-catenin signaling pathway. These findings suggest that pharmacological inhibition of YAP can be an effective and critical therapeutic target for alleviating ankle osteoarthritis.

MiR-322-5p is involved in regulating chondrocyte proliferation and differentiation in offspring's growth plate of maternal gestational diabetes

Pregestational diabetes mellitus (PGDM) has an impact on fetal bone formation, but the underlying mechanism is still obscure. Although miRNAs have been extensively investigated throughout bone formation, their effects on fetal bone development caused by PGDM still need clarification. This study intends to examine the mechanism by which hyperglycemia impairs the bone formation of offspring via miR-322-5p (miR-322). In this study, miR-322 was selected by systemically screening utilizing bioinformatics and subsequent validation experiments. Using streptozotocin (STZ)-induced diabetic mice and ATDC5 cell lines, we found that miR-322 was abundantly expressed in the proliferative and hypertrophic zones of the growth plate, and its expression pattern was disturbed in the presence of hyperglycemia, suggesting that miR-322 is involved in the chondrocyte proliferation and differentiation in absence/presence of hyperglycemia. This observation was proved by manipulating miR-322 expression in ATDC5 cells by transfecting mimic and inhibitor of miR-322. Furthermore, Adamts5, Col12a1, and Cbx6 were identified as the potential target genes of miR-322, verified by the co-transfection of miR-322 inhibitor and the siRNAs, respectively. The evaluation criteria are the chondrocyte proliferation and differentiation and their relevant key gene expressions (proliferation: Sox9 and PthIh; differentiation: Runx2 and Col10a1) after manipulating the gene expressions in ATDC5 cells. This study revealed the regulative role miR-322 on chondrocyte proliferation and differentiation of growth plate by targeting Adamts5, Col12a1, and Cbx6 in hyperglycemia during pregnancy. This translational potential represents a promising avenue for advancing our understanding of bone-related complications in diabetic pregnancy and mitigating bone deficiencies in diabetic pregnant individuals, improving maternal and fetal outcomes.

Ubiquitination of NS1 Confers Differential Adaptation of Zika Virus in Mammalian Hosts and Mosquito Vectors

Arboviruses, transmitted by medical arthropods, pose a serious health threat worldwide. During viral infection, Post Translational Modifications (PTMs) are present on both host and viral proteins, regulating multiple processes of the viral lifecycle. In this study, a mammalian E3 ubiquitin ligase WWP2 (WW domain containing E3 ubiquitin ligase 2) is identified, which interacts with the NS1 protein of Zika virus (ZIKV) and mediates K63 and K48 ubiquitination of Lys 265 and Lys 284, respectively. WWP2-mediated NS1 ubiquitination leads to NS1 degradation via the ubiquitin-proteasome pathway, thereby inhibiting ZIKV infection in mammalian hosts. Simultaneously, it is found Su(dx), a protein highly homologous to host WWP2 in mosquitoes, is capable of ubiquitinating NS1 in mosquito cells. Unexpectedly, ubiquitination of NS1 in mosquitoes does not lead to NS1 degradation; instead, it promotes viral infection in mosquitoes. Correspondingly, the NS1 K265R mutant virus is less infectious to mosquitoes than the wild-type (WT) virus. The above results suggest that the ubiquitination of the NS1 protein confers different adaptations of ZIKV to hosts and vectors, and more importantly, this explains why NS1 K265-type strains have become predominantly endemic in nature. This study highlights the potential application in antiviral drug and vaccine development by targeting viral proteins' PTMs.

E3 ubiquitin ligases: key regulators of osteogenesis and potential therapeutic targets for bone disorders

Ubiquitination is a crucial post-translational modification of proteins that mediates the degradation or functional regulation of specific proteins. This process participates in various biological processes such as cell growth, development, and signal transduction. E3 ubiquitin ligases play both positive and negative regulatory roles in osteogenesis and differentiation by ubiquitination-mediated degradation or stabilization of transcription factors, signaling molecules, and cytoskeletal proteins. These activities affect the proliferation, differentiation, survival, and bone formation of osteoblasts (OBs). In recent years, advances in genomics, transcriptomics, and proteomics have led to a deeper understanding of the classification, function, and mechanisms of action of E3 ubiquitin ligases. This understanding provides new insights and approaches for revealing the molecular regulatory mechanisms of bone formation and identifying therapeutic targets for bone metabolic diseases. This review discusses the research progress and significance of the positive and negative regulatory roles and mechanisms of E3 ubiquitin ligases in the process of osteogenic differentiation. Additionally, the review highlights the role of E3 ubiquitin ligases in bone-related diseases. A thorough understanding of the role and mechanisms of E3 ubiquitin ligases in osteogenic differentiation could provide promising therapeutic targets for bone tissue engineering based on stem cells.

Unveiling inflammatory and prehypertrophic cell populations as key contributors to knee cartilage degeneration in osteoarthritis using multi-omics data integration

OBJECTIVES

Single-cell and spatial transcriptomics analysis of human knee articular cartilage tissue to present a comprehensive transcriptome landscape and osteoarthritis (OA)-critical cell populations.

METHODS

Single-cell RNA sequencing and spatially resolved transcriptomic technology have been applied to characterise the cellular heterogeneity of human knee articular cartilage which were collected from 8 OA donors, and 3 non-OA control donors, and a total of 19 samples. The novel chondrocyte population and marker genes of interest were validated by immunohistochemistry staining, quantitative real-time PCR, etc. The OA-critical cell populations were validated through integrative analyses of publicly available bulk RNA sequencing data and large-scale genome-wide association studies.

RESULTS

We identified 33 cell population-specific marker genes that define 11 chondrocyte populations, including 9 known populations and 2 new populations, that is, pre-inflammatory chondrocyte population (preInfC) and inflammatory chondrocyte population (InfC). The novel findings that make this an important addition to the literature include: (1) the novel InfC activates the mediator MIF-CD74; (2) the prehypertrophic chondrocyte (preHTC) and hypertrophic chondrocyte (HTC) are potentially OA-critical cell populations; (3) most OA-associated differentially expressed genes reside in the articular surface and superficial zone; (4) the prefibrocartilage chondrocyte (preFC) population is a major contributor to the stratification of patients with OA, resulting in both an inflammatory-related subtype and a non-inflammatory-related subtype.

CONCLUSIONS

Our results highlight InfC, preHTC, preFC and HTC as potential cell populations to target for therapy. Also, we conclude that profiling of those cell populations in patients might be used to stratify patient populations for defining cohorts for clinical trials and precision medicine.

MiR-653-5p drives osteoarthritis pathogenesis by modulating chondrocyte senescence

BACKGROUND

Due to the unclear pathogenesis of osteoarthritis (OA), effective treatment for this ailment is presently unavailable. Accumulating evidence points to chondrocyte senescence as a key driver in OA development. This study aims to identify OA-specific microRNAs (miRNAs) targeting chondrocyte senescence to alleviate OA progression.

METHODS

We screened and identified miRNAs differentially expressed in OA and normal cartilage, then confirmed the impact of miR-653-5p on chondrocyte functions and senescence phenotypes through in vitro experiments with overexpression/silencing. We identified interleukin 6 (IL-6) as the target gene of miR-653-5p and confirmed the regulatory influence of miR-653-5p on the IL-6/JAK/STAT3 signaling pathway through gain/loss-of-function studies. Finally, we assessed the therapeutic efficacy of miR-653-5p on OA using a mouse model with destabilization of the medial meniscus.

RESULTS

MiR-653-5p was significantly downregulated in cartilage tissues and chondrocytes from OA patients. Overexpression of miR-653-5p promoted chondrocyte matrix synthesis and proliferation while inhibiting chondrocyte senescence. Furthermore, bioinformatics target prediction and the luciferase reporter assays identified IL-6 as a target of miR-653-5p. Western blot assays demonstrated that miR-653-5p overexpression inhibited the protein expression of IL-6, the phosphorylation of JAK1 and STAT3, and the expression of chondrocyte senescence phenotypes by regulating the IL-6/JAK/STAT3 signaling pathway. More importantly, the cartilage destruction was significantly alleviated and chondrocyte senescence phenotypes were remarkably decreased in the OA mouse model treated by agomiR-653-5p compared to the control mice.

CONCLUSIONS

MiR-653-5p showed a significant decrease in cartilage tissues of individuals with OA, leading to an upregulation of chondrocyte senescence phenotypes in the articular cartilage. AgomiR-653-5p emerges as a potential treatment approach for OA. These findings provide further insight into the role of miR-653-5p in chondrocyte senescence and the pathogenesis of OA.

Novel insights into the role of ubiquitination in osteoarthritis

Ubiquitination (Ub) and deubiquitination are crucial post-translational modifications (PTMs) that precisely regulate protein degradation. Under the catalysis of a cascade of E1-E2-E3 ubiquitin enzymes, ubiquitination extensively regulates protein degradation exerting direct impact on various cellular processes, while deubiquitination opposes the effect of ubiquitination and prevents proteins from degradation. Notably, such dynamic modifications have been widely investigated to be implicated in cell cycle, transcriptional regulation, apoptosis and so on. Therefore, dysregulation of ubiquitination and deubiquitination could lead to certain diseases through abnormal protein accumulation and clearance. Increasing researches have revealed that the dysregulation of catalytic regulators of ubiquitination and deubiquitination triggers imbalance of cartilage homeostasis that promotes osteoarthritis (OA) progression. Hence, it is now believed that targeting on Ub enzymes and deubiquitinating enzymes (DUBs) would provide potential therapeutic pathways. In the following sections, we will summarize the biological role of Ub enzymes and DUBs in the development and progression of OA by focusing on the updating researches, with the aim of deepening our understanding of the underlying molecular mechanism of OA pathogenesis concerning ubiquitination and deubiquitination, so as to explore novel potential therapeutic targets of OA treatment.

Specific isoforms of the ubiquitin ligase gene WWP2 are targets of osteoarthritis genetic risk via a differentially methylated DNA sequence

BACKGROUND

Transitioning from a genetic association signal to an effector gene and a targetable molecular mechanism requires the application of functional fine-mapping tools such as reporter assays and genome editing. In this report, we undertook such studies on the osteoarthritis (OA) risk that is marked by single nucleotide polymorphism (SNP) rs34195470 (A > G). The OA risk-conferring G allele of this SNP associates with increased DNA methylation (DNAm) at two CpG dinucleotides within WWP2. This gene encodes a ubiquitin ligase and is the host gene of microRNA-140 (miR-140). WWP2 and miR-140 are both regulators of TGFβ signaling.

METHODS

Nucleic acids were extracted from adult OA (arthroplasty) and foetal cartilage. Samples were genotyped and DNAm quantified by pyrosequencing at the two CpGs plus 14 flanking CpGs. CpGs were tested for transcriptional regulatory effects using a chondrocyte cell line and reporter gene assay. DNAm was altered using epigenetic editing, with the impact on gene expression determined using RT-qPCR. In silico analysis complemented laboratory experiments.

RESULTS

rs34195470 genotype associates with differential methylation at 14 of the 16 CpGs in OA cartilage, forming a methylation quantitative trait locus (mQTL). The mQTL is less pronounced in foetal cartilage (5/16 CpGs). The reporter assay revealed that the CpGs reside within a transcriptional regulator. Epigenetic editing to increase their DNAm resulted in altered expression of the full-length and N-terminal transcript isoforms of WWP2. No changes in expression were observed for the C-terminal isoform of WWP2 or for miR-140.

CONCLUSIONS

As far as we are aware, this is the first experimental demonstration of an OA association signal targeting specific transcript isoforms of a gene. The WWP2 isoforms encode proteins with varying substrate specificities for the components of the TGFβ signaling pathway. Future analysis should focus on the substrates regulated by the two WWP2 isoforms that are the targets of this genetic risk.

E3 ubiquitin ligase WWP2 as a promising therapeutic target for diverse human diseases

Mammalian E3 ubiquitin ligases have emerged in recent years as critical regulators of cellular homeostasis due to their roles in targeting substrate proteins for ubiquitination and triggering subsequent downstream signals. In this review, we describe the multiple roles of WWP2, an E3 ubiquitin ligase with unique and important functions in regulating a wide range of biological processes, including DNA repair, gene expression, signal transduction, and cell-fate decisions. As such, WWP2 has evolved to play a key role in normal physiology and diseases, such as tumorigenesis, skeletal development and diseases, immune regulation, cardiovascular disease, and others. We attempt to provide an overview of the biochemical, physiological, and pathophysiological roles of WWP2, as well as open questions for future research, particularly in the context of putative therapeutic opportunities.

Epigenomic profiling of the infrapatellar fat pad in osteoarthritis

Osteoarthritis is a prevalent, complex disease of the joints, and affects multiple intra-articular tissues. Here, we have examined genome-wide DNA methylation profiles of primary infrapatellar fat pad and matched blood samples from 70 osteoarthritis patients undergoing total knee replacement surgery. Comparing the DNA methylation profiles between these tissues reveal widespread epigenetic differences. We produce the first genome-wide methylation quantitative trait locus (mQTL) map of fat pad, and make the resource available to the wider community. Using two-sample Mendelian randomization and colocalization analyses, we resolve osteoarthritis GWAS signals and provide insights into the molecular mechanisms underpinning disease aetiopathology. Our findings provide the first view of the epigenetic landscape of infrapatellar fat pad primary tissue in osteoarthritis.

WWP2 protects against sepsis-induced cardiac injury through inhibiting cardiomyocyte ferroptosis

Background and Objectives

Cardiac injury plays a critical role in contributing to the mortality associated with sepsis, a condition marked by various forms of programmed cell deaths. Previous studies hinted at the WW domain-containing E3 ubiquitin protein ligase 2 (WWP2) involving in heart failure and endothelial injury. However, the precise implications of WWP2 in sepsis-induced cardiac injury, along with the underlying mechanisms, remain enigmatic.

Methods

Sepsis induced cardiac injury were constructed by intraperitoneal injection of lipopolysaccharide. To discover the function of WWP2 during this process, we designed and performed loss/gain-of-function studies with cardiac-specific vectors and WWP2 knockout mice. Combination experiments were performed to investigate the relationship between WWP2 and downstream signaling in septic myocardium injury.

Results

The protein level of WWP2 was downregulated in cardiomyocytes during sepsis. Cardiac-specific overexpression of WWP2 protected heart from sepsis induced mitochondrial oxidative stress, programmed cell death and cardiac injury, while knockdown or knockout of WWP2 exacerbated this process. The protective potency of WWP2 was predominantly linked to its ability to suppress cardiomyocyte ferroptosis rather than apoptosis. Mechanistically, our study revealed a direct interaction between WWP2 and acyl-CoA synthetase long-chain family member 4 (FACL4), through which WWP2 facilitated the ubiquitin-dependent degradation of FACL4. Notably, we observed a notable reduction in ferroptosis and cardiac injury within WWP2 knockout mice after FACL4 knockdown during sepsis.

Conclusions

WWP2 assumes a critical role in safeguarding the heart against injury induced by sepsis via regulating FACL4 to inhibit LPS-induced cardiomyocytes ferroptosis.

The role of WWP1 and WWP2 in bone/cartilage development and diseases

Bone and cartilage diseases are often associated with trauma and senescence, manifested as pain and limited mobility. The repair of bone and cartilage lesion by mesenchymal stem cells is regulated by various transcription factors. WW domain-containing protein 1 (WWP1) and WW domain-containing protein 2 (WWP2) are named for WW domain which recognizes PPXY (phono Ser Pro and Pro Arg) motifs of substrate. WWP1and WWP2 are prominent components of the homologous to the E6-AP carboxyl terminus (HECT) subfamily, a group of the ubiquitin ligase. Recently, some studies have found that WWP1 and WWP2 play an important role in the pathogenesis of bone and cartilage diseases and regulate the level and the transactivation of various transcription factors through ubiquitination. Therefore, this review summarizes the distribution and effects of WWP1 and WWP2 in the development of bone and cartilage, discusses the potential mechanism and therapeutic drugs in bone and cartilage diseases such as osteoarthritis, fracture, and osteoporosis.

ARMC5 controls the degradation of most Pol II subunits, and ARMC5 mutation increases neural tube defect risks in mice and humans

BACKGROUND

Neural tube defects (NTDs) are caused by genetic and environmental factors. ARMC5 is part of a novel ubiquitin ligase specific for POLR2A, the largest subunit of RNA polymerase II (Pol II).

RESULTS

We find that ARMC5 knockout mice have increased incidence of NTDs, such as spina bifida and exencephaly. Surprisingly, the absence of ARMC5 causes the accumulation of not only POLR2A but also most of the other 11 Pol II subunits, indicating that the degradation of the whole Pol II complex is compromised. The enlarged Pol II pool does not lead to generalized Pol II stalling or a generalized decrease in mRNA transcription. In neural progenitor cells, ARMC5 knockout only dysregulates 106 genes, some of which are known to be involved in neural tube development. FOLH1, critical in folate uptake and hence neural tube development, is downregulated in the knockout intestine. We also identify nine deleterious mutations in the ARMC5 gene in 511 patients with myelomeningocele, a severe form of spina bifida. These mutations impair the interaction between ARMC5 and Pol II and reduce Pol II ubiquitination.

CONCLUSIONS

Mutations in ARMC5 increase the risk of NTDs in mice and humans. ARMC5 is part of an E3 controlling the degradation of all 12 subunits of Pol II under physiological conditions. The Pol II pool size might have effects on NTD pathogenesis, and some of the effects might be via the downregulation of FOLH1. Additional mechanistic work is needed to establish the causal effect of the findings on NTD pathogenesis.

Challenges and promise of targeting miRNA in rheumatic diseases: a computational approach to identify miRNA association with cell types, cytokines, and disease mechanisms

MicroRNAs (miRNAs) are small non-coding RNAs that alter the expression of target genes at the post-transcriptional level, influencing diverse outcomes in metabolism, cell differentiation, proliferation, cell survival, and cell death. Dysregulated miRNA expression is implicated in various rheumatic conditions, including ankylosing spondylitis (AS), gout, juvenile idiopathic arthritis (JIA), osteoarthritis (OA), psoriatic arthritis, rheumatoid arthritis (RA), Sjogren's syndrome, systemic lupus erythematosus (SLE) and systemic sclerosis. For this review, we used an open-source programming language- PowerShell, to scan the massive number of existing primary research publications on PubMed on miRNAs in these nine diseases to identify and count unique co-occurrences of individual miRNAs and the disease name. These counts were used to rank the top seven most relevant immuno-miRs based on their research volume in each rheumatic disease. Individual miRNAs were also screened for publication with the names of immune cells, cytokines, and pathological processes involved in rheumatic diseases. These occurrences were tabulated into matrices to identify hotspots for research relevance. Based on this information, we summarize the basic and clinical findings for the top three miRNAs - miR-146, miR-155, and miR-21 - whose relevance spans across multiple rheumatic diseases. Furthermore, we highlight some unique miRNAs for each disease and why some rheumatic conditions lack research in this emerging epigenetics field. With the overwhelming number of publications on miRNAs in rheumatic diseases, this review serves as a 'relevance finder' to guide researchers in selecting miRNAs based on the compiled existing knowledge of their involvement in disease pathogenesis. This approach applies to other disease contexts with the end goal of developing miRNA-based therapeutics.

Proliferation, migration and phenotypic transformation of VSMC induced via Hcy related to up-expression of WWP2 and p-STAT3

To provide a theoretical basis for the prevention and treatment of atherosclerosis (AS), the current study aimed to investigate the mechanism underlying the effect of homocysteine (Hcy) on regulating the proliferation, migration and phenotypic transformation of vascular smooth muscle cells (VSMC) via sirtuin-1 (SIRT1)/signal transducer and activator of transcription 3 (STAT3) through Nedd4-like E3 ubiquitin-protein ligase WWP2 (WWP2). Here, Based on the establishment of ApoE-/- mouse models of high Hcy As and the model of Hcy stimulation of VSMC in vitro to observe the interaction between WWP2 and STAT3 and its effect on the proliferation, migration, and phenotypic transformation of Hcy-induced VSMC, which has not been previously reported. This study revealed that WWP2 could promote the proliferation, migration, and phenotype switch of Hcy-induced VSMC by up-regulating the phosphorylation of SIRT1/STAT3 signaling. Furthermore, Hcy might up-regulate WWP2 expression by inhibiting histone H3K27me3 expression through up-regulated UTX. These data suggest that WWP2 is a novel and important regulator of Hcy-induced VSMC proliferation, migration, and phenotypic transformation.

TCF12 regulates the TGF-β/Smad2/3 signaling pathway to accelerate the progression of osteoarthritis by targeting CXCR4

Objective

Osteoarthritis (OA), which involves total joint damage and dysfunction, is a leading cause of disability worldwide. However, its exact pathogenesis remains unclear. Here, we identified TCF12 as an important regulator of the progression of OA.

Methods

qRT-PCR, immunoblotting and immunohistochemistry (IHC) were used to detect the expression level of TCF12. The interaction of TCF12 with its downstream factor CXCR4 was assessed by Western blotting, immunofluorescence, qRT-PCR and luciferase assays. A mouse model was generated to examine the functions and mechanism of TCF12 in vivo.

Result

TCF12 expression was upregulated in chondrocytes stimulated with IL-1β and osteoarthritic chondrocytes. TCF12 upregulates the expression of CXCR4 and leads to dysfunction of the TGF-β signaling pathway. Furthermore, knockdown of TCF12 alleviated cartilage damage in a mouse model generated by destabilization of the medial meniscus (DMM).

Conclusion

TCF12 aggravates the progression of OA by targeting CXCR4 and then activating the TGF-β signaling pathway, suggesting that TCF12 may be a new target for the treatment of OA.

The translational potential of this article

Transcription Factor 12(TCF12), is known to regulate cell development and differentiation, It has been widely studied in various organs and diseases, but its role in OA remains unclear. Here, we identified Transcription Factor 12(TCF12) as an important regulator mediating chondrocyte senescence and cartilage extracellular matrix degradation indicating its role in OA. We found that TCF12 expression was upregulated both locally and systemically as OA advanced in patients with OA, and in mice after DMM surgery to induce OA. TCF12 expression caused striking progressive articular cartilage damage, synovial hyperplasia in OA mice, and remarkably, it was relieved by intra-articular administration of mutant mouse TCF12 lentiviral vector (shTCF12). Furthermore, TCF12 upregulated the expression of CXCR4, leading to exacerbation of experimental OA partially through activation of TGF-β signaling in chondrocytes. TCF12 expression was upregulated in chondrocytes treated with IL-1β and osteoarthritic chondrocytes. Our findings established an essential role of TCF12 in chondrocyte senescence and cartilage extracellular matrix degradation during OA, and identified intra-articular injection of TCF12 as a potential therapeutic strategy for OA prevention and treatment.

Osteoarthritis in the Elderly Population: Preclinical Evidence of Nutrigenomic Activities of Flavonoids

Osteoarthritis (OA) is a degenerative joint disease that is age-related and progressive. It causes the destruction of articular cartilage and underlying bone, often aggravated by inflammatory processes and oxidative stresses. This pathology impairs the quality of life of the elderly, causing pain, reduced mobility, and functional disabilities, especially in obese patients. Phytochemicals with anti-inflammatory and antioxidant activities may be used for long-term treatment of OA, either in combination with current anti-inflammatories and painkillers, or as an alternative to other products such as glucosamine and chondroitin, which improve cartilage structure and elasticity. The current systematic review provides a comprehensive understanding of the use of flavonoids. It highlights chondrocyte, cartilage, and subchondral bone activities, with a particular focus on their nutrigenomic effects. The molecular mechanisms of these molecules demonstrate how they can be used for the prevention and treatment of OA in the elderly population. However, clinical trials are still needed for effective use in clinical practice.

A human embryonic limb cell atlas resolved in space and time

Human limbs emerge during the fourth post-conception week as mesenchymal buds, which develop into fully formed limbs over the subsequent months1. This process is orchestrated by numerous temporally and spatially restricted gene expression programmes, making congenital alterations in phenotype common2. Decades of work with model organisms have defined the fundamental mechanisms underlying vertebrate limb development, but an in-depth characterization of this process in humans has yet to be performed. Here we detail human embryonic limb development across space and time using single-cell and spatial transcriptomics. We demonstrate extensive diversification of cells from a few multipotent progenitors to myriad differentiated cell states, including several novel cell populations. We uncover two waves of human muscle development, each characterized by different cell states regulated by separate gene expression programmes, and identify musculin (MSC) as a key transcriptional repressor maintaining muscle stem cell identity. Through assembly of multiple anatomically continuous spatial transcriptomic samples using VisiumStitcher, we map cells across a sagittal section of a whole fetal hindlimb. We reveal a clear anatomical segregation between genes linked to brachydactyly and polysyndactyly, and uncover transcriptionally and spatially distinct populations of the mesenchyme in the autopod. Finally, we perform single-cell RNA sequencing on mouse embryonic limbs to facilitate cross-species developmental comparison, finding substantial homology between the two species.

The role of E3 ubiquitin ligases in bone homeostasis and related diseases

The ubiquitin-proteasome system (UPS) dedicates to degrade intracellular proteins to modulate demic homeostasis and functions of organisms. These enzymatic cascades mark and modifies target proteins diversly through covalently binding ubiquitin molecules. In the UPS, E3 ubiquitin ligases are the crucial constituents by the advantage of recognizing and presenting proteins to proteasomes for proteolysis. As the major regulators of protein homeostasis, E3 ligases are indispensable to proper cell manners in diverse systems, and they are well described in physiological bone growth and bone metabolism. Pathologically, classic bone-related diseases such as metabolic bone diseases, arthritis, bone neoplasms and bone metastasis of the tumor, etc., were also depicted in a UPS-dependent manner. Therefore, skeletal system is versatilely regulated by UPS and it is worthy to summarize the underlying mechanism. Furthermore, based on the current status of treatment, normal or pathological osteogenesis and tumorigenesis elaborated in this review highlight the clinical significance of UPS research. As a strategy possibly remedies the limitations of UPS treatment, emerging PROTAC was described comprehensively to illustrate its potential in clinical application. Altogether, the purpose of this review aims to provide more evidence for exploiting novel therapeutic strategies based on UPS for bone associated diseases.

Identification of candidate genes and chemicals associated with osteoarthritis by transcriptome-wide association study and chemical-gene interaction analysis

BACKGROUND

Osteoarthritis (OA) is a common degenerative joint disease and causes chronic pain and disability to the elderly. Several risk factors are involved, such as aging, obesity, genetic susceptibility, and environmental factors. We conducted a transcriptome-wide association study (TWAS) and chemical-related gene set enrichment analysis (CGSEA) to investigate the susceptibility genes and environmental factors.

METHODS

TWAS analysis was conducted to identify the susceptibility genes by integrating the summary-level genome-wide association study data of knee OA (KOA) and hip OA (HOA) with the precomputed expression weights from the Genotype-Tissue Expression Project (Version 8). The FUSION software was used for both single-tissue and cross-tissue TWAS, which were combined using an aggregate Cauchy association test. The biological function and pathways of the TWAS genes were explored using the Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology (GO) databases, and the human cartilage mRNA expression profiles were utilized to validate the TWAS genes. CGSEA analysis was performed to scan the OA-associated chemicals by integrating the TWAS results with the chemical-related gene sets.

RESULTS

There were 44 and 93 unique TWAS genes identified in 7 and 11 chromosomes for KOA and HOA, respectively, fourteen and four of which showed significantly differential expression in the mRNA profiles, such as CRHR1, LTBP1, WWP2, LMX1B, and PTHLH. OA-related pathways were found in the KEGG and GO analysis, such as TGF-beta signaling pathway, MAPK signaling pathway, hyaluronan metabolic process, and chondrocyte differentiation. Forty-five OA-associated chemicals were identified, including quercetin, bisphenol A, and cadmium chloride.

CONCLUSIONS

Several candidate OA-associated genes and chemicals were identified through TWAS and CGSEA analysis, which expanded our understanding of the relationship between genes, chemicals, and their impact on OA.

High-density lipoprotein regulates angiogenesis by long non-coding RNA HDRACA

Normal high-density lipoprotein (nHDL) can induce angiogenesis in healthy individuals. However, HDL from patients with coronary artery disease undergoes various modifications, becomes dysfunctional (dHDL), and loses its ability to promote angiogenesis. Here, we identified a long non-coding RNA, HDRACA, that is involved in the regulation of angiogenesis by HDL. In this study, we showed that nHDL downregulates the expression of HDRACA in endothelial cells by activating WW domain-containing E3 ubiquitin protein ligase 2, which catalyzes the ubiquitination and subsequent degradation of its transcription factor, Kruppel-like factor 5, via sphingosine 1-phosphate (S1P) receptor 1. In contrast, dHDL with lower levels of S1P than nHDL were much less effective in decreasing the expression of HDRACA. HDRACA was able to bind to Ras-interacting protein 1 (RAIN) to hinder the interaction between RAIN and vigilin, which led to an increase in the binding between the vigilin protein and proliferating cell nuclear antigen (PCNA) mRNA, resulting in a decrease in the expression of PCNA and inhibition of angiogenesis. The expression of human HDRACA in a hindlimb ischemia mouse model inhibited the recovery of angiogenesis. Taken together, these findings suggest that HDRACA is involved in the HDL regulation of angiogenesis, which nHDL inhibits the expression of HDRACA to induce angiogenesis, and that dHDL is much less effective in inhibiting HDRACA expression, which provides an explanation for the decreased ability of dHDL to stimulate angiogenesis.

Elucidating the role of ubiquitination and deubiquitination in osteoarthritis progression

Osteoarthritis is non-inflammatory degenerative joint arthritis, which exacerbates disability in elder persons. The molecular mechanisms of osteoarthritis are elusive. Ubiquitination, one type of post-translational modifications, has been demonstrated to accelerate or ameliorate the development and progression of osteoarthritis via targeting specific proteins for ubiquitination and determining protein stability and localization. Ubiquitination process can be reversed by a class of deubiquitinases via deubiquitination. In this review, we summarize the current knowledge regarding the multifaceted role of E3 ubiquitin ligases in the pathogenesis of osteoarthritis. We also describe the molecular insight of deubiquitinases into osteoarthritis processes. Moreover, we highlight the multiple compounds that target E3 ubiquitin ligases or deubiquitinases to influence osteoarthritis progression. We discuss the challenge and future perspectives via modulation of E3 ubiquitin ligases and deubiquitinases expression for enhancement of the therapeutic efficacy in osteoarthritis patients. We conclude that modulating ubiquitination and deubiquitination could alleviate the osteoarthritis pathogenesis to achieve the better treatment outcomes in osteoarthritis patients.

Down-regulation of WWP2 aggravates Type 2 diabetes mellitus-induced vascular endothelial injury through modulating ubiquitination and degradation of DDX3X

BACKGROUND

Endothelial injury caused by Type 2 diabetes mellitus (T2DM) is considered as a mainstay in the pathophysiology of diabetic vascular complications (DVCs). However, the molecular mechanism of T2DM-induced endothelial injury remains largely unknown. Here, we found that endothelial WW domain-containing E3 ubiquitin protein ligase 2 (WWP2) act as a novel regulator for T2DM-induced vascular endothelial injury through modulating ubiquitination and degradation of DEAD-box helicase 3 X-linked (DDX3X).

METHODS

Single-cell transcriptome analysis was used to evaluate WWP2 expression in vascular endothelial cells of T2DM patients and healthy controls. Endothelial-specific Wwp2 knockout mice were used to investigate the effect of WWP2 on T2DM-induced vascular endothelial injury. In vitro loss- and gain-of-function studies were performed to assess the function of WWP2 on cell proliferation and apoptosis of human umbilical vein endothelial cells. The substrate protein of WWP2 was verified using mass spectrometry, coimmunoprecipitation assays and immunofluorescence assays. The mechanism of WWP2 regulation on substrate protein was investigated by pulse-chase assay and ubiquitination assay.

RESULTS

The expression of WWP2 was significantly down-regulated in vascular endothelial cells during T2DM. Endothelial-specific Wwp2 knockout in mice significantly aggravated T2DM-induced vascular endothelial injury and vascular remodeling after endothelial injury. Our in vitro experiments showed that WWP2 protected against endothelial injury by promoting cell proliferation and inhibiting apoptosis in ECs. Mechanically, we found that WWP2 is down-regulated in high glucose and palmitic acid (HG/PA)-induced ECs due to c-Jun N-terminal kinase (JNK) activation, and uncovered that WWP2 suppresses HG/PA-induced endothelial injury by catalyzing K63-linked polyubiquitination of DDX3X and targeting it for proteasomal degradation.

CONCLUSION

Our studies revealed the key role of endothelial WWP2 and the fundamental importance of the JNK-WWP2-DDX3X regulatory axis in T2DM-induced vascular endothelial injury, suggesting that WWP2 may serve as a new therapeutic target for DVCs.

HECTD1-Mediated Ubiquitination and Degradation of Rubicon Regulates Autophagy and Osteoarthritis Pathogenesis

OBJECTIVE

Osteoarthritis (OA) is one of the most common degenerative joint diseases and is associated with autophagy suppression. However, the molecular mechanism of autophagy regulation in the context of OA is not fully understood. In this study, we sought to determine the role that HECTD1 plays in the pathogenesis of OA.

METHODS

We used RNA sequencing analysis to explore the differential expression of E3 ubiquitin ligase genes in healthy human cartilage and human cartilage affected by OA. Using surgery- and aging-induced OA mouse models, we comprehensively analyzed the function of the screened gene Hectd1 in the development of OA; furthermore, we dissected the mechanism by which HECTD1 regulates autophagy and OA progression using a combination of molecular biologic, cell biologic, and biochemical approaches.

RESULTS

HECTD1 was significantly down-regulated in human OA cartilage samples compared to healthy cartilage samples. Overexpression of HECTD1 in mouse joints alleviated OA pathogenesis, whereas conditional depletion of Hectd1 in cartilage samples aggravated surgery- and aging-induced OA pathogenesis. Mechanistically, HECTD1 bound to Rubicon and ubiquitinated Rubicon at lysine residue 534, which targets Rubicon for proteasomal degradation. More importantly, HECTD1-mediated Rubicon degradation regulated chondrocyte autophagy, leading to mitigation of stress-induced chondrocyte death and the subsequent progression of OA.

CONCLUSION

HECTD1 plays a crucial role in the pathogenesis of OA, in that HECTD1 regulates chondrocyte autophagy by ubiquitinating and targeting Rubicon for proteasomal degradation.

Dynamic chromatin accessibility tuning by the long noncoding RNA ELDR accelerates chondrocyte senescence and osteoarthritis

Epigenetic reprogramming plays a critical role in chondrocyte senescence during osteoarthritis (OA) pathology, but the underlying molecular mechanisms remain to be elucidated. Here, using large-scale individual datasets and genetically engineered (Col2a1-CreER^T2;Eldr^flox/flox and Col2a1-CreER^T2;ROSA26-LSL-Eldr^+/+ knockin) mouse models, we show that a novel transcript of long noncoding RNA ELDR is essential for the development of chondrocyte senescence. ELDR is highly expressed in chondrocytes and cartilage tissues of OA. Mechanistically, exon 4 of ELDR physically mediates a complex consisting of hnRNPL and KAT6A to regulate histone modifications of the promoter region of IHH, thereby activating hedgehog signaling and promoting chondrocyte senescence. Therapeutically, GapmeR-mediated silencing of ELDR in the OA model substantially attenuates chondrocyte senescence and cartilage degradation. Clinically, ELDR knockdown in cartilage explants from OA-affected individuals decreased the expression of senescence markers and catabolic mediators. Taken together, these findings uncover an lncRNA-dependent epigenetic driver in chondrocyte senescence, highlighting that ELDR could be a promising therapeutic avenue for OA.

E3-ubiquitin ligases and recent progress in osteoimmunology

Ubiquitin-mediated proteasomal degradation is a post-transcriptional protein modification that is comprised of various components including the 76-amino acid protein ubiquitin (Ub), Ub-activating enzyme (E1), Ub-conjugating enzyme (E2), ubiquitin ligase (E3), deubiquitinating enzyme (DUB) and proteasome. We and others have recently provided genetic evidence showing that E3-ubiquitin ligases are associated with bone metabolism, the immune system and inflammation through ubiquitylation and subsequent degradation of their substrates. Dysregulation of the E3-ubiquitin ligase RNF146-mediated degradation of the adaptor protein 3BP2 (SH3 domain-binding protein 2) causes cherubism, an autosomal dominant disorder associated with severe inflammatory craniofacial dysmorphia syndrome in children. In this review, on the basis of our discoveries in cherubism, we summarize new insights into the roles of E3-ubiquitin ligases in the development of human disorders caused by an abnormal osteoimmune system by highlighting recent genetic evidence obtained in both human and animal model studies.

Mulberroside A alleviates osteoarthritis via restoring impaired autophagy and suppressing MAPK/NF-κB/PI3K-AKT-mTOR signaling pathways

Osteoarthritis (OA) is a trauma-/age-related degenerative disease characterized by chronic inflammation as one of its pathogenic mechanisms. Mulberroside A (MA), a natural bioactive withanolide, demonstrates anti-inflammatory properties in various diseases; however, little is known about the effect of MA on OA. We aim to examine the role of MA on OA and to identify the potential mechanisms through which it protects articular cartilage. In vitro, MA improved inflammatory response, anabolism, and catabolism in IL-1β-induced OA chondrocytes. The chondroprotective effects of MA were attributed to suppressing the MAPK, NF-κB, and PI3K-AKT-mTOR signaling pathways, as well as promoting the autophagy process. In vivo, intra-articular injection of MA reduced the cartilage destruction and reversed the change of anabolic and catabolic-related proteins in destabilized medial meniscus (DMM)-induced OA models. Thus, the study indicates that MA exhibits a chondroprotective effect and might be a promising agent for OA treatment.

WWP2 confers risk to osteoarthritis by affecting cartilage matrix deposition via hypoxia associated genes

OBJECTIVE

To explore the co-expression network of the osteoarthritis (OA) risk gene WWP2 in articular cartilage and study cartilage characteristics when mimicking the effect of OA risk allele rs1052429-A on WWP2 expression in a human 3D in vitro model of cartilage.

METHOD

Co-expression behavior of WWP2 with genes expressed in lesioned OA articular cartilage (N = 35 samples) was explored. By applying lentiviral particle mediated WWP2 upregulation in 3D in vitro pellet cultures of human primary chondrocytes (N = 8 donors) the effects of upregulation on cartilage matrix deposition was evaluated. Finally, we transfected primary chondrocytes with miR-140 mimics to evaluate whether miR-140 and WWP2 are involved in similar pathways.

RESULTS

Upon performing Spearman correlations in lesioned OA cartilage, 98 highly correlating genes (|ρ| > 0.7) were identified. Among these genes, we identified GJA1, GDF10, STC2, WDR1, and WNK4. Subsequent upregulation of WWP2 on 3D chondrocyte pellet cultures resulted in a decreased expression of COL2A1 and ACAN and an increase in EPAS1 expression. Additionally, we observed a decreased expression of GDF10, STC2, and GJA1. Proteomics analysis identified 42 proteins being differentially expressed with WWP2 upregulation, which were enriched for ubiquitin conjugating enzyme activity. Finally, upregulation of miR-140 in 2D chondrocytes resulted in significant upregulation of WWP2 and WDR1.

CONCLUSIONS

Mimicking the effect of OA risk allele rs1052429-A on WWP2 expression initiates detrimental processes in the cartilage shown by a response in hypoxia associated genes EPAS1, GDF10, and GJA1 and a decrease in anabolic markers, COL2A1 and ACAN.

Characterization of Genetic Risk of End-Stage Knee Osteoarthritis Treated with Total Knee Arthroplasty: A Genome-Wide Association Study

BACKGROUND

End-stage knee osteoarthritis (OA) is a highly debilitating disease for which total knee arthroplasty (TKA) serves as an effective treatment option. Although a genetic component to OA in general has been described, evaluation of the genetic contribution to end-stage OA of the knee is limited. To this end, we present a genome-wide association study involving patients undergoing TKA for primary knee OA to characterize the genetic features of severe disease on a population level.

METHODS

Individuals with the diagnosis of knee OA who underwent primary TKA were identified in the U.K. Biobank using administrative codes. The U.K. Biobank is a data repository containing prospectively collected clinical and genomic data for >500,000 patients. A genome-wide association analysis was performed using the REGENIE software package. Logistic regression was also used to compare the total genetic risk between subgroups stratified by age and body mass index (BMI).

RESULTS

A total of 16,032 patients with end-stage knee OA who underwent primary TKA were identified. Seven genetic loci were found to be significantly associated with end-stage knee OA. The odds ratio (OR) for developing end-stage knee OA attributable to genetics was 1.12 (95% confidence interval [CI], 1.10 to 1.14), which was lower than the OR associated with BMI (OR = 1.81; 95% CI, 1.78 to 1.83) and age (OR = 2.38; 95% CI, 2.32 to 2.45). The magnitude of the OR for developing end-stage knee OA attributable to genetics was greater in patients <60 years old than in patients ≥60 years old (p = 0.002).

CONCLUSIONS

This population-level genome-wide association study of end-stage knee OA treated with primary TKA was notable for identifying multiple significant genetic variants. These loci involve genes responsible for cartilage development, cartilage homeostasis, cell signaling, and metabolism. Age and BMI appear to have a greater impact on the risk of developing end-stage disease compared with genetic factors. The genetic contribution to the development of severe disease is greater in younger patients.

LEVEL OF EVIDENCE

Prognostic Level III . See Instructions for Authors for a complete description of levels of evidence.

Runx2 and Runx3 differentially regulate articular chondrocytes during surgically induced osteoarthritis development

The Runt-related transcription factor (Runx) family plays various roles in the homeostasis of cartilage. Here, we examined the role of Runx2 and Runx3 for osteoarthritis development in vivo and in vitro. Runx3-knockout mice exhibited accelerated osteoarthritis following surgical induction, accompanied by decreased expression of lubricin and aggrecan. Meanwhile, Runx2 conditional knockout mice showed biphasic phenotypes: heterozygous knockout inhibited osteoarthritis and decreased matrix metallopeptidase 13 (Mmp13) expression, while homozygous knockout of Runx2 accelerated osteoarthritis and reduced type II collagen (Col2a1) expression. Comprehensive transcriptional analyses revealed lubricin and aggrecan as transcriptional target genes of Runx3, and indicated that Runx2 sustained Col2a1 expression through an intron 6 enhancer when Sox9 was decreased. Intra-articular administration of Runx3 adenovirus ameliorated development of surgically induced osteoarthritis. Runx3 protects adult articular cartilage through extracellular matrix protein production under normal conditions, while Runx2 exerts both catabolic and anabolic effects under the inflammatory condition.

The role of E3 ubiquitin ligase WWP2 and the regulation of PARP1 by ubiquitinated degradation in acute lymphoblastic leukemia

Acute lymphoblastic leukemia (ALL) has been a huge threat for people's health and finding effective target therapy is urgent and important. WWP2, as one of E3 ubiquitin ligase, is involved in many biological processes by specifically binding to substrates. PARP1 plays a role in cell apoptosis and is considered as a therapeutic target of certain cancers. In this study, we firstly found that WWP2 expressed higher in newly diagnosed ALL patients comparing with complete remission (CR) ALL patients and normal control people, and WWP2 in relapse ALL patients expressed higher than normal control people. WWP2 expression was related with the FAB subtype of ALL and the proportion of blast cells in bone marrow blood tested by flow cytometry. We demonstrated knockout WWP2 inhibited the ALL growth and enhanced apoptosis induced by Dox in vitro and vivo for the first time. WWP2 negatively regulated and interacted with PARP1 and WWP2 mechanically degraded PARP1 through polyubiquitin-proteasome pathway in ALL. These findings suggested WWP2 played a role in ALL development as well as growth and apoptosis, and also displayed a regulatory pathway of PARP1, which provided a new potential therapeutic target for the treatment of ALL.

Strategies to Convert Cells into Hyaline Cartilage: Magic Spells for Adult Stem Cells

Damaged hyaline cartilage gradually decreases joint function and growing pain significantly reduces the quality of a patient's life. The clinically approved procedure of autologous chondrocyte implantation (ACI) for treating knee cartilage lesions has several limits, including the absence of healthy articular cartilage tissues for cell isolation and difficulties related to the chondrocyte expansion in vitro. Today, various ACI modifications are being developed using autologous chondrocytes from alternative sources, such as the auricles, nose and ribs. Adult stem cells from different tissues are also of great interest due to their less traumatic material extraction and their innate abilities of active proliferation and chondrogenic differentiation. According to the different adult stem cell types and their origin, various strategies have been proposed for stem cell expansion and initiation of their chondrogenic differentiation. The current review presents the diversity in developing applied techniques based on autologous adult stem cell differentiation to hyaline cartilage tissue and targeted to articular cartilage damage therapy.

NEDD4 E3 Ligases: Functions and Mechanisms in Bone and Tooth

Protein ubiquitination is a precisely controlled enzymatic cascade reaction belonging to the post-translational modification of proteins. In this process, E3 ligases catalyze the binding of ubiquitin (Ub) to protein substrates and define specificity. The neuronally expressed developmentally down-regulated 4 (NEDD4) subfamily, belonging to the homology to E6APC terminus (HECT) class of E3 ligases, has recently emerged as an essential determinant of multiple cellular processes in different tissues, including bone and tooth. Here, we place special emphasis on the regulatory role of the NEDD4 subfamily in the molecular and cell biology of osteogenesis. We elucidate in detail the specific roles, downstream substrates, and upstream regulatory mechanisms of the NEDD4 subfamily. Further, we provide an overview of the involvement of E3 ligases and deubiquitinases in the development, repair, and regeneration of another mineralized tissue—tooth.

The regulatory roles of the E3 ubiquitin ligase NEDD4 family in DNA damage response

E3 ubiquitin ligases, an important part of ubiquitin proteasome system, catalyze the covalent binding of ubiquitin to target substrates, which plays a role in protein ubiquitination and regulates different biological process. DNA damage response (DDR) is induced in response to DNA damage to maintain genome integrity and stability, and this process has crucial significance to a series of cell activities such as differentiation, apoptosis, cell cycle. The NEDD4 family, belonging to HECT E3 ubiquitin ligases, is reported as regulators that participate in the DDR process by recognizing different substrates. In this review, we summarize recent researches on NEDD4 family members in the DDR and discuss the roles of NEDD4 family members in the cascade reactions induced by DNA damage. This review may contribute to the further study of pathophysiology for certain diseases and pharmacology for targeted drugs.

WWP2 ameliorates oxidative stress and inflammation in atherosclerotic mice through regulation of PDCD4/HO-1 pathway

WWP2 is a HECT-type E3 ubiquitin ligase that regulates various physiological and pathological activities by binding to different substrates, but its role in atherosclerosis (AS) remains largely unknown. The objective of the present study is to investigate the role and underlying molecular mechanisms of WWP2 in endothelial injury. We found that WWP2 expression is significantly decreased in Apolipoprotein E (ApoE) ^-/- mice. Overexpression of WWP2 attenuates oxidative stress and inflammation in AS mice, while knockdown of WWP2 has opposite effects. WWP2 overexpression alleviates oxidized low-density lipoprotein (ox-LDL)-induced human umbilical vein endothelial cell (HUVEC) injury, evidenced by the decreased oxidative stress levels and the secretion of inflammatory cytokines. Programmed cell death 4 (PDCD4) is identified as a potential substrate of WWP2. Co-immunoprecipitation (Co-IP) further demonstrates that WWP2 interacts with PDCD4, which is enhanced by ox-LDL treatment. Furthermore, the level of PDCD4 ubiquitination is significantly increased by WWP2 overexpression under the condition of MG132 treatment, while WWP2 knockdown shows opposite results. Subsequently, rescue experiments demonstrate that WWP2 knockdown further aggravates oxidative stress and inflammation in ox-LDL-treated HUVECs, while knockdown of PDCD4 alleviates this effect. Moreover, the use of sn-protoporphyrin (SnPP), an inhibitor of HO-1 pathway, confirms that PDCD4 enhances endothelial injury induced by ox-LDL through inhibiting HO-1 pathway. In conclusion, our results suggest that WWP2 protects against atherosclerosis progression via the PDCD4/HO-1 pathway, which may provide a novel treatment strategy for atherosclerosis.

Identification of candidate enhancers controlling the transcriptome during the formation of interphalangeal joints

The formation of the synovial joint begins with the visible emergence of a stripe of densely packed mesenchymal cells located between distal ends of the developing skeletal anlagen called the interzone. Recently the transcriptome of the early synovial joint was reported. Knowledge about enhancers would complement these data and lead to a better understanding of the control of gene transcription at the onset of joint development. Using ChIP-sequencing we have mapped the H3-signatures H3K27ac and H3K4me1 to locate regulatory elements specific for the interzone and adjacent phalange, respectively. This one-stage atlas of candidate enhancers (CEs) was used to map the association between these respective joint tissue specific CEs and biological processes. Subsequently, integrative analysis of transcriptomic data and CEs identified new putative regulatory elements of genes expressed in interzone (e.g., GDF5, BMP2 and DACT2) and phalange (e.g., MATN1, HAPLN1 and SNAI1). We also linked such CEs to genes known as crucial in synovial joint hypermobility and osteoarthritis, as well as phalange malformations. These analyses show that the CE atlas can serve as resource for identifying, and as starting point for experimentally validating, putative disease-causing genomic regulatory regions in patients with synovial joint dysfunctions and/or phalange disorders, and enhancer-controlled synovial joint and phalange formation.

An epigenome-wide view of osteoarthritis in primary tissues

Osteoarthritis is a complex degenerative joint disease. Here, we investigate matched genotype and methylation profiles of primary chondrocytes from macroscopically intact (low-grade) and degraded (high-grade) osteoarthritis cartilage and from synoviocytes collected from 98 osteoarthritis-affected individuals undergoing knee replacement surgery. We perform an epigenome-wide association study of knee cartilage degeneration and report robustly replicating methylation markers, which reveal an etiologic mechanism linked to the migration of epithelial cells. Using machine learning, we derive methylation models of cartilage degeneration, which we validate with 82% accuracy in independent data. We report a genome-wide methylation quantitative trait locus (mQTL) map of articular cartilage and synovium and identify 18 disease-grade-specific mQTLs in osteoarthritis cartilage. We resolve osteoarthritis GWAS loci through causal inference and colocalization analyses and decipher the epigenetic mechanisms that mediate the effect of genotype on disease risk. Together, our findings provide enhanced insights into epigenetic mechanisms underlying osteoarthritis in primary tissues.

N1-methylpseudouridine-incorporated mRNA enhances exogenous protein expression and suppresses immunogenicity in primary human fibroblast-like synoviocytes

Studies conducted using murine arthritis models have indicated that the use of in vitro-transcribed messenger RNA (IVT mRNA) is an effective therapeutic approach for joint diseases. However, the use of IVT mRNA in human synovial cells has not been widely studied. Recently, the outbreak of the novel coronavirus disease has accelerated the development of innovative mRNA vaccines, such as those containing a modified nucleic acid, N¹-methylpseudouridine-5′-triphosphate (m1ψ). IVT mRNA is an attractive tool for biological experiments and drug discovery. To verify the protein expression from IVT mRNA in vitro, primary cultured fibroblast-like synoviocytes (FLS) and MH7A human synovial fibroblast cells were transfected with enhanced green fluorescent protein (EGFP) mRNA with or without m1ψ incorporation. EGFP was detected using western blotting and fluorescence microscopy. A multiplex assay was performed to comprehensively understand IVT mRNA-induced immunogenicity. Gene expression levels were measured using reverse transcription polymerase chain reaction. In both MH7A cells and FLS, cells transfected with EGFP mRNA containing m1ψ generated higher levels of EGFP than those transfected with unmodified EGFP or control mRNAs. The multiplex assay of the FLS culture supernatant and reverse transcription polymerase chain reaction for FLS revealed that both concentration and expression of IL-6, TNF-α, and CXCL10 were upregulated by unmodified EGFP mRNA, whereas they were suppressed by EGFP mRNA with m1ψ. Overall, m1ψ incorporation enhanced protein expression and decreased the expression of cytokines. These findings may contribute to arthritis research.

ARMC5 is part of an RPB1-specific ubiquitin ligase implicated in adrenal hyperplasia

ARMC5 is implicated in several pathological conditions, but its function remains unknown. We have previously identified CUL3 and RPB1 (the largest subunit of RNA polymerase II (Pol II) as potential ARMC5-interacting proteins. Here, we show that ARMC5, CUL3 and RBX1 form an active E3 ligase complex specific for RPB1. ARMC5, CUL3, and RBX1 formed an active E3 specific for RPB1. Armc5 deletion caused a significant reduction in RPB1 ubiquitination and an increase in an accumulation of RPB1, and hence an enlarged Pol II pool in normal tissues and organs. The compromised RPB1 degradation did not cause generalized Pol II stalling nor depressed transcription in the adrenal glands but did result in dysregulation of a subset of genes, with most upregulated. We found RPB1 to be highly expressed in the adrenal nodules from patients with primary bilateral macronodular adrenal hyperplasia (PBMAH) harboring germline ARMC5 mutations. Mutant ARMC5 had altered binding with RPB1. In summary, we discovered that wildtype ARMC5 was part of a novel RPB1-specific E3. ARMC5 mutations resulted in an enlarged Pol II pool, which dysregulated a subset of effector genes. Such an enlarged Pol II pool and gene dysregulation was correlated to adrenal hyperplasia in humans and KO mice.

Limb Mesoderm and Head Ectomesenchyme Both Express a Core Transcriptional Program During Chondrocyte Differentiation

To explain how cartilage appeared in different parts of the vertebrate body at discrete times during evolution, we hypothesize that different embryonic populations co-opted expression of a core gene regulatory network (GRN) driving chondrocyte differentiation. To test this hypothesis, laser-capture microdissection coupled with RNA-seq was used to reveal chondrocyte transcriptomes in the developing chick humerus and ceratobranchial, which are mesoderm- and neural crest-derived, respectively. During endochondral ossification, two general types of chondrocytes differentiate. Immature chondrocytes (IMM) represent the early stages of cartilage differentiation, while mature chondrocytes (MAT) undergo additional stages of differentiation, including hypertrophy and stimulating matrix mineralization and degradation. Venn diagram analyses generally revealed a high degree of conservation between chondrocyte transcriptomes of the limb and head, including SOX9, COL2A1, and ACAN expression. Typical maturation genes, such as COL10A1, IBSP, and SPP1, were upregulated in MAT compared to IMM in both limb and head chondrocytes. Gene co-expression network (GCN) analyses of limb and head chondrocyte transcriptomes estimated the core GRN governing cartilage differentiation. Two discrete portions of the GCN contained genes that were differentially expressed in limb or head chondrocytes, but these genes were enriched for biological processes related to limb/forelimb morphogenesis or neural crest-dependent processes, respectively, perhaps simply reflecting the embryonic origin of the cells. A core GRN driving cartilage differentiation in limb and head was revealed that included typical chondrocyte differentiation and maturation markers, as well as putative novel "chondrocyte" genes. Conservation of a core transcriptional program during chondrocyte differentiation in both the limb and head suggest that the same core GRN was co-opted when cartilage appeared in different regions of the skeleton during vertebrate evolution.

Cartilage Homeostasis and Osteoarthritis

Healthy limb joints are important for maintaining health and attaining longevity. Endochondral ossification (the replacement of cartilage with bone, occurring during skeletal development) is essential for bone formation, especially in long-axis bones. In contrast to endochondral ossification, chondrocyte populations in articular cartilage persist and maintain joint tissue into adulthood. Articular cartilage, a connective tissue consisting of chondrocytes and their surrounding extracellular matrices, plays an essential role in the mechanical cushioning of joints in postnatal locomotion. Osteoarthritis (OA) pathology relates to disruptions in the balance between anabolic and catabolic signals, that is, the loss of chondrocyte homeostasis due to aging or overuse of cartilages. The onset of OA increases with age, shortening a person's healthy life expectancy. Although many people with OA experience pain, the mainstay of treatment is symptomatic therapy, and no fundamental treatment has yet been established. To establish regenerative or preventative therapies for cartilage diseases, further understanding of the mechanisms of cartilage development, morphosis, and homeostasis is required. In this review, we describe the general development of cartilage and OA pathology, followed by a discussion on anabolic and catabolic signals in cartilage homeostasis, mainly microRNAs.

Identification of thrombin as a key regulator of chondrocyte catabolic activity through RNA-Seq and experimental verification

The present study was designed to explore the relationship between thrombin and catabolic activity in chondrocytes. Primary rat chondrocytes were cultured for 24 h with rat serum (RS), rat plasma (RP), or rat plasma supplemented with thrombin (RPT). RNA-sequencing was then performed. Cell proliferation was analyzed by EdU uptake, CCK-8 assays and protein-protein interaction (PPI) network of proliferation-related genes. Heatmaps were used to visualize differences in gene expression. Gene Ontology (GO) enrichment analyses of up- and down-regulated differentially expressed genes were conducted. Molecular probes were used to label the endoplasmic reticulum in chondrocytes from three treatment groups. Immunofluorescence and Safranin O staining were used to assess type II collagen (Col2a1) expression and proteoglycan synthesis, whereas Lox expression was assessed by immunocytochemistry. The expression of enzymes involved in the synthesis and maturation of extracellular matrix (ECM) components and chemokines were measured by qPCR while matrix metalloproteinases (MMPs) levels were evaluated by Western blotting. Relevant nodules were selected through further PPI network analyses. A total of 727 and 1162 genes were up- and down-regulated based on the Venn diagrams comparison among groups. Thrombin was thus able to promote chondrocyte proliferation and a shift towards fibrotic morphology, while upregulating MMPs and chemokines linked to ECM degradation. In addition, thrombin decreased the enzyme expression involved in the synthesis and maturation of ECM.

An unexpected role for BAG3 in regulating PARP1 ubiquitination in oxidative stress-related endothelial damage

Oxidative stress-associated endothelial damage is the initiation factor of cardiovascular disease, and protein posttranslational modifications play critical roles in this process. Bcl-2-associated athanogene 3 (BAG3) is a molecular chaperone regulator of the BAG family, which interacts with various proteins and influences cell survival by activating multiple pathways. BAG3 undergoes posttranslational modifications; however, research evaluating BAG3 acetylation and its regulatory mechanism is lacking. In addition, the interacting protein and regulatory mechanism of BAG3 in oxidative stress-associated endothelial damage remain unclear. Here, key molecular interactions and protein modifications of BAG3 were identified in oxidative stress-associated endothelial damage. Endothelial-specific BAG3 knockout in the mouse model starkly enhances oxidative stress-associated endothelial damage and vascular remodeling, while BAG3 overexpression in mice significantly relieves this process. Mechanistically, poly(ADP-ribose) polymerase 1 (PARP1), causing oxidative stress, was identified as a novel physiological substrate of BAG3. Indeed, BAG3 binds to PARP1's BRCT domain to promote its ubiquitination (K249 residue) by enhancing the E3 ubiquitin ligase WWP2, which leads to proteasome-induced PARP1 degradation. Furthermore, we surprisingly found that BAG3 represents a new substrate of the acetyltransferase CREB-binding protein (CBP) and the deacetylase Sirtuin 2 (SIRT2) under physiological conditions. CBP/SIRT2 interacted with BAG3 and acetylated/deacetylated BAG3's K431 residue. Finally, deacetylated BAG3 promoted the ubiquitination of PARP1. This work reveals a novel regulatory system, with deacetylation-dependent regulation of BAG3 promoting PARP1 ubiquitination and degradation via enhancing WWP2, which is one possible mechanism to decrease vulnerability of oxidative stress in endothelial cells.

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Endothelial-specific BAG3 knockout in mice aggravates oxidative stress endothelial injury.

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BAG3 transgenic mice relieves oxidative stress endothelial injury.

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BAG3 promotes ubiquitination at the K249 residue of PARP1 via mobilization of the E3 ubiquitin ligase WWP2.

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CBP/SIRT2 interacted with BAG3 and acetylated/deacetylated BAG3's K431 residue.

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Deacetylated BAG3 promoted the ubiquitination of PARP1.

Highly efficient CRISPR-Cas9-mediated editing identifies novel mechanosensitive microRNA-140 targets in primary human articular chondrocytes

OBJECTIVE

MicroRNA 140 (miR-140) is a chondrocyte-specific endogenous gene regulator implicated in osteoarthritis (OA). As mechanical injury is a primary aetiological factor in OA, we investigated miR-140-dependent mechanosensitive gene regulation using a novel CRISPR-Cas9 methodology in primary human chondrocytes.

METHOD

Primary (passage 1/2) human OA chondrocytes were isolated from arthroplasty samples (six donors) and transfected with ribonuclear protein complexes or plasmids using single guide RNAs (sgRNAs) targeting miR-140, in combination with Cas9 endonuclease. Combinations of sgRNAs and single/double transfections were tested. Gene editing was measured by T7 endonuclease 1 (T7E1) assay. miRNA levels were confirmed by qPCR in chondrocytes and in wild type murine femoral head cartilage after acute injury. Predicted close match off-targets were examined. Mechanosensitive miR-140 target validation was assessed in 42 injury-associated genes using TaqMan Microfluidic cards in targeted and donor-matched control chondrocytes. Identified targets were examined in RNAseq data from costal chondrocytes from miR-140-/- mice.

RESULTS

High efficiency gene editing of miR-140 (90-98%) was obtained when two sgRNAs were combined with double RNP-mediated CRISPR-Cas9 transfection. miR-140 levels fell rapidly after femoral cartilage injury. Of the top eight miR-140 gene targets identified (P < 0.01), we validated three previously identified ones (septin 2, bone morphogenetic protein 2 and fibroblast growth factor 2). Novel targets included Agrin, a newly recognised pro-regenerative cartilage agent, and proteins associated with retinoic acid signalling and the primary cilium.

CONCLUSION

We describe a highly efficient CRISPR-Cas9-mediated strategy for gene editing in primary human chondrocytes and identify several novel mechanosensitive miR-140 targets of disease relevance.

Immunocompromised Cas9 transgenic mice for rapid in vivo assessment of host factors involved in highly pathogenic virus infection

Targeting host factors for anti-viral development offers several potential advantages over traditional countermeasures that include broad-spectrum activity and prevention of resistance. Characterization of host factors in animal models provides strong evidence of their involvement in disease pathogenesis, but the feasibility of performing high-throughput in vivo analyses on lists of genes is problematic. To begin addressing the challenges of screening candidate host factors in vivo, we combined advances in CRISPR-Cas9 genome editing with an immunocompromised mouse model used to study highly pathogenic viruses. Transgenic mice harboring a constitutively expressed Cas9 allele (Cas9^tg/tg) with or without knockout of type I interferon receptors served to optimize in vivo delivery of CRISPR single-guide RNA (sgRNA) using Invivofectamine 3.0, a simple and easy-to-use lipid nanoparticle reagent. Invivofectamine 3.0-mediated liver-specific editing to remove activity of the critical Ebola virus host factor Niemann-Pick disease type C1 in an average of 74% of liver cells protected immunocompromised Cas9^tg/tg mice from lethal surrogate Ebola virus infection. We envision that immunocompromised Cas9^tg/tg mice combined with straightforward sgRNA in vivo delivery will enable efficient host factor loss-of-function screening in the liver and other organs to rapidly study their effects on viral pathogenesis and help initiate development of broad-spectrum, host-directed therapies against emerging pathogens.

Electroacupuncture Upregulates HIF-1α and SOX9 Expression in Knee Osteoarthritis

Electroacupuncture (EA) has been clinically used in knee osteoarthritis broadly and proved to be effective than other therapies with fewer side effects; however, the mechanism of electroacupuncture to work on cartilage remains unclear. In this study, we aimed to evaluate the effect of EA treatment on cartilage and the relationship between EA and proteins such as HIF-a and SOX9. EA (dilatational wave, 3-15 HZ, 1 mA) has been applied to bilateral Zusanli (ST36), Xuehai (SP10), Taixi (KI3), and Yanglingquan (GB34) of rats. Results showed that the cartilage of the knee osteoarthritis group had obvious damage and fissure formation while the EA group showed that the cartilage destruction was generally milder. In addition, the protein expression levels of HIF-1α, and chondrogenic markers such as Sox9, and ACAN in the electroacupuncture group were higher than those in the ACLT group. Also, the extracellular matrix protein expression levels of MMP13 and ADAMTS5 were decreased in the EA group. These findings indicate that EA could alleviate the severity of knee osteoarthritis, and HIF-a and SOX9 may closely attribute to the treatment.

Whole-Transcriptome Sequence of Degenerative Meniscus Cells Unveiling Diagnostic Markers and Therapeutic Targets for Osteoarthritis

Meniscus plays an important role in joint homeostasis. Tear or degeneration of meniscus might facilitate the process of knee osteoarthritis (OA). Hence, to investigate the transcriptome change during meniscus degeneration, we reveal the alterations of messenger RNA (mRNA), microRNA (miRNA), long noncoding RNA (lncRNA), and circular RNA (circRNA) in meniscus during OA by whole-transcriptome sequence. A total of 375 mRNAs, 15 miRNAs, 56 lncRNAs, and 90 circRNAs were significantly altered in the degenerative meniscus treated with interleukin-1β (IL-1β). More importantly, highly specific co-expression RNA (ceRNA) networks regulated by lncRNA LOC107986251-miR-212-5p-SESN3 and hsa_circ_0018069-miR-147b-3p-TJP2 were screened out during IL-induced meniscus degeneration, unveiling potential therapeutic targets for meniscus degeneration during the OA process. Furthermore, lipocalin-2 (LCN2) and RAB27B were identified as potential biomarkers in meniscus degeneration by overlapping three previously constructed databases of OA menisci. LCN2 and RAB27B were both upregulated in osteoarthritic menisci and IL-1β-treated menisci and were highly associated with the severity of OA. This could introduce potential novel molecules into the database of clinical diagnostic biomarkers and possible therapeutic targets for early-stage OA treatment.

Etomidate inhibits cell proliferation and induces apoptosis in A549 non-small cell lung cancer cells via downregulating WWP2

Etomidate (ETO) is a commonly used intravenous anesthetic that has been reported to exert a tumor suppressive effect in several types of cancer. The present study aimed to investigate the effect of ETO on cell proliferation and apoptosis in non-small cell lung cancer (NSCLC) cells and elucidate its potential mechanism of action. Therefore, Cell Counting Kit-8 assay was performed to evaluate the effect of different concentrations of ETO (0, 1, 2 or 3 µg/ml) on A549 cell viability. In addition, the possible interaction between ETO and WW domain containing E3 ubiquitin protein ligase 2 (WWP2) was predicted using the STITCH database. Additionally, a stable WWP2-overexpressing A549 cell line was constructed by transfecting A549 cells with the pcDNA3.1-WWP2 plasmid. Cell proliferation and apoptosis were assessed using colony formation and TUNEL assays, respectively. The mRNA and protein expression levels of the apoptosis-related proteins Bcl-2, Bax, caspase 3 and cleaved-caspase 3 were determined by reverse transcription-quantitative PCR and western blotting. In addition, the expression and phosphorylation levels of proliferation-associated genes (PCNA and Ki-67) and proteins in the PI3K/Akt pathway were analyzed by western blotting. The results showed that treatment with ETO attenuated the cell viability and proliferation of A549 cells. ETO also promoted cell apoptosis and decreased the expression of the anti-apoptotic protein Bcl-2, whilst increasing that of pro-apoptotic proteins Bax and cleaved caspase 3 in a dose-dependent manner. Furthermore, ETO was found to negatively regulate the expression of WWP2, such that WWP2 overexpression reversed the potentiating effects of ETO on cell apoptosis. In addition, ETO promoted the expression of PTEN and reduced the phosphorylation levels of the PI3K/AKT pathway-related proteins. These effects aforementioned could also be reversed by WWP2 overexpression. Therefore, data from the present study suggest that ETO can attenuate the progression of NSCLC through by the PI3K/AKT pathway, specifically by targeting WWP2. These findings may provide a novel target for the treatment of NSCLC.