Targeting the senescence-related genes MAPK12 and FOS to alleviate osteoarthritis.

Background: The mechanism by which chondrocyte senescence aggravate OA progression has not yet been well elucidated. The aim of this study was to investigate the chondrocyte senescence related gene biosignatures in OA, and to analyze on the underlying mechanisms of senescence in OA. Materials and methods: We intersected osteoarthritis dataset GSE82107 from GEO database and senescence dataset from CellAge database of human senescence-associated genes based on genetic manipulations experiments plus gene expression profilin, and screened out 4 overlapping genes. The hub genes were verified in vitro and in human OA cartilage tissues by qRT-PCR. We further confirmed the function of mitogen-activated protein kinase 12 (MAPK12) and Fos proto-oncogene (FOS) in OA in vitro and in vivo by qRT-PCR, western blotting, Edu staining, immunofluorescence, SA-ß-gal staining, HE, IHC, von frey test, and hot plate. Results: 1458 downregulated and 218 upregulated DEGs were determined from GSE82107, and 279 human senescence-associated genes were downloaded from CellAge database. After intersection assay, we screened out 4 overlapping genes, of which FOS, CYR61 and TNFSF15 were upregulated, MAPK12 was downregulated. The expression of MAPK12 was obviously downregulated, whereas the expression profiles of FOS, CYR61 and TNFSF15 were remarkedly upregulated in H2O2- or IL-1ß-stimulated C28/I2 cells, human OA cartilage tissues, and knee cartilage of aging mice. Furthermore, both MAPK12 over-expression and FOS knock-down can promote cell proliferation and cartilage anabolism, inhibit cell senescence and cartilage catabolism, relieve joint pain in H2O2- or IL-1ß-stimulated C28/I2 cells and mouse primary chondrocytes, destabilization of the medial meniscus (DMM) mice. Conclusion: This study explored that MAPK12 and FOS are involved in the occurrence and development of OA through modulating chondrocyte senescence. They might be biomarkers of OA chondrocyte senescence, and provides some evidence as subsequent possible therapeutic targets for OA. The translational potential of this article: The translation potential of this article is that we revealed MAPK12 and FOS can effectively alleviate OA by regulating chondrocyte senescence, and thus provided potential therapeutic targets for prevention or treatment of OA in the future.

The circUbqln1, regulated by XBP1s, interplays with 14-3-3ζ to inhibit collagen synthesis and promote osteoarthritis by controlling PRODH activity and proline metabolism.

INTRODUCTION: Osteoarthritis (OA) is a degenerative bone disease associated with ageing, characterized by joint pain, stiffness, swelling and deformation. Currently, pharmaceutical options for the clinical treatment of OA are very limited. Circular RNAs(cirRNAs) have garnered significant attention in OA and related drug development due to their unique RNA sequence characteristics.Therefore,exploring the role of cirRNAs in the occurrence and development of OA is of paramount importance for the development of effective medications for OA. OBJECTIVES: To identify a novel circRNA, circUbqln1, for treating osteoarthritis and elucidate its pathophysiological role and mechanisms in the treatment of OA. METHODS: The circUbqln1 expression and distribution were determined by qRT-PCR and FISH. XBP1 gene knockout(XBP1 cKO) spontaneous OA and DMM model and WT mouse CIOA model were used to explore the role of XBP1 and circUbqln1 in OA.Overexpression or knockdown of circUbqln1 lentivirus was used to observe the impacts of circUbqln1 on primary chondrocytes,C28/I2 and mice in vitro and in vivo.Chromatin immunoprecipitation,luciferase reporter assay,RNA pulldown,mass spectrometry,RNA immunoprecipitation,fluorescence in situ hybridization,and flow cytometry to explore the molecular mechanisms of circUbqln1. RESULTS: It was found that cartilage-specific XBP1 cKO mice exhibited a faster OA progression compared to normal's.Importantly,transcript factor XBP1s has the capacity to impede the biogenesis of circUbqln1,derived from Ubqln1. The circUbqln1 promotes cartilage catabolism and inhibits anabolism, therefore accelerates the occurrence of OA.Mechanismly,circUbqln1 can translocate to the chondrocyte nucleus with the assistance of phosphorylated 14-3-3ζ, upregulate the transcriptional activity of the proline dehydrogenase(Prodh) promoter and PRODH enzyme activity. Consequently, this leads to the promotion of proline degradation and the inhibition of collagen synthesis,ultimately culminating in the impairment of cartilage and its structural integrity. CONCLUSION: CircUbqln1 plays a crucial role in the occurrence and development of OA, indicating that the inhibition of circUbqln1 holds promise as a significant approach for treating OA in the future.

Identification and functional coordination analysis of gene co-expression networks in different tissues of XBP1 cartilage-specific deficient mice.

Abnormal differentiation and proliferation of chondrocytes leads to various diseases related to growth and development. The process of chondrocyte differentiation involves a series of complex cellular and molecular interactions. X-box binding protein 1 (XBP1), an essential molecule of the unfolded protein response (UPR) in Endoplasmic Reticulum (ER) stress, participated in cartilage development and causes other related diseases. We previously reported that XBP1 deficiency in cartilage impacts the function and associated diseases of many different tissues including cartilage. However, how differential expression of genes modulates the roles of cartilage and other tissues when XBP1 is lack of in chondrocytes remains unclear. We aimed to screen for differentially expressed (DE) genes in cartilage, brain, heart, and muscle by high-throughput sequencing in XBP1 cartilage-specific knockout (CKO) mice. Further, gene co-expression networks were constructed by weighted gene co-expression network analysis (WGCNA) algorithm and pivot genes were identified in the above four tissues. Protein detection, Hematoxylin-eosin (HE) staining and immunohistochemistry (IHC) experiments have proved that these differentially co-expressed genes participate in the downstream regulatory pathway of different tissues and affect tissue function.Significantly differentially expressed mRNAs [differentially expressed genes (DEGs)] were identified between XBP1 CKO mice and controls in cartilage, brain, heart, and muscle tissues, including 610, 126, 199 and 219 DEGs, respectively. 39 differentially co-expressed genes were identified in the above four tissues, and they were important pivot genes. Comprehensive analysis discovered that XBP1 deficiency in cartilage influences the difference of co-expressed genes between cartilage and other different tissues. These differentially co-expressed genes participate in downstream regulatory pathways of different tissues and affect tissue functions. Collectively, our conclusions may contribute potential biomarkers and molecular mechanisms for the mutual modulation between cartilage and different tissues and the diagnosis and treatment of diseases caused by abnormalities in different tissues. The analysis also provides meaningful insights for future genetic discoveries.