Study of the mechanism underlying hsa-miR338-3p downregulation to promote fibrosis of the synovial tissue in osteoarthritis patients

Mechanism of Nrf2/miR338-3p/TRAP-1 pathway involved in hyperactivation of synovial fibroblasts in patients with osteoarthritis

Our previous study has confirmed that miR338-3p/TRAP-1 axis was involved in regulation of hyperactivation in human synovial fibroblasts (HFLS) of patients with osteoarthritis (OA). Here, we aim to further investigate the underlying causes of the abnormal activation miR338-3p/TRAP-1 at the molecular level. Our results showed that the decrease of NF-E2-related factor 2(Nrf2) was the direct cause of downregulation of miR338-3p and upregulation of TRAP-1 protein expression in HFLS of OA patients. Furthermore, we also found that the phosphorylation and nuclear entry of Nrf2 protein were significantly reduced in HFLS of OA patients than that of normal individuals, and both of them were positively correlated with miR338-3p levels. Bioinformatics analysis, luciferase assay, and CHIP experiment together indicated that Nrf2 could positively regulate the transcription of miR338-3p by binding to the Transcription Factor Binding Sites (TFBS) on its promoter. It was confirmed by in vitro assays that oltipraz (agonists of Nrf2) treatment effectively inhibited the hyperactivation of HFLS induced by TGF-β1, and the effects of oltipraz could be reversed by the exogenous TRAP-1. In short, our research has revealed for the first time that Nrf2/miR338-3p/TRAP-1 pathway was involved in hyperactivation of HFLS in OA patients, Nrf2 has the potential to be used as therapy and new drug target of OA.

XBP1 Modulates the Aging Cardiorenal System by Regulating Oxidative Stress

X-box binding protein 1 (XBP1) is a unique basic-region leucine zipper (bZIP) transcription factor. Over recent years, the powerful biological functions of XBP1 in oxidative stress have been gradually revealed. When the redox balance remains undisturbed, oxidative stress plays a role in physiological adaptations and signal transduction. However, during the aging process, increased cellular senescence and reduced levels of endogenous antioxidants cause an oxidative imbalance in the cardiorenal system. Recent studies from our laboratory and others have indicated that these age-related cardiorenal diseases caused by oxidative stress are guided and controlled by a versatile network composed of diversified XBP1 pathways. In this review, we describe the mechanisms that link XBP1 and oxidative stress in a range of cardiorenal disorders, including mitochondrial instability, inflammation, and alterations in neurohumoral drive. Furthermore, we propose that differing degrees of XBP1 activation may cause beneficial or harmful effects in the cardiorenal system. Gaining a comprehensive understanding of how XBP1 exerts influence on the aging cardiorenal system by regulating oxidative stress will enhance our ability to provide new directions and strategies for cardiovascular and renal safety outcomes.

Synovial Fluid Proteomics From Serial Aspirations of ACL-Injured Knees Identifies Candidate Biomarkers

BACKGROUND

Anterior cruciate ligament (ACL) tears often result in knee effusion and an increased risk for developing knee osteoarthritis (OA) in the long run. The molecular profile of these effusions could be informative regarding initial steps in the development of posttraumatic OA after an ACL tear.

HYPOTHESIS

The proteomics of knee synovial fluid changes over time after ACL injury.

STUDY DESIGN

Descriptive laboratory study.

METHODS

Synovial fluid was collected from patients with an acute traumatic ACL tear presenting to the office for evaluation (18.31 ± 19.07 days from injury) (aspiration 1) and again at the time of surgery (35.41 ± 58.15 days after aspiration 1 (aspiration 2). High-resolution liquid chromatography mass spectrometry was used to assess the quantitative protein profile of synovial fluid, and differences in protein profile between the 2 aspirations were determined computationally.

RESULTS

A total of 58 synovial fluid samples collected from 29 patients (12 male, 17 female; 12 isolated ACL tear, 17 combined ACL and meniscal tear) with a mean age and body mass index of 27.01 ± 12.78 years and 26.30 ± 4.93, respectively, underwent unbiased proteomics analysis. The levels of 130 proteins in the synovial fluid changed over time (87 high, 43 low). Proteins of interest that were significantly higher in aspiration 2 included CRIP1, S100A11, PLS3, POSTN, and VIM, which represent catabolic/inflammatory activities in the joint. Proteins with a known role in chondroprotection and joint homeostasis such as CHI3L2 (YKL-39), TNFAIP6/TSG6, DEFA1, SPP1, and CILP were lower in aspiration 2.

CONCLUSION

Synovial fluid from knees with ACL tears exhibits an increased burden of inflammatory (catabolic) proteins relevant to OA with reduced levels of chondroprotective (anabolic) proteins.

CLINICAL RELEVANCE

This study identified a set of novel proteins that provide new biological insights into the aftermath of ACL tears. Elevated inflammation and decreased chondroprotection could represent initial disruption of homeostasis, potentially initiating the development of OA. Longitudinal follow-up and mechanistic studies are necessary to assess the functional role of these proteins in the joint. Ultimately, these investigations could lead to better approaches to predict and possibly improve patient outcomes.

Acupotomy Improves Synovial Hypoxia, Synovitis and Angiogenesis in KOA Rabbits

Purpose

Knee osteoarthritis (KOA) is a chronic inflammatory disease highly associated with intra-articular hypertension, hypoxia and angiogenesis of synovial tissue. Our previous studies showed that acupotomy could treat KOA in a variety of ways, including reducing cartilage deterioration and enhancing biomechanical qualities. However, the mechanism of hypoxia and angiogenesis induced by acupotomy in KOA synovium remains unclear. This study looked for the benign intervention of acupotomy in synovial pathology.

Methods

The rabbits were divided into 3 groups, Normal group, KOA group, and KOA + Acupotomy (Apo) group, with 11 rabbits in each group. The KOA rabbit model was established by the modified Videman method with six weeks. The KOA + Apo group performed the intervention. The tendon insertion of vastus medialis, vastus lateralis, rectus femoris, biceps femoris, and anserine bursa were selected as treatment points in rabbits. Rabbits were treated once every 7 days for 3 weeks. We observed the intra-articular pressure and oxygen partial pressure (BOLD MRI). The synovial morphology was monitored by Hematoxylin-Eosin Staining (HE Staining). The expression of hypoxia-inducible transcription factor-1α (HIF-1α), vascular endothelial growth factor (VEGF), interleukin-1β (IL-1β) and tumour necrosis factor-α (TNF-α) was detected using Immunohistochemical (IHC), Western Blot and Enzyme-Linked Immunosorbent Assay (ELISA).

Results

Acupotomy reduced intra-articular hypertension and improved the synovial oxygen situation, synovial inflammatory and angiogenesis. HIF-1α, VEGF, IL-1β and TNF-α expression were downregulated by acupotomy.

Conclusion

Acupotomy may reduce inflammation and angiogenesis in KOA rabbit by reducing abnormally elevated intra-articular pressure and improving synovial oxygen environment. The above may provide a new theoretical foundation for acupotomy treatment of KOA.

Production and Secretion of Gelsolin by Both Human Macrophage- and Fibroblast-like Synoviocytes and GSN Modulation in the Synovial Fluid of Patients with Various Forms of Arthritis

Gelsolin (GSN) is an actin-binding protein involved in cell formation, metabolism and wound closure processes. Since this protein is known to play a role in arthritis, here we investigate how the synovial membrane with its specific synoviocytes contributes to the expression of GSN and how the amount of GSN expressed is modulated by different types of arthritis. Synovial membranes from adult healthy subjects and patients with rheumatoid arthritis (RA) and osteoarthritis (OA) are analyzed by immunofluorescence, Western blot and ELISA. Macrophage-like synoviocytes (MLS) and fibroblast-like synoviocytes (FLS) were isolated, cultured and analyzed for their potential to produce and secrete GSN. In addition, the GSN concentrations in the synovial fluid of various forms of arthritis are determined by ELISA. GSN is produced by the healthy and arthritic synovial membranes. Both forms of synoviocytes (MLS and FLS) release GSN. The results show that there is a significant reduction in GSN in the synovial fluid in adult patients with OA. This reduction is also detectable in adult patients with RA but is not as evident. In juvenile arthritis, there is a slight increase in GSN concentration in the synovial fluid. This study shows that primary MLS and FLS express GSN and that these cells, in addition to articular chondrocytes, contribute to GSN levels in synovial fluid. Furthermore, GSN concentrations are modulated in different types of arthritis. Further studies are needed to fully understand how GSN is involved in joint homeostasis.

Differences in synovial fibrosis relative to range of motion in knee osteoarthritis patients

This study tests if differences exist in the severity of synovial fibrosis between patients undergoing total knee arthroplasty (TKA) for osteoarthritis (OA) to help explain disparate deficits in pre- and postoperative range of motion (ROM) between patient groups. 117 knee OA patients were grouped by women (n = 74) and men (n = 43) or those who self-reported as Black (n = 48) or White (n = 69). ROM was measured pre- and post-TKA. Condyles and synovium collected during TKA were scored histologically for OA severity and synovitis. Fibrosis was measured from picrosirius-stained sections of the synovium. Data were analyzed using Mann-Whitney, parametric, and Spearman's rho tests with alpha at 0.05. We found no significant differences between patient age, BMI, radiographic scores, or deformity type when grouped by sex or race, or between metrics or OA severity when grouped by sex. Notably, higher synovitis was measured in women (p = .039) than men. White patients had greater ROM before (p = 0.46) and after surgery (p = .021) relative to Black patients. Fibrosis, but not OA severity and synovitis scores, for the total patient sample negatively correlated with preoperative (r _s  = -0.330; p = .0003) but not postoperative (r_s  = -0.032; p = .7627) ROM. Black patients manifested more fibrosis than White patients (p = <.0001), without significant differences between sexes. Statement of Clinical Significance: Coupled with histological scoring, measuring perioperative differences in synovial fibrosis against ROM may refine OA classification and justify the in-depth preoperative assessment of the knee as a whole. Such individualized analyses could guide personalized strategies to relieve symptomatic OA when TKA is not readily accessible and promote equitable TKA outcomes.

Low-intensity pulsed ultrasound inhibits fibroblast-like synoviocyte proliferation and reduces synovial fibrosis by regulating Wnt/β-catenin signaling

OBJECTIVE

Synovial fibrosis is a characteristic symptom of osteoarthritis (OA), which is closely associated with joint pain and stiffness. Previous studies have reported that low-intensity pulsed ultrasound (LIPUS) can alleviate cartilage degradation in OA. However, the functions and mechanisms of LIPUS in OA synovial fibrosis are still unknown.

METHODS

The destabilization of the medial meniscus (DMM) mouse model of OA was established in C57 male mice and fibroblast-like synoviocytes (FLS) were isolated from synovial tissue of OA patients. The knee joint diameter, Masson's trichrome (MT) and Hematoxylin-eosin (HE) staining were used to evaluate synovial fibrosis and hyperplasia. The Immunohistochemistry (IHC) staining was performed to detected the expression of synovial fibrosis makers and the activation of Wnt/β-catenin signaling in vivo. FLS were treated with TGF-β1 to serve as an in vitro model of synovial fibrosis, Wnt3a was used to activate the Wnt/β-catenin signaling in cells. Cell proliferation was detected by using EdU assay, cell viability was performed by CCK8 assay. The protein levels of α-SMA, CTGF, Col Ⅰ, β-catenin, active β-catenin, c-Myc and cyclin D1 were examined by western blot and immunofluorescence staining.

RESULTS

Two weeks after the LIPUS treatment, the synovial fibrosis, synovial hyperplasia and synoviocyte proliferation in the DMM model were significantly decreased. In vitro, LIPUS directly inhibited the TGF-β1-induced fibrotic response and proliferation of FLS. Meanwhile, LIPUS suppressed Wnt/β-catenin signaling in the synovium of DMM mice and cultured FLS. More importantly, we found that the synovial fibrosis makers, Wnt/β-catenin pathway downstream proteins and FLS proliferation were significantly decreased in Wnt3a-stimulated FLS following LIPUS treatment.

CONCLUSIONS

Our results present a novel role of LIPUS in OA-related synovial fibrosis, which is associated with its ability to repress Wnt/β-catenin signaling in FLS.

THE TRANSLATIONAL POTENTIAL OF THIS ARTICLE

This study provides new insight into the clinical application of LIPUS as a therapeutic option to manage synovial fibrosis in OA.

Fibroblast-like Synoviocytes-derived Exosomal PCGEM1 Accelerates IL-1β-induced Apoptosis and Cartilage Matrix Degradation by miR-142-5p/RUNX2 in Chondrocytes

Background: Long non-coding RNA (lncRNA) prostate cancer gene expression marker 1 (PCGEM1) has been revealed to participate in the pathogenesis of osteoarthritis (OA). However, the molecular mechanism of PCGEM1 regulating OA progression has not been fully elucidated.Methods: Fibroblast-like synoviocytes (FLSs) were isolated from synovium tissues of OA patients (OA-FLSs) and trauma donors (Normal-FLSs). The size and morphology of the isolated exosomes were analyzed by transmission electron microscopy and nanoparticle tracking analysis. Protein levels were analyzed by western blotting. Expression levels of PCGEM1, microRNA-142-5p (miR-142-5p), runt-related transcription factor 2 (RUNX2) mRNA, and OA related genes were assessed by qRT-PCR. Cell proliferation, viability, and apoptosis were evaluated by 3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide or flow cytometry assays. The relationship between miR-142-5p and PCGEM1 or RUNX2 was verified by dual-luciferase reporter and/or RNA pull down assays.Results: PCGEM1 was overexpressed in OA cartilages and exosomes from OA-FLSs. Exosomal PCGEM1 from OA-FLSs facilitated IL-1β-induced apoptosis and cartilage matrix degradation in chondrocytes. MiR-142-5p was downregulated while RUNX2 was upregulated in OA cartilages. Exosomal PCGEM1 from OA-FLSs regulated RUNX2 expression by sponging miR-142-5p in IL-1β-induced chondrocytes. MiR-142-5p inhibitor offset exosomal PCGEM1 knockdown-mediated effects on the apoptosis and cartilage matrix degradation of IL-1β-induced chondrocytes. RUNX2 overexpression counteracted the suppressive effect of miR-142-5p mimic on apoptosis and cartilage matrix degradation of IL-1β-induced chondrocytes.Conclusion: Exosomal PCGEM1 from OA-FLSs facilitated IL-1β-induced apoptosis and cartilage matrix degradation in chondrocytes by sequestering miR-142-5p and upregulating RUNX2, which offered new insights into the pathogenesis of OA.

Fibroblast-like synoviocytes: Role in synovial fibrosis associated with osteoarthritis

The synovial membrane undergoes a variety of structural changes throughout the pathogenesis of osteoarthritis (OA), including the development of fibrosis. Fibroblast-like synoviocytes (FLS) are a heterogenous cell population of the synovium that are suggested to drive the fibrotic response, but the exact mechanisms associated with their activation in OA remain unclear. Once activated, FLS are suggested to acquire a myofibroblast-like phenotype that drives fibrogenesis through excessive extracellular matrix (ECM) component deposition and an enhanced contractile function. In this review, we define FLS in the synovium, discuss how select extracellular or endogenous factors potentially induce their activation in OA, and describe how the activity of myofibroblast-like cells affects the structure of the synovial membrane.

Synovial Fibrosis Involvement in Osteoarthritis

Bone changes have always been the focus of research on osteoarthritis, but the number of studies on synovitis has increased only over the last 10 years. Our current understanding is that the mechanism of osteoarthritis involves all the tissues that make up the joints, including nerve sprouting, pannus formation, and extracellular matrix environmental changes in the synovium. These factors together determine synovial fibrosis and may be closely associated with the clinical symptoms of pain, hyperalgesia, and stiffness in osteoarthritis. In this review, we summarize the consensus of clinical work, the potential pathological mechanisms, the possible therapeutic targets, and the available therapeutic strategies for synovial fibrosis in osteoarthritis to gain insight and provide a foundation for further study.

The inflammatory speech of fibroblasts

Activation of fibroblasts is a key event during normal tissue repair after injury and the dysregulated repair processes that result in organ fibrosis. To most researchers, fibroblasts are rather unremarkable spindle-shaped cells embedded in the fibrous collagen matrix of connective tissues and/or deemed useful to perform mechanistic studies with adherent cells in culture. For more than a century, fibroblasts escaped thorough classification due to the lack of specific markers and were treated as the leftovers after all other cells have been identified from a tissue sample. With novel cell lineage tracing and single cell transcriptomics tools, bona fide fibroblasts emerge as only one heterogeneous sub-population of a much larger group of partly overlapping cell types, including mesenchymal stromal cells, fibro-adipogenic progenitor cells, pericytes, and/or perivascular cells. All these cells are activated to contribute to tissue repair after injury and/or chronic inflammation. "Activation" can entail various functions, such as enhanced proliferation, migration, instruction of inflammatory cells, secretion of extracellular matrix proteins and organizing enzymes, and acquisition of a contractile myofibroblast phenotype. We provide our view on the fibroblastic cell types and activation states playing a role during physiological and pathological repair and their crosstalk with inflammatory macrophages. Inflammation and fibrosis of the articular synovium during rheumatoid arthritis and osteoarthritis are used as specific examples to discuss inflammatory fibroblast phenotypes. Ultimately, delineating the precursors and functional roles of activated fibroblastic cells will contribute to better and more specific intervention strategies to treat fibroproliferative and fibrocontractive disorders.

Agnuside Alleviates Synovitis and Fibrosis in Knee Osteoarthritis through the Inhibition of HIF-1α and NLRP3 Inflammasome

Increasing evidence has shown that NLRP3 inflammasome activation participates in chronic aseptic inflammation and is related to tissue fibrosis. Our last study also revealed the vital role of NLRP3 inflammasome, highly associated with tissue hypoxia, in the onset and development of knee osteoarthritis (KOA). In this study, we tried to find a possible benign intervention for that pathological process. Agnuside (AGN), a nontoxic, natural small molecule isolated from the extract of Vitex negundo L. (Verbenaceae), has been demonstrated to have antioxidation, anti-inflammatory, analgesia, and many other properties as an iridoid glycoside, although its specific target is still unclear. Therefore, we established MIA-induced KOA model rats and investigated the effects of AGN oral gavage on oxygen-containing state, NLRP3 inflammasome, synovitis, and fibrosis in KOA. Pimonidazole staining and HIF-1α immunohistochemical assay both showed that AGN at the oral dose of 6.25 mg/kg can effectively relieve local hypoxia in synovial tissue. Besides, we observed a decrease of HIF-1α, caspase-1, ASC, and NLRP3 after AGN intervention, both in the mRNA and protein levels. In addition, rats treated with the AGN showed less inflammatory reaction and fibrosis, not only in the expression of NLRP3, inflammasome downstream factors IL-1β and IL-18, and fibrosis markers TGF-β, TIMP1, and VEGF but also in the observation of HE staining, anatomical characteristics, Sirius Red staining, and type I collagen immunohistochemistry. Subsequently, we established LPS-induced models of fibroblast-like synoviocytes (FLSs) mimicking the inflammatory environment of KOA and activating NLRP3 inflammasome. FLSs treated with AGN (3 μM) resulted in a downregulation of HIF-1α and the components required for NLRP3 inflammasome activation. Meanwhile, the content of proinflammatory factors IL-1β and IL-18 in FLS supernatant was also reduced by AGN. In addition, both mRNA and protein levels of the fibrotic markers were significantly decreased after AGN management. To conclude, this study demonstrates that AGN alleviates synovitis and fibrosis in experimental KOA through the inhibition of HIF-1α accumulation and NLRP3 inflammasome activation. Additionally, not only does it reveal some novel targets for anti-inflammatory and antioxidant effects of AGN but also announces its potential value in treating KOA in humans.

Impact of Isolation Procedures on the Development of a Preclinical Synovial Fibroblasts/Macrophages in an In Vitro Model of Osteoarthritis

Simple Summary

In vitro models able to represent osteoarthritis (OA) synovial tissue (ST) inflammation are lacking. Therefore, we aimed to characterize OA ST and to compare mechanical and enzymatic digestion procedures to find the one that better preserve the heterogeneity of the main OA synovial cell populations: fibroblasts and macrophages. We demonstrated that typical macrophage phenotypical markers, like CD68, CD80 and CD163, were higher expressed on cells isolated with mechanical than enzymatic procedure. Moreover, we found that typical cytokines of inflammatory macrophages (i.e., TNFα) and anti-inflammatory macrophages (i.e., IL10) were also higher on mechanically isolated cells. Synovial fibroblasts were well conserved in both procedures. The definition of an OA ST model in vitro that better preserve the heterogeneity of specific cell populations represents a prerequisite for defining the real effects of new cell therapies or drugs for OA treatment, and could contribute to the reduction or avoidance of animal models.

Abstract

There is a lack ofin vitromodels able to properly represent osteoarthritis (OA) synovial tissue (ST). We aimed to characterize OA ST and to investigate whether a mechanical or enzymatic digestion procedures influence synovial cell functional heterogeneity in vitro. Procedures using mechanical nondigested fragments (NDF), synovial digested fragments (SDF), and filtrated synovial digested cells (SDC) were compared. An immunophenotypic profile was performed to distinguish synovial fibroblasts (CD55, CD73, CD90, CD106), macrophages (CD14, CD68), M1-like (CD80, CD86), and M2-like (CD163, CD206) synovial macrophages. Pro-inflammatory (interleukin 6 IL6), tumor necrosis factor alpha (TNFα), chemokine C-C motif ligand 3 (CCL3/MIP1α), C-X- motif chemokine ligand 10 (CXCL10/IP10) and anti-inflammatory (interleukin 10 (IL10)), transforming growth factor beta 1 (TGFβ1), C-C motif chemokine ligand 18 (CCL18) cytokines were evaluated. CD68 and CD163 markers were higher in NDF and SDF compared to the SDC procedure, while CD80, CD86, and CD206 were higher only in NDF compared to the SDC procedure. Synovial fibroblast markers showed similar percentages. TNFα, CCL3/MIP1α, CXCL10/IP10, and CCL18 were higher in NDF compared to SDC, but not compared to SDF. IL10 and TGFβ1 were higher in NDF than SDC at the molecular level, while IL6 did not show differences among procedures. We demonstrated that NDF isolation procedures better preserved the heterogeneity of specific OA synovial populations (fibroblasts, macrophages), fostering their use for testing new cell therapies or drugs for OA, reducing or avoiding the use of animal models.

MicroRNAs in Synovial Pathology Associated With Osteoarthritis

Osteoarthritis (OA) is the most common type of arthritis, a disease that affects the entire joint. The relative involvement of each tissue, and their interactions, add to the complexity of OA, hampering our understanding of the underlying molecular mechanisms, and the generation of a disease modifying therapy. The synovium is essential in maintaining joint homeostasis, and pathologies associated with the synovium contribute to joint destruction, pain and stiffness in OA. MicroRNAs (miRNAs) are post-transcriptional regulators dysregulated in OA tissues including the synovium. MiRNAs are important contributors to OA synovial changes that have the potential to improve our understanding of OA and to act as novel therapeutic targets. The purpose of this review is to summarize and integrate current published literature investigating the roles that miRNAs play in OA-related synovial pathologies including inflammation, matrix deposition and cell proliferation.