SFRP1 Negatively Modulates Pyroptosis of Fibroblast-Like Synoviocytes in Rheumatoid Arthritis: A Review

Resolution of inflammation during rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune disease that causes synovial joint inflammation as well as bone destruction and erosion, typically characterized by joint pain, swelling, and stiffness, with complications and persistent pain after remission posing a significant health burden for RA patients. The etiology of RA has not yet been fully elucidated, but a large number of studies have shown that the initiation of inflammation in RA is closely related to T-cell activation, the production of a variety of pro-inflammatory cytokines, macrophage M1/M2 imbalance, homeostatic imbalance of the intestinal flora, fibroblast-like synoviocytes (FLSs) and synovial tissue macrophages (STMs) in the synovial lumen of joints that exhibit an aggressive phenotype. While the resolution of RA is less discussed, therefore, we provided a systematic review of the relevant remission mechanisms including blocking T cell activation, regulating macrophage polarization status, modulating the signaling pathway of FLSs, modulating the subpopulation of STMs, and inhibiting the relevant inflammatory factors, as well as the probable causes of persistent arthritis pain after the remission of RA and its pain management methods. Achieving resolution in RA is crucial for improving the quality of life and long-term prognosis of patients. Thus, understanding these mechanisms provide novel potential for further drug development and treatment of RA.

The role of SFRP1 in human dermal papilla cell growth and its potential molecular mechanisms as a target in regenerative therapy

Background

Secreted frizzled-related protein 1 (SFRP1) inhibits Wnt signaling and is differentially expressed in human hair dermal papilla cells (DPCs). However, the specific effect of SFRP1 on cell function remains unclear. Telomerase reverse transcriptase (TERT) representing telomerase activity was found highly active around the hair dermal papilla. TERT levels can be enhanced by activation of the Wnt pathway in cancer cells and embryonic stem cells. Whether this regulatory mechanism is still present in DPCs has not been studied so far.

Methods

In this study, DNA plasmids and siRNAs were constructed against the SFRP1 gene and transfected into DPCs cultured in vitro. We detected the viability, proliferation, and migration of DPCs by Calcein/PI fluorescence, CCK-8, trans-well, or cell scratch experiments, and the expression of potential target genes was also determined through quantitative detection of RNA and protein.

Results

The results demonstrate a significant difference in SFRP1 levels from the control group, suggesting successful transfection of the DNA plasmid and siRNA of SFRP1 into IDPCs. Also, SFRP1 regulates the cell proliferation capacity of IDPCs and reduces their migration functions. The DPCs' living activity, proliferation, and migration function exhibited a negative correlation with the level of SFRP1. SFPR1 also inhibits the protein or RNA expression of β-catenin and TERT in DPCs.

Conclusion

It was proven that in human DPCs, different levels of SFRP1 change how cells work and control Wnt/β-catenin signaling or telomerase activity. This means that blocking SFRP1 could become a new way to treat hair loss diseases in the future.

ERG transcriptionally activates SFRP1 to promote apoptosis of keloid fibroblasts and inhibit epithelial-mesenchymal transition and fibrosis through the Wnt3a/β-catenin pathway

Keloids are benign skin tumors characterized by excessive fibrosis. Secreted frizzled-related protein 1 (SFRP1) has been linked to fibrosis regulation. Understanding SFRP1's role in keloid fibroblasts (KFs) could provide insights into the molecular mechanisms driving keloid progression and offer new therapeutic avenues. mRNA expression of SFRP1 and ETS-related gene 1 (ERG) was assessed via quantitative real-time polymerase chain reaction. Protein levels were determined by Western blotting. Cell viability was evaluated using cell counting kit-8 assay. Cell apoptosis was detected by flow cytometry. Cell invasion was assessed by transwell assay, and cell migration by wound-healing assay. Chromatin immunoprecipitation and dual-luciferase reporter assays were performed to elucidate the interaction of ERG and SFRP1. SFRP1 was downregulated in keloid tissues and KFs. Overexpression of SFRP1 induced KF apoptosis and inhibited epithelial-mesenchymal transition and fibrosis, concurrent with inactivation of the Wnt3a/β-catenin pathway. ERG was found to transcriptionally activate SFRP1. ERG overexpression promoted KF apoptosis and inhibited epithelial-mesenchymal transition and fibrosis by regulating SFRP1. Wnt3a/β-catenin pathway inactivation. Moreover, the inhibitory effects of ERG overexpression on the protein expression of Wnt3a and β-catenin were attenuated after SFRP1 knockdown. ERG's transcriptional activation of SFRP1 promoted KF apoptosis and inhibited epithelial-mesenchymal transition and fibrosis through the Wnt3a/β-catenin pathway, highlighting a potential therapeutic strategy for keloid management.

Deep topic modeling of spatial transcriptomics in the rheumatoid arthritis synovium identifies distinct classes of ectopic lymphoid structures

Single-cell RNA sequencing studies have revealed the heterogeneity of cell states present in the rheumatoid arthritis (RA) synovium. However, it remains unclear how these cell types interact with one another in situ and how synovial microenvironments shape observed cell states. Here, we use spatial transcriptomics (ST) to define stable microenvironments across eight synovial tissue samples from six RA patients and characterize the cellular composition of ectopic lymphoid structures (ELS). To identify disease-relevant cellular communities, we developed DeepTopics, a scalable reference-free deconvolution method based on a Dirichlet variational autoencoder architecture. DeepTopics identified 22 topics across tissue samples that were defined by specific cell types, activation states, and/or biological processes. Some topics were defined by multiple colocalizing cell types, such as CD34+ fibroblasts and LYVE1+ macrophages, suggesting functional interactions. Within ELS, we discovered two divergent cellular patterns that were stable across ELS in each patient and typified by the presence or absence of a "germinal-center-like" topic. DeepTopics is a versatile and computationally efficient method for identifying disease-relevant microenvironments from ST data, and our results highlight divergent cellular architectures in histologically similar RA synovial samples that have implications for disease pathogenesis.

A positive correlation of serum SFRP1 levels with the risk of developing type 2 diabetes mellitus: a case-control study

OBJECTIVE

Secreted frizzled-related protein 1 (SFRP1) is an adipokine whose production is significantly altered in metabolic disorders. Considering the relationship between dysfunction of Wnt/β-catenin signaling and metabolic disorders as well as the inhibitory effects of SFRP1 on this signaling pathway, the present work aimed to investigate the correlation between serum SFRP1 levels and type 2 diabetes mellitus (T2DM) and its developing risk factors for the first time.

METHODS

This case-control study measured serum levels of SFRP1, tumor necrosis factor (TNF)-α, interleukin (IL)-6, adiponectin, and fasting insulin using enzyme-linked immunosorbent assay kits in 80 T2DM patients and 80 healthy individuals. Biochemical parameters were determined using the AutoAnalyzer instrument.

RESULTS

The T2DM group had higher levels of SFRP1 compared with the controls (146.8100 ± 43.61416 vs 81.9531 ± 32.78545 pg/mL; P < .001). There was a positive correlation between SFRP1 and insulin (r = 0.327, P = .003), TNF-α (r = 0.420, P < .001) as well as homeostatic model assessment for insulin resistance (r = 0.328, P = .003) in the T2DM group. In addition, 10-unit changes in SFRP1 levels showed the risk of T2DM in both the unadjusted (odds ratio [OR] [95% CI] = 1.564 [1.359-1.800]) and adjusted models accounting for age, gender, and body mass index (OR [95% CI] = 1.564 [1.361-1.799]; P < .001). A cut-off value of SFRP1 (105.83 pg/mL) was identified to distinguish between the T2DM patients and the healthy subjects, with sensitivity of 75.0% and specificity of 80.0%.

CONCLUSION

According to our research, there was a significant and positive link between the amount of SFRP1 and the likelihood of developing T2DM as well as the related factors like insulin resistance index and TNF-α. These results indicated that SFRP1 might have a potential role in the development of T2DM.

Battling pain from osteoarthritis: causing novel cell death

Osteoarthritis (OA) is a significant contributor to pain and disability worldwide. Pain is the main complaint of OA patients attending the clinic and has a large impact on their quality of life and economic standards. However, existing treatments for OA-related pain have not been shown to achieve good relief. The main focus is on preventing and slowing the progression of OA so that the problem of OA pain can be resolved. Pain caused by OA is complex, with the nature, location, duration, and intensity of pain changing as the disease progresses. Previous research has highlighted the role of various forms of cell death, such as apoptosis and necrosis, in the progression of pain in OA. Emerging studies have identified additional forms of novel cell death, such as pyroptosis, ferroptosis, and necroptosis that are linked to pain in OA. Different types of cell death contribute to tissue damage in OA by impacting inflammatory responses, reactive oxygen species (ROS) production, and calcium ion levels, ultimately leading to the development of pain. Evidence suggests that targeting novel types of cell death could help alleviate pain in OA patients. This review delves into the complex mechanisms of OA pain, explores the relationship between different modes of novel cell death and pain, and proposes novel cell death as a viable strategy for the treatment of these conditions, with the goal of providing scientific references for the development of future OA pain treatments and drugs.

LncRNA HOTTIP regulates TLR4 promoter methylation by recruiting H3K4 methyltransferase MLL1 to affect apoptosis and inflammatory response of fibroblast-like synoviocyte in rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune inflammatory disease, and the role of HOXA transcript at the distal tip (HOTTIP) in its pathogenesis remains underexplored. This study investigates the mechanism by which HOTTIP influences apoptosis and the inflammatory response of fibroblast-like synoviocytes (FLS). An RA mouse model was established, and clinical scores were analyzed. Pathological changes in synovial tissues, bone mineral density (BMD) of the paws, serum tartrate-resistant acid phosphatase (TRAP) activity, and TNF-α and IL-1β levels were assessed. FLS were transfected, and cell proliferation and apoptosis were examined. The RNA-pull-down assay determined HOTTIP's interaction with mixed-lineage leukemia 1 (MLL1), while RNA immunoprecipitation assay measured HOTTIP expression pulled down by MLL1. The levels of MLL1 and toll-like receptor 4 (TLR4) after MLL1 overexpression based on HOTTIP silencing were determined. Chromatin immunoprecipitation (ChIP) was performed with H3K4me3 as an antibody, followed by the evaluation of TLR4 expression. HOTTIP expression was elevated in RA mouse synovial tissues. Inhibition of HOTTIP led to reduced clinical scores, inflammatory infiltration, synovial hyperplasia, TRAP activity, and TNF-α and IL-1β levels, along with increased BMD. In vitro Interference with HOTTIP suppressed RA-FLS apoptosis and inflammation. HOTTIP upregulated TLR4 expression by recruiting MLL1 to facilitate TLR4 promoter methylation. MLL1 overexpression reversed HOTTIP silencing-mediated repression of RA-FLS apoptosis. Activation of H3K4 methylation counteracted HOTTIP knockout, ameliorating the inflammatory response. HOTTIP regulates TLR4 expression by recruiting MLL1, leading to TLR4 promoter methylation, thereby suppressing RA-FLS proliferation and inducing cell apoptosis and inflammatory response in RA.

Wnt5a: A promising therapeutic target for inflammation, especially rheumatoid arthritis

BACKGROUND

Wnt5a is a member of the Wnt protein family, which acts on classical or multiple non-classical Wnt signaling pathways by binding to different receptors. The expression regulation and signal transduction of Wnt5a is closely related to the inflammatory response. Abnormal activation of Wnt5a signaling is an important part of inflammation and rheumatoid arthritis (RA).

OBJECTIVES

This paper mainly focuses on Wnt5a protein and its mediated signaling pathway, summarizes the latest research progress of Wnt5a in the pathological process of inflammation and RA, and looks forward to the main directions of Wnt5a in RA research, aiming to provide a theoretical basis for the prevention and treatment of RA diseases by targeting Wnt5a.

RESULTS

Wnt5a is highly expressed in activated blood vessels, histocytes and synoviocytes in inflammatory diseases such as sepsis, sepsis, atherosclerosis and rheumatoid arthritis. It mediates the production of pro-inflammatory cytokines and chemokines, regulates the migration and recruitment of various immune effector cells, and thus participates in the inflammatory response. Wnt5a plays a pathological role in synovial inflammation and bone destruction of RA, and may be an important clinical therapeutic target for RA.

CONCLUSION

Wnt5a is involved in the pathological process of inflammation and interacts with inflammatory factors. Wnt5a may be a new target for regulating the progression of RA disease and intervening therapy because of its multi-modal effects on the etiology of RA, especially as a regulator of osteoclast activity and inflammation.

The Roles of WNT Signaling Pathways in Skin Development and Mechanical-Stretch-Induced Skin Regeneration

The WNT signaling pathway plays a critical role in a variety of biological processes, including development, adult tissue homeostasis maintenance, and stem cell regulation. Variations in skin conditions can influence the expression of the WNT signaling pathway. In light of the above, a deeper understanding of the specific mechanisms of the WNT signaling pathway in different physiological and pathological states of the skin holds the potential to significantly advance clinical treatments of skin-related diseases. In this review, we present a comprehensive analysis of the molecular and cellular mechanisms of the WNT signaling pathway in skin development, wound healing, and mechanical stretching. Our review sheds new light on the crucial role of the WNT signaling pathway in the regulation of skin physiology and pathology.

Targeting the cochlin/SFRP1/CaMKII axis in the ocular posterior pole prevents the progression of nonpathologic myopia

Myopia is a major public health issue. However, interventional modalities for nonpathologic myopia are limited due to its complicated pathogenesis and the lack of precise targets. Here, we show that in guinea pig form-deprived myopia (FDM) and lens-induced myopia (LIM) models, the early initiation, phenotypic correlation, and stable maintenance of cochlin protein upregulation at the interface between retinal photoreceptors and retinal pigment epithelium (RPE) is identified by a proteomic analysis of ocular posterior pole tissues. Then, a microarray analysis reveals that cochlin upregulates the expression of the secreted frizzled-related protein 1 (SFRP1) gene in human RPE cells. Moreover, SFRP-1 elevates the intracellular Ca2+ concentration and activates Ca2+/calmodulin-dependent protein kinase II (CaMKII) signaling in a simian choroidal vascular endothelial cell line, and elicits vascular endothelial cell dysfunction. Furthermore, genetic knockdown of the cochlin gene and pharmacological blockade of SFRP1 abrogates the reduced choroidal blood perfusion and prevents myopia progression in the FDM model. Collectively, this study identifies a novel signaling axis that may involve cochlin in the retina, SFRP1 in the RPE, and CaMKII in choroidal vascular endothelial cells and contribute to the pathogenesis of nonpathologic myopia, implicating the potential of cochlin and SFRP1 as myopia interventional targets.

SMAD2 inhibits pyroptosis of fibroblast-like synoviocytes and secretion of inflammatory factors via the TGF-β pathway in rheumatoid arthritis

OBJECTIVE

Rheumatoid arthritis (RA) is a chronic, progressive autoimmune disease. Over-activation of fibroblast-like synoviocytes is responsible for the hyperplasia of synovium and destruction of cartilage and bone and pyroptosis of FLS plays a key role in those pathological processes during RA. This study investigated the detailed mechanisms that SMAD2 regulates the pyroptosis of FLS and secretion of inflammatory factors in rheumatoid arthritis.

METHODS

We collected synovial tissues of RA patients and FLS-RA and cultured FLS for detection of expression of SMAD2. ASC, NLRP3, cleaved-caspase-1, and GSDMD-N were detected by Western blot after overexpression of SMAD2. Besides, flow cytometry, electron microscope, ELISA, HE staining, and Safranin O staining were performed to further demonstrate that SMAD2 can affect the pyroptosis of FLS-RA.

RESULTS

The expression of SMAD2 was down-regulated in synovial tissues of RA patients and FLS-RA. Overexpression of SMAD2 can inhibit the expression of ASC, NLRP3, cleaved-caspase-1, and GSDMD-N. Flow cytometry and electron microscope further demonstrated that SMAD2 attenuated pyroptosis of FLS-RA. In addition, overexpression of SMAD2 also inhibited inflammatory factors such as IL-1β, IL-18, IL-6, and IL-8 secretion and release of LDH. Besides, overexpression of SMAD2 can reverse the decrease of p-SMAD2 and TGF-TGF-β induced by nigericin. In vivo experiments on CIA rats further demonstrated that overexpression of SMAD2 by local intra-articular injection of LV-SMAD2 can effectively alleviate joint redness, swelling, and destruction of cartilage and bones.

CONCLUSION

SMAD2 inhibited FLS-RA pyroptosis by down-regulating of NLRP3 inflammasomes (NLRP3, ASC, and caspase-1 complex) and eased the secretion of inflammatory factors via the TGF-β signaling pathway, thereby improving the symptom of RA. We hope that this study may provide a new research idea for RA and a potential target for the treatment of RA.

Can pyroptosis be a new target in rheumatoid arthritis treatment?

Rheumatoid arthritis (RA) is a chronic systemic autoimmune disease of undefined etiology, with persistent synovial inflammation and destruction of articular cartilage and bone. Current clinical drugs for RA mainly include non-steroidal anti-inflammatory drugs (NSAIDs), glucocorticoids, disease modifying anti-rheumatic drugs (DMARDs) and so on, which can relieve patients' joint symptoms. If we want to have a complete cure for RA, there are still some limitations of these drugs. Therefore, we need to explore new mechanisms of RA to prevent and treat RA radically. Pyroptosis is a newly discovered programmed cell death (PCD) in recent years, which is characterized by the appearance of holes in cell membranes, cell swelling and rupture, and the release of intracellular pro-inflammatory factors into the extracellular space, resulting in a strong inflammatory response. The nature of pyroptosis is pro-inflammatory, and whether it is participating in the development of RA has attracted a wide interest among scholars. This review describes the discovery and mechanism of pyroptosis, the main therapeutic strategies for RA, and the role of pyroptosis in the mechanism of RA development. From the perspective of pyroptosis, the study of new mechanisms of RA may provide a potential target for the treatment of RA and the development of new drugs in the clinics.

A single-cell transcriptome atlas of pig skin characterizes anatomical positional heterogeneity

Different anatomical locations of the body skin show differences in their gene expression patterns depending on different origins, and the inherent heterogeneous information can be maintained in adults. However, highly resolvable cellular specialization is less well characterized in different anatomical regions of the skin. Pig is regarded as an excellent model animal for human skin research in view of its similar physiology to human. In this study, single-cell RNA sequencing was performed on pig skin tissues from six different anatomical regions of Chenghua (CH) pigs, with a superior skin thickness trait, and the back site of large white (LW) pigs. We obtained 233,715 cells, representing seven cell types, among which we primarily characterized the heterogeneity of the top three cell types, including smooth muscle cells (SMCs), endothelial cells (ECs), and fibroblasts (FBs). Then, we further identified several subtypes of SMCs, ECs, and FBs, and discovered the expression patterns of site-specific genes involved in some important pathways such as the immune response and extracellular matrix (ECM) synthesis in different anatomical regions. By comparing differentially expressed genes of skin FBs among different anatomical regions, we considered TNN, COL11A1, and INHBA as candidate genes for facilitating ECM accumulation. These findings of heterogeneity in the main skin cell types from different anatomical sites will contribute to a better understanding of inherent skin information and place the potential focus on skin generation, transmission, and transplantation, paving the foundation for human skin priming.

Complete Freund's Adjuvant Induces a Fibroblast-like Synoviocytes (FLS) Metabolic and Migratory Phenotype in Resident Fibroblasts of the Inoculated Footpad at the Earliest Stage of Adjuvant-Induced Arthritis

The fibroblast-like synoviocytes (FLS) have a crucial role in the pathogenesis of Rheumatoid Arthritis (RA); however, its precise mechanisms remain partially unknown. The involvement of the fibroblast in activating adjuvant-induced arthritis (AA) has not been previously reported. The objective was to describe the participation of footpads' fibroblasts in the critical initial process that drives the AA onset. Wistar rats were injected with Complete Freund's Adjuvant (CFA) or saline solution in the hind paws' footpads and euthanized at 24 or 48 h for genetic and histological analyses. Microarrays revealed the differentially expressed genes between the groups. The CFA dysregulated RA-linked biological processes at both times. Genes of MAPK, Jak-STAT, HIF, PI3K-Akt, TLR, TNF, and NF-κB signaling pathways were altered 24 h before the arrival of immune cells (CD4, CD8, and CD68). Key markers TNF-α, IL-1β, IL-6, NFκB, MEK-1, JAK3, Enolase, and VEGF were immunodetected in fibroblast in CFA-injected footpads at 24 h but not in the control group. Moreover, fibroblasts in the CFA inoculation site overexpressed cadherin-11, which is linked to the migration and invasion ability of RA-FLS. Our study shows that CFA induced a pathological phenotype in the fibroblast of the inoculation site at very early AA stages from 24 h, suggesting a prominent role in arthritis activation processes.

DNA methylation change of HIPK3 in Chinese rheumatoid arthritis and its effect on inflammation

INTRODUCTION

Homeodomain-interacting protein kinase 3 (HIPK3) plays an important role in cell proliferation, apoptosis, and inflammation. Over-expression of HIPK3 in immune cells in rheumatoid arthritis (RA) has been reported. In this study, we investigated blood methylation levels and clinical characteristics of RA in a Chinese population.

METHODS

A total of 235 patients with RA, 30 with osteoarthritis (OA), and 30 matched healthy controls were recruited. The methylation status of seven CpGs in the differentially methylated region of HIPK3 (cg05501357) was measured using targeted methylation-sequencing technology. The association between methylation haplotypes and the overall methylation status of HIPK3 with clinical characteristics was assessed using generalized linear regression.

RESULTS

All seven CpGs showed hypomethylation status in RA blood compared with OA and normal individuals (overall p= 1.143×10-8 and FDR= 2.799×10-7), which is consistent with the previously reported high expression of HIPK3 in RA immune cells. Among all seven CpGs, 33286785 showed the highest predictive power with an area under the curve (AUC) of 0.829; we received a higher AUC=0.864 when we combined HIPK3 with anti-citrullinated protein antibodies (ACPA -) and rheumatoid factor (RF +) in the prediction model, indicating that when a patient's ACPA is negative, HIPK3 can assist RF as a new clinical index for the diagnosis of RA. We also found that HIPK3 methylation levels were negatively correlated with C-reactive protein (CRP; r= -0.16, p= 0.01). Methylation haplotypes were analyzed, and the full methylation haplotype (FMH; r= 0.16, p= 0.01) and full non-methylation haplotype (FNH; r= 0.18, p= 0.0061) were negatively correlated with CRP.

CONCLUSION

Circulating blood methylation levels in the protein region of HIPK3 can be utilized as a supportive diagnostic biomarker and CRP level indicator for RA.

Potential diabetic cardiomyopathy therapies targeting pyroptosis: A mini review

Pyroptosis is primarily considered a pro-inflammatory class of caspase-1- and gasdermin D (GSDMD)-dependent programmed cell death. Inflammasome activation promotes the maturation and release of interleukin (IL)-1β and IL-18, cleavage of GSDMD, and development of pyroptosis. Recent studies have reported that NLRP3 inflammasome activation-mediated pyroptosis aggravates the formation and development of diabetes cardiomyopathy (DCM). These studies provide theoretical mechanisms for exploring a novel approach to treat DCM-associated cardiac dysfunction. Accordingly, this review aims to summarize studies that investigated possible DCM therapies targeting pyroptosis and elucidate the molecular mechanisms underlying NLRP3 inflammasome-mediated pyroptosis, and its potential association with the pathogenesis of DCM. This review may serve as a basis for the development of potential pharmacological agents as novel and effective treatments for managing and treating DCM.