Aggrecanase degradation of type III collagen is associated with clinical knee pain

Pyroptosis: A spoiler of peaceful coexistence between cells in degenerative bone and joint diseases

BACKGROUND

As people age, degenerative bone and joint diseases (DBJDs) become more prevalent. When middle-aged and elderly people are diagnosed with one or more disorders such as osteoporosis (OP), osteoarthritis (OA), and intervertebral disc degeneration (IVDD), it often signals the onset of prolonged pain and reduced functionality. Chronic inflammation has been identified as the underlying cause of various degenerative diseases, including DBJDs. Recently, excessive activation of pyroptosis, a form of programed cell death (PCD) mediated by inflammasomes, has emerged as a primary driver of harmful chronic inflammation. Consequently, pyroptosis has become a potential target for preventing and treating DBJDs.

AIM OF REVIEW

This review explored the physiological and pathological roles of the pyroptosis pathway in bone and joint development and its relation to DBJDs. Meanwhile, it elaborated the molecular mechanisms of pyroptosis within individual cell types in the bone marrow and joints, as well as the interplay among different cell types in the context of DBJDs. Furthermore, this review presented the latest compelling evidence supporting the idea of regulating the pyroptosis pathway for DBJDs treatment, and discussed the potential, limitations, and challenges of various therapeutic strategies involving pyroptosis regulation.

KEY SCIENTIFIC CONCEPTS OF REVIEW

In summary, an interesting identity for the unregulated pyroptosis pathway in the context of DBJDs was proposed in this review, which was undertaken as a spoiler of peaceful coexistence between cells in a degenerative environment. Over the extended course of DBJDs, pyroptosis pathway perpetuated its activity through crosstalk among pyroptosis cascades in different cell types, thus exacerbating the inflammatory environment throughout the entire bone marrow and joint degeneration environment. Correspondingly, pyroptosis regulation therapy emerged as a promising option for clinical treatment of DBJDs.

Diagnostic biomarkers in knee osteoarthritis: Based on bioinformatics and experimental verification in vivo and in vitro

BACKGROUND

Knee osteoarthritis (KOA) is a multifactorial whole-joint disease with a high rate of disability. Considering the complexity of KOA, there is an urgent need to discover new molecular pathological markers and multi-target treatment strategies.

METHODS

Two datasets, GSE51588 and GSE57218, were downloaded from the Gene Expression Omnibus database and screened for differentially expressed genes (DEGs) using the Gene Expression Omnibus 2R (GEO2R). Gene Ontology (GO)/Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses of DEGs were performed. A protein-protein interaction (PPI) network was constructed and hub genes were identified using Molecular Complex Detection (MCODE). Receiver-operating characteristic curves (ROC) were plotted for the genes, and their prognostic values were evaluated. The expression levels of the hub genes in the monosodium iodoacetate (MIA)-induced KOA rat model and lipopolysaccharide (LPS)-stimulated C28/I2 cells were verified using reverse transcription quantitative real-time PCR (RT-qPCR).

RESULTS

Overall, 33 DEGs were up-regulated and 6 DEGs were down-regulated in the two datasets. A total of 12 hub genes were identified, including COL15A1, THY1, COL1A1, COL5A1, CTHRC1, MXRA5, FN1, COL1A2, COL3A1, SPARC, COL8A1, and COL2A1, which all could be used as biomarkers to differentiate KOA samples from healthy controls. More importantly, we found that THY1, CTHRC1, SPARC, and COL8A1 were significantly upregulated in vivo and in vitro compared with the controls (p < .01).

CONCLUSIONS

The expression levels of THY1, CTHRC1, SPARC, and COL8A1 were elevated and had good prognostic values as biomarkers in KOA.

Cartilage-Related Collagens in Osteoarthritis and Rheumatoid Arthritis: From Pathogenesis to Therapeutics

Collagens serve essential mechanical functions throughout the body, particularly in the connective tissues. In articular cartilage, collagens provide most of the biomechanical properties of the extracellular matrix essential for its function. Collagen plays a very important role in maintaining the mechanical properties of articular cartilage and the stability of the ECM. Noteworthily, many pathogenic factors in the course of osteoarthritis and rheumatoid arthritis, such as mechanical injury, inflammation, and senescence, are involved in the irreversible degradation of collagen, leading to the progressive destruction of cartilage. The degradation of collagen can generate new biochemical markers with the ability to monitor disease progression and facilitate drug development. In addition, collagen can also be used as a biomaterial with excellent properties such as low immunogenicity, biodegradability, biocompatibility, and hydrophilicity. This review not only provides a systematic description of collagen and analyzes the structural characteristics of articular cartilage and the mechanisms of cartilage damage in disease states but also provides a detailed characterization of the biomarkers of collagen production and the role of collagen in cartilage repair, providing ideas and techniques for clinical diagnosis and treatment.

The role of extracellular vesicles in osteoarthritis treatment via microenvironment regulation

Osteoarthritis (OA) is a degenerative joint disease that is common among the middle-aged and older populations, causes patients to experience recurrent pain in their joints and negatively affects their quality of life. Currently, therapeutic options for patients with OA consist of medications to alleviate pain and treat the symptoms; however, due to typically poor outcomes, patients with advanced OA are unlikely to avoid joint replacement. In recent years, several studies have linked disrupted homeostasis of the joint cavity microenvironment to the development of OA. Recently, extracellular vesicles (EVs) have received increasing attention in the field of OA. EVs are natural nano-microcarrier materials with unique biological activity that are produced by cells through paracrine action. They are composed of lipid bilayers that contain physiologically active molecules, such as nucleic acids and proteins. Moreover, EVs may participate in local and distal intercellular and intracellular communication. EVs have also recently been shown to influence OA development by regulating biochemical factors in the OA microenvironmental. In this article, we first describe the microenvironment of OA. Then, we provide an overview of EVs, summarize the main types used for the treatment of OA, and describe their mechanisms. Next, we review clinical studies using EVs for OA treatment. Finally, the specific mechanism underlying the application of miRNA-enriched EVs in OA therapy is described.

LPA1 antagonist BMS-986020 changes collagen dynamics and exerts antifibrotic effects in vitro and in patients with idiopathic pulmonary fibrosis

BACKGROUND

Idiopathic pulmonary fibrosis (IPF) is a debilitating lung disease with limited treatment options. A phase 2 trial (NCT01766817) showed that twice-daily treatment with BMS-986020, a lysophosphatidic acid receptor 1 (LPA₁) antagonist, significantly decreased the slope of forced vital capacity (FVC) decline over 26 weeks compared with placebo in patients with IPF. This analysis aimed to better understand the impact of LPA₁ antagonism on extracellular matrix (ECM)-neoepitope biomarkers and lung function through a post hoc analysis of the phase 2 study, along with an in vitro fibrogenesis model.

METHODS

Serum levels of nine ECM-neoepitope biomarkers were measured in patients with IPF. The association of biomarkers with baseline and change from baseline FVC and quantitative lung fibrosis as measured with high-resolution computed tomography, and differences between treatment arms using linear mixed models, were assessed. The Scar-in-a-Jar in vitro fibrogenesis model was used to further elucidate the antifibrotic mechanism of BMS-986020.

RESULTS

In 140 patients with IPF, baseline ECM-neoepitope biomarker levels did not predict FVC progression but was significantly correlated with baseline FVC and lung fibrosis measurements. Most serum ECM-neoepitope biomarker levels were significantly reduced following BMS-986020 treatment compared with placebo, and several of the reductions correlated with FVC and/or lung fibrosis improvement. In the Scar-in-a-Jar in vitro model, BMS-986020 potently inhibited LPA₁-induced fibrogenesis.

CONCLUSIONS

BMS-986020 reduced serum ECM-neoepitope biomarkers, which were previously associated with IPF prognosis. In vitro, LPA promoted fibrogenesis, which was LPA₁ dependent and inhibited by BMS-986020. Together these data elucidate a novel antifibrotic mechanism of action for pharmacological LPA₁ blockade. Trial registration ClinicalTrials.gov identifier: NCT01766817; First posted: January 11, 2013; https://clinicaltrials.gov/ct2/show/NCT01766817 .

Soluble biological markers in osteoarthritis

In recent years, markers research has focused on the structural components of cartilage matrix. Specifically, a second generation of degradation markers has been developed against type II collagen neoepitopes generated by specific enzymes. A particular effort has been made to measure the degradation of minor collagens III and X of the cartilage matrix. However, because clinical data, including longitudinal controlled studies, are very scarce, it remains unclear whether they will be useful as an alternative to or in combination with current more established collagen biological markers to assess patients with osteoarthritis (OA). In addition, new approaches using high-throughput technologies allowed to detect new types of markers and improve the knowledge about the metabolic changes linked to OA. The relative advances coming from phenotype research are a first attempt to classify the heterogeneity of OA, and several markers could improve the phenotype characterization. These phenotypes could improve the selection of patients in clinical trials limiting the size of the studies by selecting patients with OA characteristics corresponding to the metabolic pathway targeted by the molecules evaluated. In addition, the inclusion of rapid progressors only in clinical trials would facilitate the demonstration of efficacy of the investigative drug to reduce joint degradation. The combination of selective biochemical markers appears as a promising and cost-effective approach to fulfill this unmet clinical need. Among the various potential roles of biomarkers in OA, their ability to monitor drug efficacy is probably one of the most important, in association with clinical and imaging parameters. Biochemical markers have the unique property to detect changes in joint tissue metabolism within a few weeks.

A matrix metalloproteinase-generated neoepitope of CRP can identify knee and multi-joint inflammation in osteoarthritis

OBJECTIVE

To compare C-reactive protein (CRP) and matrix metalloproteinase-generated neoepitope of CRP (CRPM) as biomarkers of inflammation and radiographic severity in patients with knee osteoarthritis.

METHODS

Participants with symptomatic osteoarthritis (n=25) of at least one knee underwent knee radiographic imaging and radionuclide etarfolatide imaging to quantify inflammation of the knees and other appendicular joints. For purposes of statistical analysis, semi-quantitative etarfolatide and radiographic imaging scores were summed across the knees; etarfolatide scores were also summed across all joints to provide a multi-joint synovitis measure. Multiple inflammation and collagen-related biomarkers were measured by ELISA including CRP, CRPM, MMP-generated neoepitopes of type I collagen and type III collagen in serum (n=25), and CD163 in serum (n=25) and synovial fluid (n=18).

RESULTS

BMI was associated with CRP (p=0.001), but not CRPM (p=0.753). Adjusting for BMI, CRP was associated with radiographic knee osteophyte score (p=0.002), while CRPM was associated with synovitis of the knee (p=0.017), synovitis of multiple joints (p=0.008), and macrophage marker CD163 in serum (p=0.009) and synovial fluid (p=0.03). CRP correlated with MMP-generated neoepitope of type I collagen in serum (p=0.045), and CRPM correlated with MMP-generated neoepitope of type III collagen in serum (p<0.0001). No biomarkers correlated with age, knee pain, or WOMAC pain.

CONCLUSIONS

To our knowledge, this is the first time that CRPM has been shown to be associated with knee and multi-joint inflammation based on objective imaging (etarfolatide) and biomarker (CD163) measures. These results demonstrate the capability of biomarker measurements to reflect complex biological processes and for neoepitope markers to more distinctly reflect acute processes than their precursor proteins. CRPM is a promising biomarker of local and systemic inflammation in knee OA that is associated with cartilage degradation and is independent of BMI. CRPM is a potential molecular biomarker alternative to etarfolatide imaging for quantitative assessment of joint inflammation.

Human Bone Mesenchymal Stem Cell-Derived Exosomes Inhibit IL-1β-Induced Inflammation in Osteoarthritis Chondrocytes

Objective

Human bone marrow mesenchymal stem cell (hBMSC)-derived exosomes exhibit protective effects against inflammatory diseases. This study aimed to explore the effects of hBMSC-derived exosomes on osteoarthritis (OA) in vitro and its related mechanisms.

Materials and Methods

In this experimental study, we characterised exosomes derived from hBMSCs by transmission electron microscopy, nanoparticle tracking and Western blot analysis. Cellular uptake of exosomes was observed by fluorescent microscopy. Cell viability of chondrocytes exposed to interleukin-1 beta (IL-1β) was determined by the Cell Counting Kit-8 (CCK-8). Real-time quantitative polymerase chain reaction (RT-qPCR) was used to determine expression levels of genes related to apoptosis, inflammation, cartilage collagen metabolism and mitogen-activated protein kinases.

Results

Fluorescence microscopy revealed that hBMSC-derived exosomes could be taken up by chondrocytes. hBMSC-derived exosomes could significantly enhance cell viability of chondrocytes in response to IL-1β treatment. RT-qPCR showed significant up-regulation of Survivin, Versican, IL-1β, IL-6, NF-κB, MMP-13, MAPK p38, JNK, ERK, Aggrecan and SOX9 expression levels by IL-1β treatment, while their mRNA expression levels decreased after co- culture with exosomes. The anti-inflammatory gene TGF-β was markedly suppressed by IL-1β treatment; however, we observed its expression after co-culture with exosomes. Additionally, the pro-inflammatory genes IL-1β, IL-6, NF-κB, TNF-α and TNF-β displayed significantly elevated expression levels in the IL-1β group and reduced expression levels after co-culture with exosomes.

Conclusion

hBMSC-derived exosomes may play a protective role in chondrocytes through inhibiting cell apoptosis and the inflammatory response. These results will provide a novel therapeutic strategy for OA.

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.

Osteoarthritis year in review 2019: biomarkers (biochemical markers)

OBJECTIVE

To provide an insightful summary of studies on biochemical markers for osteoarthritis (OA).

DESIGN

Two investigators systematically searched the electronic PubMed database for clinical studies into soluble biochemical markers for OA in humans that were published between 01-03-2018 and 01-03-2019. Data from selected publications were systematically extracted and tabulated and were summarized in a narrative review.

RESULTS

Out of 1,279 publications, 124 fulfilled all selection criteria and were selected for data extraction. The majority were around knee OA, cross-sectional in design, relatively small, and/or focused on one or a few biochemical markers. Among the intervention studies, relatively many were on non-pharmacological interventions, used clinical outcomes and/or were rather short. Some leads that were provided by this year's studies pertained to less conventional inflammatory mediators, oxidative stress, acidosis, angiogenesis and/or autoantibody formation.

CONCLUSIONS

This year's biochemical marker studies did provide potential leads for therapeutic targets or other biochemical marker applications that require robust and strategic follow-up research to be validated.

Profiling of inflammatory mediators in the synovial fluid related to pain in knee osteoarthritis

Background

Inflammatory mediators in the synovial fluid (SF) play critical roles in the initiation and development of pain in knee osteoarthritis (KOA). However, data for inflammatory marker expression are conflicting, and the role of SF inflammatory mediators in neuropathic pain is not clear. Therefore, the aim of this study was to identify SF inflammatory mediators associated with nociceptive and neuropathic pain in KOA.

Methods

Levels of IL-1β, IL-6, TNF-α, macrophage colony-stimulating factor, MMP-3, MMP-13, metalloproteinase with thrombospondin motifs 5, calcitonin gene-related peptide, neuropeptide Y, substance P and bradykinin were measured using enzyme-linked immunosorbent assays in 86 patients. Nociceptive pain was assessed using the numeric rating scale (NRS), visual analog scale (VAS) and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain score. Neuropathic pain was determined using the PainDETECT questionnaire. Moreover, knee function was evaluated by the WOMAC score and range of motion (ROM) assessments. Radiological grade was defined using the Kellgren-Lawrence (K-L) grading scale.

Results

Pain scores measured using different methods correlated highly with each other. A worse K-L grade and knee function were associated with worse pain. Expression of IL-1β and IL-6 was increased in the early stage compared with the late stage. The NRS score correlated positively with age, K-L grade, and the WOMAC score and negatively with ROM and TNF-α expression. The VAS correlated positively with age, K-L grade, and the WOMAC score but negatively with ROM and levels of IL-1β, IL-6 and TNF-α. The WOMAC pain score did not correlate with any of the inflammatory mediators measured; it correlated only with ROM. The PainDETECT score correlated only with the WOMAC score. Expression of other inflammatory mediators did not correlate with any of the pain scores.

Conclusions

IL-1β, IL-6 and TNF-α play critical roles in pain in the early stage of KOA and correlate with pain. The catabolic enzymes and neuropeptides measured do not correlate with nociceptive and neuropathic pain. New biomarkers related to pain in the late stage need to be further investigated.

Degradomics in Biomarker Discovery

The upregulation of protease expression and proteolytic activity is implicated in numerous pathological conditions such as neurodegeneration, cancer, cardiovascular and autoimmune diseases, and bone degeneration. During disease progression, various proteases form characteristic patterns of cleaved proteins and peptides, which can affect disease severity and course of progression. It has been shown that qualitative and quantitative monitoring of cleaved protease substrates can provide relevant prognostic, diagnostic, and therapeutic information. As proteolytic fragments and peptides generated in the affected tissue are commonly translocated to blood, urine, and other proximal fluids, their possible application as biomarkers is the subject of ongoing research. The field of degradomics has been established to enable the global identification of proteolytic events on the organism level, utilizing proteomic approaches and sample preparation techniques that facilitate the detection of proteolytic processing of protease substrates in complex biological samples. In this review, some of the latest developments in degradomic methodologies used for the identification and validation of biologically relevant proteolytic events and their application in the search for clinically relevant biomarker candidates are presented. The current state of degradomics in clinics is discussed and the future perspectives of the field are outlined.

Aberrantly hydroxymethylated differentially expressed genes and the associated protein pathways in osteoarthritis

Background

The elderly population is at risk of osteoarthritis (OA), a common, multifactorial, degenerative joint disease. Environmental, genetic, and epigenetic (such as DNA hydroxymethylation) factors may be involved in the etiology, development, and pathogenesis of OA. Here, comprehensive bioinformatic analyses were used to identify aberrantly hydroxymethylated differentially expressed genes and pathways in osteoarthritis to determine the underlying molecular mechanisms of osteoarthritis and susceptibility-related genes for osteoarthritis inheritance.

Methods

Gene expression microarray data, mRNA expression profile data, and a whole genome 5hmC dataset were obtained from the Gene Expression Omnibus repository. Differentially expressed genes with abnormal hydroxymethylation were identified by MATCH function. Gene ontology and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses of the genes differentially expressed in OA were performed using Metascape and the KOBAS online tool, respectively. The protein–protein interaction network was built using STRING and visualized in Cytoscape, and the modular analysis of the network was performed using the Molecular Complex Detection app.

Results

In total, 104 hyperhydroxymethylated highly expressed genes and 14 hypohydroxymethylated genes with low expression were identified. Gene ontology analyses indicated that the biological functions of hyperhydroxymethylated highly expressed genes included skeletal system development, ossification, and bone development; KEGG pathway analysis showed enrichment in protein digestion and absorption, extracellular matrix–receptor interaction, and focal adhesion. The top 10 hub genes in the protein–protein interaction network were COL1A1, COL1A2, COL2A1, COL3A1, COL5A1, COL5A2, COL6A1, COL8A1, COL11A1, and COL24A1. All the aforementioned results are consistent with changes observed in OA.

Conclusion

After comprehensive bioinformatics analysis, we found aberrantly hydroxymethylated differentially expressed genes and pathways in OA. The top 10 hub genes may be useful hydroxymethylation analysis biomarkers to provide more accurate OA diagnoses and target genes for treatment of OA.