Proteomic analysis of rat cartilage: the identification of differentially expressed proteins in the early stages of osteoarthritis

A synoptic literature review of animal models for investigating the biomechanics of knee osteoarthritis

Osteoarthritis (OA) is a common chronic disease largely driven by mechanical factors, causing significant health and economic burdens worldwide. Early detection is challenging, making animal models a key tool for studying its onset and mechanically-relevant pathogenesis. This review evaluate current use of preclinical in vivo models and progressive measurement techniques for analysing biomechanical factors in the specific context of the clinical OA phenotypes. It categorizes preclinical in vivo models into naturally occurring, genetically modified, chemically-induced, surgically-induced, and non-invasive types, linking each to clinical phenotypes like chronic pain, inflammation, and mechanical overload. Specifically, we discriminate between mechanical and biological factors, give a new explanation of the mechanical overload OA phenotype and propose that it should be further subcategorized into two subtypes, post-traumatic and chronic overloading OA. This review then summarises the representative models and tools in biomechanical studies of OA. We highlight and identify how to develop a mechanical model without inflammatory sequelae and how to induce OA without significant experimental trauma and so enable the detection of changes indicative of early-stage OA in the absence of such sequelae. We propose that the most popular post-traumatic OA biomechanical models are not representative of all types of mechanical overloading OA and, in particular, identify a deficiency of current rodent models to represent the chronic overloading OA phenotype without requiring intraarticular surgery. We therefore pinpoint well standardized and reproducible chronic overloading models that are being developed to enable the study of early OA changes in non-trauma related, slowly-progressive OA. In particular, non-invasive models (repetitive small compression loading model and exercise model) and an extra-articular surgical model (osteotomy) are attractive ways to present the chronic natural course of primary OA. Use of these models and quantitative mechanical behaviour tools such as gait analysis and non-invasive imaging techniques show great promise in understanding the mechanical aspects of the onset and progression of OA in the context of chronic knee joint overloading. Further development of these models and the advanced characterisation tools will enable better replication of the human chronic overloading OA phenotype and thus facilitate mechanically-driven clinical questions to be answered.

Circ_0002715 promotes the development of osteoarthritis through regulating LXN by sponging miR-127-5p

BACKGROUND

Our study aims to investigate the role and mechanism of circular RNA_0002715 (circ_0002715) in osteoarthritis (OA) progression.

METHODS

IL-1β-induced CHON-001 cells were used to mimic OA cell model. Circ_0002715, microRNA (miR)-127-5p and Latexin (LXN) expression was detected by quantitative real-time PCR. Cell functions were determined by MTT assay, flow cytometry and ELISA assay. Protein expression was examined by western blot.

RESULTS

Circ_0002715 was highly expressed in OA cartilage tissues. Circ_0002715 silencing inhibited inflammation, apoptosis, and ECM degradation in IL-1β-interfered CHON-001 cells. Circ_0002715 could sponge miR-127-5p, and miR-127-5p could target LXN. The effect of circ_0002715 down-regulation on chondrocyte injury was partially restored by miR-127-5p inhibitor. MiR-127-5p could suppress chondrocyte injury by inhibiting LXN expression.

CONCLUSION

Circ_0002715 might be a new therapeutic target for OA, which regulated miR-127-5p/LXN axis to promote IL-1β-induced chondrocyte injury.

Loss of LXN promotes macrophage M2 polarization and PD-L2 expression contributing cancer immune-escape in mice

Latexin (LXN) plays an important role in tumorigenesis and inflammatory response and as a tumor suppressor in many tumors. However, whether LXN regulates tumorigenesis through immune regulation remains uncertain. Here, we demonstrate that LXN deficiency increases hematopoietic stem cells, as well as affects the proportion of immune cells in the peripheral system. Animal studies show that mice loss of LXN promotes tumor growth in subcutaneous tumor model and AOM/DSS-induced colorectal cancer model. We found that loss of LXN promotes macrophage M2 polarization and PD-L2 expression in macrophage, thus, inhibits the function of T cells. Adoptive transfer of wild-type macrophage rescues the function of T cells in LXN-deficient mice. LXN deficiency in hematopoietic lineage exacerbates colorectal carcinogenesis, and targeted inhibition of PD-L2 ameliorates cancer growth in LXN-deficient mice. Mechanistically, we demonstrate that LXN inhibits STAT3 transcriptional activity by targeting inhibition of JAK1 in macrophages. LXN deficiency enhances PD-L2 expression rather than PD-L1 in macrophages, which lead to inhibition of T cells in tumor microenvironment. Collectively, we define a critical role of LXN/JAK1/STAT3 signal in macrophage and highlights the potential role of LXN in tumor immune-escape by regulating macrophage polarization, as well as the expression of immune checkpoint PD-L2.

Transcriptome Analysis Reveals Novel Genes Associated with Cartilage Degeneration in Posttraumatic Osteoarthritis Progression

OBJECTIVE

The current therapeutic strategy for posttraumatic osteoarthritis (PTOA) focuses on early intervention to attenuate disease progression, preserve joint function, and defer joint replacement timing. Sequential transcriptomic changes of articular cartilage in a rat model were investigated to explore the molecular mechanism in early PTOA progression.

DESIGN

Anterior cruciate ligament transection and medial meniscectomy (ACLT + MMx)-induced PTOA model was applied on male Wistar rats. Articular cartilages were harvested at time 0 (naïve), 2 week, and 4 weeks after surgery. Affymetrix Rat genome 230 2.0 array was utilized to analyze the gene expression changes of articular cartilages.

RESULTS

We identified 849 differentially expressed genes (DEGs) at 2 weeks and 223 DEGs at 4 weeks post-ACLT + MMx surgery compared with time 0 (naïve group). Gene ontology and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis were performed to gain further insights from these DEGs. 22 novel genes and 1 novel KEGG pathway (axon guidance) in cartilage degeneration of osteoarthritis were identified. Axon guidance molecules-Gnai1, Sema4d, Plxnb1, and Srgap2 commonly dysregulated in PTOA progression. Gnai1 gene showed a concordant change in protein expression by immunohistochemistry staining.

CONCLUSIONS

Our study identified 22 novel dysregulated genes and axon guidance pathway associated with articular cartilage degeneration in PTOA progression. These findings provide the potential candidates of biomarkers and therapeutic targets for further investigation.

Overexpression of hsa_circ_0094742 inhibits IL-1β-induced decline in CHON-001 cell viability by targeting microRNA-127-5p

Osteoarthritis (OA) is a public health problem that affects 240 million people globally; however, the current treatment options for OA are not effective. Therefore, there is still an urgent need to identify novel strategies to reduce the incidence and progression of OA. The circular RNA hsa_circ_0094742 was reported to be downregulated in patients with OA. However, the underlying mechanism remains unclear. The levels of hsa_circ_0094742 in CHON-001 were detected by reverse transcription quantitative polymerase chain reaction. Moreover, Cell Counting Kit-8 assay and Ki67 staining were used to determine the cell viability. The protein expression of biomarkers was detected by western blot analysis. In addition, the putative downstream target of hsa_circ_0094742 was predicted using the Circinteractome and TargetScan online databases. The putative targeting relationship was verified by dual luciferase reporter assay and fluorescence in situ hybridization. Next, cell apoptosis was determined by Annexin V/PI staining. hsa_circ_0094742 overexpression (OE) inhibited interleukin (IL)-1β-induced decline in the viability of CHON-001 cells and primary human chondrocytes. Furthermore, IL-1β-induced alterations in aggrecan, matrix metallopeptidase 13, X-linked inhibitor of apoptosis protein (XIAP), Bax and active caspase 3 were reversed by hsa_circ_0094742 OE. Luciferase reporter assay indicated that miR-127-5p was the downstream target of hsa_circ_0094742, and latexin was the target of miR-127-5p. hsa_circ_0094742 OE inhibited IL-1β-induced decline in CHON-001 cell viability by targeting miRNA-127-5p. The findings of the present study revealed the biological rational of the use of hsa_circ_0094742 OE as an anti-IL-1β effector in human chondrocytes. These findings may prompt further research on hsa_circ_0094742 as a potent circRNA target for the treatment of OA.

Icariin alleviates osteoarthritis by inhibiting NLRP3-mediated pyroptosis

Background

Osteoarthritis (OA) is the common chronic degenerative joint bone disease that is mainly featured by joint stiffness and cartilage degradation. Icariin (ICA), an extract from Epimedium, has been preliminarily proven to show anti-osteoporotic and anti-inflammatory effects in OA. However, the underlying mechanisms of ICA on chondrocytes need to be elucidated.

Methods

LPS-treated chondrocytes and monosodium iodoacetate (MIA)-treated Wistar rats were used as models of OA in vitro and in vivo, respectively. LDH and MTT assays were performed to detect cytotoxicity and cell viability. The expression levels of NLRP3, IL-1β, IL-18, MMP-1, MMP-13, and collagen II were detected by qRT-PCR and Western blotting. The release levels of IL-1β and IL-18 were detected by ELISA assay. Caspase-1 activity was assessed by flow cytometry. Immunofluorescence and immunohistochemistry were used to examine the level of NLRP3 in chondrocytes and rat cartilage, respectively. The progression of OA was monitored with hematoxylin-eosin (H&E) staining and safranin O/fast green staining.

Results

ICA could suppress LPS-induced inflammation and reduction of collagen formation in chondrocytes. Furthermore, ICA could inhibit NLRP3 inflammasome-mediated caspase-1 signaling pathway to alleviate pyroptosis induced by LPS. Overexpression of NLRP3 reversed the above changes caused by ICA. It was further confirmed in the rat OA model that ICA alleviated OA by inhibiting NLRP3-mediated pyroptosis.

Conclusion

ICA inhibited OA via repressing NLRP3/caspase-1 signaling-mediated pyroptosis in models of OA in vitro and in vivo, suggesting that ICA might be a promising compound in the treatment of OA.

Electronic supplementary material

The online version of this article (10.1186/s13018-019-1307-6) contains supplementary material, which is available to authorized users.

Analysis of gene expression in rheumatoid arthritis and related conditions offers insights into sex-bias, gene biotypes and co-expression patterns

The era of next-generation sequencing has mounted the foundation of many gene expression studies. In rheumatoid arthritis research, this has led to the discovery of important candidate genes which offered novel insights into mechanisms and their possible roles in the cure of the disease. In the last years, data generation has outstripped data analysis and while many studies focused on specific aspects of the disease, a global picture of the disease is not yet accomplished. Here, we analyzed and compared a collection of gene expression information from healthy individuals and from patients suffering under different arthritis conditions from published studies containing the following clinical conditions: early and established rheumatoid arthritis, osteoarthritis and arthralgia. We show comprehensive overviews of this data collection and give new insights specifically on gene expression in the early stage, into sex-dependent gene expression, and we describe general differences in expression of different biotypes of genes. Many genes that are related to cytoskeleton changes (actin filament related genes) are differently expressed in early rheumatoid arthritis in comparison to healthy subjects; interestingly, eight of these genes reverse their expression ratio significantly between men and women compared early rheumatoid arthritis and healthy subjects. There are some slighter changes between men and woman between the conditions early and established rheumatoid arthritis. Another aspect are miRNAs and other gene biotypes which are not only promising candidates for diagnoses but also change their expression grossly in average at rheumatoid arthritis and arthralgia compared to the healthy condition. With a selection of intersecting genes, we were able to generate simple classification models to distinguish between healthy and rheumatoid arthritis as well as between early rheumatoid arthritis to other arthritides based on gene expression.

Latexin expression correlated with mineralization of articular cartilage during progression of post-traumatic osteoarthritis in a rat model

As latexin has been linked with chondrocyte hypertrophic differentiation it is possible that this protein may also be involved in the mineralization of cartilage in OA. Therefore, we correlated latexin expression with the mineralization marker, alkaline phosphatase and determined the mineral deposition in the articular cartilage by analyzing the Ca/P ratio and the collagen fibrils pattern, during the progression of post-traumatic OA in a rat model. OA was induced by medial meniscectomy and post-surgery exercise for 5, 10, 20 and 45 days. Protein expression in articular cartilage was evaluated by immunofluorescence, histochemistry and Western blot. Minerals and structure of collagen fibrils in the superficial zone of cartilage were analyzed by energy dispersive X-ray spectroscopy (EDX) and atomic force microscopy (AFM) respectively. Protein expression analysis showed time-dependent up-regulation of latexin during OA progression. In the cartilage, latexin expression correlated with the expression and activity of alkaline phosphatase. EDX of the superficial zone of cartilage showed a Ca/P ratio closer to theoretical values for basic calcium phosphate minerals. The presence of minerals was also analyzed indirectly with AFM, as the collagen fibril pattern was less evident in the mineralized tissue. Latexin is expressed in articular cartilage from the early stages of post-traumatic OA; however, minerals were detected after latexin expression was up-regulated, indicating that its activity precedes and remains during the pathological mineralization of cartilage. Thus, our results contribute to the identification of molecules involved in the mineralization of articular chondrocytes.

The putative tumour suppressor protein Latexin is secreted by prostate luminal cells and is downregulated in malignancy

Loss of latexin (LXN) expression negatively correlates with the prognosis of several human cancers. Despite association with numerous processes including haematopoietic stem cell (HSC) fate, inflammation and tumour suppression, a clearly defined biological role for LXN is still lacking. Therefore, we sought to understand LXN expression and function in the normal and malignant prostate to assess its potential as a therapeutic target. Our data demonstrate that LXN is highly expressed in normal prostate luminal cells but downregulated in high Gleason grade cancers. LXN protein is both cytosolic and secreted by prostate cells and expression is directly and potently upregulated by all-trans retinoic acid (atRA). Whilst overexpression of LXN in prostate epithelial basal cells did not affect cell fate, LXN overexpression in the luminal cancer line LNCaP reduced plating efficiency. Transcriptome analysis revealed that LXN overexpression had no direct effects on gene expression but had significant indirect effects on important genes involved in both retinoid metabolism and IFN-associated inflammatory responses. These data highlight a potential role for LXN in retinoid signaling and inflammatory pathways. Investigating the effects of LXN on immune cell function in the tumour microenvironment (TME) may reveal how observed intratumoural loss of LXN affects the prognosis of many adenocarcinomas.

[Establishment of chondrocyte degeneration model in vitro by rat serum]

OBJECTIVE

To establish a model of chondrocyte degeneration in vitro.

METHODS

Chondrocytes were isolated from articular cartilages of newly born SD rats by digestion with typeⅡ collagenase. The chondrocytes were cultured with H-DMEM medium containing 10%FBS, 50 ng/mL IL-1β+10%FBS, 2.5% rat serum and 5% rat serum, respectively; and the chondrocytes at passage one were used in the experiments. The morphology changes were investigated under phase contrast microscope after chondrocytes were treated with rat serum and IL-1β. Proliferation of chondrocytes was detected by MTT method. The protein expression levels of PCNA, typeⅡ collagen and MMP-13 were examined by Western blotting. The levels of ADAMTS5, MMP-9, Aggrecan and SOX-9 mRNA were detected by real-time PCR.

RESULTS

The cell morphology was changed from polygon to spindle in both rat serum groups and IL-1β group, and the proliferation of chondrocytes in these groups was much higher than that in control group. The results showed that the expression levels of typeⅡ collagen, Aggrecan and SOX-9 decreased while the expression levels of MMP-13, MMP-9 and ADMATS5 were up-regulated in rat serum and IL-1β-treated groups compared with control group.

CONCLUSION

The results indicate that rat serum can induce chondrocyte degeneration and may be used for osteoarthritis model in vitro.