Osteoarthritis: histology and pathogenesis

LncRNA-mediated cartilage homeostasis in osteoarthritis: a narrative review

Osteoarthritis (OA) is a degenerative disease of cartilage that affects the quality of life and has increased in morbidity and mortality in recent years. Cartilage homeostasis and dysregulation are thought to be important mechanisms involved in the development of OA. Many studies suggest that lncRNAs are involved in cartilage homeostasis in OA and that lncRNAs can be used to diagnose or treat OA. Among the existing therapeutic regimens, lncRNAs are involved in drug-and nondrug-mediated therapeutic mechanisms and are expected to improve the mechanism of adverse effects or drug resistance. Moreover, targeted lncRNA therapy may also prevent or treat OA. The purpose of this review is to summarize the links between lncRNAs and cartilage homeostasis in OA. In addition, we review the potential applications of lncRNAs at multiple levels of adjuvant and targeted therapies. This review highlights that targeting lncRNAs may be a novel therapeutic strategy for improving and modulating cartilage homeostasis in OA patients.

Histopathology of the Intervertebral Disc of Nothobranchius furzeri, a Fish Model of Accelerated Aging

INTRODUCTION

Osteoarthritis is a classical age-related disease, which affects millions of patients worldwide. To further understand the pathophysiology and to develop therapeutic strategies for this disease, animal models play a significant role. Nothobranchius furzeri is an established model for accelerated aging that spontaneously develops spinal deformities. Although the bone properties of N. furzeri are well described, characteristics of the intervertebral discs are still unknown. The aim of this study was to investigate the characteristics of the intervertebral discs of healthy and deformed N. furzeri.

MATERIAL AND METHODS

Intervertebral properties of healthy and deformed N. furzeri were investigated in 8-, 12-, 18- and 21.5-week-old male fish of the GRZ strain. For histological evaluations the fish were decalcified, paraffin-embedded and stained with (1) hematoxylin and eosin, (2) toluidine blue and (3) alcian blue/picrosirius red.

RESULTS

8-week-old and deformed N. furzeri showed spongy-like tissue containing vacuolated notochord cells and a beginning formation of fibrous tissue in the central area. Older healthy fish showed fibrous tissue in the central region and a spongy-like tissue in the peripheral region.

CONCLUSION

Our study revealed age- and disease-related alterations of the vertebral discs in N. furzeri. Further studies should investigate the utility of N. furzeri as a model for degenerative spine diseases.

Two Amnion-Derived Mesenchymal Stem-Cells Injections to Osteoarthritic Elbows in Dogs-Pilot Study

The aim of the study was to investigate the potential of cell-based regenerative therapy for elbow joints affected by osteoarthritis. Interest was focused on two intra-articular applications of amnion-derived mesenchymal stem cells (A-MSCs) to a group of different breeds of dogs with elbow osteoarthritis (13 joints). Two injections were performed 14 days apart. We evaluated synovial fluid biomarkers, such as IFN-γ, IL-6, IL-15, IL-10, MCP-1, TNF-α, and GM-CSF, by multiplex fluorescent micro-bead immunoassay in the treated group of elbows (n = 13) (day 0, day 14, and day 28) and in the control group of elbows (n = 9). Kinematic gait analysis determined the joint range of motion (ROM) before and after each A-MSCs application. Kinematic gait analysis was performed on day 0, day 14, and day 28. Kinematic gait analysis pointed out improvement in the average range of motion of elbow joints from day 0 (38.45 ± 5.74°), day 14 (41.7 ± 6.04°), and day 28 (44.78 ± 4.69°) with statistical significance (p < 0.05) in nine elbows. Correlation analyses proved statistical significance (p < 0.05) in associations between ROM (day 0, day 14, and day 28) and IFN-γ, IL-6, IL-15, MCP-1, TNF-α, and GM-CSF concentrations (day 0, day 14, and day 28). IFN-γ, IL-6, IL-15, MCP-1, GM-CSF, and TNF- α showed negative correlation with ROM at day 0, day 14, and day 28, while IL-10 demonstrated positive correlation with ROM. As a consequence of A-MSC application to the elbow joint, we detected a statistically significant (p < 0.05) decrease in concentration levels between day 0 and day 28 for IFN-γ, IL-6, and TNF-α and statistically significant increase for IL-10. Statistical significance (p < 0.05) was detected in TNF-α, IFN-γ, and GM-CSF concentrations between day 14 and the control group as well as at day 28 and the control group. IL-6 concentrations showed statistical significance (p < 0.05) between day 14 and the control group.

Automated Prediction of Osteoarthritis Level in Human Osteochondral Tissue Using Histopathological Images

Osteoarthritis (OA) is the most common arthritis and the leading cause of lower extremity disability in older adults. Understanding OA progression is important in the development of patient-specific therapeutic techniques at the early stage of OA rather than at the end stage. Histopathology scoring systems are usually used to evaluate OA progress and the mechanisms involved in the development of OA. This study aims to classify the histopathological images of cartilage specimens automatically, using artificial intelligence algorithms. Hematoxylin and eosin (HE)- and safranin O and fast green (SafO)-stained images of human cartilage specimens were divided into early, mild, moderate, and severe OA. Five pre-trained convolutional networks (DarkNet-19, MobileNet, ResNet-101, NasNet) were utilized to extract the twenty features from the last fully connected layers for both scenarios of SafO and HE. Principal component analysis (PCA) and ant lion optimization (ALO) were utilized to obtain the best-weighted features. The support vector machine classifier was trained and tested based on the selected descriptors to achieve the highest accuracies of 98.04% and 97.03% in HE and SafO, respectively. Using the ALO algorithm, the F1 scores were 0.97, 0.991, 1, and 1 for the HE images and 1, 0.991, 0.97, and 1 for the SafO images for the early, mild, moderate, and severe classes, respectively. This algorithm may be a useful tool for researchers to evaluate the histopathological images of OA without the need for experts in histopathology scoring systems or the need to train new experts. Incorporating automated deep features could help to improve the characterization and understanding of OA progression and development.

Mesenchymal Stromal Cells-Derived Extracellular Vesicles as Potential Treatments for Osteoarthritis

Osteoarthritis (OA) is a degenerative disease of the joints characterized by cartilage damage and severe pain. Despite various pharmacological and surgical interventions, current therapies fail to halt OA progression, leading to high morbidity and an economic burden. Thus, there is an urgent need for alternative therapeutic approaches that can effectively address the underlying pathophysiology of OA. Extracellular Vesicles (EVs) derived from mesenchymal stromal cells (MSCs) represent a new paradigm in OA treatment. MSC-EVs are small membranous particles released by MSCs during culture, both in vitro and in vivo. They possess regenerative properties and can attenuate inflammation, thereby promoting cartilage healing. Importantly, MSC-EVs have several advantages over MSCs as cell-based therapies, including lower risks of immune reactions and ethical issues. Researchers have recently explored different strategies, such as modifying EVs to enhance their delivery, targeting efficiency, and security, with promising results. This article reviews how MSC-EVs can help treat OA and how they might work. It also briefly discusses the benefits and challenges of using MSC-EVs and talks about the possibility of allogeneic and autologous MSC-EVs for medical use.

Histological features of knee osteoarthritis treated with triamcinolone acetonide and hyaluronic acid

Osteoarthritis (OA) is one of the most common degenerative joint diseases leading to disability in the end stage. Although intra-articular triamcinolone acetonide (TA) is one of the OA treatments that have been widely used, the side effects of such corticosteroids are still controversial. Intra-articular hyaluronic acid (HA) injection is another therapeutic option for patients with OA who do not want to use corticosteroids because of their side effects. However, the difference between the histological features associated with TA and HA in the treatment of OA remains unclear. Thus, the present study aimed to compare the histological effects of TA and HA on the cartilage of patients with knee OA. In the current study, 31 patients diagnosed with grade 3-4 knee OA on the Kellgren-Lawrence radiographic grading scale were separated into three groups: TA (n=12); HA (n=7) and untreated group (n=12). Histological examination of the whole articular cartilages of the patients was performed with hematoxylin and eosin and Alcian staining, as well as using a TUNEL assay. Clinical data such as cartilage thickness, structural and component deterioration, proteoglycan levels, apoptosis and empty lacunae were compared between the three groups. The results showed a high level of deterioration in both TA and HA groups but not in the untreated group, although the thickness of cartilage in the HA group was lower compared with that in the TA and untreated groups. The proteoglycan levels in the TA group were lower compared with those in the HA group. Moreover, the number of empty lacunae in the HA group was higher compared with that in the TA group, while no difference in apoptosis was found between TA and HA groups. A significant difference was not found in the histological staining between TA and HA groups. On the other hand, a significant difference was found in cartilage deterioration between the medial and lateral sides in these groups. TA and HA groups showed comparable histological results. TA injection is cheaper and easier but has more adverse effects for patients with knee OA than HA injection. Therefore, orthopaedists should select TA or HA based on the economic and specific needs of patients.

Healthy and Osteoarthritis-Affected Joints Facing the Cellular Crosstalk

Osteoarthritis (OA) is a chronic, progressive, severely debilitating, and multifactorial joint disease that is recognized as the most common type of arthritis. During the last decade, it shows an incremental global rise in prevalence and incidence. The interaction between etiologic factors that mediate joint degradation has been explored in numerous studies. However, the underlying processes that induce OA remain obscure, largely due to the variety and complexity of these mechanisms. During synovial joint dysfunction, the osteochondral unit undergoes cellular phenotypic and functional alterations. At the cellular level, the synovial membrane is influenced by cartilage and subchondral bone cleavage fragments and extracellular matrix (ECM) degradation products from apoptotic and necrotic cells. These "foreign bodies" serve as danger-associated molecular patterns (DAMPs) that trigger innate immunity, eliciting and sustaining low-grade inflammation in the synovium. In this review, we explore the cellular and molecular communication networks established between the major joint compartments-the synovial membrane, cartilage, and subchondral bone of normal and OA-affected joints.

The epigenetic players and the chromatin marks involved in the articular cartilage during osteoarthritis

Epigenetics defines the modifications of the genome that do not involve a change in the nucleotide sequence of DNA. These modifications constitute a mechanism of gene regulation poorly explored in the context of cartilage physiology. They are now intensively studied by the scientific community working on articular cartilage and its related pathology such as osteoarthritis. Indeed, epigenetic regulations can control the expression of crucial gene in the chondrocytes, the only resident cells of cartilage. Some epigenetic changes are considered as a possible cause of the abnormal gene expression and the subsequent alteration of the chondrocyte phenotype (hypertrophy, proliferation, senescence…) as observed in osteoarthritic cartilage. Osteoarthritis is a joint pathology, which results in impaired extracellular matrix homeostasis and leads ultimately to the progressive destruction of cartilage. To date, there is no pharmacological treatment and the exact causes have yet to be defined. Given that the epigenetic modifying enzymes can be controlled by pharmacological inhibitors, it is thus crucial to describe the epigenetic marks that enable the normal expression of extracellular matrix encoding genes, and those associated with the abnormal gene expression such as degradative enzyme or inflammatory cytokines encoding genes. In this review, only the DNA methylation and histone modifications will be detailed with regard to normal and osteoarthritic cartilage. Although frequently referred as epigenetic mechanisms, the regulatory mechanisms involving microRNAs will not be discussed. Altogether, this review will show how this nascent field influences our understanding of the pathogenesis of OA in terms of diagnosis and how controlling the epigenetic marks can help defining epigenetic therapies.

The sirtuin family in health and disease

Sirtuins (SIRTs) are nicotine adenine dinucleotide(+)-dependent histone deacetylases regulating critical signaling pathways in prokaryotes and eukaryotes, and are involved in numerous biological processes. Currently, seven mammalian homologs of yeast Sir2 named SIRT1 to SIRT7 have been identified. Increasing evidence has suggested the vital roles of seven members of the SIRT family in health and disease conditions. Notably, this protein family plays a variety of important roles in cellular biology such as inflammation, metabolism, oxidative stress, and apoptosis, etc., thus, it is considered a potential therapeutic target for different kinds of pathologies including cancer, cardiovascular disease, respiratory disease, and other conditions. Moreover, identification of SIRT modulators and exploring the functions of these different modulators have prompted increased efforts to discover new small molecules, which can modify SIRT activity. Furthermore, several randomized controlled trials have indicated that different interventions might affect the expression of SIRT protein in human samples, and supplementation of SIRT modulators might have diverse impact on physiological function in different participants. In this review, we introduce the history and structure of the SIRT protein family, discuss the molecular mechanisms and biological functions of seven members of the SIRT protein family, elaborate on the regulatory roles of SIRTs in human disease, summarize SIRT inhibitors and activators, and review related clinical studies.

Novel micro-MRI approach for subchondral trabecular bone analysis in patients with hip osteoarthritis is comparable to micro-CT approach

AIM

To test the agreement between a newly developed micro-magnetic resonance imaging (MRI) analysis of the subchondral bone and the micro-computed tomography (CT) approach.

METHODS

Samples obtained from 10 patients with osteoarthritis undergoing total hip arthroplasty were scanned with a 7.0 T micro-MRI. Proton density-weighted images and proton density-weighted images with fat suppression were obtained. The results were validated with a micro-CT device. Micro-MRI and micro-CT scans of the same sample were aligned, and regions of interest were delineated on equal areas of the sample. Bone volume fraction was calculated by using in-house plugins. The agreement between the methods was tested with Bland-Altman analysis.

RESULTS

The agreement between the methods was good, with average difference of 2.167%. The differences between the methods were not significant (P=0.272, t test).

CONCLUSION

The novel micro-MRI approach could be used for subchondral bone analysis. With further optimization for clinical MRI machines, the approach can be also used in the diagnostics of hip osteoarthritis.

Chondrocytes In Vitro Systems Allowing Study of OA

Osteoarthritis (OA) is an extremely complex disease, as it combines both biological-chemical and mechanical aspects, and it also involves the entire joint consisting of various types of tissues, including cartilage and bone. This paper describes the methods of conducting cell cultures aimed at searching for the mechanical causes of OA development, therapeutic solutions, and methods of preventing the disease. It presents the systems for the cultivation of cartilage cells depending on the level of their structural complexity, and taking into account the most common solutions aimed at recreating the most important factors contributing to the development of OA, that is mechanical loads. In-vitro systems used in tissue engineering to investigate the phenomena associated with OA were specified depending on the complexity and purposefulness of conducting cell cultures.

The Hunt Is On! In Pursuit of the Ideal Stem Cell Population for Cartilage Regeneration

Cartilage injury and degeneration are hallmarks of osteoarthritis (OA), the most common joint disease. OA is a major contributor to pain, loss of function, and reduced quality of life. Over the last decade, considerable research efforts have focused on cell-based therapies, including several stem cell-derived approaches to reverse the cartilage alterations associated with OA. Although several tissue sources for deriving cell-based therapies have been identified, none of the resident stem cell populations have adequately fulfilled the promise of curing OA. Indeed, many cell products do not contain true stem cells. As well, issues with aggressive marketing efforts, combined with a lack of evidence regarding efficacy, lead the several national regulatory bodies to discontinue the use of stem cell therapy for OA until more robust evidence becomes available. A review of the evidence is timely to address the status of cell-based cartilage regeneration. The promise of stem cell therapy is not new and has been used successfully to treat non-arthritic diseases, such as hematopoietic and muscle disorders. These fields of regenerative therapy have the advantage of a considerable foundation of knowledge in the area of stem cell repair mechanisms, the role of the stem cell niche, and niche-supporting cells. This foundation is lacking in the field of cartilage repair. So, where should we look for the ideal stem cell to regenerate cartilage? It has recently been discovered that cartilage itself may contain a population of SC-like progenitors. Other potential tissues include stem cell-rich dental pulp and the adolescent growth plate, the latter of which contains chondrocyte progenitors essential for producing the cartilage scaffold needed for bone growth. In this article, we review the progress on stem cell therapies for arthritic disorders, focusing on the various stem cell populations previously used for cartilage regeneration, successful cases of stem cell therapies in muscle and hemopoietic disorders, some of the reasons why these other fields have been successful (i.e., “lessons learned” to be applied to OA stem cell therapy), and finally, novel potential sources of stem cells for regenerating damaged cartilage in vivo.

Shoulder Osteoarthritis

Glenohumeral osteoarthritis has proven to be a major contributor to shoulder joint pain and dysfunction in the elderly. There are several conditions about the shoulder that contribute to the development of glenohumeral osteoarthritis, which includes traumatic injuries, rotator cuff pathology, glenohumeral instability, glenoid dysplasia, and osteonecrosis. When glenohumeral osteoarthritis pain is refractory to conservative treatment, intra-articular injections and surgery can be performed. The radiologist should be aware of the varying types of shoulder arthroplasties, what preoperative findings influence that decision and the expected postoperative appearance of the differing components.

Structural changes in the collagen network of joint tissues in late stages of murine OA

Osteoarthritis (OA) is the most prevalent degenerative joint disease, resulting in joint pain, impaired movement, and structural changes. As the ability of joint tissue to resist stress is mainly imparted by fibrillar collagens in the extracellular matrix, changes in the composition and structure of collagen fibers contribute to the pathological remodeling observed in OA joints that includes cartilage degeneration, subchondral bone (SCB) sclerosis, and meniscal damage. Using the established OA model of destabilization of the medial meniscus (DMM) in C57BL/6J mice, we performed a comprehensive analysis of the content and structure of collagen fibers in the articular cartilage, subchondral bone, and menisci using complementary techniques, which included second harmonic generation microscopy and immunofluorescence staining. We found that regions exposed to increased mechanical stress in OA mice, typically closest to the site of injury, had increased collagen fiber thickness, dysregulated fiber formation, and tissue specific changes in collagen I and II (Col I and Col II) expression. In cartilage, OA was associated with decreased Col II expression in all regions, and increased Col I expression in the anterior and posterior regions. Col I fiber thickness was increased in all regions with disorganization in the center region. In the superficial SCB, all regions exhibited increased Col I expression and fiber thickness in OA mice; no changes were detected in the deeper regions of the subchondral bone except for increased Col I fiber thickness. In the menisci, OA led to increased Col I and Col II expression in the vascular and avascular regions of the anterior meniscus with increased Col I fiber thickness in these regions. Similar changes were observed only in the vascular region of the posterior meniscus. Our findings provide, for the first time, comprehensive insights into the microarchitectural changes of extracellular matrix in OA and serve as guidelines for studies investigating therapies that target collagenous changes as means to impede the progression of osteoarthritis.

Benefits of electroacupuncture and a swimming association when compared with isolated protocols in an osteoarthritis model

Background and aim

Osteoarthritis (OA) is characterized by pain and inflammation. Electroacupuncture (EA) and swimming (SW) are non-pharmacological interventions recommended for treating OA. The study evaluated the benefits of electroacupuncture (EA) and swimming (SW) association when compared with isolated protocols in an OA rodent model. Experimental.

Procedures

An ankle monoarthritis model was induced in rats by applying Complete Freund's Adjuvant (CFA). After seven days of induced OA, the groups were submitted to EA (ST36 and the GB 30 Acupoint), SW, or the EA + SW protocol. The nociceptive behavior was measured by the Von Frey test, the Cold Stimulation test, and the Paw Flick Immersion test. Inflammatory activity was evaluated by measuring TNF levels, myeloperoxidase, NAGase, immunological parameters and the histology from the subcutaneous tissue.

Results

Compared to CFA group, EA decreased the nociceptive scores in the cold stimulation test (p < 0.05), and it also increased the latency time in thermal cold (p < 0.01) and heat hyperalgesia (p < 0.001). Also, EA reduced NAGase (p < 0.01). SW reduced the edema (p < 0.05) and did not increase the inflammatory infiltrates or congestion, neither in the histological measurements nor by analyzing the levels of TNF. The association of EA + SW decreased the neutrophils and the monocytes, MPO (p < 0.05), and the glutamate levels in the cerebrospinal fluid (CSF, p < 0.001).

Conclusion

There were statistical differences between combination therapy and monotherapy as seen by the inflammatory parameters, which could be associate to the delay of the chronification osteoarthritis retardation. However, EA + SW did not show benefits when compared to isolated protocols in nociceptive behavior.

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Electroacupuncture (EA) extended the latency time in the thermal hyperalgesia assay.

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The swimming protocol did not increase the inflammatory infiltrates.

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EA and swimming decreased the glutamate levels in the cerebral spinal fluid.

Meta-Analyses of Multiple Gene Expression Profiles to Screen Hub Genes Related to Osteoarthritis

BACKGROUND

This study aimed to screen and validate the crucial genes involved in osteoarthritis (OA) and explore its potential molecular mechanisms.

METHODS

Four expression profile datasets related to OA were downloaded from the Gene Expression Omnibus (GEO). The differentially expressed genes (DEGs) from 4 microarray patterns were identified by the meta-analysis method. The weighted gene co-expression network analysis (WGCNA) method was used to investigate stable modules most related to OA. In addition, a protein-protein interaction (PPI) network was built to explore hub genes in OA. Moreover, OA-related genes and pathways were retrieved from Comparative Toxicogenomics Database (CTD).

RESULTS

A total of 1,136 DEGs were identified from 4 datasets. Based on these DEGs, WGCNA further explored 370 genes included in the 3 OA-related stable modules. A total of 10 hub genes were identified in the PPI network, including AKT1, CDC42, HLA-DQA2, TUBB, TWISTNB, GSK3B, FZD2, KLC1, GUSB, and RHOG. Besides, 5 pathways including "Lysosome," "Pathways in cancer," "Wnt signaling pathway," "ECM-receptor interaction" and "Focal adhesion" in CTD and enrichment analysis and 5 OA-related hub genes (including GSK3B, CDC42, AKT1, FZD2, and GUSB) were identified.

CONCLUSION

In this study, the meta-analysis was used to screen the central genes associated with OA in a variety of gene expression profiles. Three OA-related modules (green, turquoise, and yellow) containing 370 genes were identified through WGCNA. It was discovered through the gene-pathway network that GSK3B, CDC42, AKT1, FZD2, and GUSB may be key genes related to the progress of OA and may become promising therapeutic targets.

Exosomes from Kartogenin-Pretreated Infrapatellar Fat Pad Mesenchymal Stem Cells Enhance Chondrocyte Anabolism and Articular Cartilage Regeneration

Objective

To evaluate the effect of Kartogenin-pretreated exosomes derived from infrapatellar fat pad mesenchymal stem cells on chondrocyte in vitro and articular cartilage regeneration in vivo.

Methods

Infrapatellar fat pad mesenchymal stem cells (IPFP-MSCs) were isolated from rabbits to harvest exosomes. After identification of mesenchymal stem cells and exosomes, rabbit chondrocytes were divided into three groups for further treatment: the EXO group (chondrocytes treated with exosomes isolated from infrapatellar fat pad mesenchymal stem cells), KGN-EXO group (chondrocytes treated with exosomes isolated from infrapatellar fat pad mesenchymal stem cells pretreated with KGN), and control group. After processing and proliferation, phenotypic changes of chondrocytes were measured. In the in vivo study, 4 groups of rabbits with articular cartilage injury were treated with KGN-EXO, EXO, IPFP-MSCs, and control. Macroscopic evaluation and histological evaluation were made to figure out the different effects of the 4 groups on cartilage regeneration in vivo.

Results

The proliferation rate of chondrocytes in the EXO or KGN-EXO group was significantly higher than that in the control group (P < 0.05). The qRT-PCR results showed that the expression of Sox-9, Aggrecan, and Col II was the highest in the KGN-EXO group compared with the EXO group and the control group (P < 0.05). The results of Western blot were consistent with the results of qRT-PCR. In vivo, the cartilage defects in the KGN-EXO group showed better gross appearance and improved histological score than those in IPFP-MSC groups, EXO groups, and control groups (P < 0.05). At 12 weeks, the defect site in the KGN-EXO group was almost completely repaired with a flat and smooth surface, while a large amount of hyaline cartilage-like structures and no obvious cracks were observed.

Conclusion

Our study demonstrates that the exosomes isolated from infrapatellar fat pad mesenchymal stem cells pretreated with KGN have potent ability to induce chondrogenic differentiation of stem cells, effectively promoting the proliferation and the expression of chondrogenic proteins and genes of chondrocytes. The KGN-EXO can also promote the repair of articular cartilage defects more effectively, which can be used as a potential therapeutic method in the future.

Autologous conditioned serum for degenerative diseases and prospects

Autologous conditioned serum (ACS) is a blood-derived product that is prepared by the incubation of whole blood with medical-grade glass beads, resulting in serum enrichment in interleukin-1 receptor antagonist (IL-1Ra), anti-inflammatory cytokines (IL-4, IL-10, and IL-13), and high concentrations of growth factors. ACS has shown qualitatively and quantitatively better therapeutic effects than most established pharmacological treatments and surgery for joint diseases given its ability to both target the inflammatory cascade to decrease cartilage destruction as well as improve endogenous repair mechanisms. ACS application is simple and safe with limited adverse effects. This article reviews the role of ACS in degenerative joint disease, in addition to other inflammatory and autoimmune diseases, given its regenerative and immune-modulating properties.

The Lysine Specific Demethylase-1 Negatively Regulates the COL9A1 Gene in Human Articular Chondrocytes

Osteoarthritis (OA) is a degenerative disease of the joints which is associated with an impaired production of the cartilage matrix by the chondrocytes. Here, we investigated the role of Lysine-Specific Demethylase-1 (LSD1), a chromatin remodeling enzyme whose role in articular chondrocytes was previously associated with a catabolic activity and which is potentially involved during OA. Following a loss of function strategy and RNA sequencing analysis, we detail the genes which are targeted by LSD1 in human articular chondrocytes and identify COL9A1, a gene encoding the α1 chain of the cartilage-specific type IX collagen, as negatively regulated by LSD1. We show that LSD1 interacts with the transcription factor SOX9 and is recruited to the promoter of COL9A1. Interestingly, we observe that OA cartilage displays stronger LSD1 immunostaining compared with normal, and we demonstrate that the depletion of LSD1 in OA chondrocytes prevents the decrease in COL9A1 following Il-1β treatment. These results suggest LSD1 is a new regulator of the anabolic activity of articular chondrocytes potentially destabilizing the cartilage matrix, since it negatively regulates COL9A1, a gene encoding a crucial anchoring collagen molecule. This newly identified role played by LSD1 may thus participate in the alteration of the cartilage matrix during OA.

Correlation Analysis of C-terminal telopeptide of collagen type II and Interleukin-1β for Early Diagnosis of Knee Osteoarthritis

Objective

To analyze the correlation between the Kellgren–Lawrence (K‐L) score of knee osteoarthritis (KOA) patients with different degrees and their urine concentration of C‐terminal telopeptide of collagen type II (CTX‐II) and interleukin‐1β (IL‐1β), and to further evaluate the diagnostic value of CTX‐II and IL‐1β during the pathological process by producing an experimental osteoarthritis (OA) model in rabbits.

Methods

From 1 January 2017 to 31 December 2018, a total of 34 subjects (7 mild, 9 moderate, 9 severe arthritis patients, and 9 healthy individuals) comprising 16 men and 18 women were included in this study. Patients were diagnosed according to the American College of Rheumatology (ACR) criteria. The urine of all subjects was collected to detect the concentration of CTX‐II and IL‐1β. The rabbits in the KOA group were subjected to protease (control group with saline) injection into the articular cavity of their right knees and immobilization with gypsum. We used radiological and histological examination to identify the KOA model. ELISA was applied to investigate the concentrations of CTX‐II and IL‐1β in urine and serum, and Spearman's rank correlation analysis was used to analyze the correlation.

Results

There was no significant difference in the mean ages and body mass index (BMI) between groups. The mean ages of mild, moderate, and severe arthritis patients and healthy individuals were 54.29 ± 5.76, 58.44 ± 6.44, 59.89 ± 6.75, and 56.67 ± 4.18 years, respectively. The mean BMI of mild, moderate, and severe arthritis patients and healthy individuals were 23.59 ± 1.56, 23.57 ± 2.06, 24.46 ± 1.64, and 23.42 ± 1.35 kg/m², respectively. The Kellgren–Lawrence (K‐L) score was higher with the aggravation of KOA. The K‐L scores of mild, moderate, and severe KOA patients were 1.14 ± 0.38, 2.56 ± 0.53, and 3.63 ± 0.52, respectively. The KOA symptoms of patients became more severe, with not only increased K‐L scores but also elevated concentrations of CTX‐II and IL‐1β. Moreover, there was a positive correlation between CTX‐II and IL‐1β of all subjects (r = 0.974, P < 0.001), between K‐L score and urine concentration of CTX‐II (r = 0.900, P < 0.001), and between K‐L score and IL‐1β (r = 0.813, P < 0.001) of all subjects. Both were significantly increased in KOA group rabbits at all time points after surgery. The serum concentration of CTX‐II and IL‐1β was elevated as early as in the 2nd week (3.69 and 4.25 times) and reached a peak (5.41 and 7.23 times) in the 4th week after surgery. Then, until 12 weeks after surgery, the CTX‐II and IL‐1β concentrations in the KOA group were slightly reduced and remained around 4.5 and 6.3 times that in the control group. Moreover, there was a positive correlation between the serum concentration of IL‐1β and CTX‐II (r = 0.967, P < 0.001).

Conclusion

CTX‐II and IL‐1β, which were significantly increased during the process of KOA, can be used as biomolecular markers to provide guidelines for early diagnosis and treatment of KOA.

Comparative Analysis of Peptide Composition and Bioactivity of Different Collagen Hydrolysate Batches on Human Osteoarthritic Synoviocytes

Collagen hydrolysates (CHs) are heterogeneous mixtures of collagen peptides that are often used as nutraceuticals for osteoarthritis (OA). In this study, we compared the peptide composition and pharmacological effects of three different CH preparations (CH-Alpha^®, Peptan^® B 2000 and Mobiforte^®) as well as their production batches. Our biochemical analysis using MALDI-TOF mass spectrometry and the ICPL™-isotope labelling method revealed marked differences between different CH preparations and even between some production batches of the same preparation. We also investigated the pharmacological effects of these CHs on human fibroblast-like synoviocytes (FLS). No significant effects on cultured FLS could be demonstrated for either production batch of CH-Alpha^®, Peptan^® B 2000, and Mobiforte^® analyzing a small number of pharmacological relevant targets. Thus, our study already shows for the first time that different production batches of the same CH preparation as well as different CH preparations can differ significantly in their peptide composition. In this line, further studies are also needed to verify equal pharmacological efficacy of CH batches on a much broader range of (patho)physiological relevant targets. If OA patients are to be offered a safe and effective nutraceutical a better knowledge about all potential effects as well as ensuring the same active-substance levels are a prerequisite.

Bioinformatics analysis to identify key genes and pathways influencing synovial inflammation in osteoarthritis

Osteoarthritis (OA) is a chronic arthropathy that occurs in the middle-aged and elderly population. The present study aimed to identify gene signature differences between synovial cells from OA synovial membrane with and without inflammation, and to explain the potential mechanisms involved. The differentially expressed genes (DEGs) between 12 synovial membrane with inflammation and 12 synovial membrane without inflammation from the dataset GSE46750 were identified using the Gene Expression Omnibus 2R. The DEGs were subjected to enrichment analysis, protein-protein interaction (PPI) analysis and module analysis. The analysis results were compared with text-mining results. A total of 174 DEGs were identified. Gene Ontology enrichment results demonstrated that functional molecules encoded by the DEGs primarily had extracellular location, molecular functions predominantly involving ‘chemokine activity’ and ‘cytokine activity’, and were associated with biological processes, including ‘inflammatory response’ and ‘immune response’. The Kyoto Encyclopedia of Genes and Genomes results demonstrated that DEGS may function through pathways associated with ‘rheumatoid arthritis’, ‘chemokine signaling pathway’, ‘complement and coagulation cascades’, ‘TNF signaling pathway’, ‘intestinal immune networks for IgA production’, ‘cytokine-cytokine receptor interaction’, ‘allograft rejection’, ‘Toll-like receptor signaling pathway’ and ‘antigen processing and presentation’. The top 10 hub genes [interleukin (IL)6, IL8, matrix metallopeptidase (MMP)9, colony stimulating factor 1 receptor, FOS proto-oncogene, AP1 transcription factor subunit, insulin-like growth factor 1, TYRO protein tyrosine kinase binding protein, MMP3, cluster of differentiation (CD)14 and CD163] and four gene modules were identified from the PPI network using Cytoscape. In addition, text-mining was used to identify the commonly used drugs and their targets for the treatment of OA. It was initially verified whether the results of the present study were useful for the study of OA treatment targets and pathways. The present study provided insight for the molecular mechanisms of OA synovitis. The hub genes and associated pathways derived from analysis may be targets for OA treatment. IL8 and MMP9, which were validated by text-mining, may be used as molecular targets for the OA treatment, while other hub genes require further validation.

Electroacupuncture inhibits sodium nitroprusside‑mediated chondrocyte apoptosis through the mitochondrial pathway

In China, electroacupuncture (EA) is a therapeutic method that is extensively applied in the clinical treatment of osteoarthritis (OA); however, the underlying molecular mechanism remains unclear. Chondrocyte apoptosis may be observed in cartilage tissue in OA, and is often considered a key target for the treatment of this condition. Therefore, the present study aimed to determine the effects of EA on sodium nitroprusside (SNP)-induced chondrocyte apoptosis. Chondrocytes were obtained from the knee joints of Sprague Dawley rats by type II collagenase digestion. Following microscopic observation and authentication with type II collagen immunohistochemistry, articular cartilage cells were used in subsequent experiments. Using inverted phase contrast microscopy, DAPI staining and flow cytometry, it was revealed that chondrocytes treated with SNP became apoptotic, whereas EA inhibited SNP-induced chondrocyte apoptosis. Subsequently, JC-1 single staining, reverse transcription-quantitative polymerase chain reaction analysis, western blotting, colorimetric assays and immunofluorescence staining were performed for further investigation. The results demonstrated that, when compared with normal chondrocytes, the mitochondrial membrane potential of SNP-treated chondrocytes was markedly lowered, B-cell lymphoma 2 (Bcl-2) expression was reduced, and the expression levels of Bcl-2-associated X protein (Bax), cytochrome c, caspase-9 and caspase-3 were increased. Compared with in SNP-treated chondrocytes, the decrease in the mitochondrial membrane potential of chondrocytes treated with SNP and EA was smaller, Bcl-2 expression was increased, and the expression levels of Bax, cytochrome c, caspase-9 and caspase-3 were decreased following EA intervention. In conclusion, the present study demonstrated that EA modulated the mitochondrial pathway to suppress SNP-mediated chondrocyte apoptosis. Therefore, EA may be of value in the treatment of OA.

Increased amount of phosphorylated proinflammatory osteopontin in rheumatoid arthritis synovia is associated to decreased tartrate-resistant acid phosphatase 5B/5A ratio

Background

Osteopontin (OPN) is an immunoregulatory protein which production increases in both rheumatoid arthritis (RA) and osteoarthritis (OA). Phosphorylated osteopontin (Phospho-OPN) is known to increase macrophage and osteoclast activation, this process is controlled by extracellular tartrate-resistant acid phosphatase (TRAcP), also a biomarker for RA. Here, we evaluated the phosphorylation status of OPN in RA and OA synovia, as well as its correlation with TRAcP isoforms.

Methods

Synovial tissue and fluid were obtained from 24 RA (14 seropositive and 10 seronegative) and 24 OA patients. Western blotting was used to analyze the extent of OPN phosphorylation. TRAcP isoforms were measured in synovial fluid using ELISA; immunohistochemistry assessed the distribution of OPN and TRAcP expressing cells in the synovial tissue, especially distinguishing between the TRAcP isoforms.

Results

Full-length OPN was more phosphorylated in RA than in OA (p<0.05). The thrombin cleaved C-terminal end of OPN was also more phosphorylated in RA (p<0.05). RA patients had a lower concentration of TRAcP 5B and higher concentration of less active 5A in their synovial fluid compared to OA patients. The TRAcP 5B/5A ratio was decreased in RA and correlated negatively with the amount of phospho-OPN (p<0.05). TRAcP positive cells for both isoforms were found all along the synovial lining; OPN antibody staining was localized in the extracellular matrix.

Conclusion

Our data suggests that in RA the synovial fluid contains insufficient amounts of TRAcP 5B which increase levels of the proinflammatory phospho-OPN. This may lead to increased macrophage and osteoclast activation, resulting in the increased local inflammation and bone resorption present in RA joints.

Principal component analysis in the evaluation of osteoarthritis

OBJECTIVES

The purpose of this study is to demonstrate advantages of principal component analysis (PCA) as a standardized procedure in the evaluation of osteoarthritis (OA) in a skeletal series to: (1) compute aggregate scores for joint complexes that accurately capture pathological expression, (2) reveal which variables describe the most sample variation in OA, (3) enable inter- and intra-sample comparison of results, and (4) formulate predictive models from component-based arthritic scores.

MATERIALS AND METHODS

The sample (144 males, 145 females) is drawn from a large skeletal cemetery collection of modern Europeans of known sex, age, and occupation. OA data was collected using standard ranked categorical scoring. PCA was conducted separately on lumbar spine, pelvis, and knee regions to generate composite OA scores from eigenequations of the first and second principal components (PC).

RESULTS

Results demonstrate that as severity in OA increases, so does the distribution of OA within the joint surface. In each region, PCA produced the same general pattern with eburnation scoring driving significant changes in composite OA scores, representing earlier to later stages of cartilage degeneration. The distribution of arthritic traits determined by PCA produced an OA score that quantifies the expression of joint changes in varied biological joint structures from most moveable to least mobile, the final stage being joint fusion. OA scores are most highly variable in the lumbar region for both males and females, as compared to the pelvis and knee.

CONCLUSIONS

PCA is a simple, non-parametric method of extracting relevant information from complex OA datasets and summarizes variation based on correlated multi-attributes to reveal a simplified structure of OA expression. Multivariate techniques like PCA should be used to describe discrete OA samples, and are useful to compute population-specific representative measurements for idiopathic joint OA in a skeletal sample.

Combined detection of serum CTX-II and COMP concentrations in osteoarthritis model rabbits: an effective technique for early diagnosis and estimation of disease severity

Background

Early diagnosis of osteoarthritis (OA) is difficult. Cartilage oligomeric matrix protein (COMP) and crosslinked C-telopeptides of type II collagen (CTX-II) are two markers which can potentially predict the destruction of articular cartilage of early OA. To comprehensively evaluate the diagnosis value of serum COMP and CTX-II markers in OA, the longitudinal and combined measurement of serum COMP and CTX-II were performed at different stages of pathological process of OA in adult rabbits with OA, compared with the sham-operated rabbits.

Methods

Thirty-six adult white rabbits were randomly divided into two groups, the OA group and the control group (n = 18 per group). OA models were established by anterior cruciate ligament transection. Sham operations were performed in the control group. Before the surgery and at weeks 2, 4, 6, 8, 10, and 12 after surgery, serum CTX-II and COMP concentrations were detected using sandwich-ELISA in all rabbits. Three rabbits in each group were killed at weeks 2, 4, 6, 8, 10, and 12 after surgery, and femoral condyle specimens were collected. Histological changes in articular cartilage were evaluated according to the Mankin scoring criteria.

Results

At each time point, the Mankin scores and serum concentrations of CTX-II and COMP were significantly higher in the OA group than in the control group. In addition, in the OA group, there was a significant relationship between the CTX-II and COMP concentrations and the Mankin score.

Conclusions

Early dynamic combined detection of serum CTX-II and COMP concentrations is effective for early OA diagnosis and evaluation of OA severity.

Increased receptor activator of nuclear factor κβ ligand/osteoprotegerin ratio exacerbates cartilage destruction in osteoarthritis in vitro

Osteoarthritis (OA) is a degenerative joint disease characterized by progressive cartilage destruction, matrix degradation and bony changes. Subchondral bone alterations in osteoarthritis are associated with cartilage destruction. It has previously been demonstrated that osteoprotegerin (OPG) and receptor activator of nuclear factor κβ ligand (RANKL) mediate this process. The RANKL/OPG ratio is altered in OA chondrocytes compared with normal chondrocytes. In the pathogenesis of OA, abnormal expression levels of matrix metalloproteinase-13 (MMP-13) are secreted by chondrocytes has a vital role in the progression of cartilage erosion. In the present study, the effect of various RANKL/OPG ratios on MMP-13 expression levels was investigated in interleukin-1β-stimulated SW1353 human chondrosarcoma cells. Cell viability was assessed by MTT assay and MMP-13 mRNA and protein expression levels were analyzed by quantitative reverse-transcription-quantitative polymerase chain reaction, ELISA and western blot analyses, respectively. The results demonstrated that an increase in MMP-13 mRNA and protein expression levels was observed with increasing RANKL/OPG ratio. These findings suggest that this mechanism may be used as a novel therapeutic strategy against OA.

Animal models of osteoarthritis: classification, update, and measurement of outcomes

Osteoarthritis (OA) is one of the most commonly occurring forms of arthritis in the world today. It is a debilitating chronic illness causing pain and immense discomfort to the affected individual. Significant research is currently ongoing to understand its pathophysiology and develop successful treatment regimens based on this knowledge. Animal models have played a key role in achieving this goal. Animal models currently used to study osteoarthritis can be classified based on the etiology under investigation, primary osteoarthritis, and post-traumatic osteoarthritis, to better clarify the relationship between these models and the pathogenesis of the disease. Non-invasive animal models have shown significant promise in understanding early osteoarthritic changes. Imaging modalities play a pivotal role in understanding the pathogenesis of OA and the correlation with pain. These imaging studies would also allow in vivo surveillance of the disease as a function of time in the animal model. This review summarizes the current understanding of the disease pathogenesis, invasive and non-invasive animal models, imaging modalities, and pain assessment techniques in the animals.

Hydrogen sulfide attenuates IL-1β-induced inflammatory signaling and dysfunction of osteoarthritic chondrocytes

Inflammatory cytokines are crucial factors in the onset of osteoarthritis (OA). The pro-inflammatory cytokine, interleukin-1β (IL-1β), is capable of stimulating a few cartilage degradation mediators and is of importance to the pathogenesis of OA. It has been demonstrated that hydrogen sulfide (H2S) exerts an inhibitory effect on inflammation. Thus, in the present study, we aimed to investigate the therapeutic effects of H2S in OA. For this purpose, an in vitro model of cartilage inflammation was created. Human OA chondrocytes were cultured and pre-treated with H2S (0.06-1.5 mM) with or without IL-1β (10 ng/ml) and then Griess reagent was used to quantify the production of nitric oxide (NO). Using enzyme-linked immunosorbent assay, we quantified the production of prostaglandin E2 (PGE2) and matrix metalloproteinase-13 (MMP-13). In addition, we determined the gene expression of inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2) and MMP-13 using reverse transcription-quantitative polymerase chain reaction and the expression of signaling molecules related to mitogen-activated protein kinases (MAPKs) and nuclear factor-κB (NF-κB) by western blot analysis. Our results revealed that H2S markedly reversed the effects of IL-1β on the gene expression of COX-2, MMP-13 and iNOS and on the production of MMP-13, PGE2 and NO. In addition, H2S inhibited the activation of the extracellular signal-regulated kinase (ERK)/IκBα/NF-κB pathway which was induced by IL-1β. On the whole, the results of the present study suggest that H2S exerts chondroprotective effects. Thus, H2S may have potential for use in the treatment of patients suffering from OA.

Plasma and synovial fluid autotaxin correlate with severity in knee osteoarthritis

BACKGROUND

This study aimed to investigate the relationships between plasma and synovial autotaxin and the severity in knee osteoarthritis (OA) patients.

METHODS

A total of 90 participants (70 knee OA patients and 20 controls) were recruited. Autotaxin and high-sensitivity C-reactive protein (hs-CRP) levels were determined. The symptomatic and radiographic severity of OA was assessed using the Western Ontario McMaster University Osteoarthritis Index (WOMAC) scores and the Kellgren-Lawrence grades.

RESULTS

OA patients had significantly higher circulating autotaxin and hs-CRP than controls. Plasma autotaxin was directly correlated with synovial fluid autotaxin (r=0.639, P<0.001). Additionally, plasma and synovial fluid autotaxin were associated with radiographic severity (P<0.001). Furthermore, plasma and synovial fluid autotaxin levels were positively correlated with WOMAC scores (r=0.558, P<0.001 and r=0.371, P=0.002, respectively).

CONCLUSION

Plasma and synovial fluid autotaxin levels were positively correlated with the severity of OA. Thus, autotaxin has potential as a biomarker reflecting the severity of knee OA.