Novel therapeutic targets in osteoarthritis: Narrative review on knock-out genes involved in disease development in mouse animal models

The Complex Interplay between the Gut Microbiome and Osteoarthritis: A Systematic Review on Potential Correlations and Therapeutic Approaches

The objective of this review is to systematically analyze the potential correlation between gut microbiota and osteoarthritis (OA) as well as to evaluate the feasibility of microbiota-targeted therapies for treating OA. Studies conducted from October 2013 to October 2023 were identified via a search on electronic databases such as PubMed, Web of Science, and Scopus, following established PRISMA statement standards. Two reviewers independently screened, assessed, and extracted relevant data, and then they graded the studies using the ROBINS I tool for non-randomized interventions studies and SYRCLE's risk-of-bias tool for animal studies. A search through 370 studies yielded 38 studies (24 preclinical and 14 clinical) that were included. In vivo research has predominantly concentrated on modifying the gut microbiota microenvironment, using dietary supplements, probiotics, and prebiotics to modify the OA status. Lactobacilli are the most thoroughly examined with Lactobacillus acidophilus found to effectively reduce cartilage damage, inflammatory factors, and pain. Additionally, Lactobacillus M5 inhibits the development of OA by preventing high-fat diet (HFD)-induced obesity and protecting cartilage from damage. Although there are limited clinical studies, certain compositions of intestinal microbiota may be associated with onset and progression of OA, while others are linked to pain reduction in OA patients. Based on preclinical studies, there is evidence to suggest that the gut microbiota could play a significant role in the development and progression of OA. However, due to the scarcity of clinical studies, the exact mechanism linking the gut microbiota and OA remains unclear. Further research is necessary to evaluate specific gut microbiota compositions, potential pathogens, and their corresponding signaling pathways that contribute to the onset and progression of OA. This will help to validate the potential of targeting gut microbiota for treating OA patients.

Thermo-Responsive Gel Containing Hydroxytyrosol-Chitosan Nanoparticles (Hyt@tgel) Counteracts the Increase of Osteoarthritis Biomarkers in Human Chondrocytes

Although osteoarthritis (OA) is a chronic inflammatory degenerative disease affecting millions of people worldwide, the current therapies are limited to palliative care and do not eliminate the necessity of surgical intervention in the most severe cases. Several dietary and nutraceutical factors, such as hydroxytyrosol (Hyt), have demonstrated beneficial effects in the prevention or treatment of OA both in vitro and in animal models. However, the therapeutic application of Hyt is limited due to its poor bioavailability following oral administration. In the present study, a localized drug delivery platform containing a combination of Hyt-loading chitosan nanoparticles (Hyt-NPs) and in situ forming hydrogel have been developed to obtain the benefits of both hydrogels and nanoparticles. This thermosensitive formulation, based on Pluronic F-127 (F-127), hyaluronic acid (HA) and Hyt-NPs (called Hyt@tgel) presents the unique ability to be injected in a minimally invasive way into a target region as a freely flowing solution at room temperature forming a gel at body temperature. The Hyt@tgel system showed reduced oxidative and inflammatory effects in the chondrocyte cellular model as well as a reduction in senescent cells after induction with H₂O₂. In addition, Hyt@tgel influenced chondrocytes gene expression under pathological state maintaining their metabolic activity and limiting the expression of critical OA-related genes in human chondrocytes treated with stressors promoting OA-like features. Hence, it can be concluded that the formulated hydrogel injection could be proposed for the efficient and sustained Hyt delivery for OA treatment. The next step would be the extraction of “added-value” bioactive polyphenols from by-products of the olive industry, in order to develop a green delivery system able not only to enhance the human wellbeing but also to promote a sustainable environment.

FGD5-AS1 Inhibits Osteoarthritis Development by Modulating miR-302d-3p/TGFBR2 Axis

OBJECTIVE

Osteoarthritis (OA) is a common joint disorder, accompanied by extracellular matrix (ECM) degradation. Reportedly, long noncoding RNAs (lncRNAs) are involved in OA pathogenesis. However, the role of lncRNA FYVE, RhoGEF, and PH domain containing 5 antisense RNA 1 (FGD5-AS1) in OA development is still not fully clarified. This study was aimed to clarify the role of FGD5-AS1 in OA.

METHODS

FGD5-AS1 and miR-302d-3p expression levels were determined in cartilage tissues and chondrocytes by quantitative real-time polymerase chain reaction (qRT-PCR). Chondrocytes (C20/A4 cells) were stimulated with interleukin 1β (IL-1β) to mimic the inflammatory environment of OA. Cell viability was detected by cell counting kit-8 and 5-ethynyl-2'-deoxyuridine assays. Cell apoptosis was measured by the caspase-3 activity assay and flow cytometry. Transforming growth factor beta receptors II (TGFBR2), matrix metalloproteinase 13 (MMP-13), and ADAM metallopeptidase with thrombospondin type 1 motif 5 expression levels were examined by qRT-PCR or Western blot. The regulatory relationships among FGD5-AS1, miR-302d-3p, and TGFBR2 were predicted by the StarBase v2.0, miRanda, miRDB, and TargetScan databases, and confirmed by dual-luciferase reporter assay and RNA immunoprecipitation assay.

RESULTS

FGD5-AS1 and TGFBR2 expression levels were downregulated while miR-302d-3p expression was increased in cartilage tissues of OA patients. Knocking down FGD5-AS1 inhibited the viability of C20/A4 cells but induced apoptosis and ECM degradation, while FGD5-AS1 overexpression exerted opposite effects. MiR-302d-3p was identified as a target of FGD5-AS1, and TGFBR2 was identified as a target of miR-302d-3p. FGD5-AS1 positively regulated TGFBR2 expression by repressing miR-302d-3p expression, and miR-302d-3p inhibition or TGFBR2 restoration reversed the changes of cell viability, apoptosis, and ECM degradation induced by FGD5-AS1 knockdown.

CONCLUSION

FGD5-AS1 can probably inhibit OA progression by regulating miR-302d-3p/TGFBR2 axis.

SNHG5 protects chondrocytes in interleukin-1β-stimulated osteoarthritis via regulating miR-181a-5p/TGFBR3 axis

Long noncoding RNAs (lncRNAs) have been considered as important modulators in the development of osteoarthritis. The present study investigates whether there is a link between lncRNA small nucleolar RNA host gene 5 (SNHG5) and osteoarthritis pathogenesis, and the underlying molecular mechanism. To establish an in vitro model of osteoarthritis, interleukin 1β (IL-1β) was used to treat chondrocytes (C20/A4 cells) for mimicking the inflammatory condition in osteoarthritis pathogenesis. SNHG5 and miR-181a-5p expression levels were then detected in cartilage tissues of osteoarthritis patients and C20/A4 cells by quantitative polymerase chain reaction (qPCR). Cell counting kit-8 and 5-ethynyl-2'-deoxyuridine assays were applied for detecting the viability of chondrocytes, and the apoptosis of chondrocytes was examined through caspase-3 activity assay and flow cytometry analysis. Western blot and qPCR were employed for determining the expression levels of TGFBR3, ADAMTS5, and MMP-13. The regulatory relationships among SNHG5, miR-181a-5p, and TGFBR3 were verified by RNA immunoprecipitation and dual-luciferase reporter assays. The expression levels of SNHG5 and TGFBR3 were markedly decreased, and miR-181a-5p expression was enhanced in osteoarthritis tissues and chondrocytes treated with IL-1β. SNHG5 knockdown inhibited the viability of chondrocytes, induced apoptosis, and promoted the expression levels of ADAMTS5 and MMP-13. Conversely, SNHG5 overexpression could counteract the effects of IL-1β, increase the viability of chondrocytes and suppress apoptosis. Mechanically, SNHG5 positively regulated TGFBR3 expression via sponging miR-181a-5p. Moreover, miR-181a-5p overexpression and TGFBR3 knockdown counteracted the effects of SNHG5 on chondrocytes. SNHG5 can probably protect chondrocytes from the inflammatory response and reduce the degradation of the extracellular matrix via modulating the miR-181a-5p/TGFBR3 axis.

MicroRNA-197 regulates chondrocyte proliferation, migration, and inflammation in pathogenesis of osteoarthritis by targeting EIF4G2

Recent studies have demonstrated that microRNAs (miRNAs) are involved in many pathological conditions including osteoarthritis (OA). In the present study, we aimed to investigate the role of miR-197 in OA and the potential molecular mechanism. The expression levels of miR-197 were detected by quantitative real-time PCR analysis. Cell proliferation and migration abilities were performed by 3-(4,5-dimethylthiazol-2-yl)-2,5-di-phenyltetrazolium bromide and transwell assays. The concentrations of inflammatory cytokines, including IL-1β, IL-6, and TNF-α, were detect using ELISA assay. Furthermore, luciferase reporter and rescue assays were applied to identify the functional target gene of miR-197 in OA. The results showed that miR-197 expression was significantly down-regulated in the OA cartilage tissues compared with normal cartilage tissues, accompanied by up-regulation of EIF4G2 expression. An inverse correlation was found between EIF4G2 and miR-197 expressions in OA cartilage tissues. Treatment with miR-197 mimics promoted the growth and migration abilities of chondrocytes, while miR-197 inhibitors induced the opposite effects. Furthermore, restoration of miR-197 significantly decreased IL-1β, IL-6, and TNF-α expression, whereas knockdown of miR-197 led to a induction in these inflammatory mediators. Moreover, EIF4G2 was predicted and confirmed as a directly target of miR-197. Overexpressed miR-197 could down-regulate EIF4G2 expression in chondrocytes, while miR-197 knockdown could elevate EIF4G2 expression. Additionally, EIF4G2 overexpression reversed the effects of miR-197 mimics on chondrocytes proliferation, migration, and inflammation. Taken together, our study demonstrated that miR-197 promotes chondrocyte proliferation, increases migration, and inhibits inflammation in the pathogenesis of OA by targeting EIF4G2, indicating the potential therapeutic targets of the miR-197/EIF4G2 axis for OA treatment.

Experimental Therapeutics for the Treatment of Osteoarthritis

Osteoarthritis (OA) therapy remains a large challenge since no causative treatment options are so far available. Despite some main pathways contributing to OA are identified its pathogenesis is still rudimentary understood. A plethora of therapeutically promising agents are currently tested in experimental OA research to find an opportunity to reverse OA-associated joint damage and prevent its progression. Hence, this review aims to summarize novelly emerging experimental approaches for OA. Due to the diversity of strategies shown only main aspects could be summarized here including herbal medicines, nanoparticular compounds, growth factors, hormones, antibody-, cell- and extracellular vesicle (EV)-based approaches, optimized tools for joint viscosupplementation, genetic regulators such as si- or miRNAs and promising combinations. An abundant multitude of compounds obtained from plants, environmental, autologous or synthetic sources have been identified with anabolic, anti-inflammatory, -catabolic and anti-apoptotic properties. Some ubiquitous signaling pathways such as wingless and Integration site-1 (Wnt), Sirtuin, Toll-like receptor (TLR), mammalian target of rapamycin (mTOR), Nuclear Factor (NF)-κB and complement are involved in OA and addressed by them. Hyaluronan (HA) provided benefit in OA since many decades, and novel HA formulations have been developed now with higher HA content and long-term stability achieved by cross-linking suitable to be combined with other agents such as components from herbals or chemokines to attract regenerative cells. pH- or inflammation-sensitive nanoparticular compounds could serve as versatile slow-release systems of active compounds, for example, miRNAs. Some light has been brought into the intimate regulatory network of small RNAs in the pathogenesis of OA which might be a novel avenue for OA therapy in future. Attraction of autologous regenerative cells by chemokines and exosome-based treatment strategies could also innovate OA therapy.

Sex Specific Determinants in Osteoarthritis: A Systematic Review of Preclinical Studies

Osteoarthritis (OA) is a highly prevalent joint disease that primarily affects about 10% of the world's population over 60 years old. The purpose of this study is to systematically review the preclinical studies regarding sex differences in OA, with particular attention to the molecular aspect and gene expression, but also to the histopathological aspects. Three databases (PubMed, Scopus, and Web of Knowledge) were screened for eligible studies. In vitro and in vivo papers written in English, published in the last 11 years (2009-2020) were eligible. Participants were preclinical studies, including cell cultures and animal models of OA, evaluating sex differences. Independent extraction of articles and quality assessments were performed by two authors using predefined data fields and specific tools (Animals in Research Reporting In Vivo Experiments (ARRIVE) guideline and Systematic Review Centre for Laboratory animal Experimentation (SYRCLE) tool). Twenty-three studies were included in the review: 4 in vitro studies, 18 in vivo studies, and 1 both in vitro and in vivo study. From in vitro works, sex differences were found in the gene expression of inflammatory molecules, hormonal receptors, and in responsiveness to hormonal stimulation. In vivo research showed a great heterogeneity of animal models mainly focused on the histopathological aspects rather than on the analysis of sex-related molecular mechanisms. This review highlights that many gaps in knowledge still exist; improvementsin the selection and reporting of animal models, the use of advanced in vitro models, and multiomics analyses might contribute to developing a personalized gender-based medicine.

The potent anti-inflammatory effect of Guilu Erxian Glue extracts remedy joint pain and ameliorate the progression of osteoarthritis in mice

BACKGROUND

Osteoarthritis (OA) is a slow progressing, degenerative disorder of the synovial joints. Guilu Erxian Glue (GEG) is a multi-component Chinese herbal remedy with long-lasting favorable effects on several conditions, including articular pain and muscle strength in elderly men with knee osteoarthritis. The present study aimed to identify the effects of Guilu Erxian Paste (GE-P) and Liquid (GE-L) extracted from Guilu Erxian Glue in anterior cruciate ligament transection (ACLT)-induced osteoarthritis mice, and to compare the effectiveness of different preparations on knee cartilage degeneration during the progression of osteoarthritis.

METHODS

Male C57BL/6J mice underwent anterior cruciate ligament transection to induce mechanically destabilized osteoarthritis in the right knee. 4 weeks later, the mice were orally treated with PBS, celecoxib (10 mg/kg/day), Guilu Erxian Paste (100 or 300 mg/kg/day), and Guilu Erxian Liquid (100 or 300 mg/kg/day) for 28 consecutive days. Von Frey and open-field tests (OFT) were used to evaluate pain behaviors (mechanical hypersensitivity and locomotor performance). Narrowing of the joint space and osteophyte formation were examined radiographically. Inflammatory cytokine (IL-1β, IL-6, and TNF-α) levels in the articular cartilage were determined by quantitative real-time PCR. Histopathological examinations were conducted to evaluate the severity and extent of the cartilage lesions.

RESULTS

Guilu Erxian Paste and Guilu Erxian Liquid (300 mg/kg/day) were significantly more effective (p < 0.01) than celecoxib (10 mg/kg/day) in decreasing secondary allodynia when compared to the saline-treated group (#p < 0.05). Open-field tests revealed no significant motor dysfunction between the Guilu Erxian Paste- and Guilu Erxian Liquid-treated mice compared to the saline-treated mice. Radiographic findings also confirmed that the administration of Guilu Erxian Paste and Guilu Erxian Liquid (100 and 300 mg/kg/day) significantly and dose-dependently reduced osteolytic lesions and bone spur formation in the anterior cruciate ligament transection-induced osteoarthritis mice when compared to the saline-treated group. Notably, Guilu Erxian Liquid (100 mg/kg/day) treatment significantly reduced the mRNA levels of IL-1β, IL-6, and TNF-α as well as relative the protein expression of IL-1β and TNF-α to the effect of celecoxib. Guilu Erxian Paste and Guilu Erxian Liquid (300 mg/kg/day) markedly attenuated cartilage destruction, surface unevenness, proteoglycan loss, chondrocyte degeneration, and cartilage erosion in the superficial layers (##p < 0.01 and ###p < 0.001 respectively).

CONCLUSIONS

As expected, our findings suggest that the anti-inflammatory effects of Guilu Erxian Liquid (GE-L), following marked decrease on both IL-1β and TNF-α during the early course of post-traumatic osteoarthrosis (OA), may be of potential value in the treatment of osteoarthritis.

MicroRNAs and Osteoarthritis

An imbalance in gene expressional events skewing chondrocyte anabolic and catabolic pathways toward the latter causes an aberrant turnover and loss of extracellular matrix proteins in osteoarthritic (OA) articular cartilage. Thus, catabolism results in the elevated loss of extracellular matrix proteins. There is also evidence of an increase in the frequency of chondrocyte apoptosis that compromises the capacity of articular cartilage to undergo repair. Although much of the fundamental OA studies over the past 20 years identified and characterized many genes relevant to pro-inflammatory cytokines, apoptosis, and matrix metalloproteinases (MMPs)/a disintegrin and metalloproteinase with thrombospondin motif (ADAMTS), more recent studies focused on epigenetic mechanisms and the associated role of microRNAs (miRs) in regulating gene expression in OA cartilage. Thus, several miRs were identified as regulators of chondrocyte signaling pathways, apoptosis, and proteinase gene expression. For example, the reduced expression of miR-146a was found to be coupled to reduced type II collagen (COL2) in OA cartilage, whereas MMP-13 levels were increased, suggesting an association between MMP-13 gene expression and COL2A1 gene expression. Results of these studies imply that microRNAs could become useful in the search for diagnostic biomarkers, as well as providing novel therapeutic targets for intervention in OA.

Bushenhuoxue formula attenuates cartilage degeneration in an osteoarthritic mouse model through TGF-β/MMP13 signaling

BACKGROUND

Articular cartilage degeneration plays a key role in the pathogenesis of osteoarthritis (OA). Bushenhuoxue formula (BSHXF) has been widely used in the treatment of OA in clinics. However, the molecular mechanisms responsible for the chondroprotective effect of BSHXF remain to be elucidated. The purpose of this study was to explore the effects of BSHXF on OA mice model.

METHODS

In this study, we investigated the effects of BSHXF on destabilization of the medial meniscus (DMM)-induced chondrocyte degradation in OA mice model. At 12 weeks post-surgery, the joints were harvested for tissue analyses, including histology, histomorphometry, TUNEL, OARSI scoring, micro-CT and immunohistochemistry for COL2, TGFBR2, pSMAD2 and MMP13. Additionally, we also evaluated the effects of BSHXF on Mmp13 mRNA and protein expression in chondrogenic ATDC5 cells through real-time PCR and Western blot respectively. Moreover, we investigated the chondroprotective effect of BSHXF on mice with Tgfbr2 conditional knockout (Tgfbr2 ^Col2ER mice) in chondrocyte, including the relative experiments mentioned above. We transfected Tgfbr2 siRNA in ATDC5 to further evaluate the changes of Mmp13 mRNA and protein expression followed by BSHXF treatment.

RESULTS

Amelioration of cartilage degradation and chondrocyte apoptosis were observed in DMM-induced mice, with increases in cartilage area and thickness, proteoglycan matrix, COL2 content and decreases in OARSI score at 12 weeks post surgery. Moreover, the elevated TGFBR2 and pSMAD2, and reduced MMP13 positive cells were also revealed in DMM-induced mice treated with BSHXF. Besides, decreased Mmp13 mRNA and protein expression were observed inchondrogenic ATDC5 cells culture in serum containing BSHXF. As expected, Tgfbr2 ^Col2ER mice exhibited significant OA-like phenotype. Interestingly, obvious improvement in articular cartilage structure was still observed in Tgfbr2 ^Col2ER mice after BSHXF treatment via up-regulated pSMAD2 and down-regulated MMP13 expressional levels in articular cartilage.

CONCLUSIONS

BSHXF could inhibit cartilage degradation through TGF-β/MMP13 signaling, and be considered a good option for the treatment of OA.

Using mouse models to investigate the pathophysiology, treatment, and prevention of post-traumatic osteoarthritis

Post-traumatic osteoarthritis (PTOA) is defined by its development after joint injury. Factors contributing to the risk of PTOA occurring, the rate of progression, and degree of associated disability in any individual, remain incompletely understood. What constitutes an "OA-inducing injury" is not defined. In line with advances in the traumatic brain injury field, we propose the scope of PTOA-inducing injuries be expanded to include not only those causing immediate structural damage and instability (Type I), but also those without initial instability/damage from moderate (Type II) or minor (Type III) loading severity. A review of the literature revealed this full spectrum of potential PTOA subtypes can be modeled in mice, with 27 Type I, 6 Type II, and 4 Type III models identified. Despite limitations due to cartilage anatomy, joint size, and bio-fluid availability, mice offer advantages as preclinical models to study PTOA, particularly genetically modified strains. Histopathology was the most common disease outcome, cartilage more frequently studied than bone or synovium, and meniscus and ligaments rarely evaluated. Other methods used to examine PTOA included gene expression, protein analysis, and imaging. Despite the major issues reported by patients being pain and biomechanical dysfunction, these were the least commonly measured outcomes in mouse models. Informative correlations of simultaneously measured disease outcomes in individual animals, was rarely done in any mouse PTOA model. This review has identified knowledge gaps that need to be addressed to increase understanding and improve prevention and management of PTOA. Preclinical mouse models play a critical role in these endeavors. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:424-439, 2017.

lncRNAs: novel players in intervertebral disc degeneration and osteoarthritis

The term long non‐coding RNA (lncRNA) refers to a group of RNAs with length more than 200 nucleotides, limited protein‐coding potential, and having widespread biological functions, including regulation of transcriptional patterns and protein activity, formation of endogenous small interfering RNAs (siRNAs) and natural microRNA (miRNA) sponges. Intervertebral disc degeneration (IDD) and osteoarthritis (OA) are the most common chronic, prevalent and age‐related degenerative musculoskeletal disorders. Numbers of lncRNAs are differentially expressed in human degenerative nucleus pulposus tissue and OA cartilage. Moreover, some lncRNAs have been shown to be involved in multiple pathological processes during OA, including extracellular matrix (ECM) degradation, inflammatory responses, apoptosis and angiogenesis. In this review, we summarize current knowledge concerning lncRNAs, from their biogenesis, classification and biological functions to molecular mechanisms and therapeutic potential in IDD and OA.

Osteoprotegerin deficiency leads to deformation of the articular cartilage in femoral head

Osteoarthritis (OA) was a degenerative joint disease characterized by articular cartilage degradation and extensive remodeling of the subchondral bone. Multiple lines of evidence indicated that Osteoprotegerin (OPG), a member of TNF receptor superfamily that was expressed in the chondrocytes of articular cartilage and adjacent locations in the physiological setting, was involved in maintaining integrity of articular cartilage. OPG could prevent subchondral bone from resorption, and also protect cartilage from degradation. In this study, we used Osteoprotegerin-knockout mice (Opg-KO mice) to find out the role of OPG in articular cartilage. We examined articular cartilage in the femoral head of Opg-KO mice began in early adulthood using modern molecular and imaging methods. We found cartilage changes starting from adulthood and progressively with age, reminiscent of pathological changes in OA. Deficiency of OPG caused thinned articular cartilage and extensive remodeling of the subchondral bone in femoral head in comparison with wild-type mice (WT mice). Also, the articular cartilage of femoral head expressed significantly less of Aggrecan, Col-II and Col-X, but more Col-I and Matrix Metalloproteinases-13 (Mmp-13) than WT mice both at gene and protein level. Moreover, increased chondrocyte apoptosis and decreased chondrocyte proliferation were observed in femoral head of Opg-KO mice compared to WT mice. These data suggested that OPG played an important role in maintaining the homeostasis of articular cartilage of femoral head.