The FTO-CMPK2 Pathway in Fibroblast-like Synoviocytes Modulates Rheumatoid Arthritis Synovial Inflammation and Cartilage Homeostasis via mtDNA Regulation.

In rheumatoid arthritis (RA), a debilitating autoimmune disorder marked by chronic synovial inflammation and progressive cartilage degradation, fibroblast-like synoviocytes (FLS) are key pathogenic players. Current treatments targeting these cells are limited. Our study focused on the Fat Mass and Obesity-associated protein (FTO), known for its roles in cell proliferation and inflammatory response modulation, and its involvement in RA. We specifically examined the inflammatory regulatory roles of FTO and CMPK2, a mitochondrial DNA synthesis protein, in FLS. Utilizing a combination of in vitro and in vivo methods, including FTO inhibition and gene knockdown, we aimed to understand FTO's influence on RA progression and chondrocyte functionality. Our findings showed that increased FTO expression in RA synovial cells enhanced their proliferation and migration and decreased senescence and apoptosis. Inhibiting FTO significantly slowed the disease progression in our models. Our research also highlighted that the FTO-CMPK2 pathway plays a crucial role in regulating synovial inflammation through the mtDNA-mediated cGAS/STING pathway, affecting chondrocyte homeostasis. This study indicates that targeting the FTO-CMPK2 axis could be a promising new therapeutic strategy for managing RA.

Rspo2 exacerbates rheumatoid arthritis by targeting aggressive phenotype of fibroblast-like synoviocytes and disrupting chondrocyte homeostasis via Wnt/ß-catenin pathway.

BACKGROUND: The aggressive phenotype of fibroblast-like synoviocytes (FLS) has been identified as a contributing factor to the exacerbation of rheumatoid arthritis (RA) through the promotion of synovitis and cartilage damage. Regrettably, there is currently no effective therapeutic intervention available to address this issue. Recent research has shed light on the crucial regulatory role of R-spondin-2 (Rspo2) in cellular proliferation, cartilage degradation, and tumorigenesis. However, the specific impact of Rspo2 on RA remains poorly understood. We aim to investigate the function and mechanism of Rspo2 in regulating the aggressive phenotype of FLS and maintaining chondrocyte homeostasis in the context of RA. METHODS: The expression of Rspo2 in knee joint synovium and cartilage were detected in RA mice with antigen-induced arthritis (AIA) and RA patients. Recombinant mouse Rspo2 (rmRspo2), Rspo2 neutralizing antibody (Rspo2-NAb), and recombinant mouse DKK1 (rmDKK1, a potent inhibitor of Wnt signaling pathway) were used to explore the role and mechanism of Rspo2 in the progression of RA, specifically in relation to the aggressive phenotype of FLS and chondrocyte homeostasis, both in vivo and in vitro. RESULTS: We indicated that Rspo2 expression was upregulated both in synovium and articular cartilage as RA progressed in RA mice and RA patients. Increased Rspo2 upregulated the expression of leucine-rich repeat-containing G-protein-coupled receptor 5 (LGR5), as the ligand for Rspo2, and ß-catenin in FLS and chondrocytes. Subsequent investigations revealed that intra-articular administration of rmRspo2 caused striking progressive synovitis and articular cartilage destruction to exacerbate RA progress in mice. Conversely, neutralization of Rspo2 or inhibition of the Wnt/ß-catenin pathway effectively alleviated experimental RA development. Moreover, Rspo2 facilitated FLS aggressive phenotype and disrupted chondrocyte homeostasis primarily through activating Wnt/ß-catenin pathway, which were effectively alleviated by Rspo2-NAb or rmDKK1. CONCLUSIONS: Our data confirmed a critical role of Rspo2 in enhancing the aggressive phenotype of FLS and disrupting chondrocyte homeostasis through the Wnt/ß-catenin pathway in the context of RA. Furthermore, the results indicated that intra-articular administration of Rspo2 neutralizing antibody or recombinant DKK1 might represent a promising therapeutic strategy for the treatment of RA.

Early unrestricted vs. partial weight bearing after uncemented total hip arthroplasty: a systematic review and meta-analysis.

Background: The choice of postoperative weight bearing protocol after uncemented total hip arthroplasty (THA) remains controversial. The aim of this study was to assess the efficacy and safety of immediate unrestricted weight bearing (UWB) compared with partial weight bearing (PWB) in patients undergoing uncemented THA. Methods: Relevant articles were retrieved from electronic databases. Both randomized controlled trials (RCTs) and non-RCTs were included but analyzed separately. All functional and clinical outcomes with at least 2 independent study outcomes were meta-analyzed. Results: A total of 17 studies were investigated. No adverse effect was found regarding micromotion of the femoral stem with immediate UWB following uncemented THA. There was also no correlation between immediate UWB and failure of ingrowth fixation and higher risks of femoral stem subsidence and surgical revision in RCTs. Harris hip score was better in patients with immediate UWB than those with PWB at 1 year post surgery, but the difference was not statistically significant. Conclusions: Immediate UWB did not have extra harm compared with PWB in patients undergoing uncemented THA. UWB was not superior to PWB. Considering the improvement of Harris score and the compliance of patients, UWB can be encouraged in THA rehabilitation.

ETS2 overexpression ameliorates cartilage injury in osteoarthritis by the ETS2/miR-155/STAT1/DNMT1 feedback loop pathway.

Osteoarthritis (OA) is the most common irreversible chronic joint dysfunction disease, which is pathologically characterized by disturbance of articular cartilage homeostasis leading to subsequent inflammatory response and cartilage extracellular matrix (ECM) degradation. Increasing evidence has demonstrated the dysregulation of transcription factors play crucial roles in the occurrence and development of osteoarthritis (OA), but the potential functions and mechanism of most transcription factors in OA has not been completely illuminated. In this study, we identified that transcription factor V-ets erythroblastosis virus E26 oncogene homolog 2 (ETS2) was significantly down-regulated in OA cartilage and IL-1ß-induced OA chondrocytes. Functional experiments in vitro demonstrated that the overexpressed ETS2 strikingly enhanced proliferation, outstandingly suppressed apoptosis, and dramatically reduced inflammation and ECM degradation in IL-1ß-induced OA chondrocytes, whereas the knockdown of ETS2 led to the opposite effects. Further in vivo studies have shown that up-regulated ETS2 dramatically ameliorates cartilage injury in DMM-induced OA mice. Mechanical studies have disclosed that DNMT1-mediated downregulation of ETS2 dramatically promotes STAT1 by inhibiting miR-155 transcription, and increased STAT1 initiates a feedback loop that may enhance DNMT1-mediated hypermethylation of ETS2 to inhibit ETS2 expression, thus forming a DNMT1/ETS2/miR-155/STAT1 feedback loop that inhibits MAPK signaling pathways and aggravates OA cartilage injury. In all, our results revealed that overexpression of ETS2 markedly ameliorated OA cartilage injury through the ETS2/miR-155/STAT1/DNMT1 feedback loop, providing a new perspective on the pathogenesis and therapeutic strategies for OA.

Treatment with FAP-targeted zinc ferrite nanoparticles for rheumatoid arthritis by inducing endoplasmic reticulum stress and mitochondrial damage.

Rheumatoid arthritis (RA) is a common chronic inflammatory disease characterized by the proliferation of fibroblast-like synoviocytes (FLS), pannus development, cartilage, and bone degradation, and, eventually, loss of joint function. Fibroblast activating protein (FAP) is a particular product of activated FLS and is highly prevalent in RA-derived fibroblast-like synoviocytes (RA-FLS). In this study, zinc ferrite nanoparticles (ZF-NPs) were engineered to target FAP+ (FAP positive) FLS. ZF-NPswere discovered to better target FAP+ FLS due to the surface alteration of FAP peptide and to enhance RA-FLS apoptosis by activating the endoplasmic reticulum stress (ERS) system via the PERK-ATF4-CHOP, IRE1-XBP1 pathway, and mitochondrial damage of RA-FLS. Treatment with ZF-NPs under the influence of an alternating magnetic field (AMF) can significantly amplify ERS and mitochondrial damage via the magnetocaloric effect. It was also observed in adjuvant-induced arthritis (AIA) mice that FAP-targeted ZF-NPs (FAP-ZF-NPs) could significantly suppress synovitis in vivo, inhibit synovial tissue angiogenesis, protect articular cartilage, and reduce M1 macrophage infiltration in synovium in AIA mice. Furthermore, treatment of AIA mice with FAP-ZF-NPs was found to be more promising in the presence of an AMF. These findings demonstrate the potential utility of FAP-ZF-NPs in the treatment of RA.

Down-regulated GAS6 impairs synovial macrophage efferocytosis and promotes obesity-associated osteoarthritis.

Obesity has always been considered a significant risk factor in osteoarthritis (OA) progression, but the underlying mechanism of obesity-related inflammation in OA synovitis remains unclear. The present study found that synovial macrophages infiltrated and polarized in the obesity microenvironment and identified the essential role of M1 macrophages in impaired macrophage efferocytosis using pathology analysis of obesity-associated OA. The present study revealed that obese OA patients and Apoe-/- mice showed a more pronounced synovitis and enhanced macrophage infiltration in synovial tissue, accompanied by dominant M1 macrophage polarization. Obese OA mice had a more severe cartilage destruction and increased levels of synovial apoptotic cells (ACs) than OA mice in the control group. Enhanced M1-polarized macrophages in obese synovium decreased growth arrest-specific 6 (GAS6) secretion, resulting in impaired macrophage efferocytosis in synovial ACs. Intracellular contents released by accumulated ACs further triggered an immune response and lead to a release of inflammatory factors, such as TNF-α, IL-1ß, and IL-6, which induce chondrocyte homeostasis dysfunction in obese OA patients. Intra-articular injection of GAS6 restored the phagocytic capacity of macrophages, reduced the accumulation of local ACs, and decreased the levels of TUNEL and Caspase-3 positive cells, preserving cartilage thickness and preventing the progression of obesity-associated OA. Therefore, targeting macrophage-associated efferocytosis or intra-articular injection of GAS6 is a potential therapeutic strategy for obesity-associated OA.

Diffuse pigmented villonodular synovitis treated with arthroscopic total synovial peel.

BACKGROUND: Diffuse pigmented villonodular synovitis (PVNS) is prone to recurrence after surgery, and it is difficult to achieve a long-term complete cure. OBJECTIVE: To reduce the recurrence rate of PVNS, the author pioneered the arthroscopic total synovial peel (ATSP). METHODS: From March 2014 to July 2020, a total of 19 patients (6 males and 13 females) with diffuse PVNS of the knee were treated in our department and underwent ATSP. It's 'peel' rather than simple excision. This method is similar to peeling bark. Relapse rates and functional scores were determined, with follow-ups ranging from 12 to 72 months, on average 36 months. RESULTS: Treatment efficacy was assessed by imaging and functional scores. Imaging results indicated a recurrence rate of 10.5%. In patients without recurrence, the visual analog score (VAS) decreased from 4.76 ± 2.02 preoperatively to 1.56 ± 1.15 postoperatively. The Tegner-Lysholm knee function score (TLS) score increased from 67.76 ± 15.64 preoperatively to 90.32 ± 8.32 postoperatively. Compared with the literature, ATSP significantly reduces the postoperative recurrence rate of diffuse PVNS. The preliminarily findings suggest that this approach could greatly reduce the recurrence rate of postoperative PVNS in follow-up studies. CONCLUSION: This approach may be a viable option for treating diffuse PVNS via arthroscopy and is worthy of clinical consideration.

Rapamycin regulates osteogenic differentiation through Parkin-mediated mitophagy in rheumatoid arthritis.

Varying degrees of bone destruction and bone loss occur in the development of rheumatoid arthritis (RA). Nevertheless, the mechanism underlying osteoporosis in the development of RA is not completely elucidated. Recent evidence indicates that mitophagy may play a vital role in regulating the differentiation and function of preosteoblast. Parkin is associated with mitophagy and various inflammatory diseases, but the precise role of Parkin in the treatment of osteoporosis in RA is unclear. In the present study, we found that the abnormal bone metabolism of RA is related to the activation of the mechanistic targets of mTORC1 pathway, and chronic inflammation which regulates the differentiation of preosteoblast through mitophagy. In this study, we found that Parkin was upregulated, and the mitochondrion was damaged in tumor necrosis factor alpha (TNF-α) stimulated preosteoblasts. Rapamycin (RAPA, an mTORC1 pathway blocker) upregulation of Parkin-mediated mitophagy tends to attenuate mitochondrial impairment caused by TNF-α in preosteoblasts. Theexperimentinvivo demonstrated that the combination therapy with TNF-α neutralizing antibody and RAPA significantly reduced osteoporosis in AIA mice. Drug inhibition of this pathway can be a potential treatment for osteoporosis in patients with RA.

FABP4 secreted by M1-polarized macrophages promotes synovitis and angiogenesis to exacerbate rheumatoid arthritis.

Increasing evidence shows that adipokines play a vital role in the development of rheumatoid arthritis (RA). Fatty acid-binding protein 4 (FABP4), a novel adipokine that regulates inflammation and angiogenesis, has been extensively studied in a variety of organs and diseases. However, the effect of FABP4 on RA remains unclear. Here, we found that FABP4 expression was upregulated in synovial M1-polarized macrophages in RA. The increase in FABP4 promoted synovitis, angiogenesis, and cartilage degradation to exacerbate RA progression in vivo and in vitro, whereas BMS309403 (a FABP4 inhibitor) and anagliptin (dipeptidyl peptidase 4 inhibitor) inhibited FABP4 expression in serum and synovial M1-polarized macrophages in mice to alleviate RA progression. Further studies showed that constitutive activation of mammalian target of rapamycin complex 1 (mTORC1) by TSC1 deletion specifically in the myeloid lineage regulated FABP4 expression in macrophages to exacerbate RA progression in mice. In contrast, inhibition of mTORC1 by ras homolog enriched in brain (Rheb1) disruption specifically in the myeloid lineage reduced FABP4 expression in macrophages to attenuate RA development in mice. Our findings established an essential role of FABP4 that is secreted by M1-polarized macrophages in synovitis, angiogenesis, and cartilage degradation in RA. BMS309403 and anagliptin inhibited FABP4 expression in synovial M1-polarized macrophages to alleviate RA development. Hence, FABP4 may represent a potential target for RA therapy.

Robust drug bioavailability and safety for rheumatoid arthritis therapy using D-amino acids-based supramolecular hydrogels.

Long-term use of disease-modifying anti-rheumatic drugs (DMARDs) such as methotrexate (MTX) shows clinical benefits for rheumatoid arthritis (RA) treatment. However, there are growing concerns over the adverse effects of systemic drug administration. Therefore, a strategy that can enhance drug bioavailability while minimizing side effects is urgently needed, but remains a challenge in RA therapy. To this end, here we conjugated MTX with a supramolecular self-assembling hydrogel composed of d-amino acids with a sequence of GDFDFDY. It was shown that MTX-GDFDFDY hydrogels exhibited a favorable drug selectivity behavior that they increased MTX toxicity toward RA synoviocytes, but reduce toxicity toward normal cells. Moreover, MTX-GDFDFDY hydrogels not only effectively inhibited the proliferation and migration of RA synoviocytes, but also inhibited the polarization of proinflammatory M1 type macrophages to reduce inflammation. After intra-articularly injected the hydrogels into the joints of adjuvant induced arthritis (AIA) mice, we found that MTX-GDFDFDY hydrogels significantly alleviated RA syndromes of joint swelling and fever compared to L-configuration MTX-GFFY hydrogels and free MTX. Furthermore, MTX-GDFDFDY hydrogels successfully protected cartilage though inhibiting synovial invasion and inflammation without causing systematic side effects. Therefore, d-amino acids supramolecular hydrogels can serve as an efficient and safe drug delivery system, showing a promising potential to improve RA therapy.

Ezrin regulates synovial angiogenesis in rheumatoid arthritis through YAP and Akt signalling.

This study aimed to investigate the role and regulatory mechanisms of Ezrin in synovial vessels in rheumatoid arthritis (RA). Synovial tissues were obtained from people with osteoarthritis people and patients with RA patients. We also used an antigen-induced arthritis (AIA) mice model by using Freund's adjuvant injections. Ezrin expression was analysed by immunofluorescence and immunohistochemical staining in synovial vessels of patients with RA and AIA mice. We investigated the role of Ezrin on vascular endothelial cells and its regulatory mechanism in vivo and in vitro by adenoviral transfection technology. Our results suggest a role for the Ezrin protein in proliferation, migration and angiogenesis of vascular endothelial cells in RA. We also demonstrate that Ezrin plays an important role in vascular endothelial cell migration and tube formation through regulation of the Hippo-yes-associated protein 1 (YAP) pathway. YAP, as a key protein, can further regulate the activity of PI3K/Akt signalling pathway in vascular endothelial cells. In AIA mice experiments, we observed that the inhibition of Ezrin or of its downstream YAP pathway can affect synovial angiogenesis and may lead to progression of RA. In conclusion, Ezrin plays an important role in angiogenesis in the RA synovium by regulating YAP nuclear translocation and interacting with the PI3K/Akt signalling pathway.

Identification and Analysis of Three Hub Prognostic Genes Related to Osteosarcoma Metastasis.

Osteosarcoma (OS) often occurs in children and often undergoes metastasis, resulting in lower survival rates. Information on the complexity and pathogenic mechanism of OS is limited, and thus, the development of treatments involving alternative molecular and genetic targets is hampered. We categorized transcriptome data into metastasis and nonmetastasis groups, and 400 differential RNAs (230 messenger RNAs (mRNAs) and 170 long noncoding RNAs (lncRNAs)) were obtained by the edgeR package. Prognostic genes were identified by performing univariate Cox regression analysis and the Kaplan-Meier (KM) survival analysis. We then examined the correlation between the expression level of prognostic lncRNAs and mRNAs. Furthermore, microRNAs (miRNAs) corresponding to the coexpression of lncRNA-mRNA was predicted, which was used to construct a competitive endogenous RNA (ceRNA) regulatory network. Finally, multivariate Cox proportional risk regression analysis was used to identify hub prognostic genes. Three hub prognostic genes (ABCG8, LOXL4, and PDE1B) were identified as potential prognostic biomarkers and therapeutic targets for OS. Furthermore, transcriptions factors (TFs) (DBP, ESX1, FOS, FOXI1, MEF2C, NFE2, and OTX2) and lncRNAs (RP11-357H14.16, RP11-284N8.3, and RP11-629G13.1) that were able to affect the expression levels of genes before and after transcription were found to regulate the prognostic hub genes. In addition, we identified drugs related to the prognostic hub genes, which may have potential clinical applications. Immunohistochemistry (IHC) and quantitative real-time polymerase chain reaction (qRT-PCR) confirmed that the expression levels of ABCG8, LOXL4, and PDE1B coincided with the results of bioinformatics analysis. Moreover, the relationship between the hub prognostic gene expression and patient prognosis was also validated. Our study elucidated the roles of three novel prognostic biomarkers in the pathogenesis of OS as well as presenting a potential clinical treatment for OS.

Cadmium chloride enhances cisplatin sensitivity in osteosarcoma cells by reducing FOXM1 expression.

Osteosarcoma is a highly malignant disease and is associated with a poor patient prognosis and a high mortality rate. Disease prognosis significantly correlates with chemotherapeutic responses. Cadmium is a heavy metal with specific effects on bone, but its benefits for osteosarcoma treatment have not been characterized. In the present study, cadmium chloride was used to treat MG63 osteosarcoma cells, and their gene expression profiles were assessed by GeneChip technology. We found that forkhead box protein M1 (FOXM1) was downregulated by cadmium chloride, and lentiviral­mediated silencing of FOXM1 confirmed a role for this factor in the cisplatin resistance of MG63 cells. In nude mice, cadmium chloride enhanced the sensitivity of osteosarcoma to cisplatin, an effect mediated by FOXM1. Collectively, these data indicate that cadmium chloride can alter the sensitivity of osteosarcoma cells to cisplatin through FOXM1, highlighting it as a potential therapeutic target and prognostic factor for osteosarcoma.

Metformin attenuates cartilage degeneration in an experimental osteoarthritis model by regulating AMPK/mTOR.

BACKGROUND: It is generally thought that the occurrence and progression of osteoarthritis (OA) results from multiple causes, including degradation and destruction of the cartilage matrix and aging of chondrocytes. Metformin is a first-line drug for the treatment of diabetes, and has great potential for the treatment of other disorders. However, the role of metformin in OA is unknown. RESULTS: Metformin displayed a protective effect against OA. There were lower OARSI scores and fewer MMP-13-positive cells in DMM mice and cartilage explants after treatment with metformin. In addition, metformin treatment decreased p16INK4a levels in OA chondrocytes, and enhanced polarization of AMPK and inhibition of mTORC1 in OA mice and chondrocytes in a dose-dependent manner. CONCLUSIONS: Metformin effectively alleviated cartilage degradation and aging through regulation of the AMPK/mTOR signaling pathways, suggesting that it could be an effective treatment for OA. METHODS: The effects of metformin on cartilage degradation and chondrocyte aging was determined in a destabilization of the medial meniscus (DMM)-induced OA mouse model and in IL-1ß-treated mouse chondrocytes and cartilage explants. Articular cartilage degeneration was graded using the Osteoarthritis Research Society International (OARSI) criteria. Immunostaining, RT-PCR, and western blot analyses were conducted to detect the relative expressions of protein and RNA.

Influence of the pore size and porosity of selective laser melted Ti6Al4V ELI porous scaffold on cell proliferation, osteogenesis and bone ingrowth.

This paper systematically investigates the biomedical performance of selective laser melted (SLM) porous Ti6Al4V ELI scaffolds for bone implantation through in vitro and in vivo experiments. Scaffolds with pore sizes of 500 µm, 600 µm and 700 µm and porosities of 60% and 70% were manufactured in order to explore the optimum pore size and porosity. Rat bone marrow mesenchymal stem cells (rBMMSCs) were used in the in vitro experiments. Cell Counting Kit-8, live/dead staining and scanning electron microscope were used to assess the cytotoxicity of the porous scaffolds. DNA content quantification was performed to investigate cell proliferation on the porous scaffolds. The osteogenic differentiation of cells was measured by alkaline phosphatase (ALP) activity and osteogenic gene expressions, including bone morphogenetic protein-2 (BMP-2), collagen type 1α1 (COL-1), osteocalcin (OCN), osteopontin (OPN) and runt-related transcription factor-2 (RUNX-2). The Sprague-Dawley (SD) rat models with distal femoral condyles defect were used in the in vivo experiments. Micro-CT analysis and histological analysis were performed after implantation surgery to reveal the bone ingrowth into the porous scaffolds. All in vitro data were analyzed by one-way ANOVA followed by Tukey post hoc tests, in vivo data were analyzed using Kruskall-Wallis ANOVA and Conover-Inman post-hoc test. Based on the in vitro and in vivo experiments, it is found that the porous scaffolds manufactured by SLM did not induce a cytotoxic effect. Among all the porous scaffolds, the scaffold with a pore size of 500 µm and porosity of 60% showed the best cell proliferation and osteogenic differentiation (in vitro experiments) and bone ingrowth (in vivo experiments).

Hesperidin inhibits synovial cell inflammation and macrophage polarization through suppression of the PI3K/AKT pathway in complete Freund's adjuvant-induced arthritis in mice.

Rheumatoid arthritis (RA) is an autoimmune disease characterized by synovitis. Synovitis can cause joint injury by releasing inflammatory factors and metalloproteinases (MMPs). Therefore, it is necessary to find drugs that can control synovitis in the process of RA. Herein, we investigate the anti-inflammatory effect of Hesperidin (HSN) on fibroblast-like synovial (FLS) cells induced by lipopolysaccharide (LPS) and the protective action of M1 polarization level of synovial macrophages on antigen-induced arthritis (AIA) in order to elucidate the reduction of inflammatory cytokines and MMPs and the inhibition of macrophage activation. The functional effect of HSN on LPS-induced mRNA and protein expressions of inflammatory cytokines and MMPs in FLS cells as well as on LPS-induced macrophage M1 and M2 polarization markers was determined by quantitative real-time PCR (qPCR) or Western blot analyses, respectively. AIA in 2-month-old mice was generated using intraperitoneal injection with HSN (20 mg/kg/day) or LY294002 (20 mg/kg/day). The results show HSN significantly inhibited the LPS-induced gene expression of the inflammatory mediators. Furthermore, treatment with HSN relieved the antigen-induced arthritis and reduced the protein levels of MMP3, MMP9, and MMP13 in FLS and inhibited the polarization of macrophages to M1. Based on the results of our analyses, we concluded that HSN has significant anti-inflammatory activities and reduces the potential of MMPs in rheumatoid arthritis and the degree of polarization of macrophages to M1. Through the study of signaling pathways, we established that the inhibition of the PI3K/AKT signaling pathway by HSN may show therapeutic effects in the progression of rheumatoid arthritis.

Blocking PI3K/AKT signaling inhibits bone sclerosis in subchondral bone and attenuates post-traumatic osteoarthritis.

PI3K/AKT signaling is essential in regulating pathophysiology of osteoarthritis (OA). However, its potential modulatory role in early OA progression has not been investigated yet. Here, a mouse destabilization OA model in the tibia was used to investigate roles of PI3K/AKT signaling in the early subchondral bone changes and OA pathological process. We revealed a significant increase in PI3K/AKT signaling activation which was associated with aberrant bone formation in tibial subchondral bone following destabilizing the medial meniscus (DMM), which was effectively prevented by treatment with PI3K/AKT signaling inhibitor LY294002. PI3K/AKT signaling inhibition attenuated articular cartilage degeneration. Serum and bone biochemical analyses revealed increased levels of MMP-13, which was found expressed mainly by osteoblastic cells in subchondral bone. However, this MMP-13 induction was attenuated by LY294002 treatment. Furthermore, PI3K/AKT signaling was found to enhance preosteoblast proliferation, differentiation, and expression of MMP-13 by activating NF-κB pathway. In conclusion, inhibition of PI3K/AKT/NF-κB axis was able to prevent aberrant bone formation and attenuate cartilage degeneration in OA mice.