Sargassum polysaccharide attenuates osteoarthritis in rats and is associated with the up-regulation of the ITGß1-PI3K-AKT signaling pathway.

Background: Osteoarthritis (OA) presents a formidable challenge, characterized by as-yet-unclear mechanical intricacies within cartilage and the dysregulation of bone homeostasis. Our preliminary data revealed the encouraging potential of a Sargassum polysaccharide (SP), in promoting chondrogenesis. The aim of our study is to comprehensively assess the therapeutic effects of SP on OA models and further elucidate its potential mechanism. Methods: The protective effects of SP were initially evaluated in an inflammation-induced human chondrocyte (C28) cell model. CCK-8 assays, Alcian blue staining, RT-qPCR and Western blotting were used to verify the chondrogenesis of SP in vitro. To assess the efficacy of SP in vivo, surgically induced medial meniscus destabilization (DMM) OA rats underwent an 8-week SP treatment. The therapeutic effects of SP in OA rats were comprehensively evaluated using X-ray imaging, micro-computed tomography (µ-CT), histopathological analysis, as well as immunohistochemical and immunofluorescent staining. Following these assessments, we delved into the potential signaling pathways of SP in inflammatory chondrocytes utilizing RNA-seq analysis. Validation of these findings was conducted through RT-qPCR and western blotting techniques. Results: SP significantly enhance the viability of C28 chondrocytes, and increased the secretion of acidic glycoproteins. Moreover, SP stimulated the expression of chondrogenic genes (Aggrecan, Sox9, Col2a1) and facilitated the synthesis of Collagen II protein in C28 inflammatory chondrocytes. In vivo experiments revealed that SP markedly ameliorated knee joint stenosis, alleviated bone and cartilage injuries, and reduced the histopathological scores in the OA rats. µ-CT analysis confirmed that SP lessened bone impairments in the medial femoral condyle and the subchondral bone of the tibial plateau, significantly improving the microarchitectural parameters of the subchondral bone. Histopathological analyses indicated that SP notably enhanced cartilage quality on the surface of the tibial plateau, leading to increased cartilage thickness and area. Immunohistochemistry staining and immunofluorescence staining corroborated these findings by showing a significant promotion of Collagen II expression in OA joints treated with SP. RNA-seq analysis suggest that SP's effects were mediated through the regulation of the ITGß1-PI3K-AKT signaling axis, thereby stimulating chondrogenesis. Verification through RT-qPCR and Western blot analyses confirmed that SP significantly upregulated the expression of ITGß1, p110δ, AKT1, ACAN, and Col2a1. Notably, knock-down of ITGß1 using siRNA in C28 chondrocytes inhibited the expression of ITGß1, p110δ, AKT1, and ACAN. However, these inhibitory effects were not completely reversed by supplemental SP intervention. Conclusions: In summary, our findings reveal that SP significantly enhances chondrogenesis both in vitro and in vivo, alleviating OA progression both in bone and cartilage. The observed beneficial effects are intricately linked to the activation of the ITGß1-PI3K-AKT signaling axis. The translational potential of this article: Our research marks the first instance unveiling the advantageous effects and underlying mechanisms of SP in OA treatment. With its clinical prospects, SP presents compelling new evidence for the advancement of a next-generation polysaccharide drug for OA therapy.

Tubson-2 decoction ameliorates rheumatoid arthritis complicated with osteoporosis in CIA rats involving isochlorogenic acid A regulating IL-17/MAPK pathway.

BACKGROUND: Osteoporosis (OP) is considered as one of the major comorbidities of rheumatoid arthritis (RA), and is responsible for fragility fracture. However, there is currently no effective treatment for RA complicated with OP. Tubson-2 decoction (TBD), a Mongolian medicine also known as Erwei Duzhong Decoction, has been shown to exert a preventive effect on post-menopausal osteoporosis (PMOP). The preventive effects of TBD on RA-induced OP, as well as the bioactive compound responsible and the underlying mechanisms, remain to be elucidated. OBJECTIVE: To explore the effects of TBD on RA-induced OP in vivo, and to elucidate the mechanism of isochlorogenic acid A (ICA), the effective component of TBD, in vitro. METHODS: To evaluate the anti-arthritic and anti-osteoporotic effects of TBD, we conducted H&E straining and safranine O/fast green, TEM, immunohistochemistry (IHC), bone histomorphometry, micro-CT imaging, and biomechanical testing in collagen induced arthritis (CIA) rats. The active ingredient in TBD was identified using network pharmacology and molecular docking. The identification was supported by in vivo IHC assay, and further confirmed using qRT-PCR, Western blot, and SEM analysis in TNF-α-treated MH7A cells and/or in LPS-exposed RAW264.7 cells. RESULTS: Oral administration of TBD attenuated the severity of arthritis and osteopenia as well as poor bone quality, in CIA rats. Additionally, TBD and the positive control, tripterygium glycosides (TG), exhibited similar effects in reducing inflammation in both the synovium and ankle joint. They also were both effective in improving bone loss, microarchitecture, and overall bone quality. TBD reduced the expression of MMP13, IL-17, and p-JNK protein in the synovium of CIA rats. ICA, which was screened, suppressed TNF-α or LPS-triggered inflammatory responses via down-regulating IL-17 signaling, involving in MMP13, IL-1ß, IL-23, and IL-17, and the MAPK pathway including p-ERK, p-JNK, and p-P38, both in MH7A cells and in RAW264.7 cells. Furthermore, ICA prevented osteoclasts from differentiating and bone resoprtion in a dose-dependent manner in vitro. CONCLUSION: This study provides the first evidence that TBD exerts intervening effects on RA-induced OP, possibly through the downregulation of the IL-17/MAPK signaling pathway by ICA. The findings of our study provides valuable insights for further research in this area.

Tanshinol Alleviates Microcirculation Disturbance and Impaired Bone Formation by Attenuating TXNIP Signaling in GIO Rats.

Impaired bone formation is the main characteristics of glucocorticoid (GC)-induced osteoporosis (GIO), which can be ameliorated by tanshinol, an aqueous polyphenol isolated from Salvia miltiorrhiza Bunge. However, the underlying mechanism is still not entirely clear. In the present study, we determined the parameters related to microstructure and function of bone tissue, bone microcirculation, and TXNIP signaling to investigate the beneficial effects of tanshinol on skeleton and its molecular mechanism in GIO rats. Male Sprague-Dawley rats aged 4 months were administrated orally with distilled water (Con), tanshinol (Tan, 25 mg kg-1 d-1), prednisone (GC, 5 mg kg-1 d-1) and GC plus tanshinol (GC + Tan) for 14 weeks. The results demonstrated that tanshinol played a significant preventive role in bone loss, impaired microstructure, dysfunction of bone metabolism and poor bone quality, based on analysis of correlative parameters acquired from the measurement by using Micro-CT, histomorphometry, ELISA and biomechanical assay. Tanshinol also showed a significant protective effect in bone microcirculation according to the evidence of microvascular perfusion imaging of cancellous bone in GIO rats, as well as the migration ability of human endothelial cells (EA.hy926, EA cells). Moreover, tanshinol also attenuated GC-elicited the activation of TXNIP signaling pathway, and simultaneously reversed the down-regulation of Wnt and VEGF pathway as manifested by using Western-blot method in GIO rats, EA cells, and human osteoblast-like MG63 cells (MG cells). Collectively, our data highlighted that tanshinol ameliorated poor bone health mediated by activation of TXNIP signaling via inhibiting microcirculation disturbance and the following impaired bone formation in GIO rats.