Metformin reduces chondrocyte pyroptosis in an osteoarthritis mouse model by inhibiting NLRP3 inflammasome activation

Abstract

Osteoarthritis (OA) is an age-related degenerative disease, and its incidence is increasing with the ageing of the population. Metformin, as the first-line medication for the treatment of diabetes, has received increasing attention for its role in OA. The purpose of the present study was to confirm the therapeutic effect of metformin in a mouse model of OA and to determine the mechanism underlying the resultant delay in OA progression. The right knees of 8-week-old C57BL/6 male mice were subjected to destabilization of the medial meniscus (DMM). Metformin (200 mg/kg) was then administered daily for 4 or 8 weeks. Safranin O-fast green staining, H&E staining and micro-CT were used to analyse the structure and morphological changes. Immunohistochemical staining was used to detect type II collagen (Col II), matrix metalloproteinase 13 (MMP-13), NOD-like receptor protein 3 (NLRP3), caspase-1, gasdermin D (GSDMD) and IL-1β protein expression. Reverse transcription-quantitative PCR was used to detect the mRNA expression of NLRP3, caspase-1, GSDMD and IL-1β. Histomorphological staining showed that metformin delayed the progression of OA in the DMM model. With respect to cartilage, metformin decreased the Osteoarthritis Research Society International score, increased the thickness of hyaline cartilage and decreased the thickness of calcified cartilage. Regarding the mechanism, in cartilage, metformin increased the expression of Col II and decreased the expression of MMP-13, NLRP3, caspase-1, GSDMD and IL-1β. In addition, in subchondral bone, metformin inhibited osteophyte formation, increased the bone volume fraction (%) and the bone mineral density (g/cm 3 ), decreased the trabecular separation (mm) in early stage of osteoarthritis (4 weeks) but the opposite in an advanced stage of osteoarthritis (8 weeks). Overall, metformin inhibited the activation of NLRP3 inflammasome, decreased cartilage degradation, reversed subchondral bone remodelling and inhibited chondrocyte pyroptosis.

Metformin alleviates osteoarthritis in mice by inhibiting chondrocyte ferroptosis and improving subchondral osteosclerosis and angiogenesis

“…Mice were injected intra-articularly with Erastin (15 mg/kg) [ 38 ], and the sham and DMM groups were injected with an equal volume of saline twice a week. Moreover, Met was administered by gavage (200 mg/kg/day) [ 23 ]. Mice were killed by overdose anesthesia 8 weeks after surgery, and the right knee joint was collected for subsequent experiments.…”

“…Subchondral osteosclerosis is an important pathological marker of OA [ 22 ]. The results of our previous study demonstrated that a mouse OA model induced by surgery developed late pathological changes with subchondral osteosclerosis 8 weeks after surgery [ 23 , 24 ]. The specific mechanisms underlying subchondral osteosclerosis in advanced stages of OA remain to be fully elucidated.…”

“…These results suggested that Met may delay disease development in OA. The results of our previous study demonstrated that Met exerted chondroprotective effects by inhibiting chondrocyte pyroptosis in a mouse OA model [ 23 ]. However, the effects of Met on ferroptosis in different tissue cells remain inconclusive, and the results of a previous study indicated that Met may affect the pathological progression of hyperlipidemia-related vascular calcification through anti-ferroptosis in vascular smooth muscle cells [ 33 ].…”

Association between Metformin Use and Risk of Total Knee Arthroplasty and Degree of Knee Pain in Knee Osteoarthritis Patients with Diabetes and/or Obesity: A Retrospective Study

“…A previous study investigating the association between MET use and disease progression in obese people with knee OA found that MET use was significantly associated with lower rates of medial cartilage volume loss, indicating that MET may have protective effects on knee OA progression in people without diabetes mellitus [ 16 ]. Moreover, basic scientific studies focusing on the effects of MET on experimental OA mice models also indicated that MET may have a protective effect on OA in non-diabetic subjects [ 11 , 13 , 22 ].…”

“…It has also been demonstrated that OA rats receiving MET treatment had a better pain tolerance, suggesting that MET may attenuate OA development and progression [ 11 ]. Furthermore, some basic research studies have reported that MET may alleviate OA via attenuating osteoclast-mediated abnormal subchondral bone remodeling, reducing chondrocyte pyroptosis, and inhibiting chondrocyte ferroptosis [ 12 , 13 , 14 ]. In addition, these pleiotropic effects of MET have been described to occur mainly through activating the adenosine monophosphate-activated protein kinase (AMPK) pathway [ 11 ].…”