Glycogen Synthase Kinase 3 Inhibition Stimulates Human Cartilage Destruction and Exacerbates Murine Osteoarthritis

Abstract

Objective. To assess the role of glycogen synthase kinase 3 (GSK-3) as a regulator of cartilage destruction in human tissue and a murine model of osteoarthritis (OA).Methods. Surgical destabilization of the medial meniscus (DMM) was performed to induce experimental murine OA, and joint damage was assessed histologically. Bovine nasal and human OA cartilage samples were incubated with interleukin-1 (IL-1) plus oncostatin M (OSM) and GSK-3 inhibitor. Collagen and proteoglycan release was assessed by hydroxyproline measurement and dye binding assay, collagenase activity was assessed by bioassay, and gene expression was analyzed by real-time polymerase chain reaction. Human articular chondrocytes were isolated by enzymatic digestion and cultured prior to gene silencing and immunoblotting of cell lysates and nuclear fractions.Results. Mice treated with GSK-3 inhibitor exhibited significantly greater cartilage damage compared with sham-operated control mice. GSK-3 inhibition in bovine cartilage dramatically accelerated IL-1 plus OSM-stimulated degradation, concomitant with a profound increase in collagenase activity. GSK-3 inhibitor induced collagen release from human OA cartilage in the presence of IL-1 plus OSM and increased proteoglycan loss. Gene expression profiling of resorbing OA cartilage revealed a marked procatabolic switch in gene expression upon GSK-3 inhibition. This was mirrored in human articular chondrocytes following GSK3 silencing, particularly with the GSK-3␤ isoform.

Lithium chloride prevents interleukin‐1β induced cartilage degradation and loss of mechanical properties

“…However, Litherland et al recently reported that inhibition of GSK alone, using the specific inhibitor CHIR-99021, does not lead to the development of osteoarthritic lesions in mice consistent with our findings both in rats in vivo and human articular chondrocytes in vitro. 25 In contrast to the protective effects reported for LiCl, Litherland et al also observed that specific inhibition of GSK-enhanced cartilage degradation in response to mechanical injury. 25 Thus, it is likely that LiCl influences additional cellular targets which counteract its effects on GSK.…”

“…25 In contrast to the protective effects reported for LiCl, Litherland et al also observed that specific inhibition of GSK-enhanced cartilage degradation in response to mechanical injury. 25 Thus, it is likely that LiCl influences additional cellular targets which counteract its effects on GSK. Indeed, it has recently been shown that lithium inhibits hedgehog signaling in pancreatic ductal adenocarcinoma cells.…”

Lithium chloride modulates chondrocyte primary cilia and inhibits Hedgehog signaling

“…It therefore seems unlikely that LiCl is functioning primarily as a GSK inhibitor in articular chondrocytes. Indeed, previous studies have shown that while GSK inhibition alone negatively affects cartilage health, resulting in increased cartilage degradation and susceptibility to injury (66), administration of dietary lithium does not lead to cartilage degradation (5, 6). Lancaster et al (67) report that the cilium exerts a negative influence over canonical Wnt signaling by sequestering β‐catenin away from the nucleus such that in the presence of cilia, LiCl cannot activate Wnt signaling in mouse embryonic fibroblasts.…”

Recent advances in the understanding of molecular mechanisms of cartilage degeneration, synovitis and subchondral bone changes in osteoarthritis

“…During OA, these mediators may be produced by a variety of cell types, including macrophages, chondrocytes, and synovial fibroblasts (110). Such cytokines as synovial factors have shown much potential to induce cartilage destruction in vitro (111). Some specific examples will be introduced below with respect to synovial inflammation in OA.…”