Transforming growth factor-β receptors mediates matrix degradation and abnormal hypertrophy in T-2 toxin-induced hypertrophic chondrocytes

Highlights

• T-2 toxin is considered to be the most toxic type A trichothecene mycotoxin.

• T-2 toxin induces hypertrophic chondrocytes death, degradation of the matrix, and abnormal terminal differentiation.

• TGF-βRs mediates matrix degradation and abnormal hypertrophy in T-2 toxin induced hypertrophic chondrocytes.

Abstract

This study investigated whether transforming growth factor-β receptor I (TGF-βRI) and TGF-βRII mediate matrix degradation and abnormal hypertrophy in T-2 toxin-induced hypertrophic chondrocytes. Hypertrophic chondrocytes were exposed to TGF-βRI and TGF-βRII binding inhibitor (GW788388) for 24 h prior to exposure to different concentrations of T-2 toxin (0, 10, 25, and 50 ng/mL for 48 h). Hypertrophic chondrocytes were assessed based on the expression of matrix-degrading and terminal differentiation-related genes and cell viability. Matrix metalloproteinases (MMPs, MMP-13, MMP-1, and MMP-9) were reduced in the GW788388+T-2 toxin group compared to the T-2 toxin group. The expression of terminal differentiation-related genes (MMP-2, MMP-10, and collagen X) was increased in hypertrophic chondrocytes in the inhibited groups compared to that in the T-2 toxin group. The survival rate of chondrocytes decreased significantly in a dose-dependent manner. GW788388 did not significantly block the reduced cell viability in hypertrophic chondrocytes exposed to T-2 toxin. The upregulated expression of TGF-βRI and TGF-βRII mediates the abnormal chondrocyte hypertrophy and extracellular matrix degeneration observed in T-2 toxin-induced hypertrophic chondrocytes.

Introduction

Kashin-Beck disease (KBD) is a chronic deforming endemic osteoarthropathy. KBD onset occurs as early as 2–3 years of age (Allander, 1994). However, the aetiology of KBD remains unclear. T-2 toxin contamination has been reported in grains in areas with endemic KBD (Del Carlo and Loeser, 2002; Dianjun Sun, 1997; Sun et al., 2019; Zhang et al., 2001), and cartilage erosion in the hypertrophic cartilage is a fundamental pathological feature of KBD. Degenerative changes in KBD are characterised by chondronecrosis in multiple foci of the deep zone of the cartilage (Guo et al., 2014). This is different from osteoarthritis (OA), which has focal and progressive hyaline articular cartilage loss from the superficial zone to the deep zone. It involves damage to the extracellular matrix (ECM), abnormal terminal differentiation, and cell death. The ECM is composed primarily of type II collagen, proteoglycan, and other matrix molecules (Cao et al., 2008). Excessive cleavage of type II collagen in KBD is associated with the upregulation of the synthesis and activities of collagenases, in particular, matrix metalloproteinase (MMP)-13 (Chen et al., 2015a; Zhou et al., 2016). KBD lesions in the hand are accompanied by the upregulation of chondrocyte differentiation-related genes implicated in the regulation of chondrocyte hypertrophy in endochondral bone formation (Liu et al., 2018). These include type X collagen, parathyroid hormone-related protein, basic FGF, and vascular endothelial growth factor (Guo et al., 2006a). As previously reported, chondrocyte necrosis occurs in the deep zone of cartilage, while necroptosis and apoptosis coexist in the middle zone of the adjacent necrotic area from cartilage in children with KBD (Zhang et al., 2018).

In a previous study, cartilage erosion in rats fed T-2 toxin was similar to that observed in KBD (Chen et al., 2012). The T-2 toxin, which has been found in food consumed by people and animals as well as agricultural products (Li et al., 2011), is considered to be the most toxic type A trichothecene mycotoxin (Schollenberger et al., 2007). Trichothecenes are significant mycotoxins that pose a potential threat to animal and human health worldwide. These are produced by several fungal genera, including Fusarium species, and are detected in a number of field crops (wheat, maize, barley, oats, etc.) and processed grains (malt, beer, bread, etc.). In vitro and in vivo studies have reported that T-2 toxin can induce apoptosis in human chondrocytes by upregulating the expression of apoptosis genes (Liu et al., 2014a). The T-2 toxin could also alter the levels of collagen II and its regulatory enzymes MMPs/TIMP-1 in a low-selenium rat model of KBD (Zhou et al., 2016). T-2 toxin has also been shown to induce a decrease in type II collagen in C28/I2 chondrocytes (Liu et al., 2020). Therefore, T-2 toxin may contribute to KBD by causing chondrocyte apoptosis and matrix degradation. However, few studies have focused on this mechanism.

Transforming growth factor-β (TGF-β) signalling regulates diverse cellular processes, including cell differentiation, proliferation, chemotaxis, and ECM production through the heteromeric serine/threonine kinases comprising type I and type II receptors (TGF-βRI and TGF-βRII). TGF-β signalling is initiated when a ligand binds to TGF-βRI/II on the cell surface, and it stabilises the phenotype of pre-hypertrophic chondrocytes. In this study, we investigated whether T-2 toxin mediates matrix degradation, abnormal terminal differentiation, and cell death by regulating TGF-βRI and II signalling in hypertrophic chondrocytes.