The effects of mycotoxins and selenium deficiency on tissue-engineered cartilage.

OBJECTIVE: To investigate the effects of 3 mycotoxins, deoxynivalenol (DON), nivalenol (NIV) and T-2 toxin, in the presence and absence of selenium (Se) on the metabolism of tissue-engineered cartilage to mimic conditions found in Kashin-Beck disease (KBD) environments. MATERIALS AND METHODS: Chondrocytes were seeded onto bone matrix gelatin (BMG) to construct engineered cartilage. The 3 toxins were added to the culture media for 3 weeks followed by immunhistochemical analyses of collagens type II and X, aggrecan, matrix metalloproteinases 1 and 3 (MMP-1 and MMP-3), MMP inhibitors 1 and 3 (TIMP-1 and TIMP-3) and α(2) macroglobulin (α2M). RESULTS: Type II collagen was decreased while type X collagen was increased in response to DON, NIV and T-2 toxin. Aggrecan was reduced by all 3 mycotoxins. Compared with the control, the 3 toxins decreased the expression of α2M, TIMP-1 and TIMP-3, and increased the expression of MMP-1 and MMP-3. Se could partially inhibit the effects of DON, NIV and T-2 toxins. CONCLUSION: Under the low Se condition, the 3 mycotoxins produced procatabolic changes in cartilage resulting in the loss of aggrecan and type II collagen and promoted a hypertrophic phenotype of chondrocytes characterized by increasing type-X-collagen expression, enhancing the expression of MMPs, while weakening the TIMPs. Se could partially block the effects mentioned above. These results support the hypothesis that the combination of mycotoxin stress and Se deficiency would be the causative factors for KBD.

Effects of moniliformin and selenium on human articular cartilage metabolism and their potential relationships to the pathogenesis of Kashin-Beck disease.

OBJECTIVE: To investigate the effects of mycotoxin moniliformin (MON) on the metabolism of aggrecan and type II collagen in human chondrocytes in vitro and the relationship between MON and Kashin-Beck disease (KBD). METHODS: Human chondrocytes were isolated and cultured on bone matrix gelatin to form an artificial cartilage model in vitro with or without MON toxin. Cell viability was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The expression of aggrecan and type II collagen in the cartilage was determined using immunocytochemical staining. RESULTS: MON toxin inhibited chondrocyte viability in dose-dependent and time-dependent manners. MON reduced aggrecan and type II collagen syntheses in the tissue-engineered cartilage. MON also increased the expression of matrix metalloproteinase-1 (MMP-1), MMP-13, BC4 epitopes, and CD44 in cartilages. However, the expression of 3B3(-) epitopes in cartilages was inhibited by MON. Selenium partially alleviated the damage of aggrecan induced by MON toxin. CONCLUSION: MON toxin promoted the catabolism of aggrecan and type II collagen in human chondrocytes.

[Effects of selenium and/or iodine deficiency on chondrocyte apoptosis in rats].

OBJECTIVE: To explore the effects of selenium and/or iodine deficiency on chondrocyte apoptosis in articular cartilage in rats. METHODS: Forty-eight Sprague-Dawley rats were randomly divided into selenium deficiency group, iodine deficiency group, combined selenium and iodine deficiency group, and control group. Chondrocyte apoptosis was detected by terminal deoxynucleotidyl transferase biotin-dUTP nick end labeling (TUNEL) method, and Bcl-2 and Bax in articular cartilage were stained by immunohistochemistry in F3 generation of rats. RESULTS: In articular cartilage, the positive rate of apoptotic chondrocytes stained by TUNEL in the upper and middle zones in selenium deficiency group, iodine deficiency group, and combined selenium and iodine deficiency group (all P < 0.05) were significantly higher than that in control group. The apoptotic chondrocytes were prominent in the middle zone. The positive percentage of chondrocytes apoptosis was not significantly different among these three groups (P > 0.05). Compared with the control group, the expressions of both Bcl-2 and Bax were significantly higher in the upper and middle zone in the selenium deficiency group, iodine deficiency group, and combined selenium and iodine deficiency group (all P < 0.05); however, the expressions of Bcl-2 and Bax were not significantly different among these three groups (P > 0.05). CONCLUSION: Selenium and/or iodine deficiency may induce chondrocyte apoptosis.

Butenolide induced cytotoxicity by disturbing the prooxidant-antioxidant balance, and antioxidants partly quench in human chondrocytes.

Butenolide (BUT), a mycotoxin produced by Fusarium species, was detected often in corns or grains from endemic Kashin-Beck disease (KBD) areas in China. In this study, we evaluated the cytotoxicity of BUT on chondrocytes and the possible toxic mechanism with the aim of understanding the pathogenesis and of directing future therapeutic interventions for KBD. Exposure of human chondrocytes and engineered cartilage to high concentration of BUT (> 1 microg/ml) resulted in significant cytotoxicity, manifested by losses in cell viability and changes in cell morphology. BUT with high concentration (> 1 microg/ml) also induced significant oxidative damage to chondrocytes in vitro evidenced by increasing both lipid peroxidation and endogenous antioxidants. Furthermore, free radical scavenging agents, such as selenium (Se), vitamin C (VC) and vitamin E (VE), partly blocked BUT-induced oxidative damage. In conclusion, this finding indicates that BUT induces cytotoxicity to human chondrocytes, and the disturbance of prooxidant-antioxidant balance may play a pivotal role in BUT-induced injuries in chondrocytes. Moreover, Se, VC or VE can quench the toxic effects of BUT to a certain extent, which will possibly direct future therapeutic interventions against KBD.

Promotion of the articular cartilage proteoglycan degradation by T-2 toxin and selenium protective effect.

OBJECTIVE: To identify the relationship between T-2 toxin and Kashin-Beck disease (KBD), the effects of T-2 toxin on aggrecan metabolism in human chondrocytes and cartilage were investigated in vitro. METHODS: Chondrocytes were isolated from human articular cartilage and cultured in vitro. Hyaluronic acid (HA), soluble CD44 (sCD44), IL-1beta and TNF-alpha levels in supernatants were measured by enzyme-linked immunosorbent assay (ELISA). CD44 content in chondrocyte membrane was determined by flow cytometry (FCM). CD44, hyaluronic acid synthetase-2 (HAS-2) and aggrecanases mRNA levels in chondrocytes were determined using reverse transcription polymerase chain reaction (RT-PCR). Immunocytochemical method was used to investigate expressions of BC-13, 3-B-3(-) and 2-B-6 epitopes in the cartilage reconstructed in vitro. RESULTS: T-2 toxin inhibited CD44, HAS-2, and aggrecan mRNA expressions, but promoted aggrecanase-2 mRNA expression. Meanwhile, CD44 expression was found to be the lowest in the chondrocytes cultured with T-2 toxin and the highest in control plus selenium group. In addition, ELISA results indicated that there were higher sCD44, IL-1beta and TNF-alpha levels in T-2 toxin group. Similarly, higher HA levels were also observed in T-2 toxin group using radioimmunoprecipitation assay (RIPA). Furthermore, using monoclonal antibodies BC-13, 3-B-3 and 2-B-6, strong positive immunostaining was found in the reconstructed cartilage cultured with T-2 toxin, whereas no positive staining or very weak staining was observed in the cartilage cultured without T-2 toxin. Selenium could partly inhibit the effects of T-2 toxin above. CONCLUSION: T-2 toxin could inhibit aggrecan synthesis, promote aggrecanases and pro-inflammatory cytokines production, and consequently induce aggrecan degradation in chondrocytes. These will perturb metabolism balance between aggrecan synthesis and degradation in cartilage, inducing aggrecan loss in the end, which may be the initiation of the cartilage degradation.

[Butenolide induces apoptosis of cultured chondrocytes: study of its mechanism].

OBJECTIVE: To observe cell apoptosis and Bcl-2 and Bax expression changes of chondrocytes induced by butenolide (BUT) and the inhibitory effect of selenium against BUT-induced chondrcyte apoptosis, to gain insights into the mechanism by which BUT induces chondrcyte apoptosis. METHODS: Cartilage tissue reestablished from human fetal articular chondrocytes in vitro were treated with BUT at the concentrations of 0.1, 1.0 and 5.0 microg/ml and with the protective factor selenium. TUNEL method was used to detect chondrocyte apoptosis, which was quantified by flow cytometry. Immunohitochemistry was performed to analyze the expression of Bcl-2 and Bax in the reestablished cartilage tissue. RESULTS: BUT exposure induced chondrocyte apoptosis, and the apoptosis rate increased with the concentration increment of BUT from 0 to 1.0 mg/ml, resulting also increased positive expression rate of Bcl-2 and Bax(P<0.05). The apoptosis rate of chondrocytes in BUT+ selenium group was significantly lower than that of BUT groups (P<0.05), as was the positivity rate of Bcl-2 and Bax expression (P<0.05). CONCLUSION: BUT induces chondrocyte apoptosis in positive relation with BUT concentration (from 0 to 1.0 mg/ml) and causes increased expressions of Bcl-2 and Bax. Selenium can inhibit the chondrocyte apoptosis induced by BUT.

[Toxic effect of butenolide on chondrocyte differentiation and the protective effect of selenium].

OBJECTIVE: To study the effect of butenolide (BUT) on cultured chondrocytes differentiation and the possible protective effects of selenium (Se). METHODS: Ex-vivo cultured chondrocytes were divided into six groups: (1) Control group (without BUT and Se); (2) Se 0.1 microg/ml control group; (3) BUT 0.1 microg/ml group; (4) BUT 1.0 microg/ml group; (5) BUT 5.0 microg/ml group; and (6) BUT 1.0 microg/ml + Se 0.1 microg/ml group. The expression of collagen II (Col II), collagen X (ColX), basic fibroblast growth factor (bFGF), and parathyroid hormone-related peptide (PTHrP) in (or around) chondrocytes in all groups were analyzed by immunohistochemistry. RESULTS: The expressions of Col II in 1.0 microg/ml BUT group and 5.0 microg/ml BUT group were significantly lower than those in the control group (P < 0.05). The expression of Col II in 1.0 microg/ml BUT + Se group were significantly higher than those in the 1.0 microg/ml BUT group and 5.0 microg/ml BUT group (P < 0.05). The expressions of bFGF and PTHrP of BUT groups were significantly higher than those in the Se and control groups (P < 0.05). No expression of ColX was observed in all groups. CONCLUSION: BUT can affect the collagen II synthesis of the chondrocytes. Selenium supplementation may play a protective role.