Effects of biological factors and health condition on mercury and selenium concentrations in the cartilage, meniscus and anterior cruciate ligament.

Due the long-term nature of joint tissue remodeling processes, knee structures including meniscus and anterior cruciate ligament (ACL) can be a model for studying the bioaccumulation of mercury (Hg) and selenium (Se). The accumulation and retention of Hg in human tissues can have a negative effect on the proper functioning of homeostasis-affecting organisms. A factor of chronic poisoning with Hg forms is probably the Se:Hg ratio in tissues. Se:Hg molar ratios below one may increase Hg toxicity potentials, while molar ratios that approach or exceed one effectively may protect against Hg toxicity. Therefore, the aim of the study was to determine total mercury (THg), Se, and Se:THg molar ratios in the cartilage, meniscus and ACL of patients with osteoarthritis (OA) from northwestern Poland. In all studied samples (n=95), we observed higher Se than THg concentration. Taking into consideration the biological factors, we found significantly higher THg levels in the cartilage of women, patients under 65 years of age, patients without hypertension and in the ACL of patients with spinal degenerative disease. We found higher Se levels in the meniscus in women than in men. In all studied parts of the knee joint, we found the Se:THg molar ratio higher than one, which suggests that the joint forming structures are not much exposed to THg. Moreover the results reported here may provide a basis for establishing reference values for the meniscus and ACL in patients with OA who had undergone knee replacement surgery.

Selenium Reduces Early Signs of Tumor Necrosis Factor Alpha-Induced Meniscal Tissue Degradation.

Meniscal integrity is a prerequisite for sustained knee joint health and prevention of meniscal degeneration is a main research goal. Cartilage-protective effects of selenium have been described, but little is known about the impact on the meniscus. We therefore investigated the influence of sodium selenite on meniscal explants under tumor necrosis factor-alpha (TNFα)-stimulated proinflammatory conditions. Meniscal explant disks (3 mm diameter × 1 mm thickness) were isolated from 2-year-old cattle and incubated with TNFα (10 ng/ml) and sodium selenite (low dose, LoD 6.7 ng/ml as being found in Insulin-Transferrin-Selenium medium supplements, ITS; medium-dose, MeD 40 ng/ml described as physiological synovial concentration; high dose, HiD 100 ng/ml described as optimal serum concentration). After 3 days of culture glycosaminoglycan (GAG) release (DMMB assay), nitric oxide (NO) production (Griess assay), gene expression of matrix-degrading enzymes (quantitative RT-PCR), and apoptosis rate were determined. TNFα led to a significant raise of GAG release and NO production. LoD and MeD selenite significantly reduced the TNFα-induced GAG release (by 83, 55 %, respectively), NO production (by 59, 40 %, respectively), and apoptosis (by 68, 39 %, respectively). LoD and MeD selenite showed a tendency to reduce the TNFα-mediated increase of inducible NO-synthase (iNOS) levels, LoD selenite furthermore matrix metalloproteinase (MMP)-3 transcription levels and a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS)-4 levels. LoD and less pronounced MeD selenite show a substantial impact on the early meniscal inflammatory response. To our knowledge this is the first study showing the protective influence of selenium on meniscal tissue maintenance. To understand the superior potency of low-dose selenium on molecular level future studies are needed.