Selenium deficiency and fulvic acid supplementation induces fibrosis of cartilage and disturbs subchondral ossification in knee joints of mice: an animal model study of Kashin-Beck disease.

Kashin-Beck disease is an acquired, chronic and degenerative osteoarticular disorder. Selenium deficiency and fulvic acid in drinking water have been implicated in the cause of this disease. Pathologically, chondronecrosis of the growth plate and articular cartilage and subconsequent disturbance of ossification were observed in the joints. In this animal model study, mice were fed with a selenium deficient diet and fulvic acid supplemented drinking water for two generations. In undecalcified histological preparations of bone we carried out histological staining to detect mineralized and unmineralized bone and cartilage. The results revealed that selenium deficiency and fulvic acid supplementation induced degeneration of the articular cartilage in the knee joints of mice. Dynamic fluorescent labelling of ossification, enzyme histochemical detection of alkaline phosphatase activity in osteoblasts and a typical immunohistochemical localization of collagens type I and II indicated the development of fibrocartilage at the articular surface of knee joints, resembling the early stages of osteoarthrosis. This became obvious by disturbed development of the articular space and meniscus, markedly impaired formation of subchondral bone and early differentiation failure during enchondral ossification. This animal model provides an approach to study the molecular pathogenesis of Kashin-Beck disease.