Ultrastructural changes of the white zone cells of the meniscus in a rat model of early osteoarthritis / 中国组织工程研究

ABSTRACT

BACKGROUND: The research focuses of knee osteoarthritis are on mainly articular cartilage, subchondral bone and synovium. There are few studies on the ultrastructure of the meniscus in animal models. OBJECTIVE: On the basis of observing the ultrastructure and types of chondrocytes in the white zone of the meniscus, to observe the ultrastructural changes of the white zone cells of the meniscus in an animal model of early osteoarthritis, in order to explore the relationship between the microstructural changes and the physiological functional changes in the meniscus. METHODS: Sprague-Dawley rats were randomly divided into a control group and a model group. Rats in the model group were made into the model of early knee osteoarthritis by intraarticular injection of papain. After 5 weeks, the meniscuses of three rat models in each group were taken, located and observed for the ultrastructure of the white zone cells through a transmission electron microscope. An ethics approval was obtained from the Animal Ethics Committee of Fujian University of Traditional Chinese Medicine. RESULTS AND CONCLUSION: In the control group, most of cells were fusiform in the superficial layer of meniscus and were triangular-like in the deeper layer. They were rich in rough endoplasmic reticulum and mitochondria, with presence of Golgi and other organelles. Extracellular collagen fibrils were mainly type II collagen fibrils. The cells in the white zone of meniscus were chondrocytes. In the model group, the meniscal surface became rough, the cells were swollen, cytoplasmic organelles were reduced and swollen, glycogen was accumulated, and most of nuclei were abnormal with heterochromatin agglutination. Extracellular collagen fibrils became disordered and sparse. These findings indicate that the mild degeneration of chondrocytes and matrix in the meniscus can reduce the ability of cells to synthesize and secrete matrix components, which may lead to the physiological hypofunction.