Dynamic changes of rat cartilage ultrastructure in the early process of papain-induced knee osteoarthritis / 中国组织工程研究

ABSTRACT

BACKGROUND:Papain-induced rat knee osteoarthritis is a common modeling method, which can obtain a stable osteoarthritis model. OBJECTIVE:To observe the change of ultrastructure of chondrocytes in the early process of papain-induced rat knee osteoarthritis under transmission electron microscope. METHODS:A total of 18 Sprague-Dawley rats were randomly divided into three groups. Two rats were considered as a normal control group, without intervention. The mixture of papain and L-cysteine was injected in right knee joint cavity of 16 rats to induce osteoarthritis models (osteoarthritis model group). Physiological saline was injected in the left side (physiological saline control group). At 1, 2, 4 and 6 weeks after injection, samples were col ected. Transmission electron microscope was used to observe the change of cartilage ultrastructure of the medial femoral condyle joint. RESULTS AND CONCLUSION:For the normal control group and physiological saline control group, their cytoplasm contained abundant rough endoplasmic reticulum and mitochondria. After 1 week of injection, mitochondria vacuoles and light expanded rough endoplasmic reticulum were visible. Two weeks later, lipid droplets appeared, mitochondria degeneration was distinct, vacuolization was serious and its number was reduced, and rough endoplasmic reticulum expansion was obvious. Four weeks later, lipid droplets became increased, and the number of mitochondria decreased significantly. Most of the rough endoplasmic reticula were highly expanded, and part of the rough endoplasmic reticula were dissolved and fractured. Six weeks later, a number of lipid droplets were visible in cytoplasm, most of the mitochondria disappeared, only a smal number of mitochondria existed, and most of the rough endoplasmic reticula were dissolved and fractured. These results confirmed that cartilage ultrastructure changes gradual y in the early process of papain-induced rat knee osteoarthritis under transmission electron microscope.