Loss of Autophagy In Tibial Growth Plate Chondrocytes Causes Increased Chondrocyte Apoptosis In Young Rats With Chronic Renal Insufficiency

Background: To observed the effect of autophagy in tibial growth plate chondrocytes on apoptosis in chronic renal insufficiency(CRI) rats. Method: Male 4-week-old Sprague Dawley(SD) rats were randomly divided into two groups (n=20/per group): (1) the normal group was intragastrically administered distilled water; and (2) the CRI group was given a 150 mg/(kg·d) adenine suspension. All rats were sacrificed after continuous gavage for 6 weeks. The tibial length and the width of the tibial growth plate were measured using micro-CT. The width of the tibial growth plate was also measured in histological sections at both 4 w and 10 w. The level of the autophagy marker Beclin-1 in chondrocytes was measured by immunofluorescence. The level of glycogenin-1, a marker of intracellular glycogen accumulation, was measured by immunohistochemistry in chondrocytes in vivo and in vitro. The apoptosis rate of chondrocytes was measured by the TUNEL method in vivo and in vitro. Results: : The results showed that the length of tibia was shorter and the width of tibia growth plate was narrower in CRF young rats. Autophagy level of chondrocytes in tibial growth plate decreased, and accumulation of glycogen granules in chondrocytes increased significantly. Meanwhile, the apoptosis rate of chondrocytes in tibial growth plate increased. Conclusion: When CRF occurred in young rats, the autophagy level of chondrocytes in tibial growth plate decreased significantly.As a result, there are not enough autophagic vesicles to swallow glycogen granules in chondrocytes and degrade them into glucose for energy supply, which leads to chondrocyte apoptosis.Autophagy of chondrocytes is at least partly involved in energy metabolism of cells.