Effect of increased mitophagy of chondrocytes in tibial growth plate of young rats with chronic renal failure on apoptosis / 中华肾脏病杂志

ABSTRACT

Objective:To explore the level of tibial growth plate chondrocyte mitophagy in young rats with chronic renal failure (CRF) and its effect on chondrocyte apoptosis.Methods:Male 4-week-old Sprague-Dawley rats were randomly divided into two groups according to random number table method: normal control group ( n=20, intragastric administration with distilled water) and CRF group ( n=20, given adenine suspension 150 mg·kg -1·d -1). All the young rats were sacrificed after continuous gavage for 6 weeks. The length of tibia was measured on X ray film, the width of tibia growth plate was measured and compared on histological section, and the apoptosis rate of chondrocytes in growth plate was detected by terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL) assay. The growth plate chondrocytes of two groups were isolated and cultured to the third generation in vitro, and the apoptosis rate of chondrocytes was detected by TUNEL assay. The co-localization of mitochondria and autophagy lysosomes in chondrocytes was observed by double fluorescence staining. Western blotting was used to detect the level of mitochondrial marker protein translocate of the outer mitochondrial membrane-20 (Tom-20) and autophagy marker light chain-3 protein (LC-3). The mitophagy of growth plate chondrocytes was observed by transmission electron microscope. Results:Compared with the normal control group, the tibia length of CRF group was shorter [(27.32±5.81) mm vs (35.43±3.61) mm, t=5.226, P<0.001], and the relative width of growth plate in histological section was narrower (0.56±0.19 vs 1.00±0.21, t=6.744, P<0.001). The apoptosis rate of chondrocytes in growth plate in CRF group was higher than that in the normal control group (17.2%±4.8% vs 5.1%±3.4%, t=6.505, P<0.001). The apoptosis rate of chondrocytes cultured in vitro in CRF group was higher than that in the normal control group (11.8%±6.2% vs 3.1%±1.2%, t=4.357, P<0.001). The result of double influorescence staining showed that there was co-localization between mitochondria and autophagy lysosomes in CRF group. Western blotting results showed that the levels of LC-3 protein ( t=8.944, P<0.001) and Tom-20 protein ( t=6.708, P<0.001) in CRF group were lower than those in the normal control group. Conclusion:The level of tibial growth plate chondrocyte mitophagy in young rats with CRF increases, which will lead to a decrease in the number of mitochondria, an increase in the apoptosis and a decrease in the number of chondrocytes, and eventually lead to dysplasia of tibia.