Abstract: BACKGROUND: Defective outgrowth of chondrocyte mitophagy causes degenerative chondrocyte pathological changes such as apoptosis and matrix loss. 
OBJECTIVE: To investigate the effects and possible mechanism of Juanbi Decoction-containing serum on interleukin-1β-induced inflammatory response and apoptosis of rat knee joint chondrocytes. 
METHODS: Fifty male Sprague-Dawley rats were randomly given saline, Juanbi Decoction in low, medium and high doses (1.24, 2.48 and 4.96 g/kg), and celecoxib (positive drug) group. Drug-containing serum was obtained by continuous gavage for 2 weeks. (1) Chondrocytes were isolated and randomly divided into control group, interleukin-1β group, Juanbi Decoction low, medium and high dose containing serum groups and positive drug serum group. Cell counting kit-8 assay was used to detect cell viability; immunofluorescence double staining was used to detect mitophagy level; immunofluorescence was used to detect the phosphorylated AMP-activated protein kinase level; western blot was used to detect the expression of PTEN induced putative kinase 1/Parkin pathway-related protein and cleaved caspase-3; and ELISA was used to detect inflammatory factor level. (2) PTEN induced putative kinase 1 siRNA and Compound C were used for intervention to explore the role of AMP-activated protein kinase/PTEN induced putative kinase 1/Parkin pathway in the regulation of mitophagy by Juanbi Decoction-containing serum. 
RESULTS AND CONCLUSION: (1) Compared with the control group, chondrocyte survival, type II collagen, phosphorylated AMP-activated protein kinase, PTEN induced putative kinase 1, Parkin, and microtubule-associated proteins 1 light chain 3 protein levels, and mitophagy levels were significantly lower in the interleukin-1β group (P < 0.05), while cleaved caspase-3 protein levels, interleukin-6, interleukin-8 and tumor necrosis factor-α levels were significantly higher (P < 0.05). Compared with the interleukin-1β group, opposite changes in all the above indexes were observed in Juanbi Decoction low, medium and high dose containing serum groups and positive drug serum group (P < 0.05). (2) PTEN induced putative kinase 1 siRNA significantly inhibited the effect of Juanbi Decoction-containing serum on mitophagy in interleukin-1β-treated chondrocytes and reduced the protective effect of Juanbi Decoction-containing serum on interleukin-1β-induced inflammation and apoptosis in chondrocytes; Compound C reversed the effect of Juanbi Decoction-containing serum on the PTEN induced putative kinase 1/Parkin signaling pathway in interleukin-1β-treated chondrocytes. To conclude, Juanbi Decoction-containing serum inhibits chondrocyte inflammation and apoptosis by affecting the level of mitochondrial autophagy, thereby attenuating interleukin-1β-induced chondrocyte degradation by a mechanism that may be related to the regulation of the AMP-activated protein kinase/PTEN induced putative kinase 1/Parkin pathway.

中国组织工程研究杂志出版内容重点：组织构建；骨细胞；软骨细胞；细胞培养；成纤维细胞；血管内皮细胞；骨质疏松；组织工程

Key words: Juanbi Decoction, chondrocyte, mitophagy, adenylate-activated protein kinase, AMPK, PTEN induced putative kinase 1/Parkin