CITED2 Mediates Mechanical Loading In The Process Of Obesity And Exercise-induced IPFP Tissue Changes

Obesity increases the risk of OA.Proper exercise can alleviate the symptoms of OA.The infrapatellar fat pad(IPFP)is a local adipose tissue.IPFP plays an important role in the development of OA.But the mechanisms of how obesity and exercise affect the changes of IPFP and thus affect the progression of OA are unclear.We found that CITED2 is a mechanically sensitive protein.CITED2 may also play a key role in the process of obesity and exercise affecting IPFP.Aims:(1)Explore the role of Cited2 in the pathological changes of IPFP caused by obesity.(2)Explore the role of Cited2 in the process of IPFP tissue changes induced by exercise.(3)Figure out of mechanism of how Cited2 regulates changes in IPFP tissue.Methods:(1)We fed mouse with high-fat diet.We measured body weight,IPFP size,and adipokines expression levels in IPFP tissues in wild-type mice and Cited2+/-mice.(2)We constructed a moderate treadmill exercise model of the mouse fed with a high-fat diet.The body weight,IPFP size,adipokines and PGC-1α expression levels were measured in both wild-type mice and Cited2+/-mice.(3)We knocked out Cited2 gene and over-expressed PGC-1α in human IPFP cells.In order to find the mechanism,we measured expression of Cited2,PGC-1α and adipokines in IPFP cells.(4)We knocked out the Cited2 gene in human IPFP cells,and used a microfluidic control system to mimic the physiological stress on IPFP cells.We detected the expression of Cited2,PGC-1α and adipokines in IPFP cells.Results:(1)The weight gain of the high-fat diet group was significantly higher.In the high-fat diet group,the increase in body weight of Cited2+/-mice was significantly higher.The volume of IPFP tissue,the expression of adipokines and MMP13 in IPFP tissues significantly increased in Cited2+/-mice.(2)Moderate exercise reduced the IPFP size,the expression of adipokines in IPFP tissues in WT group.Moderate exercise reduced the expression of Cited2 in IPFP tissue,and increased the expression of adipokines in IPFP tissues in Cited2+/-mice.(3)We knocked out Cited2 gene and over-expressed PGC-1α in human IPFP cells.The down-regulation of Cited2 led to the down-regulation of PGC-1α and the up-regulation of adipokines.The over-expression of PGC-1α led to the down-regulation adipokines,but it did not affect the expression of Cited2.(4)In human IPFP cells,moderate mechanical stimulation up-regulated the expression of PGC-1α and down-regulate the expression of adipokines.After knocked out the Cited2 gene,mechanical stimulation down-regulates the expression of PGC-1α,which in turn up-regulated the expression of adipokines.Conclusions:(1)Cited2 is a mechanical stress response gene involved in the regulation of obesity and exercise in IPFP tissues.(2)Obesity and exercise regulate the expression of adipokines in IPFP through the Cited2/PGC-1α pathway,which in turn affects the progression of OA.(3)The Cited2 gene is a potential therapeutic target for the treatment of knee OA.