Objective

2

To investigate the biological effect of circ_0036176 on myocardial fibrosis.

Methods

2

Levels of circ_0036176 and its host gene Myo9a were determined by real-time quantitative polymerase chain reaction （RT-qPCR） assay in human myocardial tissue， including 22 healthy organ donors and 26 patients with heart failure （HF）. A cell model of angiotensin Ⅱ （Ang-Ⅱ）-induced fibrosis in human atrial fibroblasts （HAFs） was achieved. To test the typical ring structure of circ_0036176， actinomycin D treatment and RNase R exonuclease digestion were performed. The expression of fibrosis-related gene in HAFs with overexpression of circ_0036176 was detected at mRNA and protein level. To select miRNAs that can effectively bind to circ_0036176， dual luciferase reporter gene assay and RNA antisense purification assay （RAP） were conducted， respectively. The neonatal mouse cardiac fibroblasts （mCFs） were used to study whether mir-218-5p mediates the effect of circ_0036176 on myocardial fibrosis phenotype.

Results

2

The expression of circ_0036176 was up-regulated in the myocardium of HF patients （

P

＜0.001）， and the expression of circ_0036176 and the host gene Myo9a was down-regulated in Ang-Ⅱ-induced HAFs （

P

＜0.01）. In response to actinomycin D treatment and RNase R exonuclease digestion， circ_0036176 was more stable than Myo9a mRNA. The expression of COL1A1， COL3A1， TGF-β1 and ACTA2 was down-regulated in HAFs with overexpression of circ_0036176 （

P

＜0.05）. Results of dual luciferase reporter gene assay and RAP assay confirmed the interaction between miR-218-5p and circ_0036176. Overexpression of miR-218-5p could promote the expression of fibrosis-related genes， and attenuate the inhibitory effect of circ_0036176 on cardiac fibrosis.

Conclusions

2

Circ_0036176 is up-regulated in the myocardium of HF patients， and circ_0036176 inhibits the expression of fibrosis-related gene through sponging miR-218-5p in CFs.