Table 5.

circRNAs associated with heart failure/hypertrophy and cardiac fibrosis

CircRNA	miRNA target	Protein target	Action	Cell/Tissue type	Reference
Heart-related circRNA (HRCR)	miR-223	Apoptosis repressor with CARD domain (ARC)	MiR-223 acted as a positive regulator of cardiac hypertrophy. Increased expression of HRCR sequesters free miR‐223	RT-PCR of heart related circRNAs responsive to saline- vs. isoproterenol-infused mice. (n = 7) and transverse aortic constriction or to sham treatment (n = 8) Biotinylated RNA pulldown. AGO2 immunoprecipitation	Wang et al 2016 [148]
CircRNA_000203	miR-26b-5p	Collagen alpha 2(I) (Col1a2) and connective tissue growth factor (CTGF)	Over-expression of circRNA_000203 could eliminate the anti-fibrosis effect of miR-26b-5p in cardiac fibroblasts	CircRNA expression analysis with microarray from mouse myocardium (n = 8 model, n = 8 control Biotinylated RNA pull-down of circRNA/miRNA. Luciferase assay for miRNA/mRNA targets	Tang et al 2017 [144]
CircRNA_010567	miR-141	TGF-β1	CircRNA_010567 promoted myocardial fibrosis via suppressing miR-141 by targeting TGF-β1	Mouse cardiac fibroblasts. CircRNA expression with microarray confirmed with RT-PCR. Luciferase assay for circRNA/miRNA association.	Zhou et al 2017 [150]
Circ-HIPK3	miR-17-3p	Adenylyl cyclase type 6 (ADCY6)	Demonstrated an increase of Adenylate cyclase type 6 (ADCY6) caused by circ-HIPK3 which was ameliorated by miR-17-3p overexpression and vice versa, implicates a circ-HIPK3 – miR-17-3p – ADCY6 axis. Downregulation of circ-HIPK3 can alleviate fibrosis and maintain cardiac function post MI in mice	24 mice divided into 4 groups – normal group (without surgery), control group (without ligation), NC (negative control) group and experiment group. Dual luciferase expression vectors with circ-HIPK3 co-transfected with miR-17-3p	Deng et al 2019 [142]
CircSlc8a1	miR-133a		Adenovirus (AAV9)-mediated RNAi knockdown of circSlc8a1 attenuates cardiac hypertrophy from pressure-overload, whereas forced cardiomyocyte specific overexpression of circSlc8a1 resulted in heart failure	Mouse cardiomyocytes. Biotin-based pull-down of circRNA/miRNA association then qPCR of miRNA and luciferase assay	Lim et al 2019 [62]
CircNFIB (nuclear factor 1 B-type)	miR-433	AZIN1 and JNK1	CircNFIB overexpression reduced cardiac fibroblast proliferation (a process involved with fibrosis) based on TGF-β stimulation), while inhibition of circNFIB promoted fibroblast proliferation. Action via miR-433.	RT-PCR of candidate circRNA expression levels in MI fibrosis mice (n = 5 control, n = 6 MI) and cardiac fibroblasts. miRNA association with dual luciferase reporter assay system.	Zhu et al 2019 [151]
CircHIPK3	miR-29b-3p	α-smooth muscle actin(α-SMA), Collagen type I alpha I (COL1A1, COL3A1	CircHIPK3 silencing reduced cardiac fibroblast proliferation, migration and the upregulation of a-SMA expression levels induced by Ang II in vitro	Mouse cardiac fibroblasts (CFs). No direct evidence for circRNA/miRNA interaction RT-PCR for circRNA expression level. RNA FISH to determine whether circHIPK3 and miR-29b-3p colocalise in CFs.	Ni et al 2019 [143]
CircRNA_000203	miR26b-5p and miR-140-3p	Gata4	CircRNA_000203 was found to be upregulated in the myocardium of cardiac hypertrophy induced mice. Demonstrated that circRNA_000203 sponged miR-26b-5p, −140-3p, abolished the suppression of Gata4 by miR-26b-5p, −140-3p, resulting in the increase of GATA4 in NMVCs	Neonatal mouse ventricular cardiomyocytes (NMVCs). Dual-luciferase assays of circRNA_000203/miR-26b-5p, and miR-140-3p Biotinylated RNA pull-down assay between circRNA_000203/miR-26b-5p,and miR-140-3pincubated	Li et al 2020 [145]
Hsa_circ_0097435	hsa_miR_6799_5P, hsa_miR_5000_5P, hsa_miR_609 and hsa_miR_1294	Unknown	Overexpression of circ_0097435 promoted cardiomyocyte apoptosis, silencing hsa_circ_0097435 inhibited apoptosis	RNA-Seq heart failure patients (n = 5) vs control (n = 4) Dysregulated expression confirmed with qPCR 40 patients with heart failure. RNA-pulldown experiments and AGO2-immunoprecipitation experiments revealed that hsa_circ_0097435 sponged multiple microRNAs	Han et al 2020 [141]