Feline hypertrophic cardiomyopathy: Does the microRNA‐mRNA regulatory network contribute to heart sarcomeric protein remodelling?

Abstract Feline primary hypertrophic cardiomyopathy (HCM) is an intrinsic myocardial disease characterized by concentric hypertrophy of the left ventricle. In the present study, we investigated the microRNA‐mRNA regulatory network in feline myocardial tissue affected by primary (HCMI) and secondary HCM (HCMII). MRNA expression levels of sarcomeric genes, including, TNNT2 , TNNI3 , MYH7 , MYBPC3 , TPM1 and ACTC1 were assessed in the FFPE myocardial tissues. FFPE tissues from healthy cats were sequenced by the NGS, to explore, in the entire non‐deposited miRNome, the expression level of microRNAs targeting the complementary sequences of selected sarcomeric mRNAs. The sarcomeric genes TNNT2 , MYH7 , MYBPC3 and TPM1 showed a statistically significant upregulation in HCMI compared to HCMII ( p < .01), except ACTC1 which was downregulated ( p < .01); TNNI3 showed no statistically significant difference. In HCMII miR‐122‐5p, miR‐338‐3p, miR‐484, miR‐370‐3p, miR‐92b‐3p, miR‐375 and miR‐370‐3p showed a significant upregulation ( p < .01) compared to control. The exception was miR‐30a‐5p which showed downregulation. Worthy of note is the 4‐fold higher expression of miR‐370‐3p, a key regulator of MYBPC3 , in HMCI compared to HMCII. This research does not solve the aetiological mystery of HCM, but it may help to find a way to help diagnose and define the prognosis of HCM in cats.