Selected Pathway Analyses to Gain Mechanistic Insights into the Pathogenesis of Feline Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is the most prevalent acquired heart disease in cats and shares many clinical, phenotypical and pathological features with human HCM. Despite its relevance, knowledge on the pathomechanisms underlying the disease is limited. The present study aimed to characterize the molecular phenotypic changes in cardiomyocytes in feline HCM (fHCM) to better understand their contribution to the pathogenesis. To achieve this, the myocardium of the left ventricular free wall of 15 cats with confirmed fHCM and 30 control cats (two age groups: 16 cats 18-month-old, and 14 older adult cats without cardiac disease) were subjected to RT-qPCRs for markers representative of cardiomyocyte function. Overall, all markers were expressed at the highest level in young control cats, and increasing age correlated with decreased expression, regardless of sex. The comparison between the older adult control cats and those with HCM showed increased transcription levels for most markers associated with the disease, and higher expression of all markers in affected male cats compared to females. The constitutive transcription of all markers provides evidence of continuous myocardial adaptation throughout cats' life. The high transcription values in the myocardium of young healthy cats and male cats affected by HCM suggest a particularly high myocardial responsiveness early in life and with HCM and reveal sex as relevant factor in the disease process. These results support the relevance of age and sex in the cardiac response to HCM in feline hearts.