Fibulin‐5 null mice with decreased arterial compliance maintain normal systolic left ventricular function, but not diastolic function during maturation

The large arteries serve as compliant vessels that store energy during systole and return it during diastole. This function is made possible by the elastic fibers in the arterial wall that are assembled during late embryonic and early postnatal development from various proteins, including fibulin‐5. Mice and humans with insufficient amounts of fibulin‐5 have reduced arterial compliance as adults. Reduced compliance of the large arteries is correlated with hypertension, reduced cardiac function, and an increased risk of death from cardiac and cardiovascular disease. The goal of this study was to quantify arterial compliance, blood pressure, and left ventricular (LV) function from early postnatal development to young adulthood in fibulin‐5 null (Fbln5−/−) mice to determine the effects of reduced arterial compliance during this critical period of elastic fiber assembly. We find that ascending aorta compliance is reduced as early as postnatal day (P) 7 and carotid artery compliance is reduced by P21 in Fbln5−/− mice. We did not find significant increases in systolic blood pressure by P60, but pulse pressures are increased by P21 in Fbln5−/− mice. LV systolic function, as measured by ejection fraction and fractional shortening, is unaffected in Fbln5−/− mice. However, LV diastolic function, as measured by tissue Doppler imaging, is compromised at all ages in Fbln5−/− mice. We propose that Fbln5−/− mice represent a suitable model for further studies to determine mechanistic relationships between arterial compliance and LV diastolic function.