In utero alcohol exposure alters the collagen profile in neonatal hearts and leads to cardiac dysfunction

Abstract

Fetal alcohol syndrome is often associated with congenital heart defects. Our studies focus on the role of cardiac fibroblasts in the developing heart, and how they are affected by prenatal ethanol exposure. Fibroblasts are the most numerous cardiac cell type and play an essential role in development of the heart. They are responsible for synthesis of the extracellular matrix, which provides the scaffold for heart muscle. Our lab has previously shown that ethanol exposure in adult hearts promote fibroblast activation and transition into myofibroblasts. Based on this, we believe that in utero ethanol exposure causes alterations in fibroblast function that could contribute to dysregulation in collagen synthesis and impaired scaffolding of the neonatal heart. Therefore, we hypothesize that in utero ethanol activates neonatal cardiac fibroblasts, which leads to a profibrotic phenotype and cardiac dysfunction.To investigate these effects, we performed in utero EtOH administration in wildtype dams. Pregnant mice were intraperitoneally injected with 2.9 g EtOH/kg body weight to achieve a blood ethanol content of approximately 0.26 on gestation day 6.75. On neonatal day 5, pups were weighed prior to sacrifice. Body weight was decreased in the WT+EtOH pups, which is a hallmark of fetal alcohol syndrome. Hearts were homogenized, and Western Blot analysis was performed to determine protein expression. Collagen I decreased in ethanol exposed neonates, but collagen III expression was significantly increased, so the collagen I/III ratio was decreased. Collagen I gives hearts a more tensile and stiff phenotype, whereas collagen III gives a more compliant phenotype; therefore, a decrease in collagen I/III ratio would correlate with a dilated heart. Subsequently, this can significantly impair diastolic function. Overall, our data shows a correlation between prenatal ethanol exposure and a profibrotic phenotype in neonatal hearts.We were further interested in assessing whether these changes in collagen translated into changes in cardiac function. Left ventricular (LV) chamber dimension and function were assessed in sedated animals on neonatal day 5 using echocardiography. Eccentric index was calculated as a ratio of LV interior diameter and LV posterior wall thickness*2 at diastole and at systole. There was a significant increase in the eccentric index at both systole and diastole in ethanol exposed animals, indicative of LV dilation. This is in agreement with our previous collagen findings, which further supports the possibility of a dilated cardiac phenotype. In analyzing systolic function, LV end systolic volume increased, and both ejection fraction and fractional shortening decreased in the ethanol treated animals. Our functional measurements demonstrate that in utero ethanol exposure decreases collagen I/III protein ratio in neonatal hearts, which ultimately causes a decline in both diastolic and systolic function.Support or Funding InformationSaving Tiny Hearts SocietyThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.