Biomedicine Discovery Institute and the Department of Anatomy and Developmental Biology, Monash University, Clayton, Victoria, Australia.
Department of Medical Imaging and Radiation Sciences, Monash University, Clayton, Victoria, Australia.
J Physiol. 2018 Dec;596(23):5965-5975. doi: 10.1113/JP275654. Epub 2018 Apr 6.
Preterm birth occurs when the heart muscle is immature and ill-prepared for the changes in heart and lung function at birth. MRI imaging studies show differences in the growth and function of the heart of young adults born preterm, with the effects more pronounced in the right ventricle. The findings of this study, conducted in sheep, showed that following moderate preterm birth the right ventricular wall was thinner in adulthood, with a reduction in the number and size of the heart muscle cells; in addition, there was impaired blood flow in the main artery leading from the right ventricle to the lungs. The findings indicate that being born only a few weeks early adversely affects the cellular structure of the right ventricle and blood flow to the lungs in adulthood. The reduced number of heart muscle cells has the potential to deleteriously affect right ventricular growth potential and function.
Preterm birth prematurely exposes the immature heart to the haemodynamic transition at birth, which has the potential to induce abnormal cardiac remodelling. Magnetic resonance imaging studies in young adults born preterm have shown abnormalities in the gross structure of the ventricles (particularly the right ventricle; RV), but the cellular basis of these alterations is unknown. The aim of this study, conducted in sheep, was to determine the effect of moderate preterm birth on RV cellular structure and function in early adulthood. Male singleton lambs were delivered moderately preterm (132 ± 1 days; n = 7) or at term (147 ± 1 days; n = 7). At 14.5 months of age, intra-arterial blood pressure and heart rate were measured. Pulmonary artery diameter and peak systolic blood flow were determined using ultrasound imaging, and RV stroke volume and output calculated. Cardiomyocyte number, size, nuclearity and levels of cardiac fibrosis were subsequently assessed in perfusion-fixed hearts using image analysis and stereological methods. Blood pressure (systolic, diastolic and mean), heart rate, levels of myocardial fibrosis and RV stroke volume and output were not different between groups. There was, however, a significant reduction in RV wall thickness in preterm sheep, and this was accompanied by a significant reduction in peak systolic blood flow in the pulmonary artery and in RV cardiomyocyte number. Cellular changes in the RV wall and reduced pulmonary artery blood flow following preterm birth have the potential to adversely affect cardiac and respiratory haemodynamics, especially when the cardiovascular system is physiologically or pathologically challenged.
早产儿的心肌不成熟，无法为出生时心肺功能的变化做好准备。磁共振成像研究表明，早产儿成年人心脏的生长和功能存在差异，右心室的影响更为明显。这项在绵羊中进行的研究结果表明，中度早产儿出生后，成年人心肌壁会变薄，心肌细胞数量和大小减少；此外，从右心室通向肺部的主要动脉的血流也会受损。这些发现表明，仅早产几周就会对成年人心肌右心室的细胞结构和向肺部的血流产生不利影响。心肌细胞数量减少有可能对右心室的生长潜力和功能产生有害影响。
早产儿的心肌过早地暴露于出生时的血液动力学转变中，这有可能导致心脏异常重塑。早产儿成年人心室（尤其是右心室；RV）大体结构的磁共振成像研究显示存在异常，但这些改变的细胞基础尚不清楚。本研究在绵羊中进行，旨在确定中度早产儿出生对成年早期 RV 细胞结构和功能的影响。雄性单胎羔羊在 132±1 天（n=7）或足月（147±1 天；n=7）时分娩。在 14.5 个月大时，测量了动脉内血压和心率。使用超声成像测量肺动脉直径和收缩期血流峰值，并计算 RV 每搏量和输出量。随后使用图像分析和体视学方法评估灌注固定心脏中的心肌细胞数量、大小、核数和心肌纤维化水平。两组间血压（收缩压、舒张压和平均压）、心率、心肌纤维化水平以及 RV 每搏量和输出量无差异。然而，早产儿的 RV 壁厚度显著降低，并且肺动脉收缩期血流峰值和 RV 心肌细胞数量也显著降低。早产出生后 RV 壁的细胞变化和肺动脉血流减少有可能对心脏和呼吸血液动力学产生不利影响，尤其是当心血管系统受到生理或病理挑战时。
