Johnson Amy C, Turko Andy J, Klaiman Jordan M, Johnston Elizabeth F, Gillis Todd E
Department of Integrative Biology, University of Guelph, Guelph, ON N1G 2W1, Canada.
Department of Integrative Biology, University of Guelph, Guelph, ON N1G 2W1, Canada
J Exp Biol. 2014 Jun 1;217(Pt 11):1868-75. doi: 10.1242/jeb.101196. Epub 2014 Feb 27.
Thermal acclimation can alter cardiac function and morphology in a number of fish species, but little is known about the regulation of these changes. The purpose of the present study was to determine how cold acclimation affects zebrafish (Danio rerio) cardiac morphology, collagen composition and connective tissue regulation. Heart volume, the thickness of the compact myocardium, collagen content and collagen fiber composition were compared between control (27°C) and cold-acclimated (20°C) zebrafish using serially sectioned hearts stained with Picrosirius Red. Collagen content and fiber composition of the pericardial membrane were also examined. Cold acclimation did not affect the volume of the contracted heart; however, there was a significant decrease in the thickness of the compact myocardium. There was also a decrease in the collagen content of the compact myocardium and in the amount of thick collagen fibers throughout the heart. Cold-acclimated zebrafish also increased expression of the gene transcript for matrix metalloproteinase 2, matrix metalloproteinase 9, tissue inhibitor of metalloproteinase 2 and collagen Type I α1. We propose that the reduction in the thickness of the compact myocardium as well as the change in collagen content may help to maintain the compliance of the ventricle as temperatures decrease. Together, these results clearly demonstrate that the zebrafish heart undergoes significant remodeling in response to cold acclimation.
热适应能够改变许多鱼类的心脏功能和形态，但对于这些变化的调节机制却知之甚少。本研究的目的是确定冷适应如何影响斑马鱼（Danio rerio）的心脏形态、胶原蛋白组成和结缔组织调节。使用天狼星红染色的连续切片心脏，比较了对照（27°C）和冷适应（20°C）斑马鱼的心脏体积、致密心肌厚度、胶原蛋白含量和胶原纤维组成。还检查了心包膜的胶原蛋白含量和纤维组成。冷适应并未影响收缩期心脏的体积；然而，致密心肌的厚度显著降低。整个心脏中致密心肌的胶原蛋白含量和粗胶原纤维的数量也有所减少。冷适应的斑马鱼还增加了基质金属蛋白酶2、基质金属蛋白酶9、金属蛋白酶组织抑制剂2和I型胶原蛋白α1基因转录本的表达。我们认为，随着温度降低，致密心肌厚度的减少以及胶原蛋白含量的变化可能有助于维持心室的顺应性。总之，这些结果清楚地表明，斑马鱼的心脏在冷适应过程中会发生显著的重塑。
