Cold acclimation alters the connective tissue content of the zebrafish (Danio rerio) heart

Abstract

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.

Cold acclimation increases cardiac myofilament function and ventricular pressure generation in trout

“…Previous studies have reported similar results in trout and zebrafish (Farrell et al, 1988;Klaiman et al, 2011;Johnson et al, 2014), and we have suggested that such a decrease in compact myocardium helps to maintain cardiac compliance at low temperatures (Johnson et al, 2014). Such an effect should translate into the heart generating lower diastolic pressures compared with a heart with more compact myocardium when measured at the same temperature, yet we observed no difference in the mean diastolic pressures between the ventricles from the 4°C-and 17°C-acclimated males.…”

“…These findings support the hypothesis, mentioned above, that the thickness of the compact myocardium plays a role in regulating the compliance of the ventricle. It has also been suggested that an increase in collagen content in the compact myocardium plays a role in regulating ventricular compliance (Johnson et al, 2014). However, while there was significantly more collagen in the compact myocardium of the female fish acclimated to 11°C than in males from the same acclimation group, the diastolic pressure was higher in the males.…”

Fish embryos on land: terrestrial embryo deposition lowers oxygen uptake without altering growth or survival in the amphibious fishKryptolebias marmoratus

“…Embryos were embedded in Shandon Cryomatrix resin (Fisher Scientific, Mississauga, ON, Canada) and cryosectioned in 10 µm thick sections. Sections were either stained routinely with hematoxylin and eosin to observe basic chorion morphology, or stained with the collagen-specific dye Picrosirius Red to observe just the collagen component of the chorion using the method of Johnson et al (2014).…”

Generating an In Vitro 3D Cell Culture Model from Zebrafish Larvae for Heart Research

“…2). The adult ZF heart showed typical mature muscle organisation (Johnson et al, 2014) with a predominantly spongy atrial and ventricular myocardium and a small outer compact layer surrounding the ventricle ( Fig. 2A).…”