Cardiomyocyte loss is not required for the progression of left ventricular hypertrophy induced by pressure overload in female mice

Morphoquantitative evaluation of the heart of cutia (Dasyprocta agouti) and capybara (Hydrochoerus hydrochaeris)

ABSTRACT The cutia (Dasyprocta agouti) and capybara (Hydrochoerus hydrochaeris ) are hystricomorphic rodents of the Brazilian fauna. The wild animal anatomy is essential to the clinic and surgery practices and conservation programs. This work aimed to evaluate the heart quantitative morphology of the cutia and the capybara. For this, three hearts of cutia and three of capybaras were used from the collection of the Anatomy Sector of Domestic and Wild Animals of the Faculty of Veterinary Medicine and Animal Science of the University of São Paulo. The hearts were weighted and measured with a pachymeter. The left ventricle volume was estimated through the Cavalieri method. The hearts’ mean weight was 16.76g (cutias) and 104.2g (capybaras). The mean values for the axis, width and base dimensions were of the cutia 4.3cm, 3.3cm and 3.3cm and for the capybara were 7.6cm, 6.0cm and 6.1cm, respectively. The mean volume of the left ventricle of the cutia and the capybara was 5.03cm3 and 54.55cm3, respectively. The quantitative results of the hearts were compatible with the average body weight of the rodents. Thus, these numerical data can be applied to veterinary cardiology.

GDF11 Decreases Pressure Overload-Induced Hypertrophy, but Can Cause Severe Cachexia and Premature Death

RATIONALE

Possible beneficial effects of GDF11 (growth differentiation factor 11) on the normal, diseased, and aging heart have been reported, including reversing aging-induced hypertrophy. These effects have not been well validated. High levels of GDF11 have also been shown to cause cardiac and skeletal muscle wasting. These controversies could be resolved if dose-dependent effects of GDF11 were defined in normal and aged animals as well as in pressure overload-induced pathological hypertrophy.

OBJECTIVE

To determine dose-dependent effects of GDF11 on normal hearts and those with pressure overload-induced cardiac hypertrophy.

METHODS AND RESULTS

Twelve- to 13-week-old C57BL/6 mice underwent transverse aortic constriction (TAC) surgery. One-week post-TAC, these mice received rGDF11 (recombinant GDF11) at 1 of 3 doses: 0.5, 1.0, or 5.0 mg/kg for up to 14 days. Treatment with GDF11 increased plasma concentrations of GDF11 and p-SMAD2 in the heart. There were no significant differences in the peak pressure gradients across the aortic constriction between treatment groups at 1 week post-TAC. Two weeks of GDF11 treatment caused dose-dependent decreases in cardiac hypertrophy as measured by heart weight/tibia length ratio, myocyte cross-sectional area, and left ventricular mass. GDF11 improved cardiac pump function while preventing TAC-induced ventricular dilation and caused a dose-dependent decrease in interstitial fibrosis (in vivo), despite increasing markers of fibroblast activation and myofibroblast transdifferentiation (in vitro). Treatment with the highest dose (5.0 mg/kg) of GDF11 caused severe body weight loss, with significant decreases in both muscle and organ weights and death in both sham and TAC mice.

CONCLUSIONS

Although GDF11 treatment can reduce pathological cardiac hypertrophy and associated fibrosis while improving cardiac pump function in pressure overload, high doses of GDF11 cause severe cachexia and death. Use of GDF11 as a therapy could have potentially devastating actions on the heart and other tissues.