S-Nitrosoglutathione Reductase Deficiency Enhances the Proliferative Expansion of Adult Heart Progenitors and Myocytes Post Myocardial Infarction

BACKGROUND: Mammalian heart regenerative activity is lost before adulthood but increases after cardiac injury. Cardiac repair mechanisms, which involve both endogenous cardiac stem cells (CSCs) and cardiomyocyte cell-cycle reentry, are inadequate to achieve full recovery after myocardial infarction (MI). Mice deficient in S-nitrosoglutathione reductase (GSNOR(-⁄-)), an enzyme regulating S-nitrosothiol turnover, have preserved cardiac function after MI. Here, we tested the hypothesis that GSNOR activity modulates cardiac cell proliferation in the post-MI adult heart.

METHODS AND RESULTS: GSNOR(-⁄-) and C57Bl6/J (wild-type [WT]) mice were subjected to sham operation (n=3 GSNOR(-⁄-); n=3 WT) or MI (n=41 GSNOR(-⁄-); n=65 WT). Compared with WT, GSNOR(-⁄-) mice exhibited improved survival, cardiac performance, and architecture after MI, as demonstrated by higher ejection fraction (P<0.05), lower endocardial volumes (P<0.001), and diminished scar size (P<0.05). In addition, cardiomyocytes from post-MI GSNOR(-⁄-) hearts exhibited faster calcium decay and sarcomeric relaxation times (P<0.001). Immunophenotypic analysis illustrated that post-MI GSNOR(-⁄-) hearts demonstrated enhanced neovascularization (P<0.001), c-kit(+) CSC abundance (P=0.013), and a ≈3-fold increase in proliferation of adult cardiomyocytes and c-kit(+)/CD45(-) CSCs (P<0.0001 and P=0.023, respectively) as measured by using 5-bromodeoxyuridine.

CONCLUSIONS: Loss of GSNOR confers enhanced post-MI cardiac regenerative activity, characterized by enhanced turnover of cardiomyocytes and CSCs. Endogenous denitrosylases exert an inhibitory effect over cardiac repair mechanisms and therefore represents a potential novel therapeutic target.