Figure 1.

Genetic Overexpression of VEGF-B Increases Nerve Density in the Female Mouse Heart and Disturbs the Transmural Patterning of Sympathetic Nerve Innervation

GAP 43 staining (brown) was used to detect nerve endings in the mouse myocardium (11 to 20 weeks old). (A) Nerve structure and density were normal in control mice (n = 6). Nerves were mainly located in the epicardium, and density was much lower in the mid-myocardium (asterisk). (B) Nerve fibers (arrows) ran parallel to muscle fibers in the control myocardium, and a few branching points were observed. Nerve distribution was normal, as nerve density was greater in the epicardium (bottom) and became sparser in the mid-myocardium (top). (C) Genetic overexpression of VEGF-B increased the total number of nerve endings (n = 6). Nerve density gradient was disturbed, and nerve fibers were also observed in the mid-myocardium (asterisk). (D) Increased density of nerve endings, aberrant anatomic structure, and increased branching of nerves (arrows) were observed in the αMHC-VEGF-B mice. A normal gradient of nerve density was missing. (E) Nerve density and patterning were not significantly reduced in VEGF-B KO mice, indicating that VEGF-B is not essential for sympathetic patterning during development (n = 6). (F) Nerve morphology in VEGF-B KO mice was normal (arrows). (G) Nerves were visualized using GAP43 immunostaining, and nerve density was calculated from transverse sections. Results are expressed as nerve endings per FOV. Nerve density was significantly increased in αMHC-VEGF-B mice as compared to WT controls (1.9-fold, p < 0.001) but was not significantly different in VEGF-B KO mice; not significant (NS) as compared to WT controls. Scale bars, 100 μm.