Figure 2.

Ad Overexpression of VEGF-B₁₈₆ Stimulates Nerve Growth in Normoxic Adult Pig Myocardium with VEGFRs Modulating Nerve Growth

(A and B) Nerve density (A) and structure (B) were normal in AdLacZ-transduced pig myocardium (n = 4) 6 days after GT. Nerves ran parallel to muscle fibers, and a few branching points were observed (arrows). (C) AdVEGF-B₁₈₆ induced rapid nerve sprouting and increased nerve density in the myocardium 6 days after GT (n = 5). (D) Nerve endings appeared tortuous, and more branching points were observed in AdVEGF-B₁₈₆-transduced hearts (arrows). Nerve branching was apparent, especially in the connective tissue surrounding blood vessels (insert). The role of known VEGF-B receptors VEGFR-1 and Nrp-1 were studied using co-transductions of adenovirally overexpressed soluble receptors. (E) Overexpression of soluble VEGFR-1 (AdsVEGFR-1) in combination with AdVEGF-B_186, did not significantly alter nerve density in the myocardium as compared to AdVEGF-B₁₈₆ alone, suggesting that the induction of nerve growth was not mediated by native, cell-membrane-bound VEGFR-1. (F) Nerve morphology was also comparable to AdVEGF-B₁₈₆. (G) In contrast, co-transduction with AdsNrp-1 increased nerve density in the GT area as compared to VEGF-B₁₈₆ alone. (H) AdsNrp-1 also increased nerve ending branching, and more transversally running nerve endings were visible. (I) Quantification of nerve density in the transduced myocardium revealed that both AdVEGF-B₁₈₆ and AdVEGF-B₁₈₆+AdsVEGFR-1 increased nerve density in the myocardium as compared to AdLacZ control (1.8-fold, p < 0.05 in both groups). AdsVEGFR-1 did not significantly alter the nerve density as compared to AdVEGF-B₁₈₆ alone. In contrast, AdsNrp-1 significantly increased nerve density as compared to AdVEGF-B₁₈₆ alone (1.8-fold, p < 0.001). NS, not significant.