VEGF dose regulates vascular stabilization through Semaphorin3A and the Neuropilin-1+ monocyte/TGF-β1 paracrine axis. (2015)
Figure 7

Sema3A restores NEM recruitment and accelerates vascular stabilization, without affecting the amount of induced angiogenesis

A–C Mice, implanted with myoblasts expressing low (V Low) or medium (V Med) VEGF levels, were treated on days 4 and 6 after cell implantation with intramuscular injections of Sema3A-Fc (0.1 or 10 mg/kg of average muscle tissue weight), or with control Fc protein. (A) Quantification of the number of NEM/cm of vessel length in sites of new angiogenesis after 1 week. Data represent the mean ± SEM of individual images (n) acquired from 3 to 5 muscles/group: V Low Fc, n = 21; V Low 0.1 mg/kg, n = 22; V Low 10 mg/kg, n = 28; V Med Fc, n = 20; V Med 0.1 mg/kg, n = 30; V Med 10 mg/kg, n = 25; **P < 0.01 and ***P < 0.001 by Kruskal–Wallis analysis with Dunn’s multiple comparisons test: V Low Fc versus V Low 10 mg/kg P = 0.0027; V Med Fc versus V Med 0.1 mg/kg P = 0.001; V Med Fc versus V Med 10 mg/kg P < 0.0001. (B) Quantification of vessel length density (VLD) in treated muscles after 1 week. Data represent the mean ± SEM of individual images (n) acquired from 3 to 4 muscles/group: V Low Fc, n = 8; V Low 0.1 mg/kg, n = 20; V Low 10 mg/kg, n = 18; V Med Fc, n = 8; V Med 0.1 mg/kg, n = 23; and V Med 10 mg/kg, n = 27. Data were subjected to Kruskal–Wallis analysis with Dunn’s multiple comparisons test, and no significant differences were detected. (C) Vascular stabilization rate was determined 2 weeks after cell implantation by measuring vessel length density after abrogation of VEGF signaling by VEGF-Trap. Treatment with 10 mg/kg Sema3A-Fc did not affect the stabilization of angiogenesis induced by low VEGF, but significantly increased the resistant fraction of vessels induced by medium VEGF. Data represent the mean ± SEM of individual images (n) acquired from 3 to 4 muscles/group: V Low Fc, n = 32; V Low Sema3A, n = 14; V Med Fc, n = 28; V Med Sema3A, n = 33; *P < 0.05 by one-way ANOVA with Bonferroni multiple comparisons test: V Med Fc versus V Med Sema3A P = 0.0458.

D–F Mice received intramuscular injections of adenovirus expressing VEGF (AdVIC) or CD8 control (AdCD8) and were treated on days 4 and 6 after vector delivery with intramuscular injections of Sema3A-Fc (10 mg/kg of average muscle tissue weight) or control Fc protein. (D) Immunofluorescence staining of endothelium (CD31, in red), pericytes (NG2, in green), smooth muscle cells (α-SMA, in cyan), and nuclei (DAPI, in blue), showing vessel density and morphology 1 week after injection of adenoviral vectors alone (no treatment) or after 3 weeks and with Fc or Sema3A-Fc treatment. Scale bar = 50 μm. (E) Quantification of vessel length density (VLD) on the same samples shows that treatment with Sema3A-Fc accelerated stabilization of vessels induced by transient and uncontrolled VEGF expression. Data represent the mean ± SEM of individual images (n) acquired from 3 to 4 muscles/group: Uninjected muscles, n = 72; AdCD8 1 week, n = 68; AdVIC 1 week, n = 53; AdVIC+Fc 3 weeks, n = 78; AdVIC+Sema3AFc 3 weeks, n = 91; **P < 0.01 and ***P < 0.001 by Kruskal–Wallis analysis with Dunn’s multiple comparisons test: AdCD8 1 week versus AdVIC+Fc 3 weeks P = 0.0037; all other comparisons indicated P < 0.0001. (F) Immunofluorescence staining of endothelial cells (CD31, in red) and NEM (CD11b, in green) on frozen sections of muscles 3 weeks after injection of adenoviral vectors and with Fc or Sema3A-Fc treatment. White arrows indicate NEM. Scale bar = 50 μm.

Source data are available online for this figure.