Angiogenesis induced by photodynamic therapy in normal rat brains.
Angiogenesis promotes tumor growth and invasiveness in brain. Because brain injury often induces expression of angiogenic-promoting molecules, we hypothesize that oxidative insult induced by photodynamic therapy (PDT) could lead to an endogenous angiogenic response, possibly diminishing the efficacy of PDT treatment of tumors. Therefore, we sought to establish whether PDT induced an angiogenic response within the nontumored brain. PDT using Photofrin as a sensitizer at an optical dose of 140 J/cm2 was performed on normal rat brain (n = 30). Animals were sacrificed at 24 h, and 1, 2, 3 and 6 weeks after PDT treatment. Fluorescein isothiocyanatedextran perfusion was performed, and brains were fixed for immunohistological study. Immunostaining revealed that vascular endothelial growth factor (VEGF) expression increased within the PDT-treated hemisphere 1 week after treatment and remained elevated for 6 weeks. Three-dimensional morphologic analysis of vasculature within PDT-treated and contralateral brain demonstrated PDT-induced angiogenesis, as indicated by a significant increase in vessel connectivity (P < 0.001) concomitant with decreased (P < 0.05) mean segment length compared with vessels within the contralateral hemisphere. Volumetric measurement of angiogenic regions indicate that neovascular expansion continued for 4 weeks after PDT. These data demonstrate that PDT induces VEGF expression and neovascularization within normal brain. Because angiogenesis promotes growth and invasiveness of tumor, antagonizing this endogenous angiogenic response to PDT may present a practical means to enhance the efficacy of PDT.
Henry Ford Health Sciences Center, Neurology Department, Detroit, MI 48202, USA.
Feng
F
Jiang
Zheng Gang
ZG
Zhang
Mark
M
Katakowski
Adam M
AM
Robin
Michelle
M
Faber
Fan
F
Zhang
Michael
M
Chopp
D043925:Angiogenesis Inducing Agents; D000818:Animals; D001921:Brain / Q000098:blood supply* / Q000187:drug effects / Q000473:pathology / Q000528:radiation effects; D017323:Dihematoporphyrin Ether / Q000494:pharmacology; D007150:Immunohistochemistry; D007834:Lasers; D009369:Neoplasms / Q000098:blood supply / Q000188:drug therapy / Q000209:etiology / Q000473:pathology; D009389:Neovascularization, Pathologic / Q000209:etiology*; D010778:Photochemotherapy / Q000009:adverse effects* / Q000379:methods*; D017319:Photosensitizing Agents / Q000494:pharmacology; D051381:Rats; D011916:Rats, Inbred F344; D042461:Vascular Endothelial Growth Factor A / Q000235:genetics / Q000378:metabolism
D043925:Angiogenesis Inducing Agents; D017319:Photosensitizing Agents; D042461:Vascular Endothelial Growth Factor A; D017323:Dihematoporphyrin Ether