Effects of irradiation on brain vasculature using an in situ tumor model

Int J Radiat Oncol Biol Phys. 2012 Mar 1;82(3):1075-82. doi: 10.1016/j.ijrobp.2011.06.1984. Epub 2011 Dec 22.


Purpose: Damage to normal tissue is a limiting factor in clinical radiotherapy (RT). We tested the hypothesis that the presence of tumor alters the response of normal tissues to irradiation using a rat in situ brain tumor model.

Methods and materials: Intravital microscopy was used with a rat cranial window to assess the in situ effect of rat C6 glioma on peritumoral tissue with and without RT. The RT regimen included 40 Gy at 8 Gy/day starting Day 5 after tumor implant. Endpoints included blood-brain barrier permeability, clearance index, leukocyte-endothelial interactions and staining for vascular endothelial growth factor (VEGF) glial fibrillary acidic protein, and apoptosis. To characterize the system response to RT, animal survival and tumor surface area and volume were measured. Sham experiments were performed on similar animals implanted with basement membrane matrix absent of tumor cells.

Results: The presence of tumor alone increases permeability but has little effect on leukocyte-endothelial interactions and astrogliosis. Radiation alone increases tissue permeability, leukocyte-endothelial interactions, and astrogliosis. The highest levels of permeability and cell adhesion were seen in the model that combined tumor and irradiation; however, the presence of tumor appeared to reduce the volume of rolling leukocytes. Unirradiated tumor and peritumoral tissue had poor clearance. Irradiated tumor and peritumoral tissue had a similar clearance index to irradiated and unirradiated sham-implanted animals. Radiation reduces the presence of VEGF in peritumoral normal tissues but did not affect the amount of apoptosis in the normal tissue. Apoptosis was identified in the tumor tissue with and without radiation.

Conclusions: We developed a novel approach to demonstrate that the presence of the tumor in a rat intracranial model alters the response of normal tissues to irradiation.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Apoptosis
  • Blood-Brain Barrier / physiology
  • Blood-Brain Barrier / radiation effects*
  • Brain / blood supply
  • Brain / metabolism
  • Brain / radiation effects*
  • Brain Neoplasms / blood supply
  • Brain Neoplasms / chemistry
  • Brain Neoplasms / pathology
  • Brain Neoplasms / radiotherapy*
  • Cell Adhesion / radiation effects
  • Coloring Agents / pharmacokinetics
  • Dose Fractionation, Radiation
  • Endothelium, Vascular / physiology
  • Endothelium, Vascular / radiation effects*
  • Glioma / blood supply
  • Glioma / chemistry
  • Glioma / pathology
  • Glioma / radiotherapy*
  • Gliosis / pathology
  • Leukocyte Rolling / physiology
  • Leukocyte Rolling / radiation effects
  • Leukocytes / physiology
  • Leukocytes / radiation effects
  • Male
  • Models, Animal
  • Permeability / radiation effects
  • Rats
  • Rats, Wistar
  • Tumor Burden / radiation effects
  • Vascular Endothelial Growth Factor A / analysis


  • Coloring Agents
  • Vascular Endothelial Growth Factor A