J Korean Med Sci.  2004 Dec;19(6):879-886. 10.3346/jkms.2004.19.6.879.

Upregulation of VEGF and FGF2 in Normal Rat Brain after Experimental Intraoperative Radiation Therapy

• Kim JH
• Chung YG
• Kim CY
• Kim HK
• Lee HK

• KMID: 1778573
• DOI: http://doi.org/10.3346/jkms.2004.19.6.879

Abstract

The expression of vascular endothelial growth factor (VEGF) and fibroblast growth factor (FGF)2 in the irradiated brain was examined to test how a single high dose radiation, similar to that used for intraoperative radiation therapy given to the normal cerebrum, can affect the vascular endothelium. After a burr hole trephination in the rat skull, the cerebral hemisphere was exposed to a single 10 Gy dose of gamma rays, and the radiation effect was assessed at 1, 2, 4, 6, and 8 weeks after irradiation. His-tological changes, such as reactive gliosis, inflammation, vascular proliferation and necrosis, were correlated with the duration after irradiation. Significant VEGF and FGF2 expression in the 2- and 8-week were detected by enzyme-linked immunosorbent assay quantification in the radiation group. Immunohistochemical study for VEGF was done and the number of positive cells gradually increased over time, compared with the sham operation group. In conclusion, the radiation injuries consisted of radiation necrosis associated with the expression of VEGF and FGF2. These findings indicate that VEGF and FGF2 may play a role in the radiation injuries after intraoperative single high-dose irradiation.

Keyword

Radiotherapy; Vascular Endothelial Growth Factor A; Fibroblast Growth Factor 2; Radiation Injuries, Experimental

MeSH Terms

Animals
Brain/metabolism/pathology/radiation effects
Brain Injuries/etiology/*metabolism/*pathology
Fibroblast Growth Factor 2/*metabolism
Necrosis
Radiation Injuries/*pathology
Radiosurgery/*adverse effects
Rats
Rats, Sprague-Dawley
Up-Regulation/radiation effects
Vascular Endothelial Growth Factor A/*metabolism

Figure

• 

  Fig. 1 Schematic drawing of a burr hole trephination and irradiation. a: diameter of radiation tube, 6 mm; b: distance from Ir-192 source to shield end, 5 mm; c: distance from source to brain surface, 20 mm (Not drawn to scale).

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  Fig. 2 Morphologic changes after irradiation (H&E, ×12). According to the time intervals, loss of cortical thickness is increased and reactive gliosis, proliferation of vascular endothelial cells, and cystic necrosis become prominent. (A) 1 week, (B) 2 weeks, (C) 4 weeks, (D) 6 weeks, (E) 8 weeks.

• 

  Fig. 3 (A) Expression of VEGF according to the time after irradiation. Whereas the level of expression of VEGF was significantly higher than in the right hemisphere(craniectomy site) of the sham operation group at 2 weeks, the expression showed a significant decrease at 1, 4, and 6 weeks (unpaired t-test, p<0.05). As compared with the left hemisphere (non-craniectomy site) of the sham operation group, the concentration of VEGF in the radiation group was significantly increased at 1, 2, 4, 6 and 8 weeks (p<0.05). (B) Although the concentration of VEGF at 8 weeks was higher than at 6 weeks in both groups, there was a significantly steep slope of expression in the radiation group between 6 and 8 weeks (unpaired t-test, p<0.05). a: right hemisphere (craniectomy site) in the radiation group; b: right hemisphere (craniectomy site) in the sham operation group; c: left hemisphere (non-craniectomy site) in the sham operation group. *p<0.05 by unpaired t-test within the radiation group; †p<0.05 by unpaired t-test compared between radiation and sham operation groups; ‡p<0.05 by unpaired t-test compared between right hemisphere of the radiation group and left hemisphere of the sham operation group.

• 

  Fig. 4 (A) Expression of FGF2 according to the time after irradiation. Whereas the level of expression of FGF2 was significantly higher at 2 and 8 weeks than in the right hemisphere (craniectomy site) of the sham operation group, the expression showed a significant decrease at 1, 4, and 6 weeks (unpaired t-test, p<0.05). As compared with the left hemisphere (non-craniectomy site) of the sham operation group, the concentration of FGF2 in the radiation group was significantly increased at 1, 2, 4, 6 and 8 weeks (p<0.05). (B) While the concentration of FGF2 at 8 weeks was lower than that at 6 weeks in the sham operation group, there was a significantly steep incline of expression in the radiation group between 6 and 8 weeks, similar to that in the VEGF study (unpaired t-test, p<0.05). a: right hemisphere (craniectomy site) in the radiation group; b: right hemisphere (craniectomy site) in the sham operation group; c: left hemisphere (non-craniectomy site) in the sham operation group. *p<0.05 by unpaired t-test within the radiation group, †p<0.05 by unpaired t-test compared between radiation and sham operation groups, ‡p<0.05 by unpaired t-test compared between right hemisphere of the radiation group and left hemisphere of the sham operation group.

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  Fig. 5 Immunohistochemical stain for VEGF of rat brain at 1 and 8 weeks after irradiation, ×400. In acute stage, there are no prominent changes in the radiation group compared to the sham operation group. According to the time interval, the cellularity becomes more prominent and stained cell counts are increased markedly in the white matter of the radiation group. (A) 1 week in the control group, (B) 1 week in the radiation group, (C) 8 weeks in the control group, (D) 8 weeks in the radiation group.

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  Fig. 6 The changes of the mean VEGF staining cell counts under ×200 magnification after irradiation. Values are expressed as mean±standard errors. *p<0.05 by one way ANOVA within the radiation group. †p<0.05 by unpaired t-test compared between radiation and sham operation groups.

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