Basic Fibroblast Growth Factor Ameliorates Endothelial Dysfunction in Radiation-Induced Bladder Injury

Abstract

This study was designed to explore the effect of basic fibroblast growth factor (bFGF) on radiation-induced endothelial dysfunction and histological changes in the urinary bladder. bFGF was administrated to human umbilical vein cells (HUVEC) or urinary bladder immediately after radiation. Reduced expression of thrombomodulin (TM) was indicated in the HUVEC and urinary bladder after treatment with radiation. Decreased apoptosis was observed in HUVEC treated with bFGF. Administration of bFGF increased the expression of TM in HUVEC medium, as well as in the urinary bladder at the early and delayed phases of radiation-induced bladder injury (RIBI). At the early phase, injection of bFGF increased the thickness of urothelium and reduced inflammation within the urinary bladder. At the delayed phase, bFGF was effective in reducing fibrosis within the urinary bladder. Our results indicate that endothelial dysfunction is a prominent feature of RIBI. Administration of bFGF can ameliorate radiation-induced endothelial dysfunction in urinary bladder and preserve bladder histology at early and delayed phases of RIBI.

Figure 1

The effect of bFGF on apoptosis and TM expression of HUVEC exposed to radiation. (a)–(c) Representative images of TUNEL staining of each experimental group. White bar indicates 100 μm. (d) Percentage of Annexin-V/PI double stained apoptotic cells determined by using flow cytometry. (e) The effects of bFGF on the TM expression in the medium of radiation treated HUVEC at different time points. NS, no significance, ^∗ P < 0.05, NS: no significance. Bars represent mean ± SD from 3 independent experiments.

Figure 2

The effect of bFGF on urothelium at the early phase of RIBI. (a)–(c) Representative images of HE stained urinary bladder sections. Magnification is 40x. High magnifications in the boxed area further show the thickness of urothelium in each group ((a)′–(c)′). (d) Results of the thickness of the urothelium from each experimental group. ^∗ P < 0.05, NS: no significance.

Figure 3

The effect of bFGF on inflammation in urinary bladder at the early phase of RIBI. (a)–(c) Representative images of bladder tissue immunohistologically stained with MPO. Black bar indicates 50 μm. (d) Results of the MPO activity in bladder tissue. ^∗ P < 0.01 compared with the R group. (e)-(f) Expressions of IL-1β (e) and TNF-α (f) in bladder tissue indicated by ELISA. ^∗ P < 0.05.

Figure 4

The effect of bFGF on bladder fibrosis at the delayed phase of RIBI. (a) Representative images of blood vessels in the submucosa of each experimental group. White bar indicates 100 μm. (b) Representative images of Masson's trichrome staining of each experimental group. Results of the number of blood vessels in the submucosa (c) and the ratio between smooth muscle and collagen (d) in each group. ^∗ P < 0.05.

Figure 5

The effect of bFGF on TM expression in urinary bladder treated with radiation. (a)-(b) TM expression in urinary bladder 1 week (a) and 12 weeks (b) after exposure to radiation in each experimental group. ^∗ P < 0.01 compared with the R group; ^# P < 0.05 compared with the R group. (c) Representative image of TM and α-SMA double stained urinary bladder section. (d) Results of the percentage of TM positive blood vessels within the urinary bladder. ^∗ P < 0.05.