Background & objective: Radiation-induced heart damage is one of the prognostic factors of the patients who had received radiation to the mediastinum. This study was to investigate the correlation of transforming growth factor-beta1 (TGF-beta1) mRNA expression to the radiation response of the heart in rats, in order to provide references for further study on irradiation-induced heart damage.
Methods: Sixty Sprague-Dawley rats were divided into 2 groups: the 30 rats in irradiation group were irradiated with 20 Gy on the heart; the 30 rats in control group received no irradiation. At each time point of the 1st day, the 2nd, 4th, 8th 12th, and 24th week after irradiation, 5 rats in each group were killed. The serum levels of cardiac troponin and isoenzyme of creatine kinase (CK-MB) were detected. The expression of TGF-beta1 mRNA was detected by polymerase chain reaction (PCR). Heart damage was observed with Masson staining under microscope.
Results: The serum level of cardiac troponin was elevated at 24 h after irradiation, and reached the peak at 2 weeks after irradiation, which was significantly higher than that in control group [(0.73+/-0.11) ng/mL vs. (0.11+/-0.04) ng/mL, P<0.05]. There was no significant difference in the serum level of CK-MB between two groups (P>0.05). The expression of TGF-beta1 mRNA was elevated at the 1st day after irradiation, and reached peaks at 2 and 12 weeks after irradiation, which were significantly higher than those in control group [(8.55+/-1.19)x10(-8) microg/mL vs. (1.27+/-0.11)x10(-8) microg/mL, (4.63+/-0.41)x10(-8) microg/mL vs. (1.35+/-0.15)x10(-8) microg/mL, P<0.05]. The proportion of collagen fibers was increased since 2 weeks after irradiation, which was significantly higher than that in control group [(2.87+/-0.37)% vs. (1.14+/-0.55)%, P<0.05]. The expression of TGF-beta1 mRNA was positively correlated to the proportion of collagen fibers in the rat hearts after irradiation (r=0.48, P<0.05).
Conclusions: TGF-beta1 is involved not only in the onset but also in the development of radiation fibrosis. Inhibiting the peak expression of TGF-beta1 mRNA may reduce the radiation-induced damage to the heart.