Effect Of Recombinant Transforming Growth Factor-β₃on Radiation Pneumonitis Of Mice

Radiation therapy is one common method in clinical cancer treatment, which is widely used for tumors in lungs,esophagus and mediastinal and also for the pretreatment of bone marrow transplantation. Since lungs are moderately sensitive organs of ionizing radiation, radiation pneumonitis is one common complication after receiving ionizing radiation. As times goes on, radiation pneumonitis can cause pulmonary fibrosis eventally, a deadly threat to the patients. Therefore, in order to defer the occurrence of pulmonary fibrosis, how to treat radiation pneumonitis has become a hot research field in radiology. It is known that TGF‐β1(Transforming growth factor‐β1, TGF‐β1) plays an important role in the development of radiation pneumonitis. TGF‐β1is a subtype of TGF‐β. In mammals, there are three subtypes: TGF‐β1, TGF‐β2and TGF‐β3. It is reported that TGF‐β1can mediate pulmonary fibrosis and TGF‐β3not have the same effect. TGF‐β3has anti‐fibrotic effect on liver fibrosis and pancreatic fibrosis. This study establishs an animal model of radiation pneumonitis. After using60Co‐γ rays, under the action of TGF‐β3, to observe pathological changes in the lungs of mice and its relationship with CF and Th17cells, and to explore the role of TGF‐β3for radiation pneumonitis in providing experimental evidence for the clinical treatment.180clean female C57BL/6mice of18‐20g were purchased from Beijing Vital River Laboratory Animal Technology Co., Ltd. They were randomly divided into control group,radiation group and TGF‐β3group. According to different exposure times, each group was divided into3days,7days,14days and1month group. Radiation group and TGF‐β3group were exposed to60Co‐γ ray with20Gy on breast and then were intraperitoneal injected of saline and TGF‐β3. They were sacrificed at different time points, they were observed in general, level of blood cells in peripheral blood and lung pathology, comparing the number of CF and Th17cells, detecting expression of cytokines in lung homogenate.Results as followed:(1) Compared with control group, weights of mice in radiation group and TGF‐β3group increased slowly with statistical significance, and there is no significant difference between the two groups.(2) Lungs of mice in each group had no significant difference in weight after radiation, while lung index of radiation group and TGF‐β3group mice were significantly higher than control group.3days and7days after radiation, lung index of TGF‐β3group was significantly lower than radiation group (P <0.05).(3)1month after radiation, numbers of WBC in peripheral blood of radiation group and TGF‐β3group were lower than control group and between the two groups where there was no statistically significant.3days after radiation,concentrations of HBG in peripheral blood declined and then returned to control levels at7days after radiation, and declined again at1month after radiation; while concentrations of HBG in peripheral blood of TGF‐β3group were lower than control group.7days after radiation, concentration of PLT in peripheral blood of radiation group declined and returned to control levels at1month after radiation; TGF‐β3group apper similar change compared with radiation group at7days and14days after irradiation.The concentration of PLT in peripheral blood increased at1m after irradiation,which was significantly higher than control group and radiation group.(4) When1month after radiation, lungs of mice in radiation group appear visible dot consolidation.With HE staining, it displays alveolar septal rupture, some alveolar integration, fibroblasts surrounding pulmonary vascular and bronchial proliferation and inflammatory cells infiltration; lungs of mice in TGF‐β3group appear alveolar lung fibroblasts fusion and less inflammatory cells infiltration.With Masson trichrome,it showes significant collagen deposition in alveolar wall in lungs of mice in radiation group, while alveolar walls of lungs in TGF‐β3group show weaker blue than radiation group, suggesting that TGF‐β3reduced collagen deposition in the alveolar wall.(5) Cytokines results as followed:①14days after radiation, concentration of TNF‐α in lungs of mice in radiation group and TGF‐β3group were significantly higher than control group, concentration of TNF‐α in lungs of mice in TGF‐β3group was significantly lower than radiation group (P<0.05).1month after radiation, concentration of TNF‐α in lungs of mice in TGF‐β3group was significantly higher than control group and radiation group (P<0.05).②As time goes on, concentration of IL‐10in lungs of mice in radiation group first decreaed and then increased.3days,7days and1month after radiation, concentration of IL‐10in lungs of mice in radiation group were significantly higher than control group (p <0.05).3days after radiation, concentration of IL‐10in lungs of mice in TGF‐β3group was significantly higher than control group and significantly higher than radiation group at7days after radiation, then gradually returned to the normal level.③3days after radiation, concentration of IL‐17in lungs of mice in radiation group were almost the same as control group.7days and1month after radiation, concentration of IL‐17in lungs of mice in radiation group was significantly lower than control group (p <0.05). The concentration of IL‐17in lungs of mice in TGF‐β3group was significantly lower than control group after radiation.7days after radiation, concentration of IL‐17in lungs of mice in TGF‐β3group was significantly higher than radiation group (p <0.05).(6) Number of Th17cells in lungs of mice declined after radiation,7days to14days after radiation, number of Th17cells in lungs of mice in radiation group was significantly lower than radiation group (p <0.05).3days and14days after radiation, Number of Th17cells in lungs of mice in TGF‐β3group was significantly lower than control group (p<0.05).1month after radiation, number of Th17cells in lungs of mice in TGF‐β3group was significantly higher than control group and radiation group (p <0.05). The proportion of Th17cells in CD4+T cells declined at7days after radiation and then increased.1month after radiation, proportion of Th17cells in CD4+T cells was significantly higher than control group.14days after radiation, TGF‐β3inhibited the increase in proportion of Th17and TGF‐β3promoted the increase in the proportion of Th17.(7)3days and7days after radiation, number of CF in lungs of mice in radiation group was significantly lower than control group(p<0.05).14days after radiation, number of CF in lungs of mice in radiation group was significantly higher than control group (p<0.05).3days and7days after radiation, which of TGF‐β3group appears almost the same as control group. When14days after radiation, TGF‐β3inhibited the increase in the number of CF (p <0.05).Thus,60Co‐γ rays cause radiation pneumonitis occurred in mice, a variety of cytokines that promote or inhibit the effect of the regulatory network imbalance together to build the occurrence of radiation pneumonitis. TGF‐β3regulates balance of Th17cells and Th1/Th2cells in lungs, reducing the recruitment of CF in lungs and regulating the balance of cytokine network, which can reduce the degree of radiation pneumonitis and delay the progress of radiation pneumonitis to radiation pulmonary fibrosis, and finally played a protective role in certain degree.