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To investigate whether the abscopal effects of cranial irradiation (C-irradiation) cause testicular damage in mice, male C57BL/6 mice (9weeks of age) were randomly divided into a sham irradiation group, a shielded group and a C-irradiation group and administered sham/shielded irradiation or C-irradiation at a dose rate of 2.33Gy/min (5Gy/d for 4 d consecutively). All mice were sacrificed at 4weeks after C-irradiation. We calculated the testis index, observed testicular histology by haematoxylin-eosin (HE) staining and observed testicular ultrastructure by transmission electron microscopy. Western blotting was used to determine the protein levels of Bax, Bcl-2, Cleaved caspase 3, glial cell line-derived neurotrophic factor (GDNF) and stem cell factor (SCF) in the testes of mice. Immunofluorescence staining was performed to detect the expression of Cleaved caspase 3 and 3β hydroxysteroid dehydrogenase (3βHSD), and a TUNEL assay was used to confirm the location of apoptotic cells. The levels of testosterone (T), GDNF and SCF were measured by ELISA. We also evaluated the sperm quality in the cauda epididymides by measuring the sperm count, abnormality, survival rate and apoptosis rate. The results showed that there was no significant difference in testicular histology, ultrastructure or sperm quality between the shielded group and sham group. Compared with the sham/shielded group, the C-irradiation group exhibited a lower testis index and severely damaged testicular histology and ultrastructure at 4weeks after C-irradiation. The levels of apoptosis in the testes increased markedly in the C-irradiation group, especially in spermatogonial stem cells. The levels of serum T and testicular 3βHSD did not obviously differ between the sham group and the C-irradiation group, but the levels of GDNF and SCF in the testes increased in the C-irradiation group, compared with the sham group. In addition, the sperm count and survival rate decreased in the C-irradiation group, while the abnormality and apoptosis rate increased. Under these experimental conditions, the abscopal effects of C-irradiation induced testicular damage with regard to both structure and function and ultimately decreased sperm quality in mice. These findings provide novel insights into prevention and treatment targets for male reproductive damage induced by C-irradiation.

The study aimed to elucidate abscopal effects of thoracic X-ray irradiation on spermatogenesis in mice. Male C57BL/6 mice were randomly divided into sham group and radiation group, and subjected to thorax fractionated X-ray irradiation or sham irradiation with the total dose of 5 Gy/day for each animal for four consecutive days. After irradiation, sperm morphology was observed, and sperm number was counted under microscope, and sperm apoptosis was detected by flow cytometry. Meanwhile, testis index was calculated, testicular morphology was observed using haematoxylin-eosin (HE) staining, and testicular ultrastructure was observed under transmission electron microscopy. The permeability of blood-testis barrier (BTB) was detected by Evans Blue fluorescence colorimetry. The protein levels of Bcl-2 associated X protein (Bax), B-cell leukemia-lymphoma-2 (Bcl-2) and Cleaved caspase 3, promyelocytic leukaemia zinc finger (PLZF) and c-kit proto-oncogene (c-kit) in testes were determined by western blotting (WB). The location of apoptotic cells was confirmed by terminal deoxynucleotidyl transferase (TdT) enzymaticated dUTP nick end labelling (TUNEL) assay. The levels of tumor necrosis factor alpha (TNF-α), transforming growth factor-β1 (TGF-β1), interleukin 10 (IL-10) were measured by enzyme-linked immunosorbent assay (ELISA). The levels of Total superoxide dismutase (T-SOD) and malondialdehyde (MDA) were measured by the biochemical assay kit. Compared with sham group, the sperm quality of mice in radiation group showed decreased number and survival rate, along with increased abnormality and total apoptosis rate. The testis index of irradiated mice was lower, the testicular apoptosis was increased, and their testicular histology and ultrastructure was severely damaged. The permeability of BTB was increased, the level of PLZF in testis was decreased, and the level of c-kit was increased by irradiation. After irradiation, the levels of TNF-α, TGF-β1, IL-10, T-SOD and MDA in testes were significantly changed. Taken together, abscopal effects of thoracic X-ray irradiation on spermatogenesis were obvious, which could decrease sperm quality and damage testicular morphology and increase the permeability of BTB, and a series of inflammation and oxidative stress factors were involved in the process. These findings provide novel insights into prevention and treatment for male reproductive damage induced by clinical thoracic irradiation.