| Brain Aging is an age-related chronic degenerative disease of brain function, and also is an important part of the whole aging of human body. Its clinical manifestations are learning and memory impairment, cognitive impairment and mental disorders, etc. The incidence of brain aging is increasing year by year, and turns into a trend of younger age, which not only affects the quality of life of the elderly, but also gives society and the family a heavy burden. However, the specific pathogenesis of brain aging is not entirely clear. At present, there has not achieve a breakthrough in the treatment. Therefore, studies about the pathogenesis of brain aging and the effective treatment methods or medications of delaying the brain aging are deeply needed to provide experimental basis for treating brain aging.Objective:1. To research the influence of endocrine recession on learning and memory impaired of brain aging;2. To research the improving effect of testicular tissue graft on endocrine recession;3. To research the influence of endocrine recession on hippocampal neurons and androgen receptor signaling pathway, and the protective effect of testicular tissue graft.Method:Forty Kunming male mice were randomly divided into four groups:sham operation group, castrated group, androgen control group (30mg/kg) and testicular tissue graft group. The bilateral testicular of mice were cut off to establish castrated mouse model. The testicular tissue blocks were implanted on the back or back subcutaneous muscle layer of castrated mice to establish allogeneic testicular tissue graft model. After modeling, androgen group mice were intragastric administrated with androgen for three months, and other groups of mice were given an equal volume of NS. At the end of treatment, the transplanted grafts of mice were removed to observe by naked eye and histological observation; Gonadal organs (prostate and seminal vesicles) coefficient of mice were weighed and calculated; The levels of serum testosterone in each group of mice were measured by ELISA; Learning and memory abilities of mice were assessed by Morris water maze behavioral test; Morphological changes in the hippocampal CA1 region were observed through hematoxylin-eosin staining (HE); The expressions of androgen receptor and apoptosis-related proteins (Bcl-2, Bax, Caspase-3and Caspase-9) in brain were measured by Western blotting; The expressions of AR and apoptosis-related genes in brain were measured by RT-PCR.Result:1. Growth conditions and morphology of testicular tissue grafts:we found a connection between testicular tissue blocks and surrounding tissue by establishment of blood vessels in visual observation; With pathological examination under the microscope, we found that graft morphological structure and cells remained substantially intact. Spermatogenic cells, including round sperm cells and elongated sperm cells were clearly observed in seminiferous tubules, while spermatogonia and spermatocytes were rarely observed. Sinus and a small amount of leydig cells were found in interstitium.2. The influence of testicular tissue graft on gonadal organs in endocrine recession dementia mice:Compared with sham operation group, the coefficient of gonadal organs in castrated group was decreased significantly (P<0.01); Compared with castrated group, the coefficient of gonadal organs in graft group was increased significantly (P<0.01); Compared with androgen group, the coefficient of gonadal organs in graft group was no significant difference (P>0.05)3. The influence of testicular tissue graft on serum testosterone in endocrine recession dementia mice:Compared with sham operation group, the levels of serum testosterone in castrated group had a significant rise (P<0.01); Compared with castrated group, the levels of serum testosterone in graft group was increased obviously (P<0.01); Compared with androgen group, The difference of the levels of serum testosterone in graft group was not statistically significant (P>0.05)4. The influence of testicular tissue graft on behavior in endocrine recession dementia mice:Compared with sham operation group, the escape latency in castrated group was shortened, the swimming distance in castrated group enhanced significantly, and the number of cross-platform in castrated group had a significant decrease (P<0.01); Compared with castrated group, the escape latency in graft group was extend, the swimming distance in graft group had a decline significantly, and the number of cross-platform in graft group was increased significantly (P<0.01); Compared with androgen group, The difference of escape latency, swimming distance and the number of cross-platform in graft group were not statistically significant (P>0.05)5. The influence of testicular tissue graft on hippocampal neuronal morphology in endocrine recession dementia mice:As the results of HE staining of brain tissue sections, hippocampal CA1 area neurons in sham operation group had 4～6 layer cells. Cell was tightly packed, neat, uniform, structured and integrated. Nucleus was large and round. Nucleoli was clearly visible; Hippocampal CA1 area neurons in castrated group was arranged in sparse and loose with pyknotic nuclei, even some regional cells were missing or cracked. The cell gap was large. There were only 1 to 2 layer neurons, and the number of cells was significantly reducing; Compared with castrated group, morphology of hippocampal CA1 area neurons in androgen group and graft group improved obviously. Neurons were neat and orderly, and the number of cells was increased significantly.6. The influence of testicular tissue graft on the expressions of androgen receptor and apoptosis-related proteins in endocrine recession dementia mice:Compared with sham operation group, the expressions of Bax, Caspase-3 and Caspase-9 proteins were increased significantly in castrated group, but the expressions of androgen receptor and Bcl-2 proteins were decreased significantly (P<0.01); Compared with castrated group, the expressions of Bax, Caspase-3 and Caspase-9 proteins werereduced significantly in graft group, but the expressions of androgen receptor and Bcl-2 proteins had an increased significantly (P<0.01); Compared with androgen group, the expressions of androgen receptor and apoptosis-related proteins in graft group were no significant difference (P>0.05)7. The influence of testicular tissue graft on the expressions of androgen receptor and apoptosis-related genes in endocrine recession dementia mice:Compared with sham operation group, the expressions of Bax, Caspase-3 and Caspase-9 genes were increased significantly in castrated group, but the expressions of androgen receptor and Bcl-2 genes were decreased significantly (P<0.01); Compared with castrated group, the expressions of Bax, Caspase-3 and Caspase-9 genes were decreased significantly in graft group, but the expressions of androgen receptor and Bcl-2 genes were increased significantly (P<0.01); Compared with androgen group, the expressions of androgen receptor and apoptosis-related genes in graft group were no significantly difference (P>0.05)Conclusion:1. After removing the testes of mice, we found the coefficient of gonadal organ was decreased significantly. The levels of serum testosterone were substantially decreased, which proved that the model of endocrine recession dementia were relatively successful.2. After transplanting testicular tissue blocks, we found a connection between testicular tissue blocks and surrounding tissue by establishment of blood vessel. The pathological of testicular tissue blocks maintained normal. The weight of gonadal organ was increased significantly. The levels of serum testosterone were substantially increased, which proved that the model of allograft testicular tissue graft was relatively successful.3. Testicular tissue graft had quite effect with androgen replacement therapy, so that it could improve learning and memory impairment of brain aging intead of exogenous androgens.4. Testicular tissue graft improve learning and memory ability probably by secreting endogenous testosterone which will combine with androgen receptor in the brain, then regulating the expression of neuronal apoptosis related genes, increasing Bcl-2 protein level and reducing the expression of Bax, Caspase-3 and Caspase-9 protein, and finally inhibiting neuronal apoptosis. |
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