Histología, actividad proliferativa y apoptótica durante la recrudescencia testicular tras fotoperiodo corto en el epitelio seminífero del hámster sirio (Mesocricetus auratus)

Resumen

Many mammals have a seasonal reproduction that causes the offspring to be born at the best time for their survival. Males suffer from a temporary infertility acquired after a process of testicular regression, from which they recover through a process known as recrudescence, in which the testes start to produce valid sperm for reproduction again. The aim of this doctoral thesis was to study the seminiferous tubule of the Syrian hamster during spontaneous recrudescence after exposure to short photoperiod. In order to do this, their histomorphometric changes during this process have been determined, as well as proliferation and apoptosis activities in germ cells and in the Sertoli cell. 53 male Syrian hamsters were used. They were kept in a 14:10 light-dark photoperiod. Out of these, 5 were used as a Control group and kept in the same photoperiod (14:10 light-dark). The other 48 animals were subjected to photoperiod of 8:16 h light-dark. The following study groups were established: mild regression (MReg), strong regression (SReg), total regression (TReg), initial recrudescence (IR), advanced recrudescence (AR) and total recrudescence (TR). The following histological techniques were used: hematoxylin-eosin, immunohistochemistry of vimentin and PCNA, histochemistry of lectins and TUNEL, and, for fluorescence: double immunofluorescence of vimentin and PCNA. A morphometric study was also carried out. During recrudescence, there is a gradual recovery of the testicular, tubular, and seminiferous epithelium volume. The interstitial volume, length and tubular diameter increased mainly in the first half of the process. The proliferative activity of the spermatogonia was always greater than that of the Control group and the apoptotic activity decreased in the first half of the recrudescence. Lectins showed changes in the pattern of glycoconjugates at the beginning of the process, but it was gradually recovering a similar pattern to that of the control group. On the other hand, spermatocytes and spermatids in apoptosis showed great affinity for the lectins PNA, GNA, AAA and Con-A, in addition, for spermatocytes in apoptosis, also the LTA lectin. Sertoli vimentin + / TUNEL + cells and vimentin + / PCNA + cells were observed in all groups. The apoptosis index was higher in MRg and SRg than in the rest of the groups, while the proliferation index was higher in TRg and IR compared to the rest of the groups. The total number of Sertoli cells increased between TRg, IR and AR, where it reached Control values. In conclusion, the spontaneous recrudescence of the Syrian hamster testis has two histomorphometric phases. The first phase involves an increase in tubular diameter and length and an increase in interstitial volume. And the second phase presents a gradual increase in tubular diameter. The recovery of the seminiferous epithelium is due to the increased proliferation in spermatogonia in recrudescence. Germ cell apoptosis decreases to control values in the half of recrudescence process. Lectin histochemistry confirmed their utility for detecting germ cells in apoptosis. Finally, the increase in proliferation and decrease in apoptosis of the Sertoli cell allowed them to reestablish their number after the loss that occurred during regression, which is essential for the recovery of fertility. The finding of a turnover rate (proliferation / apoptosis) in animals kept in long photoperiod indicates that the Sertoli cell is not terminally differentiated in the adult Syrian hamster.