Spermatogenic Structure in the Long-Lived SAMP1 Mice Prone to Accelerated Aging

Abstract

We previously described the cytogenetic features of spermatogenesis in SAMP1 mice prone to accelerated aging, which have for the first time overcome the maximum life span limit, 15 months [1]. In 18-to 28-month-old SAMP1 mice, sex cells develop against the background of a high genetic instability, namely, the extremely increased frequency of spontaneous chromosomal mutations and nuclear abnormalities. The main goal of this study was quantitative and morphological analyses of spermatogenic epithelium in these unique animals.Male SAMP1 mice aged 18-28 months were used in this study. They were also compared with young (twoto three-month-old) mice and those of the critical age (14-15-months). All animals were kept under standard vivarium conditions and received water and food ad libitum.After fixation in an acetic acid-glycerol mixture, one testis of each animal was disrupted mechanically, and the homogenate was suspended. Various spermatogenic cells were counted using a hemocytometer and a phase-contrast device (Opton, Germany) at a magnification of × 400. The quantitative data were treated statistically using the STATISTICA software package. Significant differences between mean values were determined using Strudent's t test with the standard 5% significance level.The other testis of each animal was divided in half before fixation in Bouen's solution. Sections 7 µ m in thickness were stained with hematoxylin-eosin, and their histological analysis was made. Figure 1 shows the ultimate results of spermatogenic epithelium cell count in SAMP1 mice prone to accelerated aging. It can be seen that, in the gonads of 18-to 28-month-old males, the number of spermatogonia (stem cells + those undergoing differentiation), as well as the number of pachytene spermatocytes, round spermatids, and spermia, was significantly lower than in two-to threemonth-old and 14-to 15-month-old males. The differences were statistically significant at p < 0.05. Nevertheless, note that the spermatogonium compartment is still numerically stable in 14-to 15-month-old animals, and aging of the latter leads to changes in the meiotic phase of spermatogenesis, which is seen from a significant decrease in the number of pachytene spermatocytes, spermatids, and spermia.Our calculations showed that the population density of somatic multifunctional Sertoli cells integrated into the system of spermatogenesis did not decrease with time.The quantitative analysis leads to the following conclusions. The number of spermatogenic cells changes with age (from 2-3 to 14-15 months) in a way that is in strict conformity with the concept suggesting that the number of these cells decreases with increasing sper- CELL BIOLOGY