Quantitative (stereological) study of the effects of vasectomy on spermatogenesis in rhesus monkeys (Macaca mulatta)

Abstract

Vasectomy reversal by vasovasostomy after long-term vasectomy in men results in lower sperm counts and pregnancy rates compared with controls, and severe damage to spermatogenesis has been observed in some animal models such as mice. The primary aim of this study was to evaluate, using sophisticated stereological methods, whether vasectomy of 6 and 12 months in a non-human primate would lead to, among other morphometric changes, reduced numbers of germ cells in testes and spermatozoa in epididymides. Five normal adult male rhesus monkeys (Macaca mulatta) underwent bilateral vasectomy, with another three aged-matched normal monkeys not undergoing vasectomy. One testis together with the ipsilateral epididymis was removed from each animal at 6 months, and the other testis and epididymis, the prostate gland and seminal vesicles were removed at 12 months. Various morphometric data were obtained using stereological methods and an unbiased and efficient stereological tool, the optical disector, was used to estimate nuclear numbers of all types of spermatogenic cells in testes and spermatozoa in epididymides using methacrylate-embedded sections 25 microm in thickness. As shown by a two-way repeated measures analysis of variance, vasectomy or hemicastration (removal of the organs at 6 months) had no significant effects on all quantitative parameters of stereology obtained from the testis, epididymis, prostate gland and seminal vesicle, except that (i) sperm granuloma was observed from three of five vasectomized animals both at 6 and 12 months, and (ii) hemicastration significantly reduced the diameter of the seminiferous tubules and increased the number of type A spermatogonia per testis. In conclusion, vasectomy in the non-human primate is a safe procedure in terms of effects on the structures of the reproductive organs.

A stereological study of the effects of experimental inguinal cryptorchidism and subsequent orchiopexy on spermatogenesis in adult monkeys

“…The remaining organs were removed at 1 year (another half a year later). The data obtained from control animals and animals undergoing vasectomy have recently been published (Peng et al ., 2002). Reported herein are data obtained from the cryptorchid animals in comparison with the control.…”

“…In comparison with the control organs [the mean control values have been reported by Peng et al . (2002); shown in Table 1 of the current paper were the ranges of the individual control values] (i) the mean volumes of the cryptorchid testis and epididymis were significantly reduced by 68 and 50%, respectively; (ii) the mean volumes (per organ) of the seminiferous tubules and epididymal tubules significantly reduced by 76 and 79%, respectively; (iii) the mean diameters of the seminiferous and epididymal tubules significantly reduced by 35 and 41%, respectively; (iv) the mean lengths (per organ) of the seminiferous and epididymal tubules significantly reduced by 38 and 39%, respectively; (v) the mean type A spermatogonial numbers (per testis) in the four animals were 14.8–57.2% of the mean control value, but statistical significance was not detected; (vi) the mean numbers (per testis) of other spermatogenic cell types were significantly decreased, by 86% in type B spermatogonia; 94% in preleptotene, leptotene and zygotene primary spermatocytes; 90% in pachytene primary spermatocytes; and 99% in early spermatids (the round and elongating spermatids), respectively (Table 1).…”

“…As we previously described at length (Wen & Yang, 2000; Peng et al ., 2002; Zhang et al ., 2002) (i) four to five testicular or three to four epididymal blocks per organ were randomly sampled; (ii) 25 μm‐thick resin (hydroxyethyl methacrylate)‐embedded sections were cut and stained with periodic acid‐Schiff reagent (PAS) + haematoxylin (testicular sections) or haematoxylin only (epididymal sections); (iii) numbers (per organ) of spermatogenic cells and Sertoli cells in the testis and spermatozoa in the epididymis were estimated using the stereological optical disector tool; and (iv) volume (per organ), diameter and length (per organ) of the seminiferous or epididymal tubules were obtained using other stereological methods.…”

Quantitative (stereological) study of the effects of vasectomy on spermatogenesis in rabbits

“…Many studies have reported spermatogenic damage following vasectomy whereas numerous others have not (Peng et al. 2002).…”

“…However, it was unclear whether type A spermatogonia and Sertoli cells were involved in the damage and what was the pattern of damage in terms of severity, extent and time course, which was partly attributable to the lack of detailed quantitative data on changes of different stages of germ cells in most previous studies. Using sophisticated stereological methods, we recently demonstrated that vasectomy in the monkey for 6 or 12 months induced formation of sperm granuloma in the epididymis but had no considerable impact on the testicular structures (Peng et al. 2002).…”