Ultrastructure of the aging human testis

Abstract

The ultrastructure of the progressive testicular involution with advancing age in men is reviewed. There is no definite age at which testicular involution begins, and the onset and severity of testicular lesions are subjected to pronounced individual variations. Hormone studies also indicate great individual variations, and subtle changes in both the testis and the pituitary develop progressively with age. Testicular size, sperm quality, and numbers of all germ cell types, Sertoli cells, and Leydig cells decrease with age. The volume occupied by the seminiferous tubules decreases, whereas that occupied by the testicular interstitium remains constant. The most frequent histological pattern of the aging testis is a mosaic of different seminiferous tubule lesions, varying from tubules with complete, although reduced, spermatogenesis, to completely sclerosed tubules. The tubules with complete spermatogenesis may show numerous morphological abnormalities in the germ cells, including multinucleation. Abnormal germ cells degenerate causing Sertoli cell vacuolation. These vacuoles correspond to dilations of the extracellular spaces resulting from the premature exfoliation of germ cells. Degenerating cells that are phagocytosed by the Sertoli cells give rise to an accumulation of lipid droplets in the Sertoli cell cytoplasm. The loss of germ cells begins with the spermatids, but progressively affects the earlier germ cell types, and tubules with maturation arrest at the level of the spermatocytes or spermatogonia are observed. The Sertoli cells show morphological abnormalities such as dedifferentiation, mitochondrial metaplasia, and multinucleation. Germ cell loss is associated with thickening of the tunica propria. When all seminiferous epithelial cells have disappeared, only an intensely collagenized tunica propria with myoid cells remains (sclerosed tubules). The Leydig cells progressively dedifferentiate with a decrease in the quantity of both smooth endoplasmic reticulum and mitochondria, together with an accumulation of lipid droplets, crystalline inclusions, and residual bodies, and formation of multinucleate cells. The development of tubular involution with age is similar to that observed after experimental ischemia, suggesting that vascular lesions may play an important role in age-related testicular atrophy.

Nicotine toxicity to the ultrastructure of the testis in rats

“…This effect was proposed previously in rats exposed to methyl mercury, where spermatogenic distortion was mediated through affected Sertoli cells [23]. However, the apparent sensitivity of Sertoli cells to nicotine does not exclude the possibility that germinal cells are the target, as spermatocyte and spermatid susceptibility (as shown in the present rat testis) to other toxic materials was also reported [24]. In the present study, the considerable electron-dense deposits in spermatids con®rm germ-cell sensitivity to nicotine.…”

Effects of aging on the male reproductive system

“…The progression of fibrosis with age causes separation of the germinal epithelium from the blood supply. The development of tubular involution with age is thought to have an essential role in testicular atrophy [12].…”

“…In addition, Leydig cells may also contain an underdeveloped endoplasmic reticulum (ER) and a number of lipofuscin granules. At later stages of dedifferentiation, the nucleolus shrinks or disappears completely [12].…”

Light and electron microscopic study on the effect of antischizophrenic drugs on the structure of seminiferous tubules of adult male albino rats

“…Wide intercellular spaces contained cellular debris and nearly absent spermatogenic cells leaving their location on Sertoli cells. Some authors suggested that vacuolation of Sertoli cells is attributed to the These ultrastructural changes are found in progressive testicular involution with advancing age in men, which may be related to hormonal changes found in old age [44]. These findings are also detected in rats treated by well-established antipsychotic, lithium carbonate [45].…”