Ultrastructure of immature leydig cells in the human prepubertal testis

Abstract

The cellularity of the human prepubertal testicular interstitium has not been well studied at the ultrastructural level. In this study, testicular biopsies were obtained from 35 boys aged three to nine years and examined by electron microscopy to clarify and quantitate the cell types present during the prepubertal period. The prepubertal testicular interstitium is found to consist of immature Leydig cells (9%), primitive fibroblastic cells (63%) (intertubular in location), and attenuated peritubular fibroblasts (28%). The primitive fibroblastic cells and peritubular fibroblasts appear closely related, being distinguished mainly by shape and location. The immature Leydig cell type contrasts with the fibroblastic cell types by exhibiting an irregular nucleus with relatively little heterochromatin. The most impressive cytoplasmic feature is the moderate to extensive development of smooth endoplasmic reticulum in the form of anastamosing tubules. In contrast, the rough endoplasmic reticulum is not well developed. Other cytoplasmic characteristics are the highly developed Golgi elements and occasional lipid droplets and lysosomes. Glycogen is also often present and is generally found in those cells that do not contain a well-developed smooth endoplasmic reticulum. The ultrastructure of the immature Leydig cell is compared with that of the mature fetal and adult Leydig cells. Although generally found in small clusters between tubules, these cells are often attenuated and closely associated with the seminiferous tubules. Occasional intermediate cell morphologies suggest a relationship between the primitive fibroblasts and immature Leydig cells. The presence of small cells exhibiting a steroid-producing morphology, classified as immature Leydig cells, in the prepubertal testicular interstitium is an interesting finding and is in accordance with earlier studies on nonhuman mammals. It is unknown whether these cells are remnants of the fetal Leydig cell population or have differentiated neonatally from the primitive fibroblastic cells. It is suggested that the immature Leydig cells are the progenitors of the adult Leydig cell population.

The triphasic nature of Leydig cell development in humans, and comments on nomenclature

“…The diverse cell population present at 4 months after birth (slightly past the peak of neonatal development), a mix of mature well-developed Leydig cells and smaller cells which are consistent with regressing cells, supports a continuity, in part, of the neonatal Leydig cell population with the small immature Leydig cells present during childhood (Prince 1984). Evidence of cell degeneration is also present within this time-frame.…”

“…Evidence of cell degeneration is also present within this time-frame. The finding that immature Leydig cells are present throughout childhood (Prince 1984) suggests that these cells are conserved and develop at puberty into a segment of the mature, adult Leydig cell population. It is probable that the relatively undifferentiated cells, previously referred to as primitive fibroblastic cells (Prince 1984), which are numerous in the interstitium during childhood, also contribute substantially to the cell population in the adult.…”

Peptidergic not monoaminergic fibers profusely innervate the young adult human testis

“…Using electron microscopy, Prince (1984Prince ( , 1992Prince ( , 1996 examined autonomic nerves in human testis from the neonatal period, childhood and puberty, and revealed an age-dependent change. He found that newborn gonads exhibited no adrenergic innervation.…”

Mitochondrial structure in steroid‐producing cells: Three‐dimensional reconstruction of human Leydig cell mitochondria by electron microscopic tomography

“…Cases negative for leukemic cells have been used in a number of studies regarding human Leydig cell development and cell biology (Prince, 1984(Prince, , 1992(Prince, , 1999(Prince, , 2002. The present tomography study utilizes a postpubertal specimen to reconstruct mitochondria of the adult maturation phase.…”