Continual Maintenance of the Blood-Testis Barrier During Spermatogenesis: The Intermediate Compartment Theory Revisited

Abstract

Abstract. Tight junctions occur between the lateral processes of neighboring Sertoli cells that divide the seminiferous epithelium into two compartments: basal and adluminal compartments. These tight junctions constitute the bloodtestis barrier (BTB). The established theory that the BTB must open when spermatocytes translocate from the basal compartment to the adluminal compartment is marked by one contradiction, that is, normal spermatogenesis occurs in the testis because the BTB is expected to constantly seclude the adluminal compartment from the basal compartment in order to protect haploid germ cells from the autoimmune system. Subsequently, another concept was proposed in which two BTBs divide the seminiferous epithelium into three compartments: basal, intermediate and adluminal compartments. It has been suggested that the transition from the basal region to the adluminal region without the BTB open occurs through the agency of a short-lived intermediate compartment embodying some primary spermatocytes. In contrast, the results of recent findings in the molecular architecture of the BTB suggest that the BTB in the seminiferous epithelium must "open". In this paper, I re-examine the BTBs of boar and experimental cryptorchid mouse testes by transmission electron microscope (TEM). TEM analysis showed that an atypical basal compartment existed in the thin seminiferous epithelium of 14-day post-cryptorchid mice testes. In developmental boar testes, ectoplasmic specialization (ES) of the seminiferous epithelium showed dynamic behavior. The intermediate compartment was clearly observed between the basal and adluminal compartments of the mature boar seminiferous epithelium. ESs were observed between Sertoli cells and spermatids at all developmental stages, including early, late and mature. Furthermore, ESs were situated on the apical surface of the seminiferous epithelium. From these results, I propose that the BTB is continually maintained during spermatogenesis and suggest a model of ES circulation in the seminiferous epithelium. Key words: Blood-testis barrier, Cryptorchidism, Ectoplasmic specialization, Testis, Transmission electron microscope (TEM) (J. Reprod. Dev. 54: [299][300][301][302][303][304][305] 2008) ost epithelia have tight junctions between their cells, just below their free surfaces. The seminiferous epithelium is exceptional in having tight junctions nearer the base of the epithelium. These tight junctions occur between the lateral processes of neighboring Sertoli cells that arch over the intervening spermatogonia. They divide the seminiferous epithelium into two compartments: a basal compartment containing spermatogonia and an adluminal compartment containing the later stage of germ cell differentiation. These tight junctions constitute the blood-testis barrier (BTB), and the BTB must open to accommodate elevation of the spermatocyte. This theory was established by Dym and Fawcett in 1970 [1]. The BTB is a dynamic structure that undergoes cycles of "opening" and "closing" during the epitheli...

Crosstalk between desmoglein-2/desmocollin-2/Src kinase and coxsackie and adenovirus receptor/ZO-1 protein complexes, regulates blood-testis barrier dynamics

“…Based on these observations, we hypothesize that BTB restructuring at stages VIII–IX of the seminiferous epithelial cycle (Russell, 1977b; Yazama, 2008), which facilitates transit of leptotene spermatocytes, is mediated by crosstalk between desmosome- and CAR-based protein complexes. CAR, a TJ- and basal ES-associated integral membrane protein, was previously shown to be expressed by both Sertoli and germ cells at the site of the BTB (Wang and Cheng, 2007, Mirza et al, 2007).…”

DHT deficiency perturbs the integrity of the rat seminiferous epithelium by disrupting tight and adherens junctions

“…In the epithelium, Sertoli cells support nutrition and proper hormones concentration for germ cell development. Between the lateral processes of neighboring Sertoli cells, tight junctions (TJs) exist that divide the seminiferous epithelium into a basal compartment containing diploid (2n) spermatogonia, preleptotene/leptotene spermatocytes and an adluminal compartment containing more mature, haploid (1n) spermatocytes and spermatids [2]. TJs are constituted by several TJ--integral membrane proteins such as occludin, claudin and junctional adhesion molecules (JAMs).…”

Surfing the wave, cycle, life history, and genes/proteins expressed by testicular germ cells. Part 5: Intercellular junctions and contacts between germs cells and Sertoli cells and their regulatory interactions, testicular cholesterol, and genes/proteins associated with more than one germ cell generation

“…Preleptotene and leptotene spermatocytes that lie on the basement membrane of tubules have to migrate beyond the blood testis barrier at late stage VIII and IX of the cycle, from the basal to the adluminal compartment (Pelletier and Friend, 1983;Russell, 1977b). The existence of an intermediate compartment in this migration has been suggested by some investigators but appears to be controversial (Yazama, 2008). Migration is accomplished by cytoplasmic processes of adjacent Sertoli cells slipping under the germ cells and forming new tight junctions, as the junctions above are dismantled (Fawcett, 1975;Pelletier, 2004;Pelletier and Friend, 1983;Russell, 1977b T5-936].…”