Testis

Interleukin 1 Alpha (IL1A) Is a Novel Regulator of the Blood-Testis Barrier in the Rat

Abstract
Throughout spermatogenesis, leptotene spermatocytes must traverse the blood-testis barrier (BTB) at stages VIII-XI to gain entry into the adluminal compartment for continued development. However, the mechanism underlying BTB restructuring remains somewhat elusive. In this study, IL1A was administered intratesticularly to adult rats in order to assess its effects on spermatogenesis. IL1A was shown to perturb Sertoli-germ cell adhesion, resulting in germ cell loss from ~50% of seminiferous tubules by 15 days post-treatment. Equally important, the functional integrity of the BTB was compromised when inulin-FITC was detected in the adluminal compartment of the seminiferous epithelium following its administration via the jugular vein. Interestingly, IL1A did not affect the steady-state levels of proteins that confer BTB function namely OCLN, CLDN1, F11R, TJP1 and CDH2. Instead, the localizations of OCLN, F11R and TJP1 in the seminiferous epithelium were altered; these proteins appeared to move away from sites of cell–cell contact. Moreover, IL1A was shown to perturb the orderly arrangement of F-actin at the BTB and apical ectoplasmic specialization with distinct areas illustrating loss of actin filaments. Taken collectively, these results suggest that IL1A-induced BTB disruption is not mediated via the reduction of target protein levels. Instead, IL1A's primary cellular target appears to be the Sertoli cell actin cytoskeleton. It is possible that localized production of IL1A by Sertoli and/or germ cells in vivo results in BTB restructuring, and this may facilitate the movement of leptotene spermatocytes across the BTB.

Key words: Testis • blood-testis barrier • ectoplasmic specialization • interleukin-1alpha (IL1A) • tight junction

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