Phenotyping the claudin 11 deficiency in testis: from histology to immunohistochemistry.

The testis is a heterogeneous organ that comprises a number of cell types, including germ cells at -different stages in their maturation, differentiated neighbor nursing cells, and endocrine somatic cells. Despite such cellular heterogeneity the testis is highly organized, with germ cell development and differentiation being compartmentalized into the interconnected tubular network of the seminiferous epithelium. Intratesticular scaffolds rely heavily on the basement membrane of the seminiferous tubules while germ cell development inside the seminiferous epithelium is critically dependent on the Blood Testis Barrier (BTB). The BTB is a macromolecular tight junction complex generated by somatic Sertoli cells within the seminiferous epithelium. The BTB divides the seminiferous epithelium into two compartments: the basal compartment, which delineates a niche for the proliferation and renewal of spermatogonia; and the adluminal compartment, where differentiating germ cells undergo meiosis and spermiogenesis. The BTB is unique in mammalian tissues because it is cyclically reconstructed during the spermatogenic cycle as preleptotene spermatocytes migrate from the basal compartment to the adluminal compartment and enter meiosis. In mouse, the loss of the BTB in the absence of the claudin 11 protein causes azoospermia and leads to infertility. Specifically, cldn11 deficiency results in sloughing of the cells of the seminiferous epithelium into the lumen. Understanding this pathophysiology has involved histological examination of the tissue defects as well as immunohistological characterization. Here, we present a comparative study of several modifications to the classical Hematoxylin-Eosin stain that may improve the diagnostic usefulness of this technique, as well as the use of several selective markers to identify testicular cell types.