An engineered 3D blood-testis barrier model for the assessment of reproductive toxicity potential.

We have developed an in vitro model that replicates the composition, organization, and barrier and spermatogenesis functions of the in vivo rat blood-testis barrier. This engineered blood-testis barrier (eBTB) is based on a three-dimensional (3-D) culture in a bicameral chamber of testicular cells isolated from 18-day-old rats. Peritubular cells were cultured on the bottom of the insert. On the top of the insert, a mixture of Sertoli and germ cells were coated within an artificial extracellular matrix, thereby mimicking the basement membrane. The matrix composition was defined to obtain a cord-like organization. This structure was revealed depending on morphogenetic gradients, and was made of polarized Sertoli cells and germ cells in the center of the structure. The in vivo functionality of the BTB was characterized by tight junctions between Sertoli cells. Claudin-11 protein immunodetection suggests that these junctions were also implicated in vitro in the cord-like structure, suggesting the presence of a physical compartment with apical and basal spaces. Measurement of the trans-epithelial electrical resistance characterized the relationship between the Sertoli cells, peritubular cells, and matrix/cells that influenced the tightness of their junctions during the course of the culture. In vitro germ cell differentiation was confirmed with the detection of haploid cells. The development of the eBTB under optimum conditions addresses the involvement of new models, testing the barrier and spermatogenesis functions that are sensitive to chemical compounds from the environment. In this way, the eBTB could be used as an alternative method to animal reprotoxicity studies, and would be of high interest in the scope of regulatory requests for chemical risk assessment.