FRI443 Optimizing Conditions Of Tubule-like Structures In Testicular Organoids That Will Support Spermatogenesis

Disclosure: O. Printy: None. Testicular organoids are increasingly being investigated as a potential means of fertility restoration. These organoids have been shown to self-organize to recapitulate the inner architecture of the native testis, forming tubule-like structures that resemble the seminiferous tubules. However, these tubule-like structures lack dimensionality and do not contain a large, meiotically active germ cell population. We hypothesized that if testicular organoids are cultured under appropriate microenvironmental conditions, we will observe the development of tubule-like structures with diameters that resemble what is seen in vivo, in addition to appropriate somatic cell localization and Sertoli-germ cell interactions. To test this hypothesis, we generated organoids from 5dpp male CD1 mice at three cellular seeding densities: low density (170,000 cells per well), medium density (280,000 cells per well), and high density (310,000 cells per well). The heterogenous testicular cell suspension formed compact organoids at all three seeding densities and organoid diameter increased with increasing cell number. To assess the ability of the organoids to mimic the inner architecture of a testis, we performed immunohistochemistry on 14-day-old organoids: for the major somatic cell types of the testis Leydig cells (HSD3B2), peritubular myoid cells (ACTA1), and Sertoli cells (SOX9). Thus far, only medium density organoids appear to recapitulate the compartmentalization seen in native testes. These organoids tend to contain semi-continuous ring-like structures composed exclusively of ACTA1positive cells; these structures encapsulate a population of SOX9-positive cells, while HSD3B2-expressing cells are located on the periphery of the organoids. To assess the organoids’ ability to fuse to form a larger aggregate, organoids were transferred to 3D printed troughs. However, organoids did not merge and appeared to die. However, when organoids are cultured together in microcentrifuge tubes and alginate structures, they fused to form a larger aggregate. In the future, immunohistochemistry will be used to evaluate whether any extended tubule-like structures formed within the aggregates. Additionally, spermatogonial stem cells will be injected into the aggregates and ELISA assays will be performed to assess the spermatogenic and hormonal functionality of the organoids. Presentation: Friday, June 16, 2023