Development of testicular organoids as a model for studying fish spermatogenesis and develop innovative aquaculture applications

Abstract

Organoids are tree-dimensional (3D) cell agglomerates that recapitulate de novo tissue morphogenesis, and consequently tissue cytoarchitecture and biological function of a given organ. Two-dimensional (2D) culture systems, such as organotypic cultures, are not optimal to study the complex cell-cell interaction and signaling as observed in vivo. Therefore, 3D culture system can open opportunities to better understand the spermatogenesis, including spermatogonial differentiation, interactions between spermatogonial stem cells (SSCs) and somatic cells, as well as the mechanisms involved in male infertility and early puberty. Attempts to create organoids originating several tissues have now been reported, including testis. However, there are no testicular organoid developed for fish, especially for valuable fish species. In additional, fish spermatogenesis is dependent of testicular niche growth factors and hormones that enhance spermatogenic progression, including testosterone, gonadotropins (Lh and Fsh), and recently, thyroid hormones (THs). In our previously results (Rodrigues et al., 2021, 2022; FAPESP 2019/22997-3), we demonstrated by histomorphometrical analysis that T3 and Fsh potentiate the number of type A undifferentiated spermatogonia (Aund) cysts in zebrafish testis, meanwhile, the absence/decrease of THs nullified the effects of Fsh, T3 or their combination in zebrafish spermatogenesis. In this context, the aim of this current project is to develop 3D testicular organoids in rainbow trout, and to use/explore the potential of Fsh and T3 hormones to increase type A undifferentiated (Aund), which could be an advantage for the development of organoids, as well as to increase the number of stem cells that could be cryopreserved or transplanted to generate aquaculture genetic resources of interest. Moreover, the development of organoids will contribute to investigate the cellular interaction in the niche using a model that better mimics the in vivo interactions. (AU)