Organoids as tools to investigate the molecular mechanisms of male infertility and its treatments

Abstract

Organoids are three-dimensional structures characterized by cellular spatial organizations and functions close to the native tissue they mimic. Attempts to create organoids originating from several tissues have now been reported, including the testis. Testicular organoids have the potential to improve our knowledge of the mechanisms that regulate testicular morphogenesis, physiology, and pathophysiology. They could especially prove as useful tools to understand the complex mechanisms involved in the regulation of the germ cell niche in infertility cases as they offer the possibility to control and modify the nature of cell types before self-assembly and thereby opening the perspective to developing innovative methods to restore fertility. To date, there are few studies targeted at testicular organoids’ formation and even less describing the generation of organoids with both a testis-specific structure and function. While researchers described interesting applications with regards to testicular tissue morphogenesis and drug toxicity, further research is needed before testicular organoids would eventually lead to the generation of fertilizing spermatozoa. This review will present the conventional systems used to induce in vitro maturation of testicular cells, describe the different approaches that have been used for the development of testicular organoids and discuss the potential applications they could have in the field of male reproductive biology.

In vitro complete differentiation of human spermatogonial stem cells to morphologic spermatozoa using a hybrid hydrogel of agarose and laminin

“…Another determining factor on the e ciency of threedimensional culture is cell density. Studies have shown that the organization of cells to colony formation or testicular organoids depends on the colony cell concentration used in the rst day of culture (2,11,50).…”

“…The rst attempts to develop a method that could support all levels of spermatogenesis, from SSCs to spermatozoa, focused on two-dimensional culture and tissue culture methods (10). Two-dimensional culture produced a wealth of information on the essential prerequisites for spermatogenesis, key factors controlling the differentiation and proliferation of SSCs, the main components of spermatogenesis, and ultimately the factors that drive the differentiation of SSCs into spermatozoa, but its e ciency in producing of haploid cells was low (10)(11)(12). In contrast to twodimensional culture, tissue culture was most successful in producing a fertility-competent sperm, which ultimately led to the production of a live offspring in mice (13,14).…”

Organoids of the male reproductive system: Challenges, opportunities, and their potential use in fertility research

“…Several efforts have been made in the past decades to reproduce spermatogenesis in vitro, aiming to promote the differentiation of germ cells into fertilization‐competent spermatozoa used to treat infertility associated with the male factor (J. H. Lee et al, 2006; M. Sun et al, 2018) or to restore fertility using cryopreserved prepubertal testicular tissue (de Michele et al, 2017; Kanbar et al, 2021). The absence of an adequate arrangement of testicular cells in 2D cultures at least partially explained the failure of in vitro maturation, which was surpassed by the use of 3D cell culture models, able to mimic the in vivo cell configuration required for a proper cellular response.…”

Progress, prospects, and limitations of organoid technology

“…Testicular organoids are similar to the testes in structure and function and serve as highly useful model systems to study male infertility and the mechanism of germ cell niche, germ cell functions, and the interaction between germ cells for spermatogenesis [15,16]. In addition, testis organoids can be used as high-throughput drug and toxicity screening tools that can replace animal experiments owing to ethical issues [17].…”