From Cell Clusters to Complexity: Testicular Organoids as Emerging Platforms in Male Reproductive Research and Biotechnological Innovation.

Conventional 2D cultures and animal models incompletely recapitulate the human testicular niche, limiting translation for male infertility, toxicology, and endocrine research. Limited and highly variable access to human testicular tissue restricts translational research. Testicular organoids (TOs), self-organizing assemblies of germ and somatic cells within biomimetic scaffolds, microfluidic chips, or bioprinted constructs, can reproduce seminiferous cord/tubule-like organization, elements of the blood-testis barrier and steroidogenic function, and increasingly support germ-cell progression. By integrating defined media, matrix cues, and controlled microenvironments, TO platforms enable mechanism-driven studies and human-relevant new approach methodologies for toxicology, disease modeling, and fertility-preservation research. This, in turn, supports endocrine and reprotoxicology testing, disease modeling, and prepubertal fertility-preservation strategies. Broad and responsible adoption will require clinically concordant read-outs, stable long-term cultures, reproducible and complete human spermatogenesis, and a robust ethical framework. This review aims to comprehensively evaluate TO systems, spanning cell sources, biomaterials, and microenvironmental control to functional read-outs of morphogenesis, steroidogenesis, and germ-cell progression. By synthesizing recent advances, we clarify mechanistic determinants of organoid performance and outline their translational implications for male infertility research, toxicology, and fertility-preservation strategies.