Generation and utility of endocrine functional testicular organoids

Male infertility is increasing in prevalence due to cancer treatment, environmental exposures, and patient-specific syndromes. Traditional two-dimensional culture systems inadequately recapitulate the complex three-dimensional architecture, microenvironment, and endocrine milieu essential for spermatogenesis. Testicular organoid models aim to circumvent the challenges of two-dimensional culture, mimicking key aspects of the testicular microenvironment, while enabling controlled experimental manipulation and patient-specific disease modeling. Current testicular organoids demonstrate remarkable preservation of endocrine function, including sustained testosterone and inhibin B production over as great as 12-week culture periods, while maintaining gonadotropin responsiveness that mirrors the pituitary-gonadal axis regulation a testis would experience in vivo. Testicular organoids have recently been used for drug and toxicity screening, and patient-specific organoids from men with nonobstructive azoospermia and Klinefelter syndrome have been explored for disease-relevant characteristics, providing a platform for personalized medicine approaches. Despite these significant advances, achieving complete functional spermatogenesis remains challenging. Limitations include high variability in tubular morphogenesis, with significant methodologic differences across research groups, constraining reproducibility. The primary cellular actor(s) driving this phenomenon is still under investigation. Emerging opportunities at the convergence of bioengineering fabrication techniques and stem cell biology may bridge these challenges, improving microtissue vascularization, advancing scalability, and adding options for patient-personalized experiments. In this review, recent progress in testicular organoid generation, utility for endocrine investigation, remaining technical challenges, and future scientific opportunities are specifically explored. Testicular organoids provide a promising in vitro model for the study of testicular morphogenesis and spermatogenesis, testicular endocrine signaling, and male factor infertility.