Infertility is a worldwide health issue that affects approximately 15% of couples worldwide [1]. Microdissection testicular sperm extraction (MicroTESE) is the gold standard procedure for sperm recovery in non-obstructive azoospermia (NOA) [2]. Unfortunately, microTESE does not always result in successful sperm retrieval, and the patients are left without viable sperm for assisted reproduction techniques. Donor sperm is not a choice that suits all due to cultural, religious, or individual reasons, thus leading to high demand for biological parenthood. Stem cell therapy has proven to be a promising experimental treatment in this respect to restore spermatogenesis [3]. However, stem cell therapy requires precise delivery into the testicular environment because misdirected injections can render the treatment useless. This video demonstrates two primary injection techniques to achieve optimal stem cell delivery into the testis: percutaneous ultrasound-guided injection and direct visualization with testis delivery.

This video demonstrates two types of techniques for stem cell injections according to testicular anatomy and accessibility. The first procedure, percutaneous ultrasound-guided injection, introduces stem cells into the rete testis or mediastinum testis under ultrasound guidance in real-time. This technique is less invasive and is applied by preference when the mediastinum testis or the rete testis can be clearly visualized with ultrasound. However, where ultrasound will not give an adequate view of the rete testis or mediastinum testis —i.e., in patients whose testes are very atrophic or fibrosed—this technique cannot be used. 

The second method, with testis delivery, is a more invasive technique involving a small incision in the scrotum to deliver the testis for direct visualization surgically. This method allows for accurate injection into the right anatomical site, especially when ultrasound guidance is impossible. With direct access to the rete testis, this approach minimizes the risk of injecting stem cells outside the seminiferous tubules, thus maximizing the chance of successful spermatogenesis.

Both techniques have strengths and weaknesses. Percutaneous ultrasound-guided injection is preferred because it is less invasive and can be directed quickly to the rete testis if the anatomy is precise. Testis delivery and direct visualization, as more invasive, are more accurate and, therefore, the option to use where percutaneous injection is not possible. Stem cell therapy depends on having the cells delivered inside the seminiferous tubules, as injections in any area outside the seminiferous tubules will not be useful in stimulating spermatogenesis.

Stem cell therapy is highly promising in the treatment of male infertility as a possible option for those patients who have been unsuccessful with microTESE and wish to become biological parents. However, appropriate delivery modes are still the deciding factor for the therapy's success. Percutaneous ultrasound-guided injection and direct visualization testis delivery are potential alternatives, with the choice of technique depending on testicular anatomy and clinical conditions. As technology advances, continuous clinical studies will be required to improve protocols, identify long-term outcomes, and confirm safety. The development of standardized guidelines and continued advancements in stem cell delivery methods will be crucial in translating experimental studies into a clinically viable treatment for male infertility.

Fraga, L. G., Gismondi, J. P., Sanvido, L. V., Lozano, A. F. Q., Teixeira, T. A., & Hallak, J. (2024). Clinical and Laboratorial Evaluation of Male Infertility. A Detailed Practical Approach. Archives of medical research, 55(8), 103139. https://doi.org/10.1016/j.arcmed.2024.103139
Flannigan, R., Bach, P. V., & Schlegel, P. N. (2017). Microdissection testicular sperm extraction. Translational Andrology and Urology, 6(4), 745.
Abdelaal, N. E., Tanga, B. M., Abdelgawad, M., Allam, S., Fathi, M., Saadeldin, I. M., ... & Cho, J. (2021). Cellular therapy via spermatogonial stem cells for treating impaired spermatogenesis, non-obstructive azoospermia. Cells, 10(7), 1779.