A Novel Three-Step Protocol for Laboratory Processing of Testicular Tissue in Non-Obstructive Azoospermia Patients

Many andrologists put more attention on the predictive factors of successful sperm extraction in testicular sperm aspiration (TESA) or microdissection testicular sperm extraction (micro-TESE), while the importance of laboratory processing of testicular tissue has been neglected. In fact, for non-obstructive azoospermia (NOA) patients, laboratory procedure of testicular tissue is as important as the surgery itself to find testicular sperm, yet there is no standard procedure for laboratory management of testicular tissue.

To establish a laboratory processing for testicular tissue, and to further evaluate the effectiveness of enzymatic digestion and staining for NOA patients with no spermatozoa found after mechanical mincing.

We enrolled 811 patients who underwent TESA or micro-TESE from July 2023 to December 2024, among whom 466 were diagnosed with obstructive azoospermia and 345 were diagnosed with NOA. The main outcome measure was the sperm retrieval rate (SRR) after enzymatic digestion and the sperm detection rate (SDR) after staining.

In this study, testicular spermatozoa was found after mincing in 466 TESA patients (466/583, 79.9%) and 74 micro-TESE patients (74/228, 32.5%). Of the 237 patients for whom spermatozoa were not identified after mincing, spermatozoa were detected in 55 (23.21%) patients after enzyme digestion and staining. The additional SRR contributed by enzymatic digestion alone was 13.1%, while staining contributed an additional SDR of 10.1%. Using multivariable logistic regression analysis, the seminiferous tubule diameter was the only predictor of identifying spermatozoa in NOA patients after enzymatic digestion and staining.

In conclusion, we establish a three-step laboratory processing method for testicular tissue. This study provides strong evidence that enzymatic digestion improves SRR in NOA patients, while staining contributes additional detection value (SDR) when mechanical processing fails, the combined additional value of enzymatic digestion and staining is 23.2%, although only enzymatic digestion contributes to SRR. What is more, the current study showed that seminiferous tubule diameter is a powerful predictor for sperm retrieval, offering real-time, actionable intraoperative guidance. However, the single-center design and lack of live birth outcome data limit the external validity and generalizability of this study.