TUNEL-positive sperm are spermatozoa with fragmented DNA, detected using the TUNEL assay (Terminal deoxynucleotidyl transferase dUTP nick end labeling), indicating DNA damage that negatively impacts fertility, often appearing as bright green fluorescence under a microscope, with high percentages correlating to poorer pregnancy outcomes in assisted reproduction. This assay identifies single and double-strand breaks by labeling free 3'-OH ends, distinguishing damaged (positive) sperm from intact (negative) sperm, and helps assess male infertility.
Fertil Steril. 2015 Dec;104(6):1382-7.
Higher pregnancy rates using testicular sperm in men with severe oligospermia
Objective: To evaluate assisted reproductive technology (ART) outcomes using testicular sperm in oligospermic men who previously failed to achieve paternity using TUNEL-positive ejaculated sperm.
Patient(s): Twenty-four oligospermic men who failed one or more ART cycles using ejaculated sperm with TUNEL-positive proportion >7%, and subsequently underwent microsurgical testicular sperm extraction (TESE).
Result(s): The mean TUNEL-positive level was 24.5% for ejaculated sperm, and 4.6% for testicular sperm. Clinical pregnancy was achieved in the first ART cycle with testicular sperm in 12 (50%) out of 24 couples. There was no statistically significant difference in maternal and paternal age, maternal gravity and parity, number of previous ART attempts, concentration or motility of retrieved sperm, number of oocytes retrieved, fertilization rate, or number of embryos transferred between couples who did and did not achieve pregnancy. No miscarriages occurred. All 12 pregnancies resulted in the delivery of healthy children.
Conclusion(s): The percentage of TUNEL-positive cells is lower in testicular sperm for oligospermic men who have abnormal ejaculated sperm DNA fragmentation. The use of testicular sperm for ICSI was associated with a 50% pregnancy and live-birth rate for couples who had previously failed one or more IVF-ICSI cycles with ejaculated sperm. No other clinical predictors of successful pregnancies after the use of surgically retrieved sperm could be identified. In men with elevated TUNEL-positive ejaculated sperm and failed ART, TESE may be considered.