P-067 A physiological approach for oocyte activation when using testicular spermatozoa
Authors: Elias R , Cheung S , Xie P , Rosenwaks Z , Palermo G 
Published: July 2024

Abstract

Study question
Can poor fertilization with testicular spermatozoa be rescued by oocyte activation? We propose a more physiological approach to the standard method.

Summary answer
Couples who utilized testicular spermatozoa benefitted from assisted oocyte activation (AOA), particularly when a more physiological approach such as recombinant human phospholipase-C-zeta (rhPLCζ) was utilized.

What is known already
ICSI overcomes sperm acrosomal dysfunction and other inherent defects of the male gamete. However, partial or complete fertilization failure may still occur, often attributable to the absence of PLCζ. These cases are often treated by calcium ionophore, a very popular method that is considered quite safe, however it still raises concerns because it induces intracellular calcium oscillations in a very aspecific manner. Testicular spermatozoa are particularly at risk of suboptimal fertilization; therefore, the availability of a more physiological method would be welcome.

Study design, size, duration
Over a period of 12 months, 21 couples utilizing testicular spermatozoa for ICSI, that resulted in poor fertilization, were identified and treated in subsequent ICSI cycles with assisted oocyte activation (AOA), either by exposure to ionomycin or co-injection of rhPLCζ at the time of ICSI. Embryology and clinical outcomes were recorded and compared between the two AOA methods as well as the couples’ historical and subsequent cycles.

Participants/materials, setting, methods
Couples with a history of poor/absent fertilization after undergoing ICSI using testicular spermatozoa were counseled for AOA in subsequent cycles (IRB 0712009553). For consenting couples, AOA was performed either by exposing post-ICSI oocytes to 50mM of ionomycin (Ionomycin-AOA), or by co-injecting spermatozoa with 0.4pL of rhPLCζ (5mg/mL) during ICSI (rhPLCζ-AOA). Fertilization, embryo development, and clinical outcomes were compared between the couples’ historical and AOA cycles.

Main results and the role of chance
We included 21 couples (maternal age, 35.1±4 yrs; paternal age, 36.8±7 yrs). Female partners all had negative infertility workups that consisted of a comprehensive review of their medical history as well as a targeted physical examination and tests assessing ovarian reserve, ovulatory function, and absence of uterine and tubule structural abnormalities. The couples underwent 53 historical ICSI cycles using poor testicular spermatozoa (concentration, 0.04±0.1x106/ml, 0.5±1% motility) that yielded a 22.5% (94/417) fertilization and only an 11.5% (3/26) clinical pregnancy rate.
All couples subsequently underwent ICSI-AOA cycles. Fourteen couples (maternal age, 35.5±4 yrs; paternal age, 37.6±6 yrs) who were treated with Ionomycin-AOA obtained a higher fertilization of 44.4% (99/223) (P&lt;0.00001), which resulted in a clinical pregnancy rate of 26.3% (5/19). Thus far, four couples have delivered 1 boy and 3 girls, with no major or minor congenital malformations.
The remaining 7 couples (maternal age, 35.8±4 yrs; paternal age, 37.9±7 yrs) underwent subsequent ICSI cycles with rhPLCζ-AOA, which yielded a remarkably higher fertilization of 50.0% (50/134) (P&lt;0.00001). These couples went on to achieve a clinical pregnancy rate of 27.3% (3/11), resulting in the delivery of 1 girl and 2 boys. Initial follow-up has confirmed normal neonatal development.

Limitations, reasons for caution
The effectiveness of AOA in ICSI cycles with testicular spermatozoa is very encouraging, particularly when a more physiological method is utilized. Nonetheless, these findings need to be validated in a larger cohort, confirming successful outcome and children health.

Wider implications of the findings
ICSI utilizing surgically retrieved spermatozoa, particularly testicular, are plagued by suboptimal fertilization, and using AOA may represent a way to normalize the generation of conceptuses. Moreover, a broader adoption of AOA would certainly benefit from the use of a recombinant cytosolic factor normally present in the sperm perinuclear theca.

Trial registration number
n/a