Identification and treatment of men with phospholipase Cζ-defective spermatozoa

Abstract

Objective: To identify and treat the gamete responsible for complete fertilization failure with intracytoplasmic sperm injection (ICSI) using a newly proposed assisted gamete treatment (AGT).

Design: Prospective cohort study.

Setting: Center for reproductive medicine.

Patient(s): One-hundred and fourteen couples with an adequate number of spermatozoa for ICSI and a fertilization rate of ≤10%, after controlling for maternal age.

Intervention(s): Couples with an oocyte-related oocyte activation deficiency (OAD) underwent a subsequent cycle with a modified superovulation protocol; couples with sperm-related OAD had an additional genetic and epigenetic assessment to identify mutations and expression levels of the corresponding genes.

Main outcome measure(s): Treatment cycle outcome for couples undergoing ICSI with either a modified superovulation protocol or AGT compared with their historical cycle.

Result(s): A total of 114 couples matched the inclusion criteria, representing approximately 1.3% of the total ICSI cycles performed at our center, with age-matched controls. Fifty-two couples were confirmed negative for sperm-related OAD by the phospholipase Cζ (PLCζ) assay, indicating oocyte-related factors in their failed fertilization cycles. Couples were treated by one of two AGT protocols, AGT-initial or AGT-revised, in a subsequent attempt that was compared with their historical cycle. Subsequent ICSI cycles with a tailored superovulation protocol yielded significantly higher fertilization (59.0% vs. 2.1%) and clinical pregnancy (28.6% vs. 0) rates. In 24 couples (mean ± standard deviation: maternal age, 35.6 ± 5 years; paternal age, 39.8 ± 6 years) sperm-related OAD was confirmed; in four men, a deletion on the PLCZ1 gene was identified. Additional mutations were also identified of genes supporting spermiogenesis and embryo development (PIWIL1, BSX, NLRP5) and gene deletions confirming a complete absence of the subacrosomal perinuclear theca (PICK1, SPATA16, DPY19L). Subsequent AGT treatment provided higher fertilization (42.1%) and clinical pregnancy (36% vs. 0%) rates for couples with a history of impaired (9.1%) fertilization. A comparison of the two AGT protocols, AGT-initial or AGT-revised, revealed that the latter yielded even more favorable fertilization (37.6% vs. 45.9%) and clinical pregnancy (21.1% vs. 83.3%) rates.

Conclusion(s): In couples with an oocyte-related OAD, tailoring the superovulation protocol resulted in successful fertilization, term pregnancies, and deliveries. In couples with a sperm-related OAD as determined by PLCζ assay, mouse oocyte activation test, and the assessment of gene mutations and function, AGT was successful. The AGT-revised protocol yielded an even higher fertilization rate than the AGT-initial protocol, resulting in the birth of healthy offspring in all couples who achieved a clinical pregnancy.

Keywords: Assisted oocyte activation; failed fertilization; intracytoplasmic sperm injection; male infertility; phospholipase Cζ.