Assessing the Correlation Between Phospholipase C Zeta Measurements and Semen Parameters

Overview

With declining fertility rates Worldwide, Assisted Reproductive Technology is seen as a viable solution for infertility, however, individual success rates following ART remain relatively low, rarely exceeding \~50%. The European Society for Human Reproduction and Embryology (ESHRE) indicates pregnancy rates per embryo transfer remain below 50%. Additionally, male infertility is regarded as a leading contributor to global infertility with approximately a third of cases attributed to genetic causes while half of the cases remain unexplained. In this observational study we investigate the correlation between phospholipase C Zeta (PLCζ ) measurements and semen parameters. PLCζ is a sperm-specific protein which is introduced into a mature egg (oocyte) following gamete fusion and upon introduction, PLCζ is believed to initiate a series of characteristic calcium ion oscillations which lead to oocyte activation and persist beyond the completion of meiosis. Mounting evidence implicates defects in PLCζ in cases of male factor infertility where intracytoplasmic sperm injection (ICSI; whereby a single sperm is injected into the oocyte) is unsuccessful. Furthermore, defects in PLCζ are also increasingly implicated in cases of male sub-fertility, which affects a much larger proportion of the global population. Numerous studies now indicate that PLCζ not only holds significant value as a therapeutic to rescue cases of ICSI failure, but also as a prognostic diagnostic test of male fertility. Indeed, the reduction or absence of normal PLCζ within sperm has been linked to cases of male factor infertility in humans, either due to inactivation through mutation, due to abrogation of protein levels in sperm as a result of mutation in the PLCζ promoter, or mutations within coding exonic regions of the PLCζ gene. Such data indicate both therapeutic, and diagnostic applications for PLCζ within the fertility clinic. This study seeks to determine the effect of abnormal PLCζ on semen parameters and correlate that with downstream events including clinical pregnancy and live birth rates.

Despite advances in assisted reproductive technology (ART), significant gaps remain in understanding recurrent implantation failure and abortive embryogenesis. Male factor infertility is globally the leading cause of infertility, and is particularly prevalent in GCC countries, notably the UAE; where fertility rates have halved over the past decade, driven by cultural, lifestyle, and environmental shifts. Poor semen parameters (sperm count, motility, and morphology) account for 41% of infertility cases in the region. The financial burden is substantial: a single ART cycle can exceed AED 30,000, with couples typically requiring 2-3 cycles (AED 60,000-100,000), translating to an estimated national expenditure of \~AED 0.5 billion annually in fertility treatments alone, excluding associated healthcare investigations. A critical and underexplored mechanism underlying poor ART outcomes involves oocyte activation, initiated at fertilization by characteristic intracellular calcium (Ca²⁺) oscillations. These are triggered by phospholipase C zeta (PLCζ), a sperm-specific protein delivered into the oocyte upon gamete fusion. Ca²⁺ oscillation profiles directly govern cell cycle progression, embryo gene expression, and early developmental competence; deviations in amplitude or frequency compromise embryo quality. Notably, preimplantation mouse studies show that both insufficient and excessive PLCζ impair blastocyst development, with successful outcomes occurring within a \~4-fold effective dose range - mirroring the natural variation of PLCζ levels observed across fertile men. Mounting clinical evidence links reduced or absent sperm PLCζ to fertilization failure following intracytoplasmic sperm injection (ICSI), as well as to broader male sub-fertility. PLCζ deficiencies may arise through point mutations, promoter alterations, or disrupted exonic regions, and correlate with known sperm defects including poor motility, globozoospermia, and elevated DNA fragmentation. Crucially, even when residual PLCζ is sufficient to trigger oocyte activation, it may be inadequate for full embryonic competence, a distinction with major clinical implications for sub-fertile men. Despite this evidence, the direct relationship between sperm PLCζ parameters and downstream outcomes including embryonic efficacy, recurrent implantation failure, and ART success rates has not yet been systematically investigated. We propose that abnormalities in PLCζ-mediated Ca²⁺ oscillations represent a significant and underappreciated contributor to poor global ART outcomes. Establishing this link would position PLCζ as both a prognostic diagnostic marker of sperm health and a therapeutic agent, with the potential to improve outcomes across a broad spectrum of infertility presentations beyond complete fertilization failure.