Spontaneous acrosome reaction and tyrosine phosphorylation concentration in washed spermatozoa affect double...

Do optimized sperm functional factors influence two pronuclei (2PN) formation in conventional IVF?

A prospective investigation (n = 778 IVF cycles). The influences of functional factors of prepared spermatozoa and female factors on the embryo two pronuclei (2PN) formation rate were analysed; 575 cycles were followed up after embryo transfer. Patients were classified into four groups according to 2PN formation rate (<50%, 50 to <70%, 70% to < 90% and ≥90%). Clinical outcome was compared between embryos derived from different ranks of 2PN formation rates.

Ordinal logistic regression analysis revealed that the spontaneous acrosome reaction (sAR) increased the 2PN formation rate (OR 1.331, 95% CI 1.188 to 1.491, P < 0.001), whereas tyrosine phosphorylation had the opposite effect (OR 0.717, 95% CI 0.563 to 0.914, P = 0.007). Additionally, basal-FSH had a significant effect on 2PN formation (OR 2.216, 95% CI 1.477 to 3.324, P < 0.001). Multivariate restricted cubic spline (RCS) analysis revealed that sperm sAR and tyrosine phosphorylation mainly had linear effects; however, the influence of female basal FSH on 2PN formation showed a non-linear pattern (P = 0.042). The implantation rate in young women (<35 years) in the group with a 2PN formation rate less than 50% was significantly lower than that of young women in groups with 2PN formation rates of 50-70% (P = 0.029), 70-90% (P = 0.030), and ≥90% (P = 0.046).

In addition to female basal FSH concentreations, sperm functional factors greatly contribute to normal pronucleus formation in conventional IVF. Therefore, it is necessary to evaluate the sAR and tyrosine phosphorylation in male spermatozoa before starting an IVF cycle to predict and prevent a low 2PN formation rate.