Timing of sperm capacitation varies reproducibly among men

Abstract

Sperm must mature functionally in the process of capacitation to become able to fertilize. Capacitation depends on membrane lipid changes, and can be quantitatively assessed by redistribution of the ganglioside GM1, the basis of the Cap‐Score™ sperm function test. Here, differences in Cap‐Score were compared among and within men at two time points. Ejaculates were liquefied, washed, and incubated for 3 hr under capacitating (Cap) conditions, then fixed and analyzed immediately (Day0); after being incubated 3 hr under Cap conditions then maintained 22–24 hr in fix (Day1‐fix); or after 22–24 hr incubation under Cap conditions prior to fixation (Day1). In all cases, a light fixative previously shown to allow membrane lipid movements was used. Day1‐fix and Day1 Cap‐Scores were greater than Day0 (p < 0.001; n = 25), whereas Day1‐fix and Day1 Cap‐Scores were equivalent (p = 0.43; n = 25). In 123 samples from 52 fertile men, Cap‐Score increased more than 1SD (7.7; calculated previously from a fertile cohort) from Day0 to Day1‐fix in 44% (54/123) of the samples. To test whether timing of capacitation was consistent within an individual, 52 samples from 11 fertile men were classified into either “early” or “late” capacitation groups. The average capacitation group concordance within a donor was 81%. Median absolute deviation (MAD; in Cap‐Score units) was used to assess the tightness of clustering of the difference from Day0 to Day1‐fix within individuals. The average (2.21) and median (1.98) MAD confirmed consistency within individuals. Together, these data show that the timing of capacitation differed among men and was consistent within men.

Cap‐Score™ prospectively predicts probability of pregnancy

“…Assays proposed over the years to fill these needs have not demonstrated efficacy at prospectively predicting the clinical outcome of generating a pregnancy (Barratt et al, 2018), and are often found to correlate with the traditional semen analysis parameters (Aitken, 2002;Giwercman et al, 2003;Hazary, Chaudhuri, & Wishart, 2001;Zini et al, 2009). Prospective data presented here strongly demonstrate that the Cap-Score, a measure quantifying the percentage of sperm that can capacitate and undergo acrosome exocytosis Moody et al, 2017;Ostermeier et al, 2018), successfully predicted low or high success at achieving pregnancy in three or fewer attempts at IUI. Yet from a clinical perspective, we know that male fertility does not simply switch between a binary "infertile" to "fertile"…”

“…Cap‐Scores were highly reproducible among ejaculates within a man and had no relationship with traditional semen analysis parameters (Cardona et al, ). In addition, we showed at the level of single sperm, that those cells having the “capacitated” patterns were indeed those cells that could undergo acrosome exocytosis in response to ionophore (A23187; Moody et al, ) and progesterone (Ostermeier et al, ). Using repeated Cap‐Score values over time, we also found that the timing of capacitation differed among men but was consistent within a man (Ostermeier et al, ).…”

“…That is, their success was no better than that of men whose sperm had low capacitation ability. One possible explanation is offered by our recent finding that the timing of capacitation differs among men, but is reproducible within repeated ejaculates of a given man (Ostermeier et al, ). In that study, 44% of men were shown to have sperm that took significantly longer to capacitate than those of their peers (Ostermeier et al, ).…”

“…One possible explanation is offered by our recent finding that the timing of capacitation differs among men, but is reproducible within repeated ejaculates of a given man (Ostermeier et al, 2018). In that study, 44% of men were shown to have sperm that took significantly longer to capacitate than those of their peers (Ostermeier et al, 2018). Currently, insemination is typically performed 24-36 hr after human chorionic gonadotropin (hCG) injection.…”

Proper cytoskeleton α‐tubulin distribution is concomitant to tyrosine phosphorylation during in vitro capacitation and acrosomal reaction in human spermatozoa

“…This wide time range is associated with the vast heterogeneity of semen samples, resulting in spermatozoa subpopulations with different degrees of functionality and membrane cholesterol content (Buffone, Doncel, Marin Briggiler, Vazquez-Levin, & Calamera, 2004;Buffone, Verstraeten, Calamera, & Doncel, 2009). Likewise, a previous study reported that spermatozoa need to capacitate for at least 4 hr for properly recognize the oocyte's zona pellucida (Baibakov, Boggs, Yauger, Baibakov, & Dean, 2012) and another report demonstrated that the timing of capacitation in human spermatozoa differs among men but is reproducible within each individual (Ostermeier et al, 2018).…”