Chromatin Protamination and Catsper Expression in Spermatozoa Predict Clinical Outcomes after Assisted Reproduction Programs

S Marchiani,E Baldi,F Benini,G Rastrelli,M Maggi,L Tamburrino,S Pellegrini,R Dolce,L Fanfani

doi:10.1038/s41598-017-15351-3

Abstract

Identification of parameters predicting assisted reproductive technologies (ARTs) success is a major goal of research in reproduction. Quality of gametes is essential to achieve good quality embryos and increase the success of ARTs. We evaluated two sperm parameters, chromatin maturity and expression of the sperm specific calcium channel CATSPER, in relation to ART outcomes in 206 couples undergoing ARTs. Chromatin maturity was evaluated by Chromomycin A3 (CMA3) for protamination and Aniline Blue (AB) for histone persistence and CATSPER expression by a flow cytometric method. CMA3 positivity and CATSPER expression significantly predicted the attainment of good quality embryos with an OR of 6.6 and 14.3 respectively, whereas AB staining was correlated with fertilization rate. In the subgroup of couples with women ≤35 years, CATSPER also predicted achievement of clinical pregnancy (OR = 4.4). Including CMA3, CATSPER and other parameters affecting ART outcomes (female age, female factor and number of MII oocytes), a model that resulted able to predict good embryo quality with high accuracy was developed. CMA3 staining and CATSPER expression may be considered two applicable tools to predict ART success and useful for couple counseling. This is the first study demonstrating a role of CATSPER expression in embryo development after ARTs programs.

Highlights

Physiologically retained by spermatozoa, a greater persistence of histones or a decreased protamination are an index of chromatin immaturity that can affect sperm quality and the fertilizing capacity[9]
None of the semen parameters evaluated on the day of pick up nor male age were related to early assisted reproductive technologies (ARTs) outcomes, pregnancy achievement or delivery
Among the critical steps for ART success, the development of a good quality embryo appears of upmost importance, as it is highly related to the attainment of clinical pregnancy, as demonstrated in the current and previous studies[3]

Summary

Introduction

Physiologically retained by spermatozoa, a greater persistence of histones or a decreased protamination are an index of chromatin immaturity that can affect sperm quality and the fertilizing capacity[9]. The few men with deletions in CATSPER subunits genes, leading to absence of a functional channel in spermatozoa, are infertile and show poor semen quality[25,26] Until now, it is unknown whether CATSPER expression is implicated in human fertilization process or related to ART outcomes. We here assessed chromatin maturity status (by CMA3 and AB staining) and CATSPER1 expression (by a flow cytometric method) in semen samples from male partners of 206 couples undergoing ART treatments To determine if these male molecular markers may be predictive of ART success, it was evaluated their association with ART outcomes, both as single test and in combination, taking into account several confounding factors affecting the statistical analysis

Methods

Results

Conclusion