Sperm vacuoles cannot help to differentiate fertile men from infertile men with normal sperm parameter values

Abstract

Study question: Can the assessment of sperm vacuoles at high magnification contribute to the explanation of idiopathic infertility?

Summary answer: The characteristics of sperm head vacuoles (number, area, position) are no different between fertile controls and patients with unexplained infertility.

What is known already: Until now, the assessment of sperm head vacuoles has been focused on a therapeutic goal in the intracytoplasmic morphologically selected sperm injection (IMSI) procedure, but it could be pertinent as a new diagnostic tool for the evaluation of male fertility.

Study design, size, duration: This diagnostic test study with blind assessment included a population of 50 fertile men and 51 men with idiopathic infertility. They were selected from September 2011 to May 2013.

Participants/materials, setting, methods: Fertile men were within couples who had a spontaneous pregnancy in the last 2 years. Infertile men were within couples who had unexplained infertility and were consulting in our centre. After analysis of conventional sperm parameters, we investigated the number, position and area of sperm head vacuoles at high magnification (×6000) with interference contrast using an image analysis software. We also carried out a nuclear status analysis by terminal deoxynucleotidyl transferase-mediated dUTP nick end labelling assay (TUNEL), sperm chromatin structure assay (SCSA) and aniline blue staining.

Main results and the role of chance: Concerning the vacuoles data, we did not find any significant difference between the two populations. We found no significant correlation between the vacuolar parameters (mean number of vacuoles, relative vacuole area and percentage of spermatozoa with large vacuoles) and either conventional semen parameters, male age or the data from the aniline blue staining, SCSA assay and TUNEL assay.

Limitations, reasons for caution: Despite the fact all of the vacuole parameters values were identical in fertile and infertile men, we cannot totally exclude that a very small cause of unexplained infertilities could be related to an excess of sperm vacuoles.

Wider implications of the findings: In line with its widely debated use as a therapeutic tool, sperm vacuole assessment for diagnostic purposes does not seem useful.

Study funding/competing interests: The study was funded by a grant from Association pour la Recherche sur les Traitements de la Stérilité. There are no competing interests to declare.

Keywords: IMSI; MSOME; fertile men; sperm vacuole; unexplained infertility.