Epigenetics Role in Spermatozoa Function: Implications in Health and Evolution-An Overview

Abstract

The unique properties of spermatozoa are established through the spermatogenesis and maturation processes concurrently with its epigenome. It is known that damage to epigenetic mechanisms can lead to reproductive problems. However, scientific reviews addressing the role of the spermatozoa epigenome during the reproductive process are scarce. Therefore, the aim of this review was to offer a detailed overview of current knowledge in the field of spermatozoa epigenetics and its consequent implications. A full search was performed through three databases by combining five keywords. Inclusion criteria were implemented to grant accessibility, relevance, and concretion. Besides, some articles were manually removed or added to obtain an adequate and complete collection of 485 scientific publications. This compilation was used to conduct the bibliometric analysis and the data review separately. Bibliometric results displayed that spermatozoa epigenetics is an active and growing research area. The bibliographic overview showed that sperm epigenome correlates with the development of its function, explaining the environmental influence on reproductive pathologies or abnormal inheritance. The main conclusions were that the normal performance of sperm is heavily reliant on its epigenetics and that this study area is burgeoning, with the potential ability to provide society with clinical innovations in a short-term period.

Keywords: assisted reproductive techniques; epigenetics; male infertility; paternal inheritance; spermatozoa.

Figure 1

Stages of spermatogenesis and morphological changes associated with spermatozoa maturation.

Figure 2

Flowchart summarizing the search and selection process of the articles included in the present article. The study methodology comprises a searching phase, a selection and record phase, and a phase of statistic data analysis and conceptualization. The total number of articles employed was 485 (464 by initial search + 21 by complementary search).

Figure 3

Main results of bibliometric analysis. (a) Variation of the number of annual publications (blue) and accumulation of publications (pink) in the period 2011–2022; (b) Number of publications and citations to each type of document; (c) Number of publications of each country carried out individually (brown) or in collaboration with other countries (pink). There only appear the countries with more than ten studies carried out individually; (d) Variation of the number of annual publications with specific orientation to epigenetics (brown) and with a transversal study of epigenetics (blue). The dashed line and the equation show the linear tendency. Notice that they are expressed at a different scale; (e) Percentage of publications that address each of the mechanisms in spermatozoa centrally; (f) Percentage of publications oriented to study each of the aspects mentioned about the spermatozoa epigenetics (spz. = spermatozoa).

Figure 4

Comparison between histone and protamine compaction.

Figure 5

Overview of the role of epigenetics in the main events during spermatogenesis and maturation.

Figure 6

Overview of the role of epigenetics in the main functions of spermatozoa.

Figure 7

The hypothetical model proposed: Adaptative response conditioned by intensity and assiduity.