Abstract
The analysis of spermatozoa morphology is fundamental to understand male fertility and the etiology of infertility. Traditionally scanning electron microscopy (SEM) has been used to define surface topology. Recently, however, it has become a critical tool for three-dimensional analysis of internal cellular ultrastructure. Modern SEM provides nanometer-scale resolution, but the meaningfulness of such information is proportional to the quality of the sample preservation. In this study, we demonstrate that sperm quickly and robustly adhere to gold-coated surfaces. Leveraging this property, we developed three step-by-step protocols fulfilling different needs for sperm imaging: chemically fixed monolayers for SEM examination of the external morphology, and two high-pressure freezing-based protocols for fast SEM examination of full cell internal morphology and focused ion-beam SEM tomography. These analyses allow previously unappreciated insights into mouse sperm ultrastructure, including the identification of novel structures within the fibrous sheath and domain-specific interactions between the plasma membrane and exosome-like structures.
Highlights
Sperm ultrastructure and the relationship between sperm structure and function is a primary determinant of male fertility, and infertility, and a critical driver in evolutionary processes (Roldan, 2019)
We developed a fast and reliable protocol of sperm monolayer preparation, New Insights Into Sperm Ultrastructure which can be used in chemical fixation (SEM examination of external morphology) as well as in cryogenic preservation method [high-pressure freezing (HPF) and freeze substitution] allowing the examination of internal morphology at electron microscopic resolution
Serial block-face imaging can be performed if the three-dimensional architecture is required, we found that even a single cross-section can be extremely informative as it will allow an appreciation of the internal connections between, for example, the sperm head and tail (Figure 6)
Summary
Sperm ultrastructure and the relationship between sperm structure and function is a primary determinant of male fertility, and infertility, and a critical driver in evolutionary processes (Roldan, 2019). Scanning electron microscopes (SEM) became commercially available in the late 1960s, and the first studies of sperm external morphology using SEM appeared around the same time Since this time, there have been significant advances in SEM technologies (Breton, 1999). The ability to fill this gap has the potential to inform gene function, the etiology of male infertility, sperm behavior within the female reproductive tract and how subtle changes in sperm structure-function may drive evolutionary processes Toward this goal, we developed a fast and reliable protocol of sperm monolayer preparation, New Insights Into Sperm Ultrastructure which can be used in chemical fixation (SEM examination of external morphology) as well as in cryogenic preservation method [high-pressure freezing (HPF) and freeze substitution] allowing the examination of internal morphology at electron microscopic resolution
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
