Three-Dimensional Ultrastructural and Volume Analysis of the Redundant Nuclear Envelope of Developing and Matured Sperm in Mice

Abstract

The ultrastructure of the nuclear envelope (NE) and redundant NE (RNE) of the spermatozoon cannot be observed in detail using conventional electron microscopy. Thus, this study aimed to employ transmission electron microscopy (TEM) and focused ion beam/scanning electron microscopy (FIB/SEM) tomography to fill this research gap. Male mice aged 13 weeks were deeply anesthetized, and the testes and vas deferens were extracted and processed for electron microscopy. In round spermatids, the acrosomal vesicle compressed the nucleus, and the acrosomal center was depressed. The nucleoli concentrated on the contralateral side of the acrosome formation site. In mature spermatozoa, the RNE accumulated in the neck with the residual bodies. The NE pores exhibited a hexagonal pattern. The body surface area and volume of the nuclei of spermatids and spermatozoa in each maturation phase were analyzed using FIB/SEM tomography. The body surface area and volume of the nuclei decreased during spermatid maturation into spermatozoa. The RNE converged at the sperm neck and possessed a honeycomb structure. The method used revealed that the nuclei of spermatids gradually condense as they mature into spermatozoa. This method may be used to analyze small tissues, such as RNE, and detect morphological abnormalities in microtissues, such as spermatozoa.

Three‐dimensional ultrastructural and anatomical analysis of prostatic neuroendocrine cells in mice

“…Thus far, FIB/SEM tomography has been applied to examine fibroblasts, 7 interstitial cells of tendons between bone and muscle, 8 periodontal ligaments, 9 mitochondria, 10 endocrine cells of the pituitary gland, 11 interstitial cells of the mouse vas deferens, 12 mouse circumvallate papillary taste buds before and after birth, 13 and redundant nuclear envelopes of mouse sperm. 14 Three-dimensional ultrastructural analysis of cells and intracellular organelles of various organs has been performed. In this study, we performed three-dimensional ultrastructural analysis of mouse prostatic NECs to clarify their morphology and ultrastructure, their relationship with the surrounding cells and nerves, and their position relative to the lumen of the prostatic duct.…”

“…At our institution, this technique was introduced and put into practical use in 2010, and high‐quality three‐dimensional reconstruction was established at the highest level. Thus far, FIB/SEM tomography has been applied to examine fibroblasts, 7 interstitial cells of tendons between bone and muscle, 8 periodontal ligaments, 9 mitochondria, 10 endocrine cells of the pituitary gland, 11 interstitial cells of the mouse vas deferens, 12 mouse circumvallate papillary taste buds before and after birth, 13 and redundant nuclear envelopes of mouse sperm 14 . Three‐dimensional ultrastructural analysis of cells and intracellular organelles of various organs has been performed.…”