Staging equine seminiferous tubules by Nomarski optics in unstained histologic sections and in tubules mounted in toto to reveal the spermatogenic wave.

This research paper explores the use of Nomarski optics in identifying stages of spermatogenesis in horses, and further characterizes the equine spermatogenic wave. The researchers use this method on both sectioned tissues and whole dispersed tubules.

Methodology

• The researchers used a technique called Nomarski optics, a specialized form of microscopy that generates high-contrast images without the need for staining. They used this technology to identify stages of the spermatogenic cycle of seminiferous tubules.
• The tissues for study were embedded and sectioned at 20 microns. To obtain whole dispersed tubules, the team carried out enzymatic digestion of thin slices of fresh testis.
• After obtaining the dispersed tubules, the samples were fixed, carefully dehydrated in graded levels of alcohol, infiltrated with a type of epoxy resin known as Epon, and then mounted in their entirety onto glass slides.

Findings

• The researchers were able to identify the stages of spermatogenic cycle under Nomarski optics in both histologic sections and the tubules mounted in toto (in whole).
• The study revealed apparent stage-dependent nuclear chromatin and cytoplasmic changes in spermatogonia, spermatocytes, and spermatids, the different stages of sperm cell development. These stages include chromatin condensation, nuclear elongation, acrosomal development from the Golgi and proacrosomic granules, migration of the annulus and mitochondrial alignment, and the transient appearance of the chromatoid body and manchette.
• Both nuclear and cytoplasmic details of Sertoli cells, the ‘nurse’ cells that aid in spermatogenesis, were revealed.
• In tubules mounted in toto, the spermatogenic wave, which is the process of sperm cell development along the length of the tubules, occurred as a consecutive sequence of stages occupying small regions along the tubular length.
• The researchers also found out that the spermatogenic wave in horses is more similar to that of humans than that of rats. Previous research likely used the rat as a model, but these findings indicate that the horse might be a better model for humans.

Significance of Research

• This research introduces a new technique to study spermatogenesis. By combining the enzymatic isolation of seminiferous tubules and identification of spermatogenic stages by Nomarski optics, researchers are given the capacity to examine the spermatogenic wave in species whose tubules are tightly bound and not easily teased apart. This methodology would allow researchers to study these processes effectively and with intricate detail.