Sertoli Cell Biology

Michael D. Griswold

• Publisher: Elsevier
• Year: 2014
• ISBN:
  9780124170483
• Edition: 2
• Topic: Biological Sciences
• Subtopic: Cell Biology
• Index: Biological Sciences

Sertoli Cell Biology, Second Edition summarizes the progress since the last edition and emphasizes the new information available on Sertoli/germ cell interactions. This information is especially timely since the progress in the past few years has been exceptional and it relates to control of sperm production in vivo and in vitro.

• Fully revised
• Written by experts in the field
• Summarizes 10 years of research
• Contains clear explanations and summaries
• Provides a summary of references over the last 10 years

1

Sertoli cell anatomy and cytoskeleton

Rex A. Hess^a and A. Wayne Vogl^b, ^aReproductive Biology and Toxicology, Department of Comparative Biosciences, University of Illinois, Urbana, IL, ^bDepartment of Cellular and Physiological Sciences, Faculty of Medicine, The University of British Columbia, Vancouver, BC

Sertoli cell morphology has been thoroughly reviewed in the past from basic light and electron microscopy viewpoints, all of which pointed out the uniqueness of this “mother cell” that sends its cytoplasmic arms as “branches of trees” to hold and nurture the development of germ cells. During the past decade, major advancements in Sertoli cell biology have been made using immunofluorescence and three-dimensional imaging made possible with laser-scanning confocal microscopy. Here, we review our current understanding of Sertoli cell morphology with a specific focus on the cytoskeleton. The relationship of the cytoskeleton to intercellular junctions, ectoplasmic specializations, tubulobulbar complexes, and vesicular transport systems is re-examined. Although newer techniques provide a wealth of data on the molecular components of the Sertoli cell, the results will require additional experimental approaches and careful interpretation to provide consistency in data among anatomy, molecular biology, and cell physiology.

Keywords

Testis; Sertoli cell; light microscopy; electron microscopy; immunohistochemistry; cytoskeleton; ectoplasmic specialization; tight junction; blood–testis barrier; tubulobulbar complex

I Introduction

Numerous and extensive reviews have been written about basic morphology of the mammalian Sertoli cell [1–9]. The purpose of this chapter is not to repeat all that has been covered in the past, but rather to ask how do we deal with the plethora of new data being generated using morphological techniques previously unavailable in the study of this cell [10]. The first book, titled The Sertoli Cell, was filled with photomicrographs illustrating Sertoli cell morphology [11], which was an appropriate tribute to Enrico Sertoli, the first scientist to publish drawings of the cell, later to be given his family name [12–14]. It took nearly an additional 100 years before electron microscopy revealed the intricate complexities of the Sertoli cell within the seminiferous epithelium [15]. The second book, Sertoli Cell Biology, included a review of the morphological variations in cellular organelles [9]; however, much of the book was devoted to Sertoli cell physiology and molecular biology [16]. So, with regard to Sertoli cell anatomy, what has changed during the past 10 years?

Basic Sertoli cell anatomy began with crude drawings published in 1865 [9,13], showing cellular extensions, described as “…branched out that touch two cells…” and holding germ cells in “…the canaliculi, or free, and still shut away in the mother cells.” Thus, the concept of “cellule madri” or “mother cell” was born and subsequent publications have shown the finer details, with descriptions of the Sertoli cell as “…not unlike trees…” with their cytoplasmic arms surrounding germ cells like long branches [17].

These earlier studies attempted to leave the reader with a three-dimensional view of the Sertoli cell (Figure 1.1), sending its thin cytoplasmic processes to envelope germ cells as they moved up and down through the seminiferous epithelium, from basement membrane to the luminal surface. Approximately 40% of the Sertoli cell membrane contacts the surface of the elongated spermatids [19], which results in the extension of thin strands of cytoplasm, sometimes reaching a minimum width of less than 50 nm. The cell’s unique morphology made it difficult to observe intimate relationships between cells with routine histology. Ultrastructural studies later helped to fill the gaps in our understanding of junctional complexes, the blood–testis barrier, spermiation, and Sertoli cell’s phagocytosis of the residual body [10].

Figure 1.1 Sertoli cell illustrations of three-dimensional-like projections of its cytoplasm. Each illustration was adapted from an original figure, and used with permission of the publisher. 1865: Sertoli; [13] 1993: Russell; [5] 1988: Kerr; [18] 1990: Ueno [6].

Long ago, Lonnie Russell recognized the importance of improving morphological techniques for observing Sertoli and germ cell interactions. He was one of the first to use thick, plastic-embedded tissue sections of testis for light microscopy, in addition to using thin sections for electron microscopy [20]. During the past decade, scientists have uncovered a wealth of information on genes and proteins expressed in the testis. These advances in basic knowledge were made possible in part because DNA sequencing of the mouse genome was completed. This sequence of data permitted the identification of potentially important gene products for the production of antibodies, which then could be used to localize the proteins in the testis. Thus, since 2005, two techniques have led the way in the study of reproductive morphology. First, the use of immunohistochemistry became the method of choice for identifying and localizing proteins in the cell. Use of this powerful technique has grown exponentially, as evidenced by a recent publication specifically focused on this technique for the study of spermatogenesis [21]. Second, the development of laser-scanning confocal microscopy provided the ability to three-dimensionally image Sertoli–germ cell interactions with relative ease using immunofluorescence.

Our review examines the more general morphological features of Sertoli cells using immunohistochemical and fluorescent markers (Figure 1.2), with a special focus on the cytoskeleton. Immunolocalizations of proteins in the nucleus are fairly simple to interpret if the protein of interest is restricted to the Sertoli cell within the seminiferous epithelium. However, careful interpretation is required for the staining of membrane-associated structures, in which proteins are positioned at the Sertoli–Sertoli junction, the ectoplasmic specialization or the disengagement complex during spermiation. These structural zones of the cytoplasm and membrane ...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• List of contributors
• Preface
• 1. Sertoli cell anatomy and cytoskeleton
• 2. Establishment of fetal Sertoli cells and their role in testis morphogenesis
• 3. Early postnatal interactions between Sertoli and germ cells
• 4. The spermatogonial stem cell niche in mammals
• 5. DMRT1 and the road to masculinity
• 6. Hormonal regulation of spermatogenesis through Sertoli cells by androgens and estrogens
• 7. Activins and inhibins in Sertoli cell biology: Implications for testis development and function
• 8. The initiation of spermatogenesis and the cycle of the seminiferous epithelium
• 9. Retinoic acid metabolism, signaling, and function in the adult testis
• 10. Stage-specific gene expression by Sertoli cells
• 11. MicroRNAs and Sertoli cells
• 12. Biochemistry of Sertoli cell/germ cell junctions, germ cell transport, and spermiation in the seminiferous epithelium
• 13. Sertoli cell structure and function in anamniote vertebrates
• 14. Adult Sertoli cell differentiation status in humans
• 15. Gene knockouts that affect Sertoli cell function