Abstract
The wall of the seminiferous tubule in rodents consists of an inner layer of myoid cells covered by an outer layer of endothelial cells. Myoid cells are a type of smooth muscle cell containing α-actin filaments arranged in two independent layers that contract when stimulated by endothelin-1. The irregular surface relief of the tubular wall is often considered a hallmark of contraction induced by a variety of stimuli. We examine morphological changes of the rat seminiferous tubule wall during contraction by a combination of light, confocal, transmission and scanning electron microscopy. During ET-1-induced contraction, myoid cells changed from a flat to a conical shape, but their actin filaments remained in independent layers. As a consequence of myoid cell contraction, the basement membrane became wavy, orientation of collagen fibers in the extracellular matrix was altered and the endothelial cell layer became folded. To observe the basement of the myoid cell cone, the endothelial cell monolayer was removed by collagenase digestion prior to SEM study. In contracted tubules, it is possible to distinguish cell relief: myoid cells have large folds on the external surface oriented parallel to the tubular axis, whereas endothelial cells have numerous cytoplasmic projections facing the interstitium. The myoid cell cytoskeleton is unusual in that the actin filaments are arranged in two orthogonal layers, which adopt differing shapes during contraction with myoid cells becoming cone-shaped. This arrangement impacts on other components of the seminiferous tubule wall and affects the propulsion of the tubular contents to the rete testis.
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Acknowledgments
This study was supported by the following grants: 06 J391, J025 and 06 J442 from SECyTP, UNCuyo, Argentina. The authors thank Dr. Silvia A. Belmonte for her most helpful comments on this manuscript. We appreciate the skilled technical assistance of Ing. Norberto Domizio and Ing. Elisa Bocanegra with light and electron microscopy. The authors also thank Stephen Anderson for editing assistance with the manuscript.
Author contributions
A.D.L. contributed to the study design, acquisition and analysis of data for light and confocal microscopy and preparation of the manuscript. V.S. contributed to data analysis and interpretation for scanning electron microscopy. M.E. and F.E. contributed to perform the immunolocalizations. L.A.L contributed to drafting and critical revision of the manuscript. A.M contributed to study design, acquisition and analysis of data for light and transmission electron microscopy and preparation of the manuscript. All authors revised the manuscript and have approved the final version.
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Losinno, A.D., Sorrivas, V., Ezquer, M. et al. Changes of myoid and endothelial cells in the peritubular wall during contraction of the seminiferous tubule. Cell Tissue Res 365, 425–435 (2016). https://doi.org/10.1007/s00441-016-2386-x
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DOI: https://doi.org/10.1007/s00441-016-2386-x