**5. Conclusive remarks**

The mammalian testis possesses a special microenvironment for fulfilling its functions. The adluminal compartments of the seminiferous epithelium are separated from blood circulation by the BTB, and the circulating phagocytes cannot reach these regions. Therefore, Sertoli cells are responsible for the clearance of numerous AGC and RB during spermatogenesis. The phagocytic removal of apoptotic components by Sertoli cells is not only for waste disposal but also confers more meaning. In addition to prevention of autoimmune responses by removing autoantigens, recycling of apoptotic components can be used as an energy source for Sertoli cells. These biological processes would be particularly important in the tissues where immunogenic autoantigens are produced and seldom reached by circulating nutritious substrates. The mechanisms behind cell death and their removal by phagocytes, and their tissue-specific significance, are worthwhile to investigate in depth.

### **Acknowledgements**

This work was supported by grants from the CAMS Initiative for Innovative Medicine (Nos. 2017-I2M-B&R-06, 2017-I2M-3-007) and the Major State Basic Research Project of China (Nos. 2016YFA0101001 and 2018YFC1003902).

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**Author details**

Fei Wang and Daishu Han\*

Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences, School of Basic Medicine, Peking Union Medical College, Beijing, China

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

\*Address all correspondence to: dshan@ibms.pumc.edu.cn

provided the original work is properly cited.

*Sertoli Cell Phagocytosis: An Essential Event for Spermatogenesis*

*DOI: http://dx.doi.org/10.5772/intechopen.86808*

*Sertoli Cell Phagocytosis: An Essential Event for Spermatogenesis DOI: http://dx.doi.org/10.5772/intechopen.86808*

*Male Reproductive Health*

**4.3 Providing energy**

cells to undergo apoptosis during spermatogenesis.

The mammalian testis possesses a special microenvironment for fulfilling its functions. The adluminal compartments of the seminiferous epithelium are separated from blood circulation by the BTB, and the circulating phagocytes cannot reach these regions. Therefore, Sertoli cells are responsible for the clearance of numerous AGC and RB during spermatogenesis. The phagocytic removal of apoptotic components by Sertoli cells is not only for waste disposal but also confers more meaning. In addition to prevention of autoimmune responses by removing autoantigens, recycling of apoptotic components can be used as an energy source for Sertoli cells. These biological processes would be particularly important in the tissues where immunogenic autoantigens are produced and seldom reached by circulating nutritious substrates. The mechanisms behind cell death and their removal by phagocytes, and their tissue-specific significance, are worthwhile to investigate

This work was supported by grants from the CAMS Initiative for Innovative Medicine (Nos. 2017-I2M-B&R-06, 2017-I2M-3-007) and the Major State Basic Research Project of China (Nos. 2016YFA0101001 and 2018YFC1003902).

**5. Conclusive remarks**

Another meaning of male germ cell death and removal of AGC and RB serves as energy sources for Sertoli cells [71]. After phagocytosis by Sertoli cells, AGC and RB fuse with lysosomes. AGC and RB are subsequently broken down and recycled as energy sources for ATP production. The most noticeable phenotype of Sertoli cells is the formation of numerous lipid droplets in the cell cytoplasm. These lipid droplets result from the breakdown of engulfed AGC and RB [13, 72]. Unlike the majority of cell types that mainly use glucose as an energy source, Sertoli cells predominantly use lipids to produce ATP [71]. The lipids from AGC and RB should be the main energy sources for Sertoli cells. Sertoli cells provide essential physical and environmental support for spermatogenesis, which are energy consumers. Corresponding to their function, Sertoli cells exhibit an active energy metabolism and produce high levels of ATP [71, 73]. While lipids and glucoses can be substrates for ATP production within cells under physiological conditions, the majority of cell types use glycogen to produce ATP, whereas lipids serve as energy storage. Only minor cell types, such as adipocytes, myocardial cells, and Sertoli cells, have been confirmed to actively utilize lipids to produce ATP. Why these cell types predominantly use lipids as energy sources remains unclear. However, the active usage of lipids by Sertoli cells is compatible with the special microenvironment in the testis. Sertoli cells are barely reached by the nutrition from the peripheral circulation due to the barriers in the basement membrane, BTB, and the absence of blood capillaries within the seminiferous epithelium. The simplest way for Sertoli cells to have enough energy to support spermatogenesis is to recycle the lipid contents of AGC and RB. Therefore, the phagocytic removal of AGC and RB by Sertoli cells is necessary for Sertoli cells to ensure their functions, which confers a novel meaning for a large number of germ

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in depth.

**Acknowledgements**
