Lipophagy contributes to long-term storage of spermatozoa in the epididymis of the Chinese soft-shelled turtle Pelodiscus sinensis
Hong Chen A , Yufei Huang A , Ping Yang A , Tengfei Liu A , Nisar Ahmed A , Lingling Wang A , Taozhi Wang A , Xuebing Bai A , Abdul Haseeb A and Qiusheng Chen A B
+ Author Affiliations
- Author Affiliations
A Ministry of Education (MOE) Joint International Research Laboratory of Animal Health and Food Safety, College of Veterinary Medicine, Nanjing Agricultural University, 1 Weigang, Nanjing, Jiangsu Province, 210095, China.
B Corresponding author. Email: chenqsh305@njau.edu.cn
Reproduction, Fertility and Development 31(4) 774-786 https://doi.org/10.1071/RD18307
Submitted: 7 August 2018 Accepted: 9 November 2018 Published: 10 December 2018
Abstract
Spermatozoa are known to be stored in the epididymis of the Chinese soft-shelled turtle Pelodiscus sinensis for long periods after spermiation from the testes, but the molecular mechanisms underlying this storage are largely unknown. In this study, epididymal spermatozoa were investigated to determine the potential molecular mechanism for long-term sperm storage in P. sinensis. Transmission electron microscopy (TEM) and Oil red O staining indicated that unusually large cytoplasmic droplets containing lipid droplets (LDs) were attached to the epididymal spermatozoa. However, the content of LDs decreased gradually with the sperm storage. LDs were surrounded by autophagic vesicles and sequestered as degradative cargo within autophagosome. Immunofluorescence and western blotting demonstrated that autophagy in spermatozoa increased gradually with the storage time. In vitro studies found that spermatozoa obtained from soft-shelled turtles in January can survive more than 40 days at 4°C. Furthermore, immunofluorescence and TEM showed that autophagy was involved in the degradation of LDs with the extension of sperm incubation. Inhibition of autophagy with 3-methyladenine significantly suppressed LD degradation. Moreover, adipose triglyceride lipase was involved in the metabolism of LDs. These findings indicate that lipophagy was activated to maximise LD breakdown, which contributes to long-term sperm storage in the epididymis of P. sinensis.
Additional keywords: adipose triglyceride lipase, autophagy, lipid droplets, sperm conservation in vitro, TEM.
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