165 Epididymal cauda molecular profile is altered by scrotal heat stress
M. B. R. Alves A , L. Alves A , H. F. R. A. Saraiva A , T. H. C. De Bem A , R. P. Nociti A , M. R. Chiaratti B , J. C. da Silveira A , L. A. Silva A and F. Perecin AA Department of Veterinary Medicine, School of Animal Science and Food Engineering, Universidade de São Paulo, Pirassununga, São Paulo, Brazil
B Department of Genetics and Evolution, Federal University of São Carlos, São Carlos, São Paulo, Brazil
Reproduction, Fertility and Development 35(2) 210-210 https://doi.org/10.1071/RDv35n2Ab165
Published: 5 December 2022
© 2023 The Author(s) (or their employer(s)). Published by CSIRO Publishing on behalf of the IETS
The epididymis is a key organ in which sperm acquire motility and the ability to fertilise the eggs through maturation mediated mainly by extracellular vesicles (EVs). In bulls, the epididymis is divided into the caput, corpus, and cauda segments. While the period of maturation through the caput and corpus is around 3.5 days, in cauda, sperm are stored in a quiescent state during a wide-ranging period of 1–6 days immediately before ejaculation. Thus, insults to epididymal cauda might impair sperm fertility potential. Recently, we evidenced that the molecular profile of sperm and EVs from seminal plasma are altered after scrotal heat stress (SHS) in bulls. Herein, we investigated the molecular profile of epididymal cauda tissue after SHS. Eight Nellore bulls (Bos indicus; 582.25 ± 17.58 kg; 30.50 ± 0.45 months) were distributed into SHSg (n = 4) and control (n = 4; CON) groups. SHS was induced during 48 h with scrotal bags. Scrotal surface temperature (SST) was measured using a T620 thermographic camera (FLIR Systems) immediately before and after SHS. Rectal temperature (RT) and environmental temperature (ET) were also measured. The epididymides were collected immediately after SHS, followed by the slaughter of the bulls; caudae were isolated for morphology (length, height, and width), histology, and RNA sequencing. For histology, fragments were fixed in periodate lysine paraformaldehyde 4% for 72 h and were embedded in paraffin, stained with hematoxylin-eosin, and evaluated for the degree of degeneration, lumen/epithelium ratio, and number of nuclei per μm of the epithelium basal pole in ImageJ software (National Institutes of Health). RNA sequencing was performed on ducts collected following the retrograde perfusion using Illumina platform with a library of RNAs > 200 nts. All samples displayed RIN > 6. Groups were compared by ANOVA and statistical difference was considered when P < 0.05. For RNA sequencing, P-adjusted value and log2FC > 0.6 and < −0.6 were considered. Epidydimal cauda area SST was similar (P = 0.60) before SHS and higher (P = 0.0004) in SHSg after stress (SHSg: 32.75 ± 0.79°C vs CON: 26.98 ± 0.17°C). RT and ET were similar between the groups before and after SHS. No differences were found in morphology or in the degree of degeneration and lumen/epithelium ratio. SHSg tended (P = 0.06) to show a higher number of nuclei per μm of the epithelium basal pole. RNA sequencing indicated that, out of 20,172 identified transcripts, 3,314 showed a different expression related to, among others, PI3K-AKT pathway (e.g. alteration in FOXO6 expression), an intracellular signal transduction pathway that promotes metabolism, proliferation, cell survival, growth, and angiogenesis. Thus, cauda epididymis is susceptible to SHS-induced alterations in metabolism and cell proliferation. Our results shed light on the mechanisms that might impair sperm fertility potential during the storage in epididymal cauda.
This research was supported by FAPESP 2021/08759-2, FAPESP 2019/23685-5 and CNPq 308014/2021-9.
