HISTOLOGY AND HISTOPATHOLOGY

From Cell Biology to Tissue Engineering

 

Bovine oviduct epithelial cells suppress the phagocytic activity of neutrophils towards sperm but not for bacteria in vitro: Immunofluorescence and electron microscopic observations

Mohamed Ali Marey1,2, Haruhisa Matsukawa1, Motoki Sasaki3, Mohamed Aboul Ezz1,4, Mohamed Samy Yousef1,5, Ken-ichi Takahashi6 and Akio Miyamoto1

1Graduate School of Animal and Food Hygiene, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Japan, 2Department of Theriogenology, Faculty of Veterinary Medicine, Damanhur University, Behera, Egypt, 3Department of Basic Veterinary Science, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Japan, 4Department of Theriogenology, Faculty of Veterinary Medicine, Mansoura University, Mansoura, 5Department of Theriogenology, Faculty of Veterinary Medicine, Assiut University, Assiut, Egypt and 6Genetics Hokkaido Association, Shimizu-cho, Japan

Offprint requests to: Akio Miyamoto, PhD, Animal Medical Science Department, Graduate School of Animal and Food Hygiene, Obihiro University of Agriculture and Veterinary Medicine, Obihiro 080-8555, Japan. e-mail: akiomiya@obihiro.ac.jp


Summary. Previously, we reported that polymorpho-nuclear neutrophils (PMNs) are constantly existent in the bovine oviduct fluid during the pre-ovulatory stage under physiological conditions. Moreover, incubation of PMNs with bovine oviduct epithelial cells-conditioned medium (BOEC-CM) resulted in suppression of their phagocytic activity for sperm. During pathophysiological conditions, cows may be inseminated by infected semen which exposes oviductal PMNs to allogenic sperm simultaneously with pathogens. This study aimed to visually investigate the role of oviduct epithelium in regulating the phagocytic behavior of PMNs toward sperm as a physiological stimulus, with Escherichia coli (E. coli) as a pathological stimulus. In our experiment, PMNs were incubated for 2 h in BOEC-CM. Phagocytosis was then assayed by co-incubation of these PMNs either with sperm, E. coli, or latex beads. BOEC-CM significantly suppressed the direct phagocytosis of PMNs for sperm, but did not affect their phagocytic activity for E. coli or latex beads. Additionally, an investigation with scanning electron microscopy revealed that BOEC-CM suppressed the formation of DNA-based neutrophil extracellular traps (NETs) for sperm entanglement. BOEC-CM did not alter NETs formation towards E. coli. A quantification of NETs formation using an immunofluorescence microscopy showed that the areas of NETs formation for E. coli were significantly larger than those formed for sperm. Our data clearly show that the bovine oviduct, through secretions, protects sperm from phagocytosis by PMNs and eliminates bacterial dissemination through maintaining the phagocytic activity of PMNs towards bacteria. Histol Histopathol 35, 589-597 (2020)

Key words: Oviduct, Neutrophils, Sperm, Bacteria, Phagocytosis

DOI: 10.14670/HH-18-172