Macrophages in bovine term placenta: An ultrastructural and molecular study.

Reyhaneh Hooshmandabbasi,Holm Zerbe,Karl Klisch,Ali Kazemian,Mariusz P Kowalewski

doi:10.1111/rda.13983

Abstract

Retention of foetal membranes (RFM) is a major reproductive disorder in dairy cows. An appropriate immune response is important for a physiological expulsion of the foetal membranes at parturition. Our study aims to provide a deeper insight into characteristics of foetal and maternal macrophages in bovine term placenta. We used transmission electron microscopy (TEM), immunohistochemistry and semi‐quantitative RT‐PCR to provide a deeper insight into characteristics of foetal and maternal macrophages in bovine term placenta. Semi‐quantitative RT‐PCR was used to define macrophage polarization in foetal and maternal compartments of normal term placenta. Gene expression of factors involved in M1 polarization [interferon regulatory factor‐5 (IRF5), interleukin (IL)‐12A, IL12B] and in M2 polarization (IL10) were studied. Ultrastructurally, foetal macrophages showed an irregular shape and large vacuoles, whereas the maternal macrophages were spindle shaped. By immunohistochemistry, macrophages were identified by a strong staining with the lysosomal marker Lysosome‐associated membrane glycoprotein 1 (LAMP‐1), while myofibroblast in the maternal stroma was positive for alpha‐smooth muscle actin. We used the LAMP‐1 marker to compare the density of foetal stromal macrophages in placentas of cows with RFM and in controls, but no statistically significant difference was observed. RT‐PCR showed a higher expression of all studied genes in the maternal compartment of the placenta and generally a higher expression of M1‐, compared to M2‐associated genes. Our results indicated that at parturition placental macrophages predominantly show the pro‐inflammatory M1 polarization. The higher expression of all the target genes in the maternal compartment may denote that maternal macrophages in bovine term placenta are more frequent than foetal macrophages.

Highlights

Retention of foetal membranes (RFM) is a common problem in bovine reproduction
Our study aims to provide a deeper insight into characteristics of foetal and maternal macrophages in bovine term placenta
Together with the typical morphology of the foetal macrophages, which was observed in transmission electron microscopy (TEM) and light microscopy, and a strong Lysosome-associated membrane glycoprotein 1 (LAMP-1) expression, we are confident that the counted cells are macrophages

Summary

Introduction

Retention of foetal membranes (RFM) is a common problem in bovine reproduction. It occurs in 3%–12% of parturitions (Esslemont & Kossaibati, 1996; Sheldon, 2004) and negatively affects the subsequent reproductive capability of affected cows and leads to significant economic losses (Dubuc et al, 2011; Kumari et al, 2014). RFM is defined as the failure of expulsion of foetal membranes (FM) within 12–24 hr after delivery of the calf (Beagley et al, 2010). Several factors that lead to RFM have been identified (Beagley et al, 2010; Mahnani et al, 2021), the precise biochemical and morphological mechanisms remain elusive. The increased incidence of RFM in cows which share MHC class I antigens with their conceptus highlights the possible role of immunological mechanisms in the release of FM (Benedictus et al, 2015; Joosten et al, 1991)

Objectives

Methods

Findings

Discussion

Conclusion