Gene expression profiling of bovine peripartal placentomes: detection of molecular pathways potentially involved in the release of foetal membranes

Abstract

The mechanisms underlying detachment of foetal membranes after birth in cows are still unclear. To address this problem in a systematic manner, we performed the first holistic transcriptome study of bovine placentomes antepartum (AP; nZ4 cows) and intrapartum (IP; nZ4 cows) using Affymetrix GeneChip Bovine Genome Arrays. Three placentomes were extracted from each cow, and tissue samples from the contact zones of the placentomes (foeto-maternal units) were recovered by systematic random sampling and processed for RNA extraction and for stereological quantification of cellular composition. Statistical analysis of microarray data (false discovery rate 1%) revealed 759 mRNAs with at least twofold higher levels in the samples of the AP group, whereas 514 mRNAs showed higher levels in the IP group. The differentially expressed genes were classified according to biological processes and molecular functions using the Functional Annotation Clustering tool of the DAVID Bioinformatics Resources. Genes with higher mRNA levels in the AP group were nearly completely related to mitotic cell cycle and tissue differentiation. During parturition, a complete shift occurred because the genes with higher mRNA levels in IP were nearly all related to three different physiological processes/complexes: i) apoptosis, ii) degradation of extra cellular matrix and iii) innate immune response, which play a fundamental role in placental detachment. These results are an excellent basis for future studies investigating the molecular basis of retained foetal membranes.

Innate immunity and inflammation of the bovine female reproductive tract in health and disease

“…In several species, the reduction in the influence of progesterone is associated with an increase in inflammatory mediators, such as IL1b, IL6, IL8, and TNFa, and an influx of leukocytes (Challis et al 2009). Similar mechanisms are likely important in cattle, as there is increased expression of genes such as CXCL8, CXCL2 and CXCL6 in the placentomes of healthy cattle during parturition (Streyl et al 2012). Another feature of the peripartal bovine uterus is the accumulation of CD14…”

Investigations into the mechanisms controlling parturition in cattle

“…In contrast, in our study using immunohistochemical detection of the pan-leucocyte marker CD45, irrespective of the experimental group and the presence or absence of RFM, no noteworthy leucocyte infiltration was observed in any of the placentomes investigated, challenging the concept of feto-maternal separation as an immune cell mediated event. However, a role of 'inflammatory cytokines' in the control of placental release cannot be excluded from this observation particularly since a transcriptome study of bovine placentomes ante-and intrapartum revealed an upregulation of the genes related to innate immune response at parturition (Streyl et al 2012).…”

The role of placental MHC class I expression in immune-assisted separation of the fetal membranes in cattle

“…In humans, IL-8 stimulates the release of MMP-9 from neutrophils. IL-8 is an important chemotactic factor for neutrophils in at term cotyledons (Kimura et al, 2002) and normally, the expression of IL-8 in placentomes is upregulated around parturition (Streyl et al, 2012). IL-8 serum levels around parturition were lower in RFM than in non-RFM dams.…”

“…Indeed many genes associated with the degradation of the ECM are upregulated around parturition (Streyl et al, 2012) and disruption of the ECM by the infusion of collagenase into the placenta led to a marked reduction in retention time of fetal membranes in experimentally induced RFM (Eiler and Hopkins, 1993). Macrophages are potent producers of many cytokines and play an important role in breakdown and remodeling of the ECM (Chazaud, 2014;Galdiero et al, 2013).…”

“…Matrix metalloproteinases (MMP) are enzymes capable of breaking down the ECM. MMP-2, MMP-9 and MMP-14 have been detected in the bovine placenta (Dilly et al, 2011;Maj and Kankofer, 1997;Walter and Boos, 2001) and are upregulated before parturition (Streyl et al, 2012). MMP's can be activated by many (inflammatory) cytokines (Hirata et al, 2003), including IL-1, IL-6 and TNF-α.…”