Expression of Monocyte Chemoattractant Protein-1 in the Bovine Corpus Luteum Around the Time of Natural Luteolysis1

Abstract

Monocyte chemoattractant protein (MCP-1) is a specific chemoattractant for monocytes/macrophages that could have a role in the influx of macrophages into the corpus luteum (CL) during structural luteolysis. In this study, reverse transcription-polymerase chain reaction and in situ hybridization were used to investigate MCP-1 mRNA expression in CL collected from 18 heifers between Days 15 and 20 of the estrous cycle. There was expression of mRNA encoding MCP-1 in luteal tissue from all cows; however, expression was greater in animals that had undergone luteolysis at the time of CL collection as compared to animals in which the CL was still functional. Similarly, in situ hybridization showed greater expression of mRNA encoding MCP-1 in CL after functional luteolysis. There was also evidence of increased MCP-1 mRNA expression in an animal with a functional CL where the systemic concentration of prostaglandin F2alpha metabolite was high at the time of tissue collection. T lymphocyte populations, identified by immunohistochemistry, had a distribution similar to that of cells expressing MCP-1 mRNA within the CL, but other cell types were also involved. These results demonstrate an increase in MCP-1 mRNA after functional luteolysis in the cow, which may be related to the influx of macrophages that occurs at this time.

Expression Pattern of Prokineticin 1 and Its Receptors in Bovine Ovaries During the Estrous Cycle: Involvement in Corpus Luteum Regression and Follicular Atresia

“…In the course of follicular atresia and CL involution, chemokine expression and leukocyte infiltration increase [23,[25][26][27][28]. These stages are therefore considered proinflammatory events [24,43,47,48].…”

“…While luteal development is accompanied by a dramatic increase in the number of blood vessels, luteal demise is characterized by increased chemokine expression and leukocyte infiltration [23,[25][26][27][28]. PROK1 may therefore assume different roles at different stages of the cycle.…”

Determination of Cell Type Specificity and Estrous Cycle Dependency of Monocyte Chemoattractant Protein-1 Expression in Corpora Lutea of Normally Cycling Rats in Relation to Apoptosis and Monocyte/Macrophage Accumulation1

“…The presence of MCP-1 mRNA or protein in the corpus luteum has been reported for various animal species, including murine [7,12,13], bovine [8,10,14], ovine [8,9], and human [11], but the identity of the cell type(s) responsible for the Mcp-1 gene expression has been ambiguous. In the present study, we have shown that cells expressing MCP-1 mRNA are steroidogenic luteal cells in normally cycling rats.…”

“…The reasons for this discrepancy are not certain at present, but they could include 1) the fact that small luteal cells in the sheep express MCP-1, 2) a difference in the conditions of the animals (normal rats vs. prostaglandin F 2␣ -treated sheep), or 3) a difference in the antibodies used to identify steroidogenic cells. Penny et al [10] has raised the possibility that MCP-1 is expressed in CD5-positive T lymphocytes in corpora lutea of the cow; however, their experimental procedure was not accurate enough to identify cell types expressing MCP-1. Penny et al compared two serial luteal sections, one analyzed by in situ hybridization for MCP-1 mRNA and the other by immunohistochemistry with an anti-CD5 antibody.…”

“…Previous studies have shown that immune cells, including monocytes/macrophages and lymphocytes, accumulate, that apoptotic luteal cells increase in number, and that the expression of some cytokines is activated during regression of the corpus luteum [5,6]. In particular, augmented expression of monocyte chemoattractant protein-1 (MCP-1), a C-C chemokine that provokes migration of monocytes/macrophages toward the place of inflammation, in regressive corpora lutea at the mRNA [7][8][9][10][11] and protein [7,[11][12][13][14] levels has been reported by several investigators. However, the possibility that monocytes/macrophages accumulate in corpora lutea because of the action of MCP-1 and play a role in luteolysis has been only speculative.…”