The equine endometrial mast cell during the puerperal period: evaluation of mast cell numbers and types in comparison to other inflammatory changes.

The research article investigates the role and prevalence of inflammatory cells, particularly the endometrial mast cells, in the postpartum phase of horses. It concludes that mast cells may play a crucial role in a normal postnatal period and introduces the hypothesis of a mast cell subtype that lacks tryptase and chymase.

Research Methodology

• The researchers took endometrial biopsies of 44 broodmares (female horses used for breeding) on the 3rd, 6th, and 9th day after giving birth.
• These mares were divided into three groups based on different conditions during the postpartum period: normal birthing process, problematic birthing (dystocia), and a condition where the placenta was not expelled within the predicted time frame (retained placenta).
• The researchers then examined these tissue samples histologically, a method that studies the microscopic structure of tissues, to record the average count of various inflammatory cells including granulocytes, lymphocytes, macrophages, siderophages, and mast cells.

Mast Cell Analysis

• Researchers further analysed the mast cells for their protease content that could provide insights into their function and type. Two types of protease enzymes, chymase and tryptase, were specifically tested for.
• The test involved the use of a double-enzyme immunohistochemical staining technique, using two different staining reactions to detect these enzymes.
• The results from this analysis were then assessed using statistical software Statistica.

Findings

• Postpartum, a marked inflammatory reaction was observed in the uterus lining, with the number of granulocytes decreasing but lymphocytes, macrophages, and siderophages increasing over the first nine days.
• Comparing the three different postpartum conditions, no significant difference was observed in the numbers of these cell types. But, mares with dystocia seemed to have lower numbers.
• Except for the mast cells, the various cell types didn’t show any significant change during the postpartum period. However, in mares with a retained placenta, considerably fewer mast cells were found.
• The mast cell analysis revealed that only tryptase-positive cells were present and no chymase activity could be detected. Moreover, the number of mast cells identified using the metachromatic staining technique was considerably higher than what was detected with double labeling.

Research Implications

• The observed decrease in mast cell count in mares with retained placenta suggested that a sufficient number of mast cells may be necessary for a normal postnatal period in horses.
• The absence of chymase and the discrepancy in mast cell counts detected through metachromatic and double-staining techniques hinted at a subtype of mast cell in the equine uterus that lacks both tryptase and chymase.