AUTHOR=Miró Jordi , Gutiérrez-Reinoso Miguel , Silva Joana Aguiar da , Fernandes Carina , Rebordão Maria Rosa , Alexandre-Pires Graça , Catalán Jaime , Ferreira-Dias Graça 

TITLE=Collagen and Eosinophils in Jenny's Endometrium: Do They Differ With Endometrial Classification?

JOURNAL=Frontiers in Veterinary Science

VOLUME=Volume 7 - 2020

YEAR=2020

URL=https://www.frontiersin.org/journals/veterinary-science/articles/10.3389/fvets.2020.00631

DOI=10.3389/fvets.2020.00631

ISSN=2297-1769

ABSTRACT=Collagen fibres and inflammatory cells are the basis for jenny endometrium Kenney and Doig´s classification developed for the mare. Infiltration of large number of eosinophils in jenny endometrium is intriguing. Eosinophil and fibroblast produced IL33 has been related to fibrosis development and chronicity. This work on endometrium consisted on (i) quantification of collagen type I (COL1A2), type III (COL3A1) and IL33 transcripts; (ii) histological localization and quantification of COL1 and COL3 protein; and (iii) eosinophil and neutrophil count and correlation with collagen area and IL33 transcripts. Localization of COL protein in jenny endometrium was also compared to mare endometrium. As fibrosis increased, eosinophil and neutrophil count decreased (P < 0.05). A 5-fold increase in IL33 transcripts was noted from category IIA to III. There was a tendency towards a positive correlation between eosinophil count and IL33 transcripts in category IIA endometrium (𝑃= 0.055). Neither transcripts of COL1A2 nor COL3A1, nor the areas of COL1 or COL3 differed with endometrial categories. Unlike for the mare, and regardless jenny endometrium classification, COL3 was always found to different extents in the stratum compactum, while COL1 was mainly present in deep stroma. As fibrosis progressed in the mare, an extensive increase in COL1 fibres was notorious under the surface epithelium. Correlations between neutrophil count and COL1 and COL3 areas were observed in jenny endometrium, although no correlation was found for eosinophil count. Neutrophil count positive correlation with COL1 area, and negative correlation with COL3 area in endometria with mild lesions, suggest that neutrophils in jenny endometrium may be involved in fibrogenesis. In addition, when eosinophilia subsides, endometrium reacts with fibrosis establishment, which could be stimulated by the pro-fibrotic cytokine IL33, whose release might then be ascribed to fibroblasts.  Further studies are needed to analyze the effect of the presence of COL3 next to the surface epithelium in the stratum compactum, or around the endometrial glands on jenny´s endometrial function and fertility.