Endometritis-associated alterations in major proteins in uterine flush fluids from mares

Abstract

Endometritis is a common cause of infertility and early embryonic death inmares. Manymares fail to be diagnosed with endometritis despite different diagnostic tests available, especially in subclinical cases. The purpose of this study was to identify the major proteins in endometrial flush fluids of mares, and to identify changes associated with endometritis. Low volume uterine lavage (LVL, 250 ml of saline) followed by endometrial biopsy was performed on 38 light breed mares in estrus (E) and diestrus (D). Endometritis was diagnosed in mares with two or more of five criteria (1. uterine fluid on ultrasound or excessive edema or history of subfertility; 2. one or more neutrophils per high power field on cytology; 3. cloudy LVL; 4. positive bacterial culture; and 5. active endometrial inflammation on biopsy). Mares in estrus were grouped into four categories based in part on the Kenney and Doig grading of endometrial biopsies. Group 1E included mares negative for endometritis with biopsy grade I or IIA; Group 2E included mares with endometritis (biopsy grade I or IIA); Group 3E included mares with endometritis and biopsy grade IIB or III; Group 4E included mares negative for endometritis but with biopsy grade of IIB or III. Mares in diestrus were similarly organized (Groups 1D to 4D). Flush fluid samples for protein analysis were centrifuged, and the supernatant was concentrated by centrifugal dialysis (10kDa). Proteins in supernatant were identified by LC-MS/ MS after in-solution trypsin digestion and ranked in