Equine endometrial development during late fetal and postnatal periods.

Equine uterine development, including endometrial histogenesis, begins prenatally and is completed postnatally. Little is known about this process in the horse. Uterine tissue was acquired from 38 foals, ranging in developmental age from gestational day (GD) 300 to postnatal day (PND) 180, for assessment of endometrial histogenesis. Patterns of endometrial cell proliferation were evaluated by multispectral imaging of uterine tissue sections stained immunofluorescently for Ki-67. Labeling index (LI, % labeled cells) for Ki-67 was calculated for each endometrial cell compartment (luminal epithelium, glandular epithelium, stroma). Histologically, nascent endometrial glands were present in all pre- and postnatal uterine tissues. Overall, Ki-67 LI increased (P < 0.0001) from the pre-to postnatal periods, and was higher (P < 0.0001) in epithelium as compared to stroma. Postnatally, endometrial Ki-67 LI increased (P < 0.0001) from week 1 to week 24. Our findings confirm that, in contrast to neonatal patterns of uterine development described for domestic ungulates, equine endometrial histogenesis begins prenatally, marked by the appearance of uterine glands as early as GD 300. Epithelial proliferation associated with maturation of the equine endometrium is pronounced by postnatal week 24.

Evaluation of chlorhexidine hydrochloride treatment on endometrial health of normal mares.

Chlorhexidine gluconate solution is a potent antimicrobial and therefore could be used effectively for treatment of endometritis, but historically this substance has been implicated as irritating to mucous membranes, including the endometrium of the mare. The use of chlorhexidine hydrochloride suspension (Nolvasan Suspension, Zoetis, Florham Park, NJ, USA) was evaluated in the uterus of normal mares to determine if adverse effects on endometrial health were noted. Twelve healthy, adult light breed mares were included in this study. Procedures were approved by the Auburn University Institutional Animal Care and Use Committee. All mares were determined to be reproductively normal by evaluation of endometrial histopathology, cytology, and bacterial culture. Mares were randomly assigned to treatment or control groups (n = 6 per group). Each mare was treated during estrus with an intrauterine infusion of 1 g (28 mLs per tube; 35.7 mg/mL) of chlorhexidine hydrochloride suspension (treatment group) or an equal volume of lactated ringer's solution (control group) once daily for 3 consecutive days. Biopsy and cytology samples were taken 3, 7, and 14 days after completion of treatment. Cytology and biopsy samples were read by a board-certified pathologist (L.N.) blinded to treatments, and biopsy samples were graded using a standardized Kenney-Doig score. There was no difference with respect to biopsy grade, degree of endometrial fibrosis, or presence of cytologic inflammation comparing control and treatment groups (P = 0.55, 0.7, and 0.06, respectively), neither when accounting for sampling day. The suspension was visible within the uterine lumen when mares were examined with transrectal ultrasonography for up to 4 days after treatment. Treatment with chlorhexidine hydrochloride in this formulation and at this concentration does not appear to have a deleterious effect on short term endometrial health in mares.