Improving Techniques to Study Equine Cervical Mucociliary Clearance

Postbreeding bacterial uterine infections inflict major losses on the equine industry. Microcurrents propelled by ciliated cells between the folds of the uterus and cervix have been proposed as a means by which contaminants are expelled. Previous data have shown possible ciliary microcurrents propelling carbon particles, occasionally rotating, through cervical folds. However, adherence to the epithelium may have interfered with movement of carbon in these studies. Therefore, we tested potentially nonadherent substances to reveal ciliary microcurrents on the equine cervix under high magnification videoendoscopy. We hypothesized that polyethylene green microspheres 1-5 and 70 μm in diameter, would be superior to carbon in revealing microcurrents on the cervical epithelium and that 50 μm hemispherically coated bichromal microspheres would display rotation. A suspension containing these microspheres and carbon was deposited onto the cervix of five estrous mares, and movement of each type of particle was recorded under high-magnification videoendoscopy for 10-20 minutes. Particles were subjectively assessed for movement between folds, past stationary points, in opposing directions and at different speeds. Visibility, aggregation, motion, and rotation were scored numerically and analyzed by the Kruskal-Wallis test. Backward rotation of bichromal spheres was interpreted as evidence of ciliary activity. Overall, carbon scored equal to or higher than the microspheres, leading to rejection of the hypothesis. Subjective assessment concluded that cervical movement was closely related to respiratory movements of the mare, and that the constantly moving cervical folds helped clear the deposited particles.