Effect of uterine lavage solution temperature on vascularization, inflammatory process and oxidative stress in mares

• Grant number: 24/15094-5
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: November 01, 2024
• End date: October 31, 2025
• Field of knowledge: Agronomical Sciences - Veterinary Medicine - Animal Reproduction
• Principal Investigator: Eneiva Carla Carvalho Celeghini
• Grantee: Ana Luiza Carriel Griffo
• Host Institution: Faculdade de Medicina Veterinária e Zootecnia (FMVZ). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

The most important obstacle in equine reproduction today is infertility in mares, which is mainly related to inflammation of the endometrium. After mating, a natural inflammatory response occurs in the mare's uterus, which can become exacerbated, leading to the accumulation of intrauterine contents, compromising fertility rates. One of the treatment methods for this condition is the use of uterine lavages, which aim to remove the contents, as well as possible debris. Currently, this procedure is performed with solutions heated to 42°C, in order to stimulate the muscles and the inflammatory process. On the other hand, cryotherapy is a treatment, with cold active ingredients, used mainly to reduce the inflammatory process, cause peripheral vasoconstriction, thus avoiding secondary cellular damage and can reduce local infiltration. Thus, the present study aims to evaluate the effects of temperature (42°C and 5°C) of Ringer's solution with sodium lactate used for uterine lavage on uterine hemodynamics, inflammatory response and endometrial oxidative stress. Three estrous cycles of 15 mares will be used, which will undergo follicular monitoring and ovulation induction (follicle ¿35 mm). After ovulation detection, a uterine infusion (UI) will be performed using a skim milk-based extender added with pentoxifylline to simulate the response to semen deposited in artificial insemination (AI). After 6 hours of UI, the cycles will be distributed into three treatments: Negative control group (GC, n = 15 cycles) will not be performed uterine lavage; The positive control group (GA, n = 15 cycles) will receive uterine lavage with heated solution (42°C) and the cryotherapy group (GR, n = 15 cycles) will receive uterine lavage with refrigerated solution (5°C). All mares will receive all treatments, which will be performed randomly, alternating the sequences. After the deposition of 1L of solution (heated or refrigerated), the contents will be kept for 5 minutes, and after recovery, another 1L will be deposited and kept for another 5 minutes. The entire contents will be removed from the uterus. The uterus will be evaluated immediately before UI (T0), 6 hours after UI and immediately before treatment (T6a), 6 hours after UI and immediately after treatment (T6d), 12 hours (T12) and 48 hours (T48) after UI, considering: content (cm), uterine vascularization score (VS, 1-4) and resistance index (RI, 0-1) of the uterine artery by ultrasonography in B, color-Doppler and spectral modes, respectively, and samples will be collected for endometrial cytology. After 6 hours of UI and immediately before (T6a) and after (T6d) treatment, uterine samples will be collected to measure oxidative stress. Cytology slides will be evaluated by optical microscopy to assess the percentage of polymorphonuclear cells. Data will be evaluated by ANOVA and group means compared by Tukey's test, considering difference when p ¿0.05.