Avaliação morfológica, citoquímica e estereológica do útero de camundongos prenhes após estresse induzido por exercício físico extenuante

Abstract

Aerobic exercise increases blood flow to skeletal muscle, decreasing the flow in other organs such as uterus and placenta, which may impair embryo oxygenation and nutrition. Furthermore, the continuous exercise can be stressful, changing the hypothalamic-pituitary-adrenal axis leading to secretion of glucocorticoids that may cause complications during pregnancy, such as those observed in other situations such as dietary and infection-mediated stress . Uterine natural killer cells (uNK) are the largest population of decidual leukocytes from humans and rodents. The mouse uNK have been extensively investigated by the use of DBA lectin cytochemistry, which has affinity for N-acetyl-D-Galactosamia selectively expressed in the granules and plasma membrane of these cells. This selectivity allowed the characterization of four subtypes of uNK related to their stages of differentiation. The most accepted function of uNK is the secretion of IFN-y leading to dilation of the uterine spiral arteries, maintaining the decidua and embryo nutrition. the goal of this study was to investigate whether strenuous exercise has effect in the embryo implantation and integrity, as well as, in the number, differentiation, distribution and DBA lectin reactivity pattern of uNK cells. Ten female Swiss mice were sedentary (group 1). Other 10 (group 2) were submitted to swimming, from 1st to 10th gestation day (gd) for 60 minutes daily, been the last 20 minutes conducted with a steel caudal dumbbell with 4% of their body masses, attached in alternately days from the 1st to 5th gd, and 10% of this mass from the 6th to 10th gd. The animals from group 3 after pregnancy were submitted to swimming in the same way as group 2, but went through a training program for 3 weeks, 5 days a week, being 15 minutes/day in the first week, increasing gradually by 10 minutes a day up to 60 minutes in the second week and 60 minutes a day in the third week. All mice were anesthetized and perfused with 4% PFA at 10°dg. The rates of embryo implantation, viability resorption were evaluated and the implantatio sites of these animals were collected and embedded in paraffin to obtain histological sections that were submitted to DBA lectin and H&E. We quantified the four DBA reactive uNK cells subtypes in three areas of the mesometrial region of the implantation sites. Our results showed that strenuous exercise can cause a decrease in implantation embryo viability and increased fetal loss, as well as increase in number and differentiation of uNK cells, without apparent activation of its cytotoxicity. The exercise performed prior to pregnancy decreased these effects, since restored the normal rates of implantation and the total number of UNK, as well as increased viability and decreased embryonic loss, without completely prevent the deleterious effects of exercise during pregnancy. Our results indicate that this stress model established here may be useful for future studies about the neuroimmunoendocrinology of preterm labor and abortion caused by often unknown stress factors.