Introduction: As the world population ages, so does the pool of donors for organs transplant. Studies showed that female sex hormones concentration could be associated with inflammation after brain death (BD) and menopause could be a risk factor for female donors. Thus, we aim to investigate the role of female sex hormones in the intestinal injury of female rats submitted to BD, utilizing a surgical menopause model (Ovariectomy - OVx).
Method: Wistar rats (female) were divided into four experimental groups: Control – non-manipulated; Control-OVx – animals not submitted to BD but ovariectomized; BD – animals submitted to BD (6h); BD-OVx –ovariectomized animals submitted to BD. OVx was performed 10 days before BD induction, whereas other females were chosen during proestrus phase of the estral cycle (heat period, when estradiol is high). At the end of the experiment, intestine samples were separated for histopathological analysis, myeloperoxidase (MPO) activity assay (neutrophil presence/activity), Evans blue extravasation assay (microvascular permeability), and immunohistochemistry (ICAM-1, eNOS and iNOS). Additionally, the mesentery was exposed for blood flow and leukocyte infiltration analysis.
Results: On the intestine, BD increased leukocyte infiltration (P_ANOVA BD<0.0001) and MPO activity (P _ANOVA BD <0.0001), independently of OVx, possibly related to increased ICAM-1 protein expression (p Control-OVx vs BD-OVx = 0.0231). Regarding villus height, BD reduced it in both groups (P _ANOVA BD = 0.0096), with OVx animals presenting lower height (p BD vs BD-OVx = 0.0884). Similarly, microvascular permeability was higher in BD-only animals (p Control vs BD = 0.0723), and BD-OVx had lower permeability compared to BD animals (p BD vs BD-OVx = 0.0522). On eNOS and iNOS protein expression, OVx alone increased their expression (eNOS: p Control vs Control-OVx = 0.0212; iNOS: p Control vs Control-OVx = 0.0401) and in OVx groups BD reduced the expression (eNOS: p Control-OVx vs BD-OVx = 0.0392; iNOS: p Control-OVx vs BD-OVx = 0.0333). Additionally, mesenteric blood flow decreased in BD-OVx group compared to BD and Control-OVx (p Control-OVx vs BD-OVx = 0.0052; p BD vs BD-OVx = 0.0197). Finally, Control-OVx animals presented higher leukocyte infiltration to the mesentery (p Control vs Control-OVx = 0.0024), which was not altered further by BD. Conversely, BD was able to increase the number of migrated leukocytes in the mesenteric microcirculation of non-OVx animals (p Control vs BD<0.0001).
Conclusion: In summary, BD influences intestinal inflammation by increasing leukocyte mobilization. Whereas, OVx and its consequences on the female hormonal profile influences homeostasis and inflammatory response to BD, lowering blood flow and altering intestinal morphology. Once menopause alters intestinal status, the study of its influence in the donor could contribute to maintain organ viability in female organ donors.

Grant 2023/00728-6, 2021/13020-6, São Paulo Research Foundation (FAPESP).