Tregs Fail to Expand in Pregnancy after Recovery from Acute Kidney Injury in Sprague Dawley Rats

Abstract

Recent clinical studies report that women with a history of acute kidney injury (AKI) have adverse maternal and fetal outcomes in pregnancy, despite having normal renal function prior to conception. Pregnancy is a unique state of immunosuppression, with immunosuppressive cells, such as regulatory T cells (Tregs), increasing to combat the immune response to the allogenic fetus. Tregs are also known to play a critical role in recovery after AKI, and may serve as a critical link between AKI and poor pregnancy outcomes. Our laboratory has developed an animal model of pregnancy after recovery from AKI to further explore the mechanisms by which AKI predisposes women to poor pregnancy outcomes. In the current study, we hypothesized that the Tregs would be decreased during pregnancy after recovery from AKI. Renal ischemia reperfusion (IR) injury was used as our experimental model of AKI. Briefly, female Sprague Dawley rats (12 wks of age, n=4) were randomized to receive either 45 minutes of warm, bilateral renal IR injury or sham surgery. Rats were then allowed 30 days to recover, and renal recovery was confirmed by plasma creatinine and urinary protein excretion. Rats were then randomized to either be mated or serve as an age‐matched virgin control. Pregnancy was confirmed by vaginal cytology, with presence of sperm on the slide indicative of day 1 of pregnancy. Pregnancies were terminated on pregnancy day 20, and blood and kidneys were collected for flow cytometric analysis of T cells. Total CD3+ cells increased in sham and IR pregnant dams compared to virgin controls in the kidney (Table , Effect of pregnancy, p=0.02, 2‐way ANOVA). Pro‐inflammatory Th17 cells also increased in pregnancy in both IR and sham dams compared to virgin controls, as anticipated (Table , Effect of pregnancy, p=0.01 kidney, p=0.03 blood). Interestingly, Tregs only increased in sham pregnant dams (Table , Interaction effect p<0.001 kidney, p=0.004 blood). Tregs in IR dams and virgin controls were similar to the virgin sham rats. These data suggest that Tregs fail to expand during pregnancy after AKI, potentially contributing to the increased rate of fetal demise and poor pregnancy outcomes observed in this model. Ongoing studies in the laboratory are further exploring the role of Tregs in pregnancy in this model, testing the hypothesis that expanding Tregs in pregnancy will improve fetal and maternal outcomes after AKI. Renal CD3 (% renal cells) Renal Tregs (%CD3+CD4+ cells) Renal Th17 (%CD3+CD4+ cells) Blood CD3 (% renal cells) Blood Tregs (%CD3+CD4+ cells) Blood Th17 (%CD3+CD4+ cells) Sham Virgin 0.9±0.2 4.7±0.7 1.9±0.2 27±2 5.7±0.3 5.0±0.3 Sham Pregnant 4.3±0.5 12.6±0.3 8.5±0.6 28±2 13.4±1.2 9.3±0.7 IR Virgin 1.1±0.4 5.0±0.3 2.1±0.2 26±4 6.6±0.4 5.3±0.1 IR Pregnant 4.0±0.3 5.2±0.7 8.7±0.5 27±3 6.8±0.5 9.0±0.6