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Background: CKD and obesity are marked by elevated pro-inflammatory cytokines, including IL-6. Pregnant obese women are associated with 1.5- to 2-fold increase in serum IL-6, newborns with smaller kidney/body weight ratio, kidney anomalies and increased susceptibility to CKD. Maternal IL-6, but not TNFα or IL-1β, can cross the placental barrier and enter fetal compartment.

Objective: We examined the role of (a) maternal injection of IL-6 during mid-gestation, similar to levels observed in pregnant obese women, on kidney development as a specific molecular surrogate of gestational inflammation and (b) IL-6 on glomerular filtration barrier.

Design/Methods: Pregnant mice received IL-6 (10 pg/g ip) on alternate days from E12.5 to end of gestation while the control pregnant mice received normal saline. Following euthanasia, newborn kidneys were fixed in 10% formalin or OCT, or used to isolate RNA or protein lysate. We used in vitro albumin permeability assay to study the effect of IL-6 on filtration barrier.

Results: Mid-gestational administration of IL-6 (10 pg/g) to pregnant mice resulted in newborns with lower body (p<0.001) and kidney (p<0.001) weights [Figure i]. Histomorphometry showed decreased nephrogenic zone width (p=0.039), increased numbers of mature glomeruli (p=0.002), and pretubular aggregates (p=0.041) [Figure ii]. Immunostaining for podocyte markers showed increased number of mature glomeruli (p<0.001), LC-MS for CpG DNA methylation revealed increased 5mC levels (p<0.05), and Western blotting showed upregulated JAK2/STAT3 (p<0.05) [Figure iii]. RT-qPCR Array analysis of cell-cycle and apoptosis genes also suggested accelerated maturation. In vitro studies using isolated rat glomeruli showed that IL-6 (0.01-5 pg/mL) significantly increased glomerular albumin permeability (p<0.001) which was blocked by pretreatment with anti-IL-6 antibody suggesting its direct effect on the glomerular filtration barrier. IL-6 caused derangement of the actin cytoskeleton and upregulation of pJAK2/pSTAT3 in murine podocytes that maintain the glomerular barrier function.

Conclusion(s): Perinatal exposure to IL-6, a surrogate of maternal inflammation, resulted in small kidneys with accelerated maturation and upregulated JAK-STAT signaling. IL-6 injures the glomerular filtration barrier. We propose to use this animal model to study susceptibility to CKD in adult offspring to determine the long-term effects of the growing incidence of maternal obesity, obesity and CKD across the globe.

Presented at the 2021 PAS Virtual Conference


Nephrology | Pediatrics

Perinatal exposure to Interleukin-6 (IL-6): a model to study influence of developmental insult on susceptibility to chronic kidney disease (CKD)