Immune cells and compensatory renal hypertrophy after unilateral nephrectomy

Background: The underlying mechanisms of compensatory renal hypertrophy (CRH) after unilateral nephrectomy (UNX) are complex and incompletely understood. Most studies have examined hemodynamic and tubular epithelial factors. We studied immune cells in CRH after UNx in mice. Methods: Following UNx of the left kidney of C57BL/6J WT mice, GFR measurements, flow cytometry, single-cell RNA sequencing, and measurements of remnant kidney were performed over 8-weeks period. Rag1-/- mice lacking T and B cells were studied to begin to study the role of direct role of adaptive immune cells in CRH. Results: The largest increase in GFR and increase in kidney weight-to-body weight ratio (KW:BW) in WT mice was at 24 hours, after which GFR remained relatively constant while KW:BW steadily increased. Immune cell populations exhibited dynamic and time-dependent fluctuations following UNx. Early responses (4 and 72 hours) were characterized by significant changes in CD4+ T cells, CD8+ T cells, macrophages, neutrophils, and dendritic cells. Later time points (1 to 8 weeks) showed increased effector memory T cells and B cells, with decline in naïve T cells and macrophages. GFR was significantly higher at 1 week and 4 weeks in Rag1-/- mice compared to controls. Conclusions: Immune cells undergo significant changes in numbers, phenotype and transcriptional programming during CRH after UNx, and could have a direct role in modifying GFR adaptations. Flow-sorted CD45+ kidney cells from nephrectomized mice were partitioned and barcoded using the 10X Chromium Controller, with approximately 10,000 cells loaded onto the NovaSeq 6000 S4 200-cycle flow cell. The library was constructed using the Chromium Next GEM Single Cell 5' HT v2 Kit and sequenced on the Illumina NovaSeq 6000 system