Generation of Distal Renal Segments Involves a Unique Population of Aqp2+ Progenitor Cells

Abstract

BackgroundProgenitor cells have clonogenicity, self-renewal, and multipotential capacity, and they can generate multiple types of cells during development. Evidence demonstrating the existence of such progenitor cells for renal distal segments is lacking.MethodsTo identify Aqp2+ progenitor (AP) cells, we performed in vivo lineage tracing using both constitutive (Aqp2Cre RFP/+) and Tamoxifen-inducible (Aqp2ECE/+ RFP/+, Aqp2ECE/+ Brainbow/+, and Aqp2ECE/+ Brainbow/Brainbow) mouse models. Aqp2Cre RFP/+ mice were analyzed from E14.5 to adult stage. The inducible models were induced at P1 and examined at P3 and P42, respectively. Multiple segment- or cell-specific markers were used for high-resolution immunofluorescence confocal microscopy analyses to identify the cell types derived from Aqp2+ cells.ResultsBoth Aqp2Cre and Aqp2ECE/+ faithfully indicate the activation of the endogenous Aqp2 promoter for lineage tracing. A subset of Aqp2+ cells behaves as potential AP. Aqp2Cre-based lineage tracing revealed that embryonic APs generate five types of cells, which form the late distal convoluted tubule (DCT2), connecting tubule segments 1 and 2 (CNT1 and CNT2, respectively), and collecting ducts (CDs). The α- and β-intercalated cells were apparently derived from embryonic AP in a stepwise manner. Aqp2ECE/+-based lineage tracing identified cells coexpressing Aqp2 and V-ATPase subunits B1 and B2 as the potential AP. Neonate APs generate daughter cells either inheriting their property (self-renewal) or evolving into various DCT2, CNT, or CD cells (multipotentiality), forming single cell-derived multiple-cell clones (clonogenicity) during development.ConclusionOur study demonstrates that unique Aqp2+ B1B2+ cells are the potential APs to generate DCT2, CNT, CNT2, and CD segments.