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

Background: Progenitor 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.

Methods: To identify Aqp2 + progenitor (AP) cells, we performed in vivo lineage tracing using both constitutive ( Aqp2Cre RFP/+ ) and Tamoxifen-inducible ( Aqp2 ECE/+ RFP/+ , Aqp2 ECE/+ Brainbow/+ , and Aqp2 ECE/+ 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.

Results: Both Aqp2Cre and Aqp2 ECE/+ 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. Aqp2 ECE/+ -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.

Conclusion: Our study demonstrates that unique Aqp2 + B1B2 + cells are the potential APs to generate DCT2, CNT, CNT2, and CD segments.