Table 1.

Summary of published studies on parietal epithelial cells (PEC) as adult podocyte progenitors

	Model System	Data supporting PEC as adult podocyte progenitors	Reference
Studies strongly supporting PECs as adolescent podocyte progenitors	PEC reporter mice	A subset of labeled PECs is detected in the glomerular tuft in newborn and adolescent mice and co-express podocyte markers Labeled PECs migrate to the glomerular tuft following podocyte depletion, augmented by administering a GSK3 inhibitor	[62] [37]
	Human kidney	A subpopulation of PECs at tubular pole co-stains for the stem/progenitor markers CD133/CD24 When these cells are isolated, and grown ex vivo, they have self-renewal potential and high cloning efficiency Under certain culture conditions they acquire podocyte phenotypic features Cells harvested from normal kidneys that double-labeled for PEC and stem/progenitor markers improved disease outcomes when injected into mice with experimental FSGS	[53] [45] [55]
Studies suggesting, but not definitively proving, that a subset of PECs are adult podocyte progenitors	Rat model	ACE-inhibition affects a subset of cells lining Bowman’s capsule that co-express PEC proteins and NCAM (used as a differentiation marker)	[28]
	Diabetic mouse	Blockade of the chemokine stromal-derived factor (SFD/CXCL12) enhanced the differentiation of renal progenitors towards a podocyte phenotype	[56]