What are the cells that make up crescents, the histopathologic hallmark of rapidly progressive glomerulonephritis (RPGN)?
Classically these have been thought to be the parietal epithelial cells which make up Bowman's capsule.
However there is now some thought that podocytes may be contributing to this histologic feature which has long been known to portend a worse renal prognosis. A 2008 JASN paper shows that most crescents from a variety of human biopsy specimens demonstrating crescent formation contain cells which stain positive for nestin, a marker which appears to be relatively podocyte-specific. Other podocytes markers (e.g., podocin, WT1) are not present--so either the theory of podocyte origin of crescents is incorrect, or perhaps these genes are turned off as the podocytes change cell fate.