PNNL

Abstract

Progression of glomerulosclerosis is associated with loss of podocytes with subsequent glomerular tuft instability. A diminished number of podocytes may be able to preserve tuft stability through cell hypertrophy associated with cell cycle re-entry. At the same time, re-entry into the cell cycle risks leading to podocyte detachment, if podocytes cross the G1/S checkpoint and undergo abortive cytokinesis. In order to study cell cycle dynamics during CKD development, we used a FUCCI mouse model (fluorescence ubiquitination-based cell cycle indicator) of X-linked Alport Syndrome mice. This model has progressive CKD and expresses fluorescent reporters of cell cycle stage exclusively in podocytes. We showed that with development of CKD, an increasing fraction of podocytes in vivo are in G1 or later cell cycle stages. G1 and G2 podocytes are hypertrophic. Heterozygous female mice, with milder manifestations of CKD, show G1 fraction numbers intermediate between wild-type and male AS mice. Proteomic analysis of podocytes in different cell cycle phases showed differences in cytoskeleton reorganization and metabolic processes between G0 and G1 in disease. In addition, in vitro experiments confirmed that damaged podocytes re-enter the cell cycle comparable to in vivo podocytes. In conclusion, our data showed that, during progressive CKD, the podocyte cell cycle distribution changes dramatically, suggesting that cell cycle manipulation approaches may have a role in treatment of various progressive glomerular diseases characterized by podocytopenia.