1. Figure 5 Mechanisms of crystal granuloma formation
Figure 5 | Mechanisms of crystal granuloma formation. a | Supersaturation of calcium oxalate (CaOx) in the urine leads to the formation of CaOx crystal nuclei (1). CaOx crystals activate TNF receptors (TNFRs) 1 or 2 on the tubular cell surface (2), which leads to internalization of TNFRs and activation of the TNF signalling pathway (3). Crystal phagocytosis by tubular cells and lysosome formation could be involved in this process and contribute to activation of theTNFR pathway (4). Activation of the TNF pathway results in increased expression of crystal adhesion molecules (CAMs) such as CD44 and annexin II on the tubular cell surface (5). Crystal nuclei adhere to the CAMs (6) and create a nidus for crystal growth, which leads to crystal plug formation in the tubular lumen and obstruction of the tubule (7). b | Tubular cells dedifferentiate and grow on the hard surface of the crystal plug, eventually leading to translocation of the crystal plug into the interstitial compartment. c | In the interstitial compartment, frustrated phagocytosis of the large crystal plugs triggers the formation of giant cells (polyploid proinflammatory macrophages), subsequently leading to a granuloma, which isolates the crystal plug from the renal parenchyma.
Mulay, S. R. & Anders, H.-J. (2017) Crystal nephropathies: mechanisms of crystal-induced kidney injury
Nat. Rev. Nephrol. doi: /nrneph