The cells observed at the phalloidin gaps appeared to be dysmorphic, with fissures in anti-GFP staining suggestive of cytoplasmic disruptions. By 48 hpi, the luminal space within the tubules was collapsed ( Fig 5, B) and some areas appeared to be filled with cells and/or cellular debris (data not shown), suggestive

of tubular disorganization and epithelial cell death. In addition, phalloidin staining was diffuse and disorganized although it was generally dispersed in regions closely adjacent to the debris-filled lumen. Thus, independent lines of evidence demonstrate that gentamicin triggers AKI, causing damage to the zebrafish pronephros that grossly mimics mammalian AKI damage, with disrupted apical-basal polarity of the tubular epithelium and Protease Inhibitor Library concentration massive tubule cell shedding. Although the injury following gentamicin is similar, several groups have now documented that gentamicin treatment is lethal to the zebrafish embryo.68 and 72 We have also found through further testing of gentamicin

doses that all embryos that developed edema were unable to survive. From these data, it appears that gentamicin exposure causes nephron tubular damage learn more that is far too catastrophic for the embryo to recoup through any type of repair or regeneration without some form of intervention. The embryonic and larval zebrafish possess only two nephrons, and both are exposed during gentamicin systemic administration. Thus, the generalized damage to both nephrons may be one explanation for this outcome. Whether the embryo can repopulate its damaged pronephros epithelium in this context remains unknown.68 However, a very promising venue for future study has been demonstrated through an innovative approach to identify small molecules capable of rescuing gentamicin-induced edema. In a recent report, zebrafish larvae injected with gentamicin were treated with a specific histone deacetylase

aminophylline inhibitor (HDACi), methyl-4-(phenylthio)butanoate (m4PTB) beginning at 2 days postinjection (dpi), when AKI symptoms like edema and loss of cell polarity were first evident.73 Results revealed that m4PTB treatment increased zebrafish embryo survival.73 m4PTB treatment also led to elevated cell proliferation, and the dividing cells were found to express paired box 2—a long-appreciated hallmark of nephron tubule regeneration in the mouse.73 While m4PTB enhances the functional recovery of the zebrafish kidney after gentamicin-induced AKI,73 the same research group initially reported this HDACi was able to expand the embryonic renal progenitor cell field that initially produces the pair of pronephric nephrons.