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Re-evaluation of foot process effacement in acute puromycin aminonucleoside nephrosis
S Inokuchi1, I Shirato, N Kobayashi
1Department of Medicine, Juntendo University, School of Medicine, Tokyo, Japan.
Abstract:
The sequence of morphological changes during foot process effacement in acute puromycin aminonucleoside (PAN) nephrosis was examined by means of NaOH maceration and freeze cracking for scanning electron microscopy (SEM). The micrographs of SEM and those of transmission electron microscopy (TEM) were quantitatively analyzed by computerized morphometry, and were correlated with renal function. On day 2 after PAN injection, the slit length was moderately decreased by both shortening and degradation of the foot processes. On day 4, membrane-bounded vesicles were scattered in the lamina rara externa. During foot process effacement, the basal surface of podocytes developed palm-like domains that represented the cytoplasmic areas between interdigitation. The decrease in the length of podocyte cell borders paralleled the decrease of 24-hour creatinine clearance. The development of the palm-like domains on the basal aspects of podocytes estimated by distance class analysis was closely correlated with the sudden onset of proteinuria. We conclude that foot process effacement in PAN nephrosis caused by the retraction and degradation of foot processes leads to the development of palm-like domains, which is correlated with podocyte detachment as well as massive proteinuria.
Insights
Puromycin aminonucleoside (PAN) nephrosis causes foot process effacement, leading to palm-like domains on podocytes. This morphological change correlates with podocyte detachment and significant proteinuria in kidney disease.
Area of Science:
- Nephrology
- Cell Biology
- Pathology
Background:
- Puromycin aminonucleoside (PAN) induces acute nephrosis, a model for studying podocyte injury.
- Foot process effacement is a key feature of glomerular podocyte damage in various kidney diseases.
Purpose of the Study:
- To investigate the sequential morphological changes during foot process effacement in PAN nephrosis.
- To correlate these ultrastructural changes with renal function and proteinuria.
Main Methods:
- Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to examine podocyte morphology.
- NaOH maceration and freeze cracking techniques were employed for SEM.
- Computerized morphometry and distance class analysis were performed for quantitative assessment.
- Measurements were correlated with 24-hour creatinine clearance and proteinuria levels.
Main Results:
- PAN injection led to decreased slit length due to foot process shortening and degradation by day 2.
- Membrane-bounded vesicles appeared in the lamina rara externa by day 4.
- Podocytes developed basal palm-like domains during effacement.
- A decrease in podocyte cell border length correlated with reduced creatinine clearance.
- Development of palm-like domains correlated with the onset of massive proteinuria.
Conclusions:
- Foot process effacement in PAN nephrosis involves retraction and degradation of foot processes.
- The development of basal palm-like domains in podocytes is a consequence of this effacement.
- These morphological changes are linked to podocyte detachment and severe proteinuria, offering insights into kidney disease pathogenesis.