Podocyte
Podocytus
Also known as: visceral epithelial cell, podocytes
Highly specialised, terminally differentiated epithelial cells of the visceral layer of Bowman capsule whose interdigitating foot processes and slit diaphragms form the outer layer of the glomerular filtration barrier.
Overview
Each podocyte has a cell body that bulges into Bowman space, major (primary) processes, and numerous foot processes (pedicels) that wrap around the capillaries and interdigitate with those of neighbouring podocytes. The gaps between them (filtration slits) are bridged by the zipper-like slit diaphragm (nephrin, podocin). An actin cytoskeleton keeps the foot processes in shape; podocytes also synthesise GBM components and VEGF that maintains the endothelial fenestrae.
Podocytes cannot divide in adults, so podocyte loss is cumulative and leads to glomerulosclerosis. Foot-process effacement (flattening and fusion), seen by electron microscopy, is the common final structural sign of heavy proteinuria.
- Location
Visceral layer of the glomerular capsule, covering the glomerular capillaries.
Anatomy
- Histology
Large cells with prominent processes; foot processes and slit diaphragms visible only by electron microscopy.
Function
- Form the slit diaphragm (final size barrier)
- Support capillary loops against distending pressure
- Synthesise and maintain the GBM; secrete VEGF for the endothelium
Clinical significance
Minimal change disease
Diffuse foot-process effacement with normal light microscopy; commonest cause of nephrotic syndrome in children; highly selective albumin loss; steroid-responsive.
Focal segmental glomerulosclerosis
Podocyte loss leads to sclerosis of parts of some glomeruli; causes nephrotic syndrome (common in adults, African ancestry with APOL1 variants, HIV, obesity, heroin); often steroid-resistant.
Test yourself
A 4-year-old boy has periorbital oedema, proteinuria of 5 g/day and hypoalbuminaemia. Light microscopy is normal and electron microscopy shows effacement of podocyte foot processes. What is the diagnosis?
- Post-streptococcal glomerulonephritis
- IgA nephropathy
- Minimal change disease
- Alport syndrome
Answer: Minimal change disease
Minimal change disease is the commonest cause of nephrotic syndrome in children; glomeruli look normal on light microscopy, foot-process effacement is seen on EM, and it responds to corticosteroids.
Compiled from standard anatomy and physiology references — see the Urinary System sources. For education only; not medical advice.