Podocyte

Podocytes, also known as visceral epithelial cells, are specialized cells that line the outer aspect of glomerular capillaries in the kidney. They reside within Bowman's capsule and encircle the capillaries with a cell body and long interdigitating foot processes (pedicels). The spaces between these foot processes are bridged by slit diaphragms, multiprotein junctions that form a final barrier in conjunction with the glomerular basement membrane and endothelial cells.

Functionally, podocytes contribute to the selective filtration barrier that prevents protein loss while permitting water and small solutes to pass. They rely on a dynamic actin cytoskeleton to maintain foot process architecture and can remodel in response to physiologic and pathologic stimuli. Key slit diaphragm components, such as nephrin and podocin, help regulate permeability and signal pathways that preserve glomerular integrity. Injury to podocytes can lead to foot process effacement, disruption of the filtration barrier, and proteinuria.

Podocytes originate from the metanephric mesenchyme during kidney development and are largely postmitotic in adulthood, making them particularly vulnerable to damage and with limited regenerative capacity. Sustained injury can result in progressive podocyte loss and glomerulosclerosis. Podocyte pathology is central to several kidney diseases, including minimal change disease, focal segmental glomerulosclerosis, and diabetic nephropathy, as well as hereditary nephrotic syndromes caused by mutations in genes such as NPHS1 (nephrin) and NPHS2 (podocin).

In clinical practice, podocytopathy refers to diseases characterized by podocyte injury and altered slit diaphragm function, often presenting with proteinuria and edema. Electron microscopy and targeted genetic testing can aid in diagnosis and management.