Podocyten

Podocytes, sometimes referred to as visceral epithelial cells (podocyten in Dutch), are specialized cells of the kidney that cover the outer aspect of glomerular capillaries in the Bowman's capsule. They extend primary processes that branch into interdigitating foot processes, which surround the capillaries and contribute to the formation of the glomerular filtration barrier.

The filtration barrier consists of three layers: the fenestrated endothelium of glomerular capillaries, the glomerular basement membrane, and the slit diaphragm formed between adjacent foot processes. The slit diaphragm is a protein-rich junction that includes nephrin (NPHS1), Neph1, Neph2, podocin (NPHS2), CD2AP, and other cytoskeletal links. These components regulate the passage of solutes and restrict protein leakage, helping to maintain selective filtration.

Podocytes are derived from the visceral layer of the Bowman's capsule; they are highly specialized and largely terminally differentiated, with limited regenerative capacity. Injury or stress can cause foot process effacement, detachment from the basement membrane, and loss of slit diaphragms, leading to proteinuria and potentially progressive glomerulosclerosis.

Dysfunction or mutation of podocytes is linked to several glomerular diseases, including minimal change disease, focal segmental glomerulosclerosis (FSGS), membranous nephropathy, and congenital nephrotic syndrome due to NPHS1 or NPHS2 mutations. Genetic and acquired podocyte injury disrupt the filtration barrier, often driving nephrotic-range proteinuria.

Ongoing research on podocytes focuses on the slit diaphragm molecular complex, cytoskeletal dynamics, and strategies to protect or restore podocyte integrity to treat glomerular diseases.