Glomerular Filtration Barrier Assembly: An insight

Abstract

A glomerulus is the network of capillaries that resides in the Bowman's capsule that functions as a filtration unit of kidney. The glomerular function ensures that essential plasma proteins are retained in blood and the filtrate is passed on as urine. The glomerular filtration assembly is composed of three main cellular barriers that are critical for the ultrafiltration process, the fenestrated endothelium, glomerular basement membrane and highly specialized podocytes. The podocytes along with their specialized junctions "slit diaphragm" form the basic backbone of this filtration assembly. The presence of high amounts of protein in urine a condition commonly referred as proteinuria indicates a defective glomerular filtration barrier. Various glomerular disorders including Nephrotic syndrome are characterized by significant alteration in the structure of podocytes that is associated with prolonged increase in the glomerular permeability leading to heavy proteinuria. Recent identification of proteins that are specifically localized at the slit diaphragm whose mutations and knockouts are known to result in loss of renal function has significantly advanced our understanding of the molecular makeup of this filtration assembly. The present review is an effort to summarize the recent developments in this field and highlight our understanding of the glomerular filtration barrier assembly.

Keywords: Endothelial cells; Glomerular basement membrane; Glomerulus; podocytes.

Figure 1. Schematic presentation of glomerular filtration barrier

Glomerular filtration barrier showing three distinguished layers: Fenestrated endothelial cells, glomerular basement membrane and podocytes.

Figure 2. Schematic presentation of slit diaphragm proteins

Structural component proteins involved in the formation of glomerular slit diaphragm.