mésangium

The mesangium is the central region of the renal glomerulus, comprising mesangial cells and the mesangial matrix, located between the glomerular capillary loops. It provides structural support to the glomerular tuft and participates in regulation of filtration surface area.

Mesangial cells are specialized pericyte-like cells embedded in a dense extracellular matrix. They synthesize matrix components, respond to vasoactive and inflammatory signals, and have phagocytic properties that help clear immune complexes and debris from the glomerulus. The mesangial matrix, rich in type IV collagen and proteoglycans, connects mesangial cells and supports the capillary network with mesangial filaments.

Functions of the mesangium include maintaining capillary stability, modulating the filtration surface by contracted or relaxed mesangial cells, and contributing to turnover and repair after injury. Mesangial cells also produce cytokines and growth factors that influence neighboring glomerular cells, including podocytes and endothelial cells.

Clinical relevance arises when the mesangium undergoes proliferation or matrix expansion, as seen in various glomerulonephritides. IgA nephropathy often features mesangial deposition of IgA with increased mesangial cellularity. Diabetic nephropathy commonly shows mesangial expansion and, in advanced stages, nodular sclerosis. Other conditions may involve mesangiolysis or mesangial immune deposits. Diagnostic assessment relies on light microscopy for cellularity and matrix changes, immunofluorescence for immune deposits in the mesangium, and electron microscopy for mesangial expansion and deposits.

Etymology derives from Greek mesos, middle, and angeion, vessel.