Mesangiolysis

Mesangiolysis is defined as “dissolution or attenuation of mesangial matrix and degeneration of mesangial cells” [1]. In essence, it is an injurious process which affects the glomerular mesangium without causing obvious damage to the capillary basement membranes. The matrix swells, loosens, and eventually dissolves; the mesangial cells may show only edema and vacuolization, or may undergo severe degeneration and necrosis. Mesangiolysis appears to play a significant role in a wide variety of glomerular diseases, from those caused by toxins and poisons to several forms of glomerulonephritis. With light microscopy mesangiolysis is recognized by widening and poor staining of the mesangial areas (see Fig. 8). However, this change can be transitory and inconspicuous. A much more obvious manifestation is dilatation of the capillary lumina which attain aneurysmatic proportions and often end as a huge “blood cyst” occupying most of the glomerular space. As has been shown by electron microscopy, formation of blood cysts is secondary to the dissolution of mesangial matrix and loss of the “anchoring points” of the capillary walls. As a result, the basement membranes are no longer held in a fixed position by their attachments to the mesangium: They unfold and the adjoining capillary lumina merge.