Ultrastructure of glomerular mesangial matrix by quick freeze and deep-etch methods

The mesangium is the central connective core of the individual lobules of glomerular tufts. The mesangial cells are surrounded by matriceal materials. This mesangial matrix (MM) is similar in appearance, but not identical to the peripheral glomerular basement membrane (GBM). The MM is composed of more coarsely fibrillar and slightly less electron-dense materials than that of the GBM observed on conventional ultrathin sections by electron microscopy. Moreover, the MM is a matter of interest to many investigators, because it is believed to play a role in the mediation of molecules passing through the glomerulus [1,2], and is involved in a variety of kidney diseases [3]. However, the three-dimensional organization of the MM is still poorly defined. The purpose of this study is to clarify the three-dimensional ultrastructure of the MM in situ by quick-freeze and deep-etch replica methods at high resolution [4, 5].