Glomerular deposition of homotrimeric type I collagen in the COL1A2 deficient mouse

A novel type I collagen glomerulopathy was identified in COL1A2 deficient mice, which are homozygous null for functional proα2(I) collagen chains and synthesize exclusively homotrimeric type I collagen. The COL1A2 deficient mice accumulate fibrillar type I collagen in their renal mesangium. Under normal physiologic conditions, type I collagen is not present in the renal mesangium. The accumulation of glomerular collagen is pathologic, and occurs as a component of many chronic renal diseases. The aims of this study were to 1) determine the natural progression of the type I collagen glomerulopathy, 2) determine if the pathologic findings correlate with progression of the glomerulopathy, 3) identify the mechanism responsible for glomerular type I collagen deposition in COL1A2 deficient mice, and 4) determine if matrix metalloproteinases (MMPs) cleave heterotrimeric and homotrimeric type I collagen similarly. Picrosirius red staining of formalin-fixed kidneys from COL1A2 deficient, heterozygous, and wildtype mice demonstrates that both COL1A2 deficient and, to a lesser degree, heterozygous animals develop glomerular collagen deposition, exhibiting a gene dose effect. Further, the glomerulopathy begins postnatally, within one week of life, following a pattern of glomerular maturation. The glomerulopathy appears