Collagen VII expression in glomerular sclerosis

Glomerular sclerosis is the final stage of a variety of kidney diseases and matrix molecules not normally expressed in the extracellular matrix are sy nthesized and accumulate during the sclerotic process. Collagen type VII is the major component of the anchoring fibrils at the dermal-epidermal junct ion, but it is usually not present in normal glomeruli. The aim of this stu dy was to investigate whether this type of fibrillary collagen, different f rom types I and III, is expressed in chronically diseased glomerular extrac ellular matrix. The presence and distribution of collagen VII have been exa mined in 50 renal biopsies by indirect immunofluorescence staining, standar d electron microscopy, and immuno-electron microscopy. In selected cases, c ollagen VII mRNA expression was also measured by RT-PCR on isolated glomeru li. Cases included focal segmental glomerulosclerosis, minimal change disea se, membranous glomerulonephritis, IgA nephropathy, SLE nephritis, diabetic glomerulosclerosis, ischaemic renal disease, extracapillary glomerulonephr itis, and end-stage renal disease. Collagen VII protein and mRNA expression was absent or present in trace amounts in normal kidneys or in disorders w ith only a mild increase of mesangial matrix, without scarring of the tuft. Maximal expression was evident in the presence of adhesions between the gl omerular tuft and Bowman's capsule or fibrous crescents. The results showed that collagen VII is actively synthesized and laid down in areas of glomer ular and/or tubular scarring, irrespective of the underlying disease, confi rming the de novo expression of fibrillary collagens in diseased renal extr acellular matrix. The appearance of an anchoring collagen may be a response to support mechanical stress and it takes part in the process of cell prol iferation and tissue repair. Copyright (C) 2001 John Wiley & Sons, Ltd.