RENAL GLOMERULAR FIBROSIS IN 2 PIGS

Massive deposition of collagen fibrils was found in the renal glomerul i of two pigs. The affected pigs were a 6-month-old female hybrid pig with systemic mycobacteriosis and a retired sow showing azotemia. Micr oscopically, various amounts of a homogeneous eosinophilic substance w ere deposited within the expanded mesangium of almost all renal glomer uli in both cases. The deposit was also seen occasionally on the glome rular capillary walls in the sow. Capillary lumens were occluded in th e glomerular segments with heavy deposition. Obsolescent glomeruli wer e often surrounded by lymphoid cells. The deposited substance was Cong o red negative and stained deep blue with Heidenhain's azan staining. Immunohistochemical evaluation revealed that the major component of th e homogeneous substance was type-III collagen. Electron microscopic ex amination showed that the deposits were masses of fibrils of variable length, width, and shape. The fibrils had transverse bands with a peri odicity of approximately 60 nm, consistent with collagen fibrils. Thes e glomerular changes were identical to those of collagenofibrotic glom erulonephropathy that has recently been described as a new glomerular disease in humans. The glomerular lesion may be the result of unusual production of type-III collagen by mesangial cells.