Morphological study of progressive glomerulonephropathy in common marmosets (Callithrix jacchus)

Spontaneous progressive glomerulonephropathy often occurs in common marmosets. However, there are few detailed reports concerning the age-related progressive process of glomerular changes. We discuss the glomerular changes in the early stage and the progressive changes in the advanced stage of nephropathy. We investigated the kidneys of common marmosets (2-11 years old; 9 males and 12 females) using hematoxylin and eosin, periodic acid-Schiff, periodic acid-methenamine-silver, and Masson's trichrome (MT) stains and a transmission electron microscope. There was no remarkable change in urine cytology, hematology, or blood chemistry. In the early stage of nephropathy, effacement of podocyte foot processes was observed ultrastructurally even though there were no marked glomerular lesions in the light microscopy. Subsequently, mesangial proliferation occurred from the hilar to peripheral side along the tuft. In the middle stage, red deposits were visible at the glomerular basement membrane (GBM) and the mesangial region directly under the GBM (paramesangial area) with the MT stain. Electron dense deposits were seen at the same area. In the advanced stage, the irregularity became prominent with or without dense deposits. It is necessary to investigate in detail whether the change of podocyte in the early stage was immuno-mediated or due to podocyte failure.