Intussusceptive capillary growth is required for glomerular repair in rat Thy-1.1 nephritis

Background. Injection of anti-Thy-1.1 antibodies to rats causes mesangiolysis, with subsequent capillary loss. This dramatic event is followed by almost complete recovery of glomerular architecture. However, the precise cellular mechanisms of revascularization are not fully understood. Methods. Glomerulonephritis was induced by the injection of monoclonal anti-Thy-1.1 antibody to rats. Structural changes in the glomerular vasculature, with special emphasis on the repair phase, were studied with corrosion casting technique, light microscopy (LM), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). Results. Specifically during the extensive revascularization period, numerous tiny holes of about 1.5 mum in diameter were found on the glomerular cast. The presence of transluminal tissue pillar was confirmed with LM and SEM. These findings indicate the involvement of intussusceptive capillary growth. TEM study demonstrated that some tissue pillars were composed of endothelial cells only and others had cytoplasmic process of mesangial cells in their cores sandwiched both sides by endothelial walls. Conclusion. Intussusceptive capillary growth, or nonsprouting angiogenesis is involved in the postinjury angiogenesis in the glomeruli, in which process mesangial cells as well as endothelial cells may play important roles.