Glomerular deposition of galactose-deficient IgA1-containing immune complexes via glomerular endothelial cell injuries

Background Galactose-deficient immunoglobulin A1 (Gd-IgA1) plays a crucial role in the development of IgA nephropathy (IgAN). However, the pathological role of Gd-IgA1-containing immune complexes (ICs) and the mechanism of deposition in the mesangial region remain unclear. Methods To examine the deposition of Gd-IgA1-containing ICs in the mesangial region through glomerular endothelial cell injury, we evaluated the alteration of renal microvascular endothelial glycocalyx in nude mice injected with Gd-IgA1-IgG ICs. Human renal glomerular endothelial cells (HRGECs) were used to assess the potential capacity of Gd-IgA1-IgG ICs to activate endothelial cells. Results Nude mice injected with Gd-IgA1-containing ICs showed podocyte and endothelial cell injuries, with IgA, IgG and C3 depositions in glomerular capillaries and the mesangium. Moreover, albuminuria and hematuria were induced. Real-time glycocalyx imaging showed that renal microvascular glycocalyx was decreased immediately after injection of Gd-IgA1-containing ICs and then mesangial IgA deposition was increased. After coculture of Gd-IgA1-containing ICs with HRGECs, messenger RNA expression levels of endothelial adhesion molecules and proinflammatory mediators were upregulated significantly. Conclusion Gd-IgA1-IgG ICs had a high affinity for glomerular endothelial cells, which resulted in glomerular filtration barrier dysfunction mediated by glycocalyx loss. Furthermore, Gd-IgA1-IgG ICs accelerated the production of adhesion factors and proinflammatory cytokines in glomerular endothelial cells. The glomerular endothelial cell injury induced by Gd-IgA1-containing ICs may enhance the permeability of Igs in the mesangial region and subsequent inflammatory responses in the pathogenesis of IgAN.

Automated summary

Galactose-deficient immunoglobulin A1 (Gd-IgA1) plays a crucial role in the development of IgA nephropathy (IgAN). The study found that Gd-IgA1-containing immune complexes (ICs) have a high affinity for glomerular endothelial cells, leading to dysfunction of the glomerular filtration barrier mediated by glycocalyx loss. This enhances the permeability of antibodies in the mesangial region and induces inflammatory responses in the pathogenesis of IgAN.