Development of angiogenic periglomerular microvessels after acute glomerular lesions in IgA nephropathy.

Aim: To clarify the clinicopathological characteristics and role of periglomerular angiogenesis in IgA nephropathy.

Methods And Results: The renal biopsy specimens of 114 patients with IgA nephropathy were examined. Among them, 46 (40%) showed periglomerular angiogenesis around the glomeruli. CD34 and α-smooth muscle actin (α-SMA) staining in serial sections revealed that these vessels contained CD34+ α-SMA+ microarterioles along with CD34+ α-SMA- capillaries. We termed these "periglomerular microvessels (PGMVs)". Patients with PGMVs (PGMV group) had clinically and histologically more severe disease than those without PGMVs (non-PGMV group) at the time of biopsy. Even after adjusting for age, there were significant differences in the degree of proteinuria and estimated glomerular filtration rate reduction between the PGMV and non-PGMV groups. The PGMV group showed a higher incidence of segmental and global glomerulosclerosis and crescentic lesions than the non-PGMV group (P < 0.01). Here, PGMVs were undetectable in the acute and active inflammation phase, but were observed in the acute to chronic or chronic glomerular remodelling phase. PGMVs mainly developed around glomerular adherent lesions to the Bowman's capsule with small or minimal glomerular sclerotic lesions. Conversely, they were rarely observed in segmental sclerosis areas.

Conclusion: The PGMV group is clinically and pathologically more severe than the non-PGMV group; however, they were undetectable in segmental sclerosis with mesangial matrix accumulation. PGMVs might occur after acute/active glomerular lesions, suggesting that PGMVs may inhibit segmental glomerulosclerosis progression and could be a marker for good repair response after acute/active glomerular injury in severe IgA nephropathy cases.