COL4A3 and focal segmental glomerulosclerosis: We observed a significant linear increase in COL4A3/4/5 expression as well as the mesangial cell marker PDGFRβ in both MCD and FSGS cases when compared to HC group, accompanied by structural alterations in Podocin and Nephrin, resulting in a decrease in their expression levels (Figs 1A and B, 2A and B, 3A and B; Fig. S1C and D, see online supplementary material).