ACTA1 and glomerulonephritis: In association with these observations, there have been reports indicating that an increase in the number of interstitial alpha-smooth muscle actin (α-SMA)-positive cells, which are believed to be myofibroblasts, is a good marker of disease progression in various types of human glomerulonephritis, including IgA nephropathy [45], membranous nephropathy [46], and diabetic nephropathy [47].