CDKN2A and diabetic kidney disease: Moreover, computerized morphometric analysis of immunohistochemistry staining of Serpin E1 (Fig. 6A) and p16INK4A (Fig. 1C) as well as Masson trichrome staining (Fig. 1C) revealed that the relative staining intensity of Serpin E1 positively correlated with that of p16INK4A (Fig. 6B) or collagen volume fraction of Masson staining (Fig. 6C) in control and diabetic kidneys, suggesting that increased renal tubular expression of Serpin E1 is associated with renal tubular premature senescence and degenerative changes in DKD.