However, there was no significant downregulation of claudin 5 expression (claudin 5/β-actin: 1.27 ± 0.24, 1.26 ± 0.41, 1.05 ± 0.11, 1.17 ± 0.24 and 1.22 ± 0.22 in the Sham, 1 day, 3 day, 7 day and 28 day groups, respectively) and ZO-1 expression (ZO-1/β-actin: 17.57 ± 2.63, 19.44 ± 3.57, 18.60 ± 3.51, 19.34 ± 3.17 and 18.05 ± 2.54 in the Sham, 1 day, 3 day, 7 day and 28 day groups, respectively) following CCH (Additional file 1: Figure S4). Here, CLDN5 is linked to columnar cell hyperplasia of the breast.