MBP and columnar cell hyperplasia of the breast: At 4 weeks after the surgery, the model group still showed decreased myelin density and MBP protein and mRNA levels relative to the sham group (all P < 0.001); moreover, demyelination was more severe in these rats compared to those sacrificed at 2 weeks (all P < 0.05; Figures 3A–D), reflecting the progressive loss of myelin over time after CCH.