Figure 7 Histological alterations and immunohistochemistry analyses in the mid-palatal sutures. ( A – C ) HE staining showed the changes of the mid-palatal suture in histological sections. ( D–F ) Masson staining showed the changes of the mid-palatal suture in histological sections. b, maxillary bone; c, cartilage; f, fibrous tissue; black arrow: the direction of stretch force; black triangle: the chondrocyte; black pentagram: the capillary; black dotted line: expanded region. Scale bar: 50 μm. ( G – I ) ALP was detected by immunohistochemistry analyses. ( J–L ) BMP2 was detected by immunohistochemistry analyses. Yellow triangle: the positive signal. Scale bar: 20 μm. ( M  and  N ) Quantification of the expression level of ALP and BMP2 (one-way analysis of variance). The columns represent the means. Error bars represent standard deviations. *P < 0.05, **P < 0.01, ***P < 0.001.