PCNA expression in the midpalatal suture. SC: suture cartilage. SB: suture bone. On day 5, some of the chondrocytes in the proliferating layer of the suture cartilage and osteoblasts at the end of the cartilage were PCNA-positive in the ME group. On day 11, many osteoblasts adjacent to the bone trabeculae were positive in the ME group. (Original magnification ×40).