Changes of Skin during Callotasis of the Tibiae in Sprague - Dawley Rats: A Verification of Neogenesis by BrdU Immunohistochemistry

ABSTRACT

We investigated the effect of bone lengthening by callotasis, the gradual distraction lengthening, on the skin of tibia in rats. A pair of small external fixator were placed in the left tibiae of twenty Spraugue-Dawley rats. At two weeks and one year after 25% lengthening, skin flaps of both right and left tibia of each ten animals were removed and prepared for BrdU immunohistochemical study and H&E staining to observe any evidences of proliferative activity of skin. At 2 weeks, compared to the unlengthened skins, the number of BrdU labeled cells, which represents the DNA synthesis, increased 4.35 times(p < 0.001) in the lengthened skin, while that of one year samples did not show any differences. The H&E staining at 2 weeks failed to reveal any remarkable cell proliferation evidences such as mitosis, epidermal cell proliferation and hyperkeratosis except a marked thinning of skin, which became as thick as unlengthened skin at 1 year after lengthening. Though the physical properties of skin such as stretch and relaxation as well as migration can accomodate the lengthened bone, this study might suggest that distraction lengthening offers the gain of skin flap by way of synthesis an6 also support that the bone lengthening procedure stimulate soft tissue proliferation simultaneously.