A novel in vivo model of human hemangioma: xenograft of human hemangioma tissue on nude mice.

BACKGROUND: Experimental models of human infantile hemangiomas are needed, although none of the current ones is ideal in representing the natural development of hemangioma. In this article, the authors present a nude mice model of human hemangioma with serial morphologic findings on grafts.
METHODS: A specimen of rapidly growing hemangioma tissue was obtained surgically from a 2-month-old boy and was cut into 96 pieces, which were implanted subcutaneously into nude mice, six pieces each. During the 6-month experimental period, gross view, hematoxylin and eosin staining, double immunofluorescent labeling with mouse antihuman CD31 and fluorescein isothiocyanate-labeled rat antimouse CD34, and transmission electron microscopic observation were performed.
RESULTS: Eighty-one of the 96 grafts (84.4 percent) survived and grew during the second month to 3 to 4 months after transplantation, followed by gradual involution. Histologic examination showed cellular edema, degeneration, and necrosis in the early stage. From approximately 30 days, cellular density increased and karyokinesis was identified at 45 days. At 2 months, the grafts were composed mainly of hemangioma tissue and signs of involution appeared. Thereafter, signs of involution turned significant and the grafts were replaced with fibrofatty tissue. It was confirmed through double immunofluorescent labeling that the chief cellular components were endothelial cells of human origin. Findings on ultrastructural investigation were concordant with those on light microscopic observation.
CONCLUSIONS: With human hemangioma tissue implanted into nude mice, an animal model was established successfully. The development of grafts after ischemia resembled the natural course of human infantile hemangioma.