PR40P PROGENITOR CELLS IN HAEMANGIOMA.

Purpose: We have recently shown mesenchymal stem cells (MSCs) isolated from haemangioma stained strongly for OPG. Vimentin immunoreactivity (IR) is an established marker for immature cells of mesenchymal origin. This study characterises haemangioma biopsies at different phases of progression to identify the presence of progenitor cells. Methods: Immunohistochemical staining was carried out on formalin-fixed paraffin sections of haemangioma at different phases of progression for vimentin, osteoprotegerin (OPG), von Willebrand factor and glucose transporter-1 (Glut-1). Results: Positive staining for OPG and vimentin was observed on progenitor cells in the proliferating and early involuting phases of haemangioma. Strong Glut-1 staining of mature capillaries of the involuted phase was inversely related to the degree of OPG and vimentin IR. Positive vimentin staining of cells in the interstitium of involuted heamangioma and weak vimentin IR of blood vessels was found suggesting that these vimentin-positive cells may be MSCs that eventually differentiate into adipocytes that characterise involuted lesions. OPG IR diminished as haemangioma involuted, with little staining seen in involuted lesions. Conclusions: OPG and vimentin IR are early progenitor cell markers that stain immature capillaries of proliferating haemangioma. In involuted haemangioma OPG IR is scant whereas vimentin-positive cells are present in the interstitium. This finding supports our hypothesis that OPG IR is a marker for progenitor cells present in immature capillaries of proliferating haemangioma that is lost as the lesions involute. [ABSTRACT FROM AUTHOR]