Vasculogenic Mimicry in Osteosarcoma : Histomorphologic Studies in Vivo and in Vitro

This study was to examine whether there is evidence for vasculogenic mimicry in osteosarcoma. In vivo and in vitro studies were conducted. Studies using hematoxylin and eosin (HE) stain and CD31 immunohistochemical stain to observe the micro vascular channels in human osteosarcoma specimens were performed. Osteosarcoma cell lines (U-20S) were also tested in vitro for their ability to form tubular networks in three- dimensional culture containing type I collagen. The structures of the tubular networks were observed with phase contrast microscope and transmission electron microscope (TEM). Morphometric observation using HE stain and CD31 immunohistochemical stain showed that tumor cell-lined channels were detected in vivo in osteosarcoma; By comparison, all vascular areas in the pedicel of osteochondroma or outside osteochondroma were endothelial-lined. Morphometric Observation with light microscope and TEM showed that highly aggressive osteosarcoma cell lines (U-20S) formed networks containing channels when grown in three-dimensional culture containing type I collagen, in the absence of endothelial cells or fibroblasts. These observations strongly suggest that aggressive osteosarcoma cells may generate vascular channels that facilitate tumor perfusion independent of tumor angiogenesis and have the ability of vasculogenic mimicry.