The human rectum is located in the lower gastrointestinal tract and functions as a temporary storage site for fecal material. Endothelial cells in the rectum line the interior surface of the blood vessels and form the interface between intravascular and extravascular compartments. Endothelial cells limit the passage of cellular and soluble substances between the blood vessels and the tissues. Endothelial cells also play critical roles in angiogenesis, vasculogenesis, and the inflammatory response. Rectal microvascular endothelial cells (RecMEC) have been implicated as a major contributing factor to the progression of rectal cancer. Human RecMEC (HRecMEC) are a useful in vitro model to elucidate the mechanisms of angiogenesis and to develop treatments for rectal cancer. HRecMEC from ScienCell Research Laboratories are isolated from human rectum. HRecMEC are cryopreserved at passage one and delivered frozen. Each vial contains >5 x 105 cells in 1 ml volume. HRecMEC are characterized by immunofluorescence with antibodies specific to vWF/Factor VIII and/or CD31 (PECAM1). HRecMEC are negative for HIV-1, HBV, HCV, mycoplasma, bacteria, yeast, and fungi. HRecMEC are guaranteed to further expand for 10 population doublings under the conditions provided by ScienCell Research Laboratories. Recommended Medium It is recommended to use Endothelial Cell Medium (ECM, Cat. #1001) for culturing HRecMEC in vitro.