IN-SITU FLUORESCENCE LABELING OF SHEEP LUNG MICROVASCULAR ENDOTHELIUM

Endothelial cells are intimately involved in a variety of biological p rocesses such as inflammatory disorders, wound healing, and tumor inva sion. The finding of endothelial heterogeneity in various tissues has led to major efforts to isolate and culture microvascular endothelial cells in human and animal tissue. In this report we have used phosphat idyl ethanolamine (PE)-labeled liposomes to fluorescently label the sh eep lung microvasculature in situ. Using normotensive perfusion pressu re, the PE-labeled liposomes did not extravasate into extravascular lu ng tissue. Mechanical and enzymatic digestion of the lung tissue demon strated that the PE-labeled liposomes provided a stable label of the v ascular lining cells during ex vivo processing. After digestion, the o verwhelming majority of the fluorescent label appeared in cellular agg regates, Approximately 80% of these cells demonstrated an in vitro phe notype consistent with microvascular endothelium. A novel monoclonal a ntibody selective for sheep endothelial cells was developed to confirm the presence of lung endothelium in the fluorescently labeled cellula r aggregates. We conclude that in situ fluorescence labeling of vascul ar lining cells provides an anatomic marker for relevant vascular lini ng cells and an opportunity to study these cells in vitro.