Inducible expression of human endoglin during inflammation and wound healing in vivo

OBJECTIVE: Because angiogenesis and inflammation are intimately associated and endoglin is required for angiogenesis, we wished to determine whether it also plays a role in inflammation. METHODS: Using an immunohistochemical approach, we examined spatial and temporal changes in endoglin expression during inflammation and angiogenesis. RESULTS: We found low levels of endoglin expression in quiescent endothelium in a range of normal adult human tissues. However, constitutive levels of expression are higher in dermal capillaries surrounding hair follicles and in alveolar capillaries as well as in the high endothelial cells of lymph tissue. During inflammatory disease, endoglin expression is strongly upregulated and is consistently associated with an infiltrate of inflammatory cells. For the first time, we have determined the relative changes in endoglin expression from the normal quiescent state through the inflammatory changes and angiogenesis that occur during dermal wound healing in vivo using a timed human wound healing model. Endoglin expression increases rapidly, reaching a peak of expression co-incident with maximal T cell infiltrate and persisting at an elevated level for at least 28 days in both activated and proliferating endothelial cells. CONCLUSION: Enhanced endoglin expression is not limited to angiogenesis, it is also associated with inflammation.