Ph.D Thesis

Ph.D StudentBen-Yosef Yaara
SubjectMatrix Metalloproteinase (MMP)-2 Modulation by Hypoxia and
its Role in Endothelial Cells Survival
DepartmentDepartment of Medicine
Supervisors ASSOCIATE PROF. Nitza Lahat
PROF. Ariel Miller


Exposure of endothelial cells (ECs) to hypoxia has separately been shown to induce their angiogenesis or death. Matrix Metalloproteinase (MMP)-2 is associated with ECs angiogenesis, though recent studies also implicate this molecule in ECs death. We studied the effect of hypoxia, in the absence or presence of TNF-a (characteristic of the inflammatory microenvironment accompanying hypoxia), on MMP-2 expression and its role in angiogenesis (proliferation, migration and tube formation) and death of primary human umbilical vein endothelial cells (HUVEC). Hypoxia (24-48h; 3% oxygen), furthermore when combined with TNF-a, significantly enhanced MMP-2 expression and activity. Hypoxia also led to a reduction of MT1-MMP and TIMP-2 mRNA and protein while enhancing the expression of aVb3 integrin, and the cytoskeletal protein, phosphopaxillin. Moreover hypoxia led to co-localization of aVb3 and MMP-2, but not MT1-MMP, with phosphopaxillin in ECs. These results suggest MT1-MMP-independent activation of MMP-2 during hypoxia and support interactions between the ECM, integrins and cytoskeleton in hypoxia-induced MMP-2-related functions.

Hypoxia enhanced ECs migration in an MMP-2-dependent manner, while leading to a reduction of cell number via their apoptotsis, also dependent on MMP-2. In addition hypoxia caused aberrant tube-like formation on Matrigel that appeared to be unaffected by MMP-2. The hypoxia-induced MMP-2-dependent migration of ECs is in accordance with the pro-angiogenic role ascribed to MMP-2, while the involvement of this protease in the hypoxia-related death of ECs, supports an additional apoptotic role for this protease. Hence MMP-2, in the hypoxic microenvironment, appears to have a dual autocrine role in determining the fate of ECs.