| Recent work has demonstrated that soluble matrix metalloproteinases (MMPs) are involved in tissue regression events both in vitro and in vivo. Specifically, it has been shown that plasminogen/plasmin activate human endothelial cell (EC) derived MMP-1, which induces regression of newly formed capillary tubes during EC morphogenesis in three-dimensional collagen matrices. The goal of the research presented herein is to determine, at the molecular level, the central role human matrix metalloproteinase-1 (MMP-1) and its activators play in the regulation of capillary tube regression events.; In chapter II, a novel, 384 micro-well regression assay is developed to effectively quantify the capillary tube regression response. Data are presented which demonstrate that six additional serine proteases are capable of activating proMMP-1 leading to capillary tube regression: plasma kallikrein, trypsin, neutrophil elastase, cathepsin G, tryptase, and chymase.; In chapter III, the central role of human MMP-1 as a key downstream mediator of vascular regression events is further established. To evaluate the role of MMP-1 and MMP-10 as mediators of vascular regression in vivo, cells expressing wild type MMP-1 or MMP-10, or spontaneously active forms of MMP-1, were utilized to either inhibit formation or induce regression of VEGF-induced angiogenic fields using the chicken chorioallantoic membrane (CAM) model of angiogenesis.; In chapter IV, the ability of the mouse equivalent of human MMP-1 (murine MMP-13) and human collagenase-3 (human MMP-13) to induce capillary tube regression in type I and type II collagen matrices is investigated. These results demonstrate that additional collagenases, both murine and human, are capable of inducing regression of EC capillary tube networks. Thus, multiple collagenases from different species are capable of inducing capillary tube networks, indicating this regression system is broadly relevant.; In conclusion, this work demonstrates that a well regulated system of serine proteases and stromelysins (MMPs) exists to activate proMMP-1, which functions as a vascular regression factor in vitro and in vivo. These data also demonstrate that the collagenase-mediated regression of capillary networks is accomplished by multiple collagenases from various species. (Abstract shortened by UMI.)... |
