Remodelación vascular por enzimas proteolíticos y factores vasoactivos en modelos de patología cardiovascular

Resumen

Vascular neointimal hyperplasia is a significant clinical problem. It happens under certain circumstances, including those surgical procedures involved in the reopening of occluded arteries by mechanical stress. Therefore, investigation towards the onset, progression, and monitoring of endothelial regeneration, and prevention of neointima formation, is crucial to provide adequate treatments and to improve life quality in this set of patients. By using animal models of endothelial denudation, we and others found that NOS3 inhibits neointima formation, and prompts a better endothelial recovery, although the precise mechanisms elicited by NO are poorly understood. In NOS3 null mice, we found extensive neointima formation, and a significant delay of endothelial recovery. These mice also exhibited sustained inflammation, showing a significant accumulation of pro-inflammatory M1 macrophages overtime. Likewise, we also found that in the absence of NOS3, resolving M2 macrophages repolarized into M1 pro-inflammatory cells, thereby preserving a sustained pro-inflammatory environment long after the procedure. In order to shed light about the mechanisms elicited by NO, we detected high levels of pro-inflammatory cytokines and chemokines IL-5, IL-6, GM-CSF, MCP1, IFNγ and VEGF, involved in macrophage recruitment and polarization to M1 phenotype in the absence of NOS3. This pro-inflammatory environment contributed to increase the migration and proliferation of vascular smooth muscle cells (VSMC) and to induce the expression and activation of several matrix metalloproteinases, including MMP-13. We propose MMP-13 as one key target of NOS3 during this process, since lack of MMP-13 does not have any effect on neointima formation, but the neointimal layer of double NOS3/MMP-13 mice was reverted to the phenotype exhibited by NOS3 expressing animals. Finally, and having the relevance of monitoring vascular regeneration in patients, and that non invasively methods have been yet provided, we developed a non invasive molecular imaging MRI procedure with a specific contrast agent to track endothelial regeneration, providing with a brand new tool for future interventions in humans. This doctoral thesis contributes to shed light about the molecular mechanisms by which Nitric Oxide prevents neointimal hyperplasia, and provides with new technical procedures for non invasively follow-up the evolution of endothelial regeneration in damaged vessels by means of molecular Magnetic Resonance Imaging.