Aspects of arterial wall healing : re-endothelialization, intimal hyperplasia and vascular remodeling

Abstract

Cardiovascular disease is the leading cause of mortality in the world. Despite prevention, the need for interventions remains high. Patients with type 2 diabetes mellitus have an increased cardiovascular burden and are at higher risk of complications following invasive vascular interventions. Complications related to an excessive healing response are a major clinical problem, which results in increased morbidity and possibly death. The arterial wall healing response consists of re-endothelialization, intimal hyperplasia (IH) formation and vascular remodeling. Current pharmacological treatment relies on non-selective anti-proliferative drugs, which reduces IH formation but increases the risk of thrombosis due to a delayed re-endothelialization. Hence, there is a need for development of selective treatments.

Evaluation of the re-endothelialization process in the rat carotid balloon injury model has previously been limited to histological staining and invasive imaging techniques. We demonstrate that it is possible to estimate the re-endothelialization process in ultrasound biomicroscopy using IH morphology as a surrogate marker. This technique will be a useful tool for non-invasive real-time evaluation of the re-endothelialization process in pharmacological studies.

Incretin-modulating drugs is a group of antidiabetic drugs, which targets the glucagon-like peptide-1 (GLP-1) receptor by either direct activation or suppressing breakdown of native GLP-1 with dipeptidylpeptidase-4 (DPP-4) inhibitors. GLP-1 receptor activation has been shown to reduce IH formation by selective inhibition of smooth muscle cell (SMC) proliferation. However, we show that treatment with linagliptin, a DPP-4 inhibitor, does not influence the arterial wall healing in normal or type 2 diabetic conditions. Large-scale transcriptomic analysis is an important tool for confirmation and identification of novel molecular mechanisms in experimental research.

In Study III, we generated an encyclopedia of the transcriptomic landscape over time in the rat carotid balloon injury model. We could detect three separate phases of the healing process and contribution of novel molecular mechanisms. This resource includes a biobank of tissue samples, which will be a powerful tool for validation and identification of novel treatment targets. The utilization of transcriptomic data to identify new biological pathways in the arterial wall healing process can be exemplified with proprotein convertase subtilisin/kexin 6 (PCSK6). Previously, we could identify an increased expression of PCSK6 in patients with symptomatic carotid artery stenosis. PCSK6 has been associated with tumor invasiveness and extracellular matrix modulation in cancer but its function in the vasculature remains elusive. We demonstrate that PCSK6 deletion increases outward remodeling, reduces SMC differentiation and influences contractility in a murine model of flow-mediated remodeling. These results indicate that PCSK6 could be a potential target to reduce the risk of constrictive remodeling and restenosis.