This proposal focuses on novel molecular mechanisms underlying aortic valve (AV) development in health and disease. The preliminary data presented in this proposal shows that extracellular matrix (ECM) proteins play a key role in healthy AV structure and function during development, and when dysregulated contribute AV thickening and dysfunction (i.e., congenital aortic valve stenosis, CAVS). Specifically, we have identified collagen type proteins to be particularly dysregulated along with a collagen stabilizing post-translational modification, hydroxylation of prolines (HYP). Identifying the molecular mechanisms behind collagen stabilization during development and the rapid collagen dysregulation seen in this valve disease are the basis for this proposal. CAVS will account for 10% of all congenital heart defects, which affect 1 in every 150 people. CAVS progresses as valvular thickening that narrows the aortic opening, leading to restricted blood flow, left ventricular hypertrophy and eventual heart failure. Despite the clinical significance of this disease, patients must ?watch and wait? until surgical valve replacement and repair is necessary, as currently no pharmacotherapeutics exist. There are two distinct CAVS subtypes: i) adult fibrocalcific, accounting for 90% of cases in which the end-stage requiring valve replacement is valve calcification, and ii) pediatric, accounting for the remaining 10%, where end-stage is rapid and excessive ECM deposition at a young age, with no calcification. In pediatric cases, bioengineered valve replacement options are not suitable, creating a critical need for pharmacotherapeutic target development. The proposed research capitalizes on a unique cohort of clinically defined, biorepository-obtained, human pediatric CAVS tissue samples and age matched normal samples. It is our central hypothesis that reduced collagen HYP modifications contributes to rapid ECM dysregulation in pediatric end-stage CAVS. We will address our hypothesis through the following Specific Aims:
Aim 1 will define the spatial localization of collagen HYP sequences relative to histopathology-defined collagen structural signatures in AV development and pathologies. State-of-the-art imaging mass spectrometry (IMS) methodologies, coupled with previously acquired peptides databases, will report expression levels and spatial localization of HYP modified collagen peptides, across a clinically and histopatholgoically well-defined cohort of human AV tissues.
Aim 2 will determine the local ECM ?niche? of differentially activated valvular interstitial cells. Immunohistological staining of VICs will be coupled with IMS to profile corresponding ECM ?niches? of these cells.
This aim will identify the cell-mediated mechanism to the etiology of pediatric CAVS. Understanding the molecular mechanisms driving collagen organization and deposition in CAVS is key to identifying biomarkers and pharmacotherapeutic targets that may halt progression in pediatric cases.
Congenital Aortic Valve Stenosis (CAVS) is a common birth defect, the only treatment for which is surgical repair or replacement, which is particularly unsuitable for pediatric cases. Our aim for this proposal is to elucidate the molecular mechanisms behind the rapid extracellular matrix dysregulation of pediatric end-stage CAVS, with the hope of identifying novel biomarkers and pharmacotherapeutic targets. We aim to change the paradigm of treatment from ?watch-and-wait? surgical replacement to biomarker identification and early intervention with antifibrotics targeted to specific modifications of collagen subtypes, to halt progression until bioengineered solutions are feasible.
