Moedder, Ulrike

Objective To test the hypothesis that the numbers of circulating endothelial progenitor cells (EPC) co-expressing an osteogenic phenotype (EPC-OC) are increased in patients with clinically severe calcific aortic valve stenosis (AoC). Background AoC is one of the most common valvular heart diseases. Recent studies have shifted the old paradigm of AoC being a passive, degenerative process to an active biological process associated with an osteoblast-like phenotype. We have recently identified circulating EPC-OC which are significantly increased in patients with severe coronary artery disease (CAD). Methods and Results Of 38 patients, 14 underwent aortic valve replacement due to AoC with only mild angiographic CAD. Patients with normal aortic valves and coronary arteries (n=12) or severe CAD without aortic valve disease (n=12) served as controls (Table ). Peripheral blood mononuclear cells were analyzed using flow cytometry following staining for EPC markers (CD133, CD34, KDR) and the osteoblastic marker, osteocalcin (OC). Patients with AoC had significantly higher fractions of OC co-expression on EPC of different maturity than normal patients, similar to patients with CAD (Figure ). Conclusions Circulating EPC co-expressing an osteoblastic phenotype are increased and may potentially play a role in the active process of aortic valve calcification. Table. Clinical Data.

Wnt signaling plays a central role in the development of bone forming osteoblasts and bone remodeling. This study analyzed Wnt‐10b control of gene expression throughout osteoblast differentiation. Genes regulated by Wnt‐10b were identified by analyzing five mouse osteoblast lines (C3H10T1/2, ST‐2, bone marrow stromal cells, MC‐3T3, and calvarial osteoblasts). These cell lines were exposed to media from a Wnt‐10b producing cell line via a transwell system. mRNA levels of 32 osteoblastic, Wnt and BMP responsive genes were quantified by qPCR. Several genes were consistently up/down regulated, representing different stages of osteoblast commitment and differentiation. In the second part of the study, C3H10T1/2 cells were treated with BMP2 osteoblast differentiation media to stimulate the growth of osteoblastic cells. The control and Wnt‐10b treated cells were harvested at 0, 6, 9, 12, or 15 days to observe the effect of Wnt‐10b during differentiation. Analysis of 64 genes showed two known Wnt‐3a targets, complement component 3 (C3) and chemokine ligand 16 (Cxcl16), were highly regulated by Wnt‐10b. This study indentifies a number of important genes that are regulated by Wnt‐10b during osteoblast differentiation. This project was funded by the Mayo Graduate School and the Summer Undergraduate Research Fellowship.