Abstract
The deployment of endovascular implants such as stents in the treatment of cardiovascular disease damages the vascular endothelium, increasing the risk of thrombosis and promoting neointimal hyperplasia. The rapid restoration of a functional endothelium is known to reduce these complications. Circulating endothelial progenitor cells (EPCs) are increasingly recognized as important contributors to device re-endothelialization. Extracellular matrix proteins prominent in the vessel wall may enhance EPC-directed re-endothelialization. We examined attachment, spreading and proliferation on recombinant human tropoelastin (rhTE) and investigated the mechanism and site of interaction. EPCs attached and spread on rhTE in a dose dependent manner, reaching a maximal level of 56±3% and 54±3%, respectively. EPC proliferation on rhTE was comparable to vitronectin, fibronectin and collagen. EDTA, but not heparan sulfate or lactose, reduced EPC attachment by 81±3%, while full attachment was recovered after add-back of manganese, inferring a classical integrin-mediated interaction. Integrin αVβ3 blocking antibodies decreased EPC adhesion and spreading on rhTE by 39±3% and 56±10% respectively, demonstrating a large contribution from this specific integrin. Attachment of EPCs on N-terminal rhTE constructs N25 and N18 accounted for most of this interaction, accompanied by comparable spreading. In contrast, attachment and spreading on N10 was negligible. αVβ3 blocking antibodies reduced EPC spreading on both N25 and N18 by 45±4% and 42±14%, respectively. In conclusion, rhTE supports EPC binding via an integrin mechanism involving αVβ3. N25 and N18, but not N10 constructs of rhTE contribute to EPC binding. The regulation of EPC activity by rhTE may have implications for modulation of the vascular biocompatibility of endovascular implants.
Highlights
Circulating endothelial progenitor cells (EPCs) [1] are increasingly recognized to play an important role in cardiovascular regeneration
Fibroblast attachment was greatest, reaching 83 ±2% at the highest tropoelastin concentration, in contrast to smooth muscle cells (SMCs) which only had 39±1% of cells attached. recombinant human tropoelastin (rhTE) enhanced EPC spreading in a concentration-dependent manner reaching 54±3% at 25 μg/ml and 58±2% at 40 μg/ml
As for rhTE, we investigated the mechanism of interaction between N-terminal constructs representing the first 25 (N25) and N18 constructs with EPCs
Summary
Circulating endothelial progenitor cells (EPCs) [1] are increasingly recognized to play an important role in cardiovascular regeneration. Increased levels of EPCs correlate with reduced risk of cardiovascular mortality [2] and contribute to angiogenesis, vasculogenesis [3] and the repair of injured vasculature [4]. There is increasing interest in the potential for EPCs to facilitate re-endothelialization of endovascular prostheses such as stents following implantation in the vasculature [5]. It is increasingly recognized that circulating EPCs substantially contribute to vascular prosthesis endothelialization [11,12], making them important mediators of implant compatibility. In animal models of induced vascular injury the use of pharmacological stimulation [13,14] or infusion of endothelial-like mononuclear cells has been met with variable success [15,16], perhaps reflecting the limitations of a systemic, less locally targeted approach
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