Paper Title
Potential Of Autologous Circulating Cd34+45- Source Cells To Inhibit Smooth Muscle Cell Dedifferentiation For Intracranial And Vascular Stent Applications

Abstract
Balloon angioplasty � stenting is often complicated by restenosis, initiated in part by endothelial denudation, leading to smooth muscle cell dedifferentiation and proliferation. These complications could possibly be mitigated by re-endothelialization of the stented vessel lumen including the stent surface using autologous cells. Circulating CD34+CD45- cells are the source cells of late-outgrowth endothelial progenitor cells and can be isolated by FDA-approved immuno-magnetic selection. Our pilot studies tested the hypotheses that the CD34+45- source cells could adhere to (Ti), the blood-contacting surface material of nitinolintracranial and vascular stents, and that the CD34+45- source cells on Ti would differentiate into endothelial cells with the potential to inhibit smooth muscle cell dedifferentiation. Our results show that the an average of 39.7� 6.0%, 19.7� 2.1%, 14.7� 6.8% ofsource cells remained adherent on Ti under laminal fluid flow shear stress of 10, 15, and 20dynes/cm2 (n=3 for each shear stress). The cells differentiated into endothelial cells on Ti, shown by EC-characteristic cobblestone morphology, Di-Ac-LDL uptake, PECAM-1 positive staining and thrombomodulin expression. Lining bare Ti surfaces with a confluent monolayer of the CD34+45- cellssignificantly reduced the ability of platelets to adhere to those surfaces, with only 149.4 � 178.0 platelets/mm2 adhered to the cell-lined Ti surfaces, compared to 2372.9 � 29.2 for the bare surfaces. Further, the CD34+45- source cells showed potential to inhibit SMC dedifferentiation as assessed by increased smooth muscle cell-specific differentiation marker -SMA. Future in vivo studies are warranted to investigate the effect of CD34+45- source cells to regenerate damaged endothelium after angioplasty � stenting by lining the blood-contacting surface of stents and potentially replacing endothelial cells that were sheared off from the vessel lumen. Keywords: Endothelial Progenitor Cell, Stent, Smooth-muscle cell, Immuno-magnetic selection, -SMA, Thrombomodulin