John Ranieri

Spatial control of neuronal cell attachment and differentiation on covalently patterned laminin oligopeptide substrates

The spatial control of neuronal cell attachment and differentiation via specific receptor mediated interactions, may provide an effective means for the in vitro reconstruction of neuronal cell architecture. In this study, receptor‐specific oligopeptide sequences derived from the extracellular matrix (ECM) molecule laminin, a potent neural cell attachment and differentiation promoter were covalently bound on fluorinated ethylene propylene (FEP) films. The degree of receptor‐specific cell attachment and the ability to spatially control neurite outgrowth by covalently patterning the oligopeptide sequences on the FEP film surface were assessed.

eNOS-overexpressing endothelial cells inhibit platelet aggregation and smooth muscle cell proliferation in vitro.

Endothelial cell seeding of synthetic small diameter vascular grafts (SSDVG) has been shown to diminish thrombosis and intimal hyperplasia, resulting in improved graft patency. However, endothelial cell retention on seeded grafts when exposed to physiological shearing conditions remains poor. We report that the genetic engineering of endothelial cells to overexpress endothelial nitric oxide synthase (eNOS), may create improved anti-thrombotic and anti-hyperplastic endothelial cell phenotypes for SSDVG seeding. eNOS-overexpressing endothelial cells may potentially overcome the biochemical loss due to shear induced reduction in endothelial cell coverage on SSDVG. Bovine aortic endothelial cells (BAEC) were transfected with the human eNOS gene, and co-incubated with either human whole blood or bovine aortic smooth muscle cells (BASMC) in vitro. eNOS-transfected BAEC significantly overexpressed eNOS compared to control beta-Gal-transfected and untransfected BAEC up to 120 h post transfection. In co-incubation and co-culture assays, human platelet aggregation decreased by 46% and BASMC proliferation decreased by 67.2% when compared to incubation with untransfected BAEC.

Vascular graft endothelialization: Comparative analysis of canine and human endothelial cell migration on natural biomaterials

Canines are typically used as the standard preclinical model to gauge the success of vascular graft materials. However, canines spontaneously re-endothelialize vascular grafts, whereas humans do not, even after years. This raises questions of why there are differences in vascular healing between humans and other species and whether the canine is the appropriate preclinical model. In the present study we evaluated human and canine endothelial cell (EC) migration on the novel cross-linked collagen biomaterial PhotoFix(TM) pericardium. We compared in vitro migration of these cells on PhotoFix alone and on PhotoFix adsorbed with various growth factors (aFGF and bFGF) and adhesion proteins (fibronectin, collagen IV, vitronectin, and laminin). We also compared human and canine ECs in terms of their morphologies and prostacyclin production. We found that human umbilical vein ECs (HUVECs) and canine ECs (CECs) migrated well on PhotoFix, suggesting that this biomaterial may be a good vascular graft candidate. Both cell types responded similarly to different growth factors and adhesive proteins, but HUVEC migration was consistently higher than that for CECs. This suggested that human in vivo graft re-endothelialization is likely not hindered by poor endothelial migration but is hindered by other cellular or graft properties.