Extracellular matrix proteins adsorbed to microporous scaffolds can enhance the function of transplanted islets, with collagen IV maximizing graft function relative to the other proteins tested. These scaffolds enable the creation of well-defined microenvironments that promote graft efficacy at extrahepatic sites.

Localized and efficient gene transfer can be promoted by exploiting the interaction between the vector and biomaterial. Regulation of the vector-material interaction was investigated by capitalizing on the binding between lentivirus and phosphatidylserine (PS), a component of the plasma membrane. PS was incorporated into microspheres composed of the copolymers of lactide and glycolide (PLG) using an emulsion process. Increasing the weight ratio of PS to PLG led to a greater incorporation of PS. Lentivirus, but not adenovirus, associated with PS-PLG microspheres, and binding was specific to PS relative to PLG alone or PLG modified with phosphatidylcholine. Immobilized lentivirus produced large numbers of transduced cells, and increased transgene expression relative to virus alone. Microspheres were subsequently formed into porous tissue engineering scaffolds, with retention of lentivirus binding. Lentivirus immobilization resulted in long-term and localized expression within a subcutaneously implanted scaffold. Microspheres were also formed into multiple channel bridges for implantation into the spinal cord. Lentivirus delivery from the bridge produced maximal expression at the implant and a gradient of expression rostrally and caudally. This specific binding of lentiviral vectors to biomaterial scaffolds may provide a versatile tool for numerous applications in regenerative medicine or within model systems that investigate tissue development.

Oxidation of low density lipoprotein (LDL) may be of critical importance in the pathogenesis of atherosclerosis. Recent studies suggest that oxidized phospholipids render LDL atherogenic. However, both the structures and the physiologically relevant pathways for the formation of modified phospholipids in oxidized LDL remain poorly understood. We previously showed that phydroxyphenylacetaldehyde (pHA) is the major product of L-tyrosine oxidation by the myeloperoxidase/hydrogen peroxide/chloride system of phagocytes. In the current studies, we demonstrate that this reactive aldehyde targets the aminophospholipids of LDL in vitro and in vivo. Activated human neutrophils generated pHA-ethanolamine, the reduced adduct of pHA with the amino group of phosphatidylethanolamine, on LDL phospholipids by a reaction that required myeloperoxidase, H 2 O 2 , and L-tyrosine. The cellular system could be replaced by HOCl and L-tyrosine but not by a wide variety of other oxidation systems, indicating that pHA-ethanolamine is a specific marker for covalent modification of aminophospholipids by myeloperoxidase. To determine whether aldehydes modify aminophospholipids in vivo, we quantified levels of pHA-ethanolamine in acid hydrolysates of reduced lipid extracts through isotope dilution gas chromatography/mass spectrometry. Circulating LDL contained undetectable levels of pHA-modified phospholipid (<0.1 mmol/mol). In contrast, the concentration of pHA-ethanolamine in LDL isolated from human atherosclerotic lesions was strikingly elevated (4.5 mmol/mol). Collectively, these results demonstrate a novel, myeloperoxidase-based mechanism for modifying the amino group of LDL phospholipids. They also offer the first evidence that myeloperoxidase may damage LDL lipids in vivo, raising the possibility that aldehydemodified aminophospholipids play a role in inflammation and vascular disease.An elevated level of low density lipoprotein (LDL), 1 the major blood transporter of cholesterol, is a major risk factor for atherosclerosis (1). Many lines of evidence suggest, however, that LDL must be oxidatively modified to trigger atherosclerotic vascular disease (reviewed in Refs. 2-4). One potentially important class of reactions that render LDL atherogenic involves aldehydes, which are generated through decomposition of peroxidized lipids (2-4). These products can attract monocytes into the artery wall (5, 6) and covalently modify LDL (7-9), rendering it a ligand for macrophage scavenger receptors. Unregulated internalization of modified LDL by these receptors may play a key role in foam cell formation, the cellular hallmark of atherosclerosis.Because reactive aldehydes are implicated in the pathogenesis of atherosclerotic vascular disease (2-4, 10, 11), their reaction with biological molecules has been widely investigated. The physiologically relevant target is generally assumed to be the ⑀-amino group of protein lysine residues (2-4, 10 -13). Thus LDL that has been oxidized (14, 15) or chemically modified by acetylation (16) or treatment with ma...

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Islet transplantation on extracellular matrix (ECM) protein-modified biodegradable microporous poly(lactide-coglycolide) scaffolds is a potential curative treatment for type 1 diabetes mellitus (T1DM). Collagen IV-modified scaffolds, relative to control scaffolds, significantly decreased the time required to restore euglycemia from 17 to 3 days. We investigated the processes by which collagen IV-modified scaffolds enhanced islet function and mediated early restoration of euglycemia post-transplantation. We characterized the effect of collagen IVmodified scaffolds on islet survival, metabolism, and insulin secretion in vitro and early-and intermediate-term islet mass and vascular density post-transplantation and correlated these with early restoration of euglycemia in a syngeneic mouse model. Control scaffolds maintained native islet morphologies and architectures as well as collagen IV-modified scaffolds in vivo. The islet size and vascular density increased, while b-cell proliferation decreased from day 16 to 113 post-transplantation. Collagen IV-modified scaffolds promoted islet cell viability and decreased early-stage apoptosis in islet cells in vitro-phenomena that coincided with enhanced islet metabolic function and glucose-stimulated insulin secretion. These findings suggest that collagen IV-modified scaffolds promote the early restoration of euglycemia post-transplantation by enhancing islet metabolism and glucose-stimulated insulin secretion. These studies of ECM proteins, in particular collagen IV, and islet function provide key insights for the engineering of a microenvironment that would serve as a platform for enhancing islet transplantation as a viable clinical therapy for T1DM.