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Tissue engineering has been widely applied in different areas of regenerative medicine, including retinal regeneration. Typically, artificial biopolymers require additional surface modification (e.g. with arginine-glycine-aspartate-containing peptides or adsorption of protein, such as fibronectin), before cell seeding. Here, we describe an alternative approach for scaffold design: the manufacture of hybrid interphotoreceptor matrix-poly (ε-caprolactone) scaffolds, in which the insoluble extracellular matrix of the retina is incorporated into a biodegradable polymer well suited for transplantation. The incorporation of interphotoreceptor matrix did not change the topography of polycaprolactone film, although it led to a slight increase in hydrophilic properties (water contact angle measurements). This hybrid scaffold provided sufficient stimuli for human retinal progenitor cell adhesion and inhibited proliferation, leading to differentiation toward photoreceptor cells (expression of Crx, Nrl, rhodopsin, ROM1). This scaffold may be used for transplantation of retinal progenitor cells and their progeny to treat retinal degenerative disorders. [ABSTRACT FROM AUTHOR]

We provide the first comprehensive analysis of the extracellular matrix (ECM) composition of peri-islet capsules, composed of the peri-islet basement membrane (BM) and subjacent interstitial matrix (IM), in development of type 1 diabetes in NOD mice and in human type 1 diabetes. Our data demonstrate global loss of peri-islet BM and IM components only at sites of leukocyte infiltration into the islet. Stereological analyses reveal a correlation between incidence of insulitis and the number of islets showing loss of peri-islet BM versus islets with intact BMs, suggesting that leukocyte penetration of the peri-islet BM is a critical step. Protease- and protease inhibitor--specific microarray analyses (CLIP-CHIP) of laser-dissected leukocyte infiltrated and noninfiltrated pancreatic islets and confirmatory quantitative real time PCR and protein analyses identified cathepsin S, W, and C activity at sites of leukocyte penetration of the peri-islet BM in association with a macrophage subpopulation in NOD mice and human type 1 diabetic samples and, hence, potentially a novel therapeutic target specifically acting at the islet penetration stage. Interestingly, the peri-islet BM and underlying IM are reconstituted once inflammation subsides, indicating that the peri-islet BM-producing cells are not lost due to the inflammation, which has important ramifications to islet transplantation studies. [ABSTRACT FROM AUTHOR]

Unlike most receptors, Notch serves as both the receiver and direct transducer of signaling events. Activation can be mediated by one of five membrane-bound ligands of either the Delta-like (-1, -2, -4) or lagged/Serrate (-1, -2) families. Alternatively, dissociation of the Notch heterodimer with consequent activation can also be mediated experimentally by calcium chelators or by mutations that destabilize the Notch1 heterodimer, such as in the human disease T cell acute lymphoblastic leukemia. Here we show that MAGP-2, a protein present on microfibrils, can also interact with the EGF-like repeats of Notch1. Co-expression of MAGP-2 with Notch1 leads to both cell surface release of the Notch1 extracellular domain and subsequent activation of Notch signaling. Moreover, we demonstrate that the C-terminal domain of MAGP-2 is required for binding and activation of Notch1. Based on the high level of homology, we predicted and further showed that MAGP-1 can also bind to Notch1, cause the release of the extracellular domain, and activate signaling. Notch1 extracellular domain release induced by MAGP-2 is dependent on formation of the Notch1 heterodimer by a furin-like cleavage, but does not require the subsequent ADAM metallo-protease cleavage necessary for production of the Notch signaling fragment. Together these results demonstrate for the first time that the microfibrillar proteins MAGP-1 and MAGP-2 can function outside of their role in elastic fibers to activate a cellular signaling pathway. [ABSTRACT FROM AUTHOR]