Synthesis of MR-49, a deiodinated analog of tetraiodothyroacetic acid (tetrac), as a novel pro-angiogenesis modulator.

The tyrosine-based hormones 3,3',5-triiodo-l-thyronine (l-T3) and l-thyroxine (l-T4) that are produced by the thyroid gland control metabolic functions. Iodothyronine deiodinase enzymes convert l-T4 to l-T3, the form of thyroid hormone critical to genomic actions within cells and regulation of metabolism, and to reverse-l-T3, a hormone isoform that is largely inactive. We used tertiary amines in a study of deiodination based on derivatives of tetraiodothyroacetic acid (tetrac)-a naturally occurring derivative of l-T4-to mimic the action of the iodothyronine deiodinases and deiodination of the outer ring iodines. Deiodinated tetrac, MR-49, was found to be pro-angiogenic, with this activity exceeding that of l-T3 and l-T4 in a hemoglobin Matrigel® plug assay of angiogenesis. Tetrac is anti-angiogenic via several nongenomic pathways, and the present studies of MR-49 reveal the critical contribution of outer ring iodines to the angiogenic properties of thyroid hormone analogues, which may have utility as pro-angiogenic pharmaceuticals.

Sugar-based peptidomimetics as potential inhibitors of the vascular endothelium growth factor binding to neuropilin-1.

Neuropilin-1 (NRP-1) is a co-receptor of VEGFR(165) and molecules interfering with VEGF(165) binding to NRP-1 seem to be promising candidates as new angiogenesis modulators. Based on the minimal four amino acid sequence of peptidic ligands known to bind NRP-1, we describe here the design, synthesis and biological evaluation of series of original sugar-based peptidomimetics using a C-glycosyl compound, derived from d-gulonolactone, as a scaffold, which was functionalized with side chains of the amino-acids arginine, and tryptophane or threonine. At 100 microM, all compounds exhibited a weak affinity for NRP-1, the most efficient being the bis-guanidinylated compound 32 (IC(50)=92 microM) which could be considered as a new NRP-1 non-peptidic ligand.

Promotion of angiogenesis by an artificial extracellular matrix protein containing the laminin-1-derived IKVAV sequence.

The laminin-1-derived IKVAV sequence is known for its angiogenic function. We previously developed artificial extracellular matrix (ECM) proteins containing the IKVAV sequence. They were designed to have collagen-binding activity and active functional units that promote network formation of vascular endothelial cells. The resultant fusion protein, called EREI2CBD, was confirmed to bind to collagen type I and promote tubular network formation of endothelial cells cultured in collagen gel in vitro. In this study, EREI2CBD was applied to the chick chorioallantoic membrane (CAM) assay to investigate in vivo angiogenic activity. The CAM assay results showed that EREI2CBD caused the number and area of vascular branches to be increased. The constructed fusion protein and the engineering strategy of designing multifunctional ECM proteins support current tissue engineering techniques.

Angiogenic competency of biodegradable hydrogels fabricated from polyethylene glycol-crosslinked tyrosine-derived polycarbonates.

Synthetic biomaterials can be used as instructive biological milieus to guide cellular behaviour and function. To further realize this application, we synthesized a series of structurally similar hydrogels and tested their ability to modulate angiogenesis. Hydrogels were synthesized from poly(DTE-co-x% DT carbonate) crosslinked by y% poly(ethylene glycol) (PEG). Hydrogel desaminotyrosyl tyrosine (DT) contents (x%) ranged from 10-100%, and crosslink densities (y% PEG-crosslinker) ranged from 5-80%. The hydrogels were fashioned into porous scaffolds with highly interconnected macro- and micro-pore (>100 and 10 mm in diameter, respectively) architecture using poly(DTE-co-10%DT carbonate% crosslinked with 8% PEG. Under physiological conditions (in vitro), the hydrogels degraded into three major products: desaminotyrosyl-tyrosine ethyl ester (DTE), desaminotyrosyl tyrosine (DT), and poly(ethylene glycol)-di-DT-hydrazide (PEG-di-DT hydrazide). Increasing either DT content or crosslink density brought quickened degradation. Because DT and DTE, two of the three major degradation products, have not demonstrated any noticeable cytotoxicity or angiogenic effect in previous studies, we measured the cytotoxicity of PEG-di-DT hydrazide, the third major degradation product. We found that PEG-di-DT hydrazide only displayed significant cytotoxicity at the high concentration of 100 mg/mL. Interestingly, PEG-di-DT hydrazide and its further degradation product PEG-dihydrazide stimulated in vitro endothelial cell migration and tubulogenesis, which is comparable to results found with FGF-beta treatment. Subcutaneous implantation of the PEG-crosslinked poly(DTE-co-10%DT carbonate) scaffolds into the backs of rats elicited greater tissue growth over time and superior vascularization than poly(DTE carbonate) implantation. These results show that this new class of biomaterials has a strong potential to modulate angiogenesis.