We have studied the role of the basic helix-loop-helix-PAS transcription factor EPAS-1͞hypoxia-inducible factor 2␣ in vascular development by gene targeting. In ICR͞129 Sv outbred background, more than half of the mutants displayed varying degrees of vascular disorganization, typically in the yolk sac, and died in utero between embryonic day (E)9.5 and E13.5. In mutant embryos directly derived from EPAS-1 ؊/؊ embryonic stem cells (hence in 129 Sv background), all embryos developed severe vascular defects both in the yolk sac and embryo proper and died between E9.5 and E12.5. Normal blood vessels were formed by vasculogenesis but they either fused improperly or failed to assemble into larger vessels later during development. Our results suggest that EPAS-1 plays an important role at postvasculogenesis stages and is required for the remodeling of the primary vascular network into a mature hierarchy pattern.

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Wound healing is a complicated process, and fibroblast is a major cell type that participates in the process. Recent studies have shown that bioglass (BG) can stimulate fibroblasts to secrete a multitude of growth factors that are critical for wound healing. Therefore, we hypothesize that BG can stimulate fibroblasts to have a higher bioactivity by secreting more bioactive growth factors and proteins as compared to untreated fibroblasts, and we aim to construct a bioactive skin tissue engineering graft for wound healing by using BG activated fibroblast sheet. Thus, the effects of BG on fibroblast behaviors were studied, and the bioactive skin tissue engineering grafts containing BG activated fibroblasts were applied to repair the full skin lesions on nude mouse. Results showed that BG stimulated fibroblasts to express some critical growth factors and important proteins including vascular endothelial growth factor, basic fibroblast growth factor, epidermal growth factor, collagen I, and fibronectin. In vivo results revealed that fibroblasts in the bioactive skin tissue engineering grafts migrated into wound bed, and the migration ability of fibroblasts was stimulated by BG. In addition, the bioactive BG activated fibroblast skin tissue engineering grafts could largely increase the blood vessel formation, enhance the production of collagen I, and stimulate the differentiation of fibroblasts into myofibroblasts in the wound site, which would finally accelerate wound healing. This study demonstrates that the BG activated skin tissue engineering grafts contain more critical growth factors and extracellular matrix proteins that are beneficial for wound healing as compared to untreated fibroblast cell sheets.

In this article, near-infrared (NIR) CdHgTe alloyed quantum dots (QDs) were directly synthesized in water by heating a mixed solution of CdCl 2 , Hg(ClO 4 ) 2 and NaHTe in the presence of thiol stabilizers. The CdHgTe QDs exhibit photoluminescence (PL) ranging from 600 to 830 nm that can be tuned by size and composition. The quantum yields (QYs) of QDs were about 20-50%, associated with their emission wavelength and composition. Compared to other reported NIR QDs such as CdTe/CdHgTe and InAs, the as-prepared CdHgTe alloyed QDs have much narrower emission spectra, and their full widths at half-maximum (fwhm) are only 60-80 nm. Characterization by HRTEM and XRD showed that the CdHgTe QDs have good monodispersity and a nice crystal structure. To improve the photostability and reduce the cytotoxity of the CdHgTe QDs, a CdS nanocrystal shell was added to the surface of the CdHgTe QD core. Furthermore, the CdHgTe/CdS core/shell QDs were successfully applied for the imaging of living animals. Our preliminary results illustrate that our synthesis procedure is very simple and inexpensive and that the as-prepared products CdHgTe/CdS core/shell QDs are water-soluble and photostable and will be an alternative probe in the imaging of living animals.

Epidermal growth factor receptor (EGF-R) is an important target in anticancer therapy. Here we report how a novel EGF-R peptide ligand (D4: Leu-Ala-Arg-Leu-Leu-Thr) is identified using a computer-aided design approach from a virtual peptide library of putative EGF-R binding peptides by screening against the EGF-R X-ray crystal structure in silico and in vitro. The selected peptide is conjugated with a polyethylene glycol (PEG) lipid, and the lipid moiety of the peptide-PEG-lipid conjugate is inserted into liposome membranes by a postmodification process. D4 peptide-conjugated liposomes are found to bind to and enter cells by endocytosis specifically and efficiently in vitro in a process apparently mediated by EGF-R high-expressing cancer cells (H1299). In vivo, the D4 peptide-conjugated liposomes are found to accumulate in EGF-R-expressing xenograft tumor tissues up to 80 h after intravenous delivery, in marked contrast to controls. These results demonstrate how structure-based peptide design can be an efficient approach to identify highly novel binding ligands against important receptors. These data could have important consequences for the development of peptide-directed drug delivery systems with engineered specificities and prolonged times of action.

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The ␥ subunit of the Na,K-ATPase, a 7-kDa single-span membrane protein, is a member of the FXYD gene family. Several FXYD proteins have been shown to bind to Na,K-ATPase and modulate its properties, and each FXYD protein appears to alter enzyme kinetics differently. Different results have sometimes been obtained with different experimental systems, however. To test for effects of ␥ in a native tissue environment, mice lacking a functional ␥ subunit gene (Fxyd2) were generated. These mice were viable and without observable pathology. Prior work in the mouse embryo showed that ␥ is expressed at the blastocyst stage. However, there was no delay in blastocele formation, and the expected Mendelian ratios of offspring were obtained even with Fxyd2 ؊/؊ dams. In adult Fxyd2 ؊/؊ mouse kidney, splice variants of ␥ that have different nephron segment-specific expression patterns were absent. Purified ␥-deficient renal Na,K-ATPase displayed higher apparent affinity for Na ؉ without significant change in apparent affinity for K ؉ . Affinity for ATP, which was expected to be decreased, was instead slightly increased. The results suggest that regulation of Na ؉ sensitivity is a major functional role for this protein, whereas regulation of ATP affinity may be context-specific. Most importantly, this implies that ␥ and other FXYD proteins have their effects by local and not global conformation change. Na,K-ATPase lacking the ␥ subunit had increased thermal lability. Combined with other evidence that ␥ participates in an early step of thermal denaturation, this indicates that FXYD proteins may play an important structural role in the enzyme complex.

Dual adhesiveness to tissue and implant biomaterials and bioactivity to stimulate tissue regeneration are interesting properties for developing new generations of tissue-repairing hydrogels with potential new clinical applications. In this study, we developed a unique bioglass (BG)/oxidized sodium alginate (OSA) composite hydrogel with adipic acid dihydrazide (ADH)-modified γ-polyglutamic acid (γ-PGA) as the cross-linking agent, in which the BG plays a multifunctional role to endow the hydrogel with both dual-adhesive and bioactive properties. On one hand, the BG could improve the tissue-bonding strength by providing an alkaline microenvironment to stimulate the bond formation between OSA and the amino groups on the surrounding tissues. On the other hand, BG endows the hydrogel with adhesiveness to implantable materials by releasing Ca ions, which might chelate with the carboxyl groups of the hydrogel matrix. In addition, the composite hydrogel showed excellent bioactivity to promote vascularization and accelerate tissue regeneration. This study demonstrates that a multifunctional hydrogel can be designed by utilizing the multifunctional ions released from silicate BG, and the BG/OSA hydrogel shows good potential as an adhesive and bioactive material for woundhealing applications.