Hypoxia-inducible factor-1␣ (HIF-1␣) plays an essential role in cellular and systemic O 2 homeostasis by regulating the expression of genes important in glycolysis, erythropoiesis, angiogenesis, and catecholamine metabolism. It is also believed to be a key component of the cellular response to hypoxia and ischemia under pathophysiological conditions, such as stroke. To clarify the function of HIF-1␣ in the brain, we exposed adult mice with late-stage brain deletion of HIF-1␣ to hypoxic injuries. Contrary to expectations, the brains from the HIF-1␣-deficient mice were protected from hypoxia-induced cell death. These surprising findings suggest that decreasing the level of HIF-1␣ can be neuroprotective. Gene chip expression analysis revealed that, contrary to expectations, the majority of hypoxia-dependent gene-expression changes were unaltered, whereas a specific downregulation of apoptotic genes was observed in the HIF-1␣-deficient mice. Although the role of HIF-1␣ has been extensively characterized in vitro, in cancer models, and in chronic preconditioning paradigms, this is the first study to evaluate the role of HIF-1␣ in vivo in the brain in response to acute hypoxia/ischemia. Our data suggest, that in acute hypoxia, the neuroprotection found in the HIF-1␣-deficient mice is mechanistically consistent with a predominant role of HIF-1␣ as proapoptotic and loss of function leads to neuroprotection. Furthermore, our data suggest that functional redundancy develops after excluding HIF-1␣, leading to the preservation of gene expression regulating the majority of other previously characterized HIF-dependent genes.

The current model to explain the organization of the mammalian nervous system is based on studies of anatomy, embryology, and evolution. To further investigate the molecular organization of the adult mammalian brain, we have built a gene expression-based brain map. We measured gene expression patterns for 24 neural tissues covering the mouse central nervous system and found, surprisingly, that the adult brain bears a transcriptional ''imprint'' consistent with both embryological origins and classic evolutionary relationships. Embryonic cellular position along the anteriorposterior axis of the neural tube was shown to be closely associated with, and possibly a determinant of, the gene expression patterns in adult structures. We also observed a significant number of embryonic patterning and homeobox genes with region-specific expression in the adult nervous system. The relationships between global expression patterns for different anatomical regions and the nature of the observed region-specific genes suggest that the adult brain retains a degree of overall gene expression established during embryogenesis that is important for regional specificity and the functional relationships between regions in the adult. The complete collection of extensively annotated gene expression data along with data mining and visualization tools have been made available on a publicly accessible web site (www.barlow-lockhartbrainmapnimhgrant.org).database ͉ development ͉ evolution ͉ gene expression profiling ͉ inbred strains of mice T he adult nervous system achieves its mature form as the result of neuroectodermal cells committing to a specific fate and then segregating into distinct regional collectives of neurons that become fully functional through establishment of connections to other neurons. Our current understanding of brain architecture and organization is based on studies of embryology, anatomy, and evolution in which direct observation of anatomic structures was the foundation for postulated models of brain structure (1). Recent models of brain development and maturation consider relationships between different regions based on the expression of specific genes in assigning developmental origins of adult structures (2, 3). Here, we have constructed a regional gene expression atlas of the adult mouse brain and analyzed the quantitative results by using molecular classification algorithms.Genome-wide gene expression profiling is a powerful technique for deriving information about specific brain regions (4, 5). This approach has been used to measure gene expression patterns in particular regions, subregions, or cell populations in the brain (6-11). Two previous studies have analyzed gene expression differences across multiple regions of the mammalian brain by using multiple strains or species (12,13). However, the current study is the most extensive to date in terms of the number of genes and the coverage of different neural tissues. Our goal was to create a publicly accessible gene-based brain map with data sets, metadata, datab...

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Introduction. Tissue engineering is a rapidly developing area of research with potential to provide alternative tissues and treatments for a variety of clinical conditions. Ability to manipulate and promote angiogenesis is crucial for most of tissue engineering applications. Depending on the substrate, presence of support cells, such as fibroblasts, and exogenous angiogenic factors, angiogenesis in engineered tissues and in vitro models can be either promoted or inhibited by the matrix proteolysis and substrate degradation. Recently, we have reported that a novel cell-native biomaterial -selfassembling peptide scaffold -supports capillary-like network formation, promotes angiogenesis and inhibits endothelial cell apoptosis in the absence of exogenous angiogenic factors. The goal of the present study was to test the hypothesis that self-assembling peptide scaffold promotes angiogenesis and cell migration through enhanced expression of angiogenic factors angiopoitin 1 (Ang1), vascular endothelial growth factor (VEGF) and proteolytic factors matrix metalloproteinases 2 and 9 (MMP-2 and MMP-9) in three-dimensional cultures of endothelial cells and fibroblasts. Methods. Human microvascular endothelial cells and human dermal fibroblasts (Cascade Biologics)were cultured on gelatin-coated dishes. Cells (passage 4-9) were trypsinized, and embedded in 1% RADI-16 peptide scaffold either as mono-cultures or as mixed co-cultures (1:1 ratio of endothelial cells and fibroblasts) and cultured for up to 7 days. Cells embedded in the collagen type I gel served as controls. Medium samples were collected on days 1-6, and concentrations of Ang1, VEGF, MMP-2 and MMP-9 were determined as pg/ml using ELISA assays (R&D Systems). At day 7, samples were embedded in paraffin. Serial 5 um-thick sections were used to quantify cell apoptosis (TUNEL assay, Roche). Results & Discussion.In both monocultures and co-cultures with fibroblasts, endothelial cells migrated and formed single cell lumens and multi-cell capillary-like structures by day 3. In contrast, fibroblasts did not form lumens, but spread out. The peptide scaffold had a protective effect against apoptosis of endothelial cells, with much lower levels of apoptosis detected up to day 7 of culture, as compared with collagen type I gel controls (p<0.01, ANOVA). These results demonstrate that endothelial cells embedded in the peptide scaffold with or without fibroblasts undergo activation and change phenotype in a manner similar to the process of sprouting in vivo. ELISA results showed significantly increased expression of Ang1 and VEGF in all peptide scaffold cultures, relative to the collagen type I cultures (p<0.01, ANOVA, n=4). MMP-2 expression in the peptide scaffold cultures containing fibroblasts was higher, compared with endothelial cells only and collagen type I cultures. In contrast, MMP-9 expression was increased for all peptide scaffold cultures only at days 3&4 and was similar to collagen cultures for other time points. These results indicate that increased expression of VEGF...