Studies were performed to examine the extent to which mechanical stimuli mediate control of angiogenesis in bladder cells both in vitro and in vivo. Differential gene expression between control nonstretched and cyclically stretched bladder smooth muscle cells was assessed using oligonucleotide microarrays and pathway analysis by the web tool Fast Assignment and Transference of Information (FatiGO). Data showed that a substantial proportion (33 of 86) of mechanically responsive genes were angiogenesis-related and include cytokines, growth-related factors, adhesion proteins, and matricellular, signal transduction, extracellular matrix (ECM), and inflammatory molecules. Integrative knowledge of protein-protein interactions revealed that 12 mechano-sensitive gene-encoded proteins have interacting partner(s) in the vascular system confirming their potential role in paracrine regulation of angiogenesis. Angiogenic genes include matricellular proteins such as Cyr61/CCN1, CTGF/CCN2 and tenascin C, components of the VEGF and IGF systems, ECM proteins such as type I collagen and proteoglycans, and matrix metalloproteinases. In an in vivo model of bladder overdistension, 5 of 11 mechano-responsive angiogenic genes, independently tested by real-time PCR, were upregulated as a result of pressure overload including Cyr61/CCN1, CTGF/CCN2, MCP-1, VEGF-A, MMP-1, and midkine. Meanwhile, the molecular anatomy of angiogenic gene promoters reveals the presence of GA box-binding for the myc-associated zinc finger protein, MAZ, often found adjacent to binding sites for mechano-responsive transcription factors (e.g., NF-B), suggesting that the coordinated activity of these factors may induce selective angiogenic gene transcription. These data suggest that mechanical control of angiogenic genes is an integral part of the adaptive and plasticity responses to mechanical overload.

Peroxisome proliferator-activated receptor (PPAR) regulates lipid metabolism at the transcriptional level and modulates the expression of genes involved in inflammation, cell proliferation, and differentiation. Although PPAR has been shown to mitigate cardiac hypertrophy, knowledge about underlying mechanisms and the nature of signaling pathways involved is fragmentary and incomplete. The aim of this study was to identify the processes and signaling pathways regulated by PPAR in hearts challenged by a chronic pressure overload by means of whole genome transcriptomic analysis. PPAR–/– and wild-type mice were subjected to transverse aortic constriction (TAC) for 28 days, and left ventricular gene expression profile was determined with Affymetrix GeneChip Mouse Genome 430 2.0 arrays containing >45,000 probe sets. In unchallenged hearts, the mere lack of PPAR resulted in 821 differentially expressed genes, many of which are related to lipid metabolism and immune response. TAC resulted in a more pronounced cardiac hypertrophy and more extensive changes in gene expression (1,910 and 312 differentially expressed genes, respectively) in PPAR–/– mice than in wild-type mice. Many of the hypertrophy-related genes were related to development, signal transduction, actin filament organization, and collagen synthesis. Compared with wild-type hypertrophied hearts, PPAR–/– hypertrophied hearts revealed enrichment of gene clusters related to extracellular matrix remodeling, immune response, oxidative stress, and inflammatory signaling pathways. The present study therefore demonstrates that, in addition to lipid metabolism, PPAR is an important modulator of immune and inflammatory response in cardiac muscle.

The molecular networks underlying the lung response to hypoxia are not fully understood. We employed systems biology approaches to study temporal effects of intermittent or sustained hypoxia on gene expression in rat lungs. We obtained gene expression profiles from rats exposed to intermittent or sustained hypoxia lasting 0–30 days and identified differentially expressed genes, their patterns, biological processes, and regulatory networks critical for lung response to intermittent or sustained hypoxia. We validated selected genes with quantitative real-time PCR. Intermittent and sustained hypoxia induced two distinct sets of genes in rat lungs that displayed different temporal expression patterns. Intermittent hypoxia induced genes mostly involved in ion transport and homeostasis, neurological processes, and steroid hormone receptor activity, while sustained hypoxia induced genes principally participating in immune responses. The intermittent hypoxia-activated network suggested a role for cross talk between estrogen receptor 1 (ESR1) and other key proteins in hypoxic responses. The sustained hypoxia-activated network was indicative of vascular remodeling and pulmonary hypertension. We confirmed the temporal expression changes of 12 genes (including the Esr1 gene and 4 ESR1 target genes) in intermittent hypoxia and 8 genes in sustained hypoxia with quantitative real-time PCR. Conclusions: intermittent and sustained hypoxia induced distinct gene expression patterns in rat lungs. The functional characteristics of genes activated by these two distinct perturbations suggest their roles in the downstream physiological effects of intermittent and sustained hypoxia. Our results demonstrate the discovery potential of applying systems biology approaches to the understanding of mechanisms underlying hypoxic lung response.

Determination of the genetic factors that control the progression of left ventricular hypertrophy (LVH) to heart failure has been difficult despite extensive study in animal models. Here we have characterized a consomic rat model of LVH resulting from the introgression of chromosome 16 from the normotensive Brown Norway (BN) rat onto the genetic background of the Dahl salt-sensitive (SS/Mcwi) rat by marker assisted breeding. The SS-16^BN/Mcwi consomic rats are normotensive but display LVH equivalent to the hypertensive SS/Mcwi rats at early ages. In this study we tracked the development of LVH by echocardiography and analyzed changes in cardiac function and morphology with aging in the SS-16^BN/Mcwi, SS/Mcwi, and BN to determine if the consomic SS-16^BN/Mcwi was a model of hypertrophic cardiomyopathy (HCM). Aging SS-16^BN/Mcwi rats showed no evidence of heart failure or impaired cardiac function upon extensive analysis of left ventricle function by echocardiography and pressure-volume relationships, while their parental SS/Mcwi experienced deterioration in function between 18 and 36 wk of age. In addition aging SS-16^BN/Mcwi did not exhibit tissue remodeling common to pathological hypertrophy and HCM such as increased fibrosis and reduced capillary density in the myocardium. In fact, SS-16^BN/Mcwi were better protected from developing LV fibrosis with age than either the hypertensive SS/Mcwi or normotensive BN parental strains. This suggests that a gene or genes on chromosome 16 may be involved with both blood pressure regulation and preservation of cardiac function with aging.

In insulin-resistant status such as obesity, failure of pancreatic islets to increase insulin secretion leads to diabetes. We sought to screen for the islet genes that facilitate islet adaptation to obesity by comparing gene expression profiles between two strains of obesity-prone inbred mice with different propensities for hyperglycemia. C57BL/6J and AKR/J were fed regular rodent chow or high-fat diet, after which islet morphology, secretory function, and gene expression were assessed. AKR/J had lower blood glucose and higher insulin levels compared with C57BL/6J mice on regular rodent chow or high-fat diet. Insulin secretion was 3.2-fold higher in AKR/J than C57BL/6J mice following intraperitoneal glucose injection. Likewise, glucose-stimulated insulin secretion from isolated islets was higher in AKR/J. Additionally, islet mass was 1.4-fold greater in AKR/J compared with C57BL/6J. To elucidate the factors associated with the differences in islet function, we analyzed the gene expression profiles in islets in AKR/J and C57BL/6J mice. Of 14,000 genes examined, 202 were upregulated and 270 were downregulated in islets from diet-induced obese AKR/J mice compared with C57BL/6J mice. Key genes involved in islet signaling and metabolism, e.g., glucagon-like peptide-1 receptor, sterol Co-A desaturase 1 and 2, and fatty acid desaturase 2 were upregulated in obese AKR/J mice. The expression of multiple extracellular matrix proteins was also increased in AKR/J mice, suggesting a role in modulation of islet mass. Functional analyses of differentially regulated genes hold promise for elucidating factors linking obesity to alterations in islet function.

The Dahl salt-sensitive rat is a widely used model of human salt-sensitive forms of hypertension. The kidney plays an important role in the pathogenesis of Dahl salt-sensitive hypertension, but the molecular mechanisms involved remain a subject of intensive investigation. Gene expression profiling studies suggested that 11β-hydroxysteroid dehydrogenase type 1 might be dysregulated in the renal medulla of Dahl salt-sensitive rats. Additional analysis confirmed that renal medullary expression of 11β-hydroxysteroid dehydrogenase type 1 was downregulated by a high-salt diet in SS-13^BN rats, a consomic rat strain with reduced blood pressure salt sensitivity, but not in Dahl salt-sensitive rats. 11β-Hydroxysteroid dehydrogenase type 1 is known to convert inactive 11-dehydrocorticosterone to active corticosterone. The urinary corticosterone/11-dehydrocorticosterone ratio as well as urinary excretion of corticosterone was higher in Dahl salt-sensitive rats than in SS-13^BN rats. Knockdown of renal medullary 11β-hydroxysteroid dehydrogenase type 1 with small-interfering RNA attenuated the early phase of salt-induced hypertension in Dahl salt-sensitive rats and reduced urinary excretion of corticosterone. Knockdown of 11β-hydroxysteroid dehydrogenase type 1 did not affect blood pressure in SS-13^BN rats. Long-term attenuation of salt-induced hypertension was achieved with small hairpin RNA targeting renal medullary 11β-hydroxysteroid dehydrogenase type 1. In summary, we have demonstrated that suppression of 11β-hydroxysteroid dehydrogenase type 1 expression in the renal medulla attenuates salt-induced hypertension in Dahl salt-sensitive rats.