Knockout of beta(1)- and beta(2)-adrenoceptors attenuates pressure overload-induced cardiac hypertrophy and fibrosis.

BACKGROUND AND PURPOSE: The role of beta-adrenoceptors in heart disease remains controversial. Although beta-blockers ameliorate the progression of heart disease, the mechanism remains undefined. We investigated the effect of beta-adrenoceptors on cardiac hypertrophic growth using beta(1)- and beta(2)-adrenoreceptor knockout and wild-type (WT) mice. EXPERIMENTAL APPROACH: Mice were subjected to aortic banding or sham surgery, and their cardiac function was determined by echocardiography and micromanometry. KEY RESULTS: At 4 and 12 weeks after aortic banding, the left ventricle:body mass ratio was increased by 80-87% in wild-type mice, but only by 15% in knockouts, relative to sham-operated groups. Despite the blunted hypertrophic growth, ventricular function in knockouts was maintained. WT mice responded to pressure overload with up-regulation of gene expression of inflammatory cytokines and fibrogenic growth factors, and with severe cardiac fibrosis. All these effects were absent in the knockout animals. CONCLUSION AND IMPLICATIONS: Our findings of a markedly attenuated cardiac hypertrophy and fibrosis following pressure overload in this knockout model emphasize that beta-adrenoceptor signalling plays a central role in cardiac hypertrophy and maladaptation following pressure overload.

Endothelial progenitor cells' "homing" specificity to brain tumors.

Current treatment of malignant glioma brain tumors is unsatisfactory. Gene therapy has much promise, but target-specific vectors are needed. Endothelial progenitor cells (EPCs) have in vivo homing specificity to angiogenic sites and are thus potential vehicles for site-specific gene therapy. However, reports of EPCs "homing" to intracranial solid tumors are lacking. We investigated EPCs' "homing" specificity using a murine intracranial glioma model. EPCs, derived from human cord blood, were labeled with a fluorogenic agent CFSE and intravenously injected into SCID mice bearing orthotopic gliomas. At 7-14 days after EPC injection, mouse brains and other vital organs were examined for distribution of transplanted EPCs. As controls, CFSE-labeled human umbilical vein endothelial cells (HUVECs) and EPCs were intravenously injected into matched glioma SCID mice (HUVEC control groups) and nontumor SCID mice (nontumor-bearing control groups), respectively. Fluorescence image analysis revealed that systemically transplanted EPCs 'homed' to brain tumors with significantly higher specificity as compared to other organs within the experimental group (P<0.001) and to anatomically matched brain sections from the control groups (P<0.001). Our study demonstrates EPCs' in vivo tropism for intracranial gliomas, with potential for cell delivery of brain tumor spatial-specific gene therapy.

Expression of the 11beta-hydroxysteroid dehydrogenase 2 gene in the mouse.

Aldosterone acts via mineralocorticoid receptors (MRs) to control salt and water flux in epithelial organs such as the kidney and colon to maintain circulatory homeostasis. Inappropriate glucocorticoid-mediated activation of MRs in aldosterone-target tissues is prevented by the glucocorticoid-metabolizing enzyme 11beta-hydroxysteroid dehydrogenase type 2 (HSD2). We have studied HSD2 expression in the mouse at the level of gene transcription and further analyzed, with HSD1, its pattern of tissue-restricted gene expression. The mouse HSD2 gene, including upstream regulatory regions, has been cloned, and its transcription start site has been mapped in colon and kidney. A 2.5 kb upstream region has been sequenced, and its proximal promoter region has been analyzed. We have compared the relative expression of HSD1 and HSD2 in a variety of tissues from male mice using ribonuclease protection analysis. HSD1 was expressed in liver, kidney, adrenal, lung, spleen, thymus, fat, small intestine, stomach, heart, skin, and epididymis. HSD2 was expressed in kidney, colon, small intestine, stomach, and epididymus. No expression of either HSD1 and HSD2 was detected in bladder, testis, seminal vesicles, vas deferens, prostate, or skeletal muscle. Finally, to investigate the specific roles of HSD2 in vivo, we have created "floxed" HSD2 alleles using gene targeting in mouse embryonic stem cells with the aim to create tissue-specific ablation of HSD2 in mice via Cre recombinase mediated gene targeting.