Publications

During carcinogenesis of pancreatic islets in transgenic mice, an angiogenic switch activates the quiescent vasculature. Paradoxically, vascular endothelial growth factor (VEGF) and its receptors are expressed constitutively. Nevertheless, a synthetic inhibitor (SU5416) of VEGF signalling impairs angiogenic switching and tumour growth. Two metalloproteinases, MMP-2/gelatinase-A and MMP-9/gelatinase-B, are upregulated in angiogenic lesions. MMP-9 can render normal islets angiogenic, releasing VEGF. MMP inhibitors reduce angiogenic switching, and tumour number and growth, as does genetic ablation of MMP-9. Absence of MMP-2 does not impair induction of angiogenesis, but retards tumour growth, whereas lack of urokinase has no effect. Our results show that MMP-9 is a component of the angiogenic switch.

The goal of this study was to develop a primary culture model of differentiated murine tracheal epithelium. When grown on semipermeable membranes at an air interface, dissociated murine tracheal epithelial cells formed confluent polarized epithelia with high transepithelial resistances ( approximately 12 kOmega. cm(2)) that remained viable for up to 80 days. Immunohistochemistry and light and electron microscopy demonstrated that the cells were epithelial in nature (cytokeratin positive, vimentin and alpha-smooth muscle actin negative) and differentiated to form ciliated and secretory cells from day 8 after seeding onward. With RT-PCR, expression of the cystic fibrosis transmembrane conductance regulator (Cftr) and murine beta-defensin (Defb) genes was detected (Defb-1 was constitutively expressed, whereas Defb-2 expression was induced by exposure to lipopolysaccharide). Finally, Ussing chamber experiments demonstrated an electrophysiological profile compatible with functional amiloride-sensitive sodium channels and cAMP-stimulated CFTR chloride channels. These data indicate that primary cultures of murine tracheal epithelium have many characteristics similar to those of murine tracheal epithelium in vivo. This method will facilitate the establishment of primary cultures of airway epithelium from transgenic mouse models of human diseases.

To determine whether beta-adrenergic agonist therapy increases alveolar liquid clearance during the resolution phase of hydrostatic pulmonary edema, we studied alveolar and lung liquid clearance in two animal models of hydrostatic pulmonary edema. Hydrostatic pulmonary edema was induced in sheep by acutely elevating left atrial pressure to 25 cmH(2)O and instilling 6 ml/kg body wt isotonic 5% albumin (prepared from bovine albumin) in normal saline into the distal air spaces of each lung. After 1 h, sheep were treated with a nebulized beta-agonist (salmeterol) or nebulized saline (controls), and left atrial pressure was then returned to normal. beta-Agonist therapy resulted in a 60% increase in alveolar liquid clearance over 3 h (P < 0.001). Because the rate of alveolar fluid clearance in rats is closer to human rates, we studied beta-agonist therapy in rats, with hydrostatic pulmonary edema induced by volume overload (40% body wt infusion of Ringer lactate). beta-Agonist therapy resulted in a significant decrease in excess lung water (P < 0.01) and significant improvement in arterial blood gases by 2 h (P < 0.03). These preclinical experimental studies support the need for controlled clinical trials to determine whether beta-adrenergic agonist therapy would be of value in accelerating the resolution of hydrostatic pulmonary edema in patients.

Echocardiographic predictors of long-term survival for patients with low gradient aortic stenosis who undergo aortic valve replacement have not been previously reported. This study shows that patients with larger pre- and postoperative left ventricular volumes, a lower mean preoperative aortic pressure gradient, and failure of volumes to decrease and ejection fraction to increase postoperatively may have a poor prognosis.