In vivo monitoring of pancreatic beta-cells in a transgenic mouse model.

We generated a transgenic mouse model (RIP-luc) for the in vivo monitoring of pancreatic islet mass and function in response to metabolic disease. Using the rat insulin promoter fused to firefly luciferase, and noninvasive technology to detect luciferase activity, we tracked changes in reporter signal during metabolic disease states and correlated the changes in luciferase signal with metabolic status of the mouse. Transgene expression was found to be specific to the pancreatic islets in this transgenic model. Basal transgene expression was tracked in male and female mice fed either a chow or a high-fat diet and in response to treatment with streptozotocin. Pancreatic bioluminescent signal increased in mice fed a high-fat diet compared with chow-fed animals. In a model of chemically induced diabetes, the bioluminescent signal decreased in accordance with the onset of diabetes and reduction of islet beta-cell number. Preliminary studies using islets transplanted from this transgenic model suggest that in vivo image analysis can also be used to monitor transplanted islet viability and survival in the host. This transgenic model is a useful tool for in vivo studies of pancreatic beta-cells and as a donor for islet transplantation studies.

Noninvasive bioluminescence imaging of normal and spontaneously transformed prostate tissue in mice.

Several transgenic mouse models of prostate cancer have been developed recently that are able to recapitulate many key biological features of the human condition. It would, therefore, be desirable to employ these models to test the efficacy of new therapeutics before clinical trial; however, the variable onset and non-visible nature of prostate tumor development limit their use for such applications. We now report the generation of a transgenic reporter mouse that should obviate these limitations by enabling noninvasive in vivo bioluminescence imaging of normal and spontaneously transformed prostate tissue in the mouse. We used an 11-kb fragment of the human prostate-specific antigen (PSA) promoter to achieve specific and robust expression of firefly luciferase in the prostate glands of transgenic mice. Ex vivo bioluminescence imaging and in situ hybridization analysis confirmed that luciferase expression was restricted to the epithelium in all four lobes of the prostate. We also show that PSA-Luc mice exhibit decreased but readily detectable levels of in vivo bioluminescence over extended time periods following androgen ablation. These results suggest that this reporter should enable in vivo imaging of both androgen-dependent and androgen-independent prostate tumor models. As proof-of-principle, we show that we could noninvasively image SV40 T antigen-induced prostate tumorigenesis in mice with PSA-Luc. Furthermore, we show that our noninvasive imaging strategy can be successfully used to image tumor response to androgen ablation in transgenic mice and, as a result, that we can rapidly identify individual animals capable of sustaining tumor growth in the absence of androgen.

Altered activities of anti-atherogenic enzymes LCAT, paraoxonase, and platelet-activating factor acetylhydrolase in atherosclerosis-susceptible mice.

We examined whether the putative anti-atherogenic enzymes LCAT, paraoxonase (PON), and platelet-activating factor acetylhydrolase (PAF-AH) are impaired in 8 week old atherosclerosis susceptible apolipoprotein E (apoE)(-/-) and LDL receptor (LDLr)(-/-) mice and whether plasma concentrations of bioactive oxidized phospholipids accumulate in plasma. ApoE(-/-) mice had reduced (28%) LCAT activity and elevated lysophosphatidylcholine and bioactive oxidized phospholipids (1-palmitoyl-2-oxovaleryl-sn-glycero-3-phosphocholine and 1-palmitoyl-2-glutaryl-sn-glycero-3-phosphocholine) compared with controls on the chow diet. Elevated oxidized phospholipids and reduced LCAT activity may, in part, contribute to spontaneous lesions in these mice on a chow diet. A Western diet decreased LCAT activity further (50% of controls) and PON activity was decreased 38%. The LDLr(-/-) mice showed normal LCAT activity on chow diet and little accumulation of oxidized phospholipids. On a Western diet, LDLr(-/-) mice had reduced LCAT activity (21%), but no change in PON activity. All genotypes had reduced PAF-AH activity on the Western diet. ApoE(-/-) and LDLr(-/-) mice, but not controls, had elevated plasma bioactive oxidized phospholipids on the Western diet. We conclude that impairment of LCAT activity and accumulation of oxidized phospholipids are part of an early atherogenic phenotype in these models.