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Laser-induced mouse model of chronic ocular hypertension.

PURPOSE: To develop an inducible mouse model of glaucoma. METHODS: An obstruction of aqueous humor outflow in adult C57BL6/J mice was induced by combined injection of indocyanine green (ICG) dye into the anterior chamber and diode laser treatment. To evaluate intraocular pressure (IOP), tonometry was performed with a modified Goldmann tonometer. The function of the retina was evaluated with electroretinography (ERG). RESULTS: IOP was significantly elevated in surgical eyes compared with control eyes: before surgery, 15.2 +/- 0.6 mm Hg; 10 days after surgery, 33.6 +/- 1.5 mm Hg (P < 0.001); and 30 days after surgery, 27.4 +/- 1.2 mm Hg (P < 0.001). However, 60 days after surgery, IOP in the surgical eyes decreased to 19.5 +/- 0.9 mm Hg and was not significantly different compared with control eyes (control, 17.3 +/- 0.7 mm Hg; P = 0.053). ERG amplitudes, expressed as a ratio (surgical/control), were decreased in surgical eyes. The amplitudes for b-wave were: before surgery, 107.6% +/- 4.6%; 28 days after surgery, 61% +/- 4% (P < 0.001); and 56 days after surgery, 62% +/- 5.6% (P < 0.001). Oscillatory potentials were the most dramatically affected: before surgery, 108.6% +/- 6.7%; 28 days after surgery, 57.5% +/- 5% (P < 0.01); and 56 days after surgery, 57% +/- 8.5% (P < 0.001). Amplitudes of the a-waves had relatively smaller but still significant deficits: before surgery, 105.8% +/- 6.9%; 28 days after surgery, 72.2% +/- 5.4% (P < 0.01); and 56 days after surgery, 79.8% +/- 11.0% (P < 0.01). Histologic analysis of the surgical eyes revealed development of anterior synechia, loss of retinal ganglion cells (RGCs), and thinning of all retinal layers. Electron microscopy of optic nerve cross sections revealed swelling and degeneration of the large diameter axons and gliosis. CONCLUSIONS: Diode laser treatment of ICG saturated episcleral veins causes a chronic elevation of IOP and sustained ERG deficits.

Animals↗

Harnessing preclinical mouse models to inform human clinical cancer trials.

The urgent need for better cancer treatments has stimulated interest in employing small-animal models to evaluate potential drug therapies. Robust mouse models of many human cancers have been generated using sophisticated technologies for engineering germ-line mutations. As we enter into an age of targeted therapeutics, these strains provide novel platforms for validating new anticancer drugs, assessing therapeutic index, identifying surrogate markers of tumor progression, and defining epigenetic and environmental influences on tumorigenesis.

Animals↗

High-resolution large-scale mosaic imaging using multiphoton microscopy to characterize transgenic mouse models of human neurological disorders.

The thorough characterization of transgenic mouse models of human central nervous system diseases is a necessary step in realizing the full benefit of using animal models to investigate disease processes and potential therapeutics. Because of the labor- and resource-intensive nature of high-resolution imaging, detailed investigation of possible structural or biochemical alterations in brain sections has typically focused on specific regions of interest as determined by the researcher a priori. For example, Parkinson's disease researchers often focus imaging on regions of the brain expected to exhibit pathology such as the substantia nigra and striatum. Because of limitations in acquiring and storing high-resolution imaging data, additional data contained in the specimen is not usually acquired or disseminated/reported to the research community. Here we present a method of imaging large regions of brain at close to the resolution limit of light microscopy using a mosaic imaging technique in conjunction with multiphoton microscopy. These maps are being used to characterize several genetically modified animal models of neurological disease by filling the information "gap" among techniques such as magnetic resonance imaging and electron microscopic analysis.

Animals↗

[A mouse model of hypospadias induced by flutamide].

OBJECTIVE: To establish a mouse model of hypospadias induced by flutamide to further studying molecular mechanisms of hypospadias etiology. METHODS: Eighty timed pregnant ICR mice were randomly divided into four groups. Flutamide was injected subcutaneously (s.c.) with mixture sesame oil at 0 (Group A), 25 (Group B), 50 (Group C), 100 (Group D) mg.kg-1.d-1 from GD (gestation days) 12 to 16, respectively. The fetuses of two pregnants from each group were anatomized to observe the position of testes and the development of prostates on the day of delivery. Urethras and the position of testes were examined on postnatal day 28. RESULTS: Hypospadias was seen in Group A (0), B (44.2%), C (92.7%) and D (100%), and cryptorchidism in Group A (0), B (4.8%), C (23.2%) and D (32.4%), respectively. Flutamide caused 100% incidence of prostate agenesis in Group C and D and 19.2% in Group B, and 100% incidence of female-like anogenital distance in Group B, C, and D. CONCLUSION: The experimental model of hypospadias induced by flutamide is steadier and more suitable for popularization.

Androgen Antagonists↗

Developmental hematopoiesis from prenatal to young-adult life in the mouse model.

Five measurements of hematopoietic function were made in the mouse from midfetal life to young adulthood. These included two in vivo (day-8 colony-forming unit-spleen [CFU-S8] and day-12 CFU-S [CFU-S12]) and two in vitro clonal measurements of hematopoietic stem and progenitor cells (high proliferative potential colony-forming cell [HPP-CFC] and CFC of low proliferative potential [LPP-CFC]) as well as an in vitro clonal measurement of colony-forming unit-fibroblast (CFU-F). The appearance, increase, subsequent decrease, and later emergence and increase of each of these parameters in the fetal-liver, newborn, growing-infant, and young-adult bone marrow were correlated and found to be in parallel. Exceptions to this included the earlier appearance in the fetal liver of CFU-F and the relatively differentiated hematopoietic LPP-CFC. The pattern of emergence of these progenitor cell subpopulations in the fetal liver may be related, in part to the timing of the hematopoietic microenvironment development and the relative frequencies of progenitor cell types in the circulation. This developmental study in the mouse model describes additional correlations between in vivo and in vitro colony-forming stem cells and fibroblastic stromal colony-forming cells, and it suggests the dependence of hematopoietic stem cells upon the stromal microenvironment for the necessary conditions for hematopoietic stem cell lodgment, growth, and maturation.

Aging↗

Polyglutamine and transcription: gene expression changes shared by DRPLA and Huntington's disease mouse models reveal context-independent effects.

Recent evidence indicates that transcriptional abnormalities may play an important role in the pathophysiology of polyglutamine diseases. In the present study, we have explored the extent to which polyglutamine-related changes in gene expression may be independent of protein context by comparing mouse models of dentatorubral-pallidoluysian atrophy (DRPLA) and Huntington's disease (HD). Microarray gene expression profiling was conducted in mice of the same background strain in which the same promoter was employed to direct the expression of full-length atrophin-1 or partial huntingtin transproteins (At-65Q or N171-82Q mice). A large number of overlapping gene expression changes were observed in the cerebella of At-65Q and N171-82Q mice. Six of the gene expression changes common to both huntingtin and atrophin-1 transgenic mice were also observed in the cerebella of mouse models expressing full-length mutant ataxin-7 or the androgen receptor. These results demonstrate that some of the gene expression effects of expanded polyglutamine proteins occur independently of protein context.

Animals↗

AAV8-mediated expression of glucocerebrosidase ameliorates the storage pathology in the visceral organs of a mouse model of Gaucher disease.

BACKGROUND: Gaucher disease is the most common of the lysosomal storage disorders. The primary manifestation is the accumulation of glucosylceramide (GL-1) in the macrophages of liver and spleen (Gaucher cells), due to a deficiency in the lysosomal hydrolase glucocerebrosidase (GC). A Gaucher mouse model (D409V/null) exhibiting reduced GC activity and accumulation of GL-1 was used to evaluate adeno-associated viral (AAV)-mediated gene therapy. METHODS: A recombinant AAV8 serotype vector bearing human GC (hGC) was administered intravenously to the mice. The levels of hGC in blood and tissues were determined, as were the effects of gene transfer on the levels of GL-1. Histopathological evaluation was performed on liver, spleen and lungs. RESULTS: Vector administration to pre-symptomatic Gaucher mice resulted in sustained hepatic secretion of hGC at levels that prevented GL-1 accumulation and the appearance of Gaucher cells in the liver, spleen and lungs. AAV administration to older mice with established disease resulted in normalization of GL-1 levels in the spleen and liver and partially reduced that in the lung. Analysis of the bronchoalveolar lavage fluid (BALF) from treated mice showed significant correction of the abnormal cellularity and cell differentials. No antibodies to the expressed hGC were detected following a challenge with recombinant enzyme suggesting the animals were tolerized to human enzyme. CONCLUSIONS: These data demonstrate the effectiveness of AAV-mediated gene therapy at preventing and correcting the biochemical and pathological abnormalities in a Gaucher mouse model, and thus support the continued consideration of this vector as an alternative approach to treating Gaucher disease.

Animals↗

The genetics of pancreatic adenocarcinoma: a roadmap for a mouse model.

Pancreatic cancer is among the leading causes of cancer death. Although a genetic profile for pancreatic cancer is emerging, many biological aspects of this disease are poorly understood. Indeed, fundamental questions regarding progenitor cell lineages, host stromal milieu, and the role of specific genetic alterations in tumor progression remain unresolved. A mouse model engineered with signature mutations would provide a powerful ally in the study of pancreatic cancer biology and may guide improved prognostic assessment and treatment for the human disease. In this review, we discuss the molecular basis for normal pancreatic development and the genetics of human pancreatic adenocarcinoma in the hope of charting a course for the development of a faithful mouse model for this lethal cancer.

Adenocarcinoma↗

Use of pulse wave and color flow Doppler echocardiography in mouse models of human disease.

The noninvasive assessment of cardiovascular physiology in mice is challenging because of their small size and extremely rapid heart rates. In this study, we sought to determine the feasibility and utility of pulse wave (PW) and color flow Doppler imaging techniques when applied to mouse models of cardiac remodeling. We performed transverse aortic banding, induced aortic insufficiency (AI), or sham procedures in wild-type mice. Animals were anesthetized and transthoracic echocardiography was performed, including PW and color flow Doppler imaging. In aortic banded mice, color flow Doppler imaging was used to identify flow around the aortic arch, and PW measurements were performed distal to the constriction. A high-velocity jet across the aortic constriction was detected in all 4 banded animals. Both modalities were applied to AI mice in which AI was detected in all 5 mice but in none of the 5 shams. Pulse wave and color flow Doppler imaging were also used to screen senescent mice for valve abnormalities; AI was detected in 3 of 20 and mitral regurgitation in 2 of 20. We demonstrate here that PW and color flow Doppler imaging techniques are useful in the evaluation of mouse models of cardiac remodeling. In addition, this study indicates that these modalities may be potentially useful to screen transgenic mice for valve abnormalities.

Animals↗

Induction of tumor arrest and differentiation with prolonged survival by intermittent hypoxia in a mouse model of acute myeloid leukemia.

We showed previously that mild real hypoxia and hypoxia-mimetic agents induced in vitro cell differentiation of acute myeloid leukemia (AML). We here investigate the in vivo effects of intermittent hypoxia on syngenic grafts of leukemic blasts in a PML-RARalpha transgenic mouse model of AML. For intermittent hypoxia, leukemic mice were housed in a hypoxia chamber equivalent to an altitude of 6000 m for 18 hours every consecutive day. The results show that intermittent hypoxia significantly prolongs the survival of the leukemic mice that received transplants, although it fails to cure the disease. By histologic and cytologic analyses, intermittent hypoxia is shown to inhibit the infiltration of leukemic blasts in peripheral blood, bone marrow, spleen, and liver without apoptosis induction. More intriguingly, intermittent hypoxia also induces leukemic cells to undergo differentiation with progressive increase of hypoxia-inducible factor-1alpha protein, as evidenced by morphologic criteria of maturating myeloid cells and increased expression of mouse myeloid cell differentiation-related antigens Gr-1 and Mac-1. Taken together, this study represents the first attempt to characterize the in vivo effects of hypoxia on an AML mouse model. Additional investigations may uncover ways to mimic the differentiative effects of hypoxia in a manner that will benefit human patients with AML.

Animals↗

Collagen from the osteogenesis imperfecta mouse model (oim) shows reduced resistance against tensile stress.

Osteogenesis imperfecta (OI) is a disease attributable to any of a large number of possible mutations of type I collagen. The disease is clinically characterized in part by highly brittle bone, the cause of this feature being unknown. Recently a mouse model of OI, designated as osteogenesis imperfecta murine (oim), and having a well defined genetic mutation, has been studied and found to contain mineral crystals different in their alignment with respect to collagen and in their size. These observations are consistent with those reported in human OI and the unusual crystal alignment and size undoubtedly contribute to the reduced mechanical properties of OI bone. While the mineral has been investigated, no information is available on the tensile properties of oim collagen. In this study, the mechanical properties of tendon collagen under tension have been examined for homozygous (oim/oim), heterozygous (+/oim), and control (+/+) mice under native wet conditions. The ultimate stress and strain found for oim/oim collagen were only about half the values for control mice. Assuming that prestrained collagen molecules carry most of the tensile load in normal bone while the mineral confers rigidity and compression stability, the reported results suggest that the brittleness of OI bone in the mouse model may be related to a dramatic reduction of the ultimate tensile strain of the collagen.

Analysis of Variance↗

Down syndrome mouse models Ts65Dn, Ts1Cje, and Ms1Cje/Ts65Dn exhibit variable severity of cerebellar phenotypes.

Two mouse models are widely used for Down syndrome (DS) research. The Ts65Dn mouse carries a small chromosome derived primarily from mouse chromosome 16, causing dosage imbalance for approximately half of human chromosome 21 orthologs. These mice have cerebellar pathology with direct parallels to DS. The Ts1Cje mouse, containing a translocated chromosome 16, is at dosage imbalance for 67% of the genes triplicated in Ts65Dn. We quantified cerebellar volume and granule cell and Purkinje cell density in Ts1Cje. Cerebellar volume was significantly affected to the same degree in Ts1Cje and Ts65Dn, despite that Ts1Cje has fewer triplicated genes. However, dosage imbalance in Ts1Cje had little effect on granule cell and Purkinje cell density. Several mice with dosage imbalance for the segment of the Ts65Dn chromosome not triplicated in Ts1Cje had phenotypes that contrasted with those in Ts1Cje. These observations do not readily differentiate between two prevalent hypotheses for gene action in DS.

Animals↗

Embryonic stem cells and mouse models of human syndromes: examples from the T-box gene family.

Synergism between the fields of reproduction and development has long been an important factor for advances in each field, and the development of gene modification technology in mammals has progressed hand in hand with advances in reproductive technology. The discovery and exploitation of embryonic stem cells for producing targeted gene mutations in the mouse, combined with advances in genome analysis, has provided a means of producing mouse models of human genetic diseases, including congenital defects. This review presents examples of how gene targeting and reproductive biology techniques are being applied to the production of mouse models for specific human developmental syndromes caused by mutations in genes of the T-box transcription factor gene family. The ulnar-mammary syndrome and the DiGeorge syndrome are two developmental syndromes that are currently being explored in this way.

Animals↗

Inducible mouse models for inherited skin diseases: implications for skin gene therapy.

Stem cells are crucial for the formation and maintenance of tissues and organs. To understand the role of stem cells in the pathogenesis of mosaic skin disorders, we generated inducible mouse models for two autosomal dominant keratin disorders, epidermolytic hyperkeratosis (EHK) and epidermolysis bullosa simplex (EBS), that enable activation of the respective mutation in epidermal stem cells in a spatially and temporally controlled manner using a ligand-inducible Cre recombinase. Whereas mosaic forms have been reported for EHK, which is caused by mutations in the suprabasal keratins K1 or K10, this has never been reported for EBS, which is due to mutations in the basal keratins K5 or K14. When we induced the phenotype in these models by topical application of the inducer, we found phenotypic areas in the EHK model that persisted for the life of the mouse. On the contrary, the induced blisters in the EBS model healed within a few weeks by migration of surrounding non-phenotypic stem cells into the wound bed. Our results indicate that lack of selective pressure against certain mutations in epidermal stem cells could explain why mosaic forms exist for EHK, but not for EBS. These findings have important implications for the development of new strategies for somatic gene therapy of dominant genodermatoses, and we are currently using these inducible mouse models to test gene therapy approaches.

Animals↗

Increased glutathione levels in cortical and striatal mitochondria of the R6/2 Huntington's disease mouse model.

Huntington's disease (HD) is a progressive neurodegenerative disease characterized by a severe neuronal loss that occurs primarily in the neostriatum. It has been postulated that mitochondria dysfunction and oxidative stress may play significant roles in the etiology of the disease. Indeed, markers of oxidative stress damage have been detected in the brains of HD patients and in mouse models of HD. In this study, we evaluate the changes in the levels of the potent, endogenous antioxidant glutathione and enzymes involved in its metabolism or recycling in the cortex and striatum of an extensively studied HD mouse model (R6/2). In both cortex and striatum, the levels of cellular glutathione were not significantly different in the R6/2 mice when compared with littermate wild type controls. Remarkably, the levels of glutathione were significantly increased in mitochondria isolated from the cortex and striatum of R6/2 mice when compared with wild type control mice. This specific increase in the levels of glutathione in mitochondria suggests that a compensatory mechanism is induced in the R6/2 mice to protect against an increase in oxidative stress in mitochondria.

Adaptation, Physiological↗

Behavioral phenotyping of the MPTP mouse model of Parkinson's disease.

In mice, the systemical or intracranial application of the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) can lead to severe damage to the nigrostriatal dopaminergic system. This can result in a variety of symptoms concerning motor control resembling those in human Parkinson's disease, such as akinesia, rigidity, tremor, gait and posture disturbances. The aim of this work is to review a variety of behavioral paradigms for these and other symptoms, which have been used to characterize behavioral changes in mice after MPTP treatment. Main results are summarized, and general influential factors as well as potential problems in the experimental procedures are discussed, which should be taken into account when conducting behavioral analyses in mice with parkinsonian symptoms. Since there is reliable evidence (e.g. from strain comparisons) that the susceptibility of the nigrostriatal pathway to neurodegeneration is probably genetically influenced, relevant genes can be expected to be identified in the future. Therefore, the points discussed here will be useful not only for further applications in the MPTP mouse model, but also more generally for the behavioral characterization of future mouse models of PD, e.g. mice with a manipulation of genes relevant to the function of the basal ganglia.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗

A transgenic mouse model genetically tags all activated CD8 T cells.

Identifying and characterizing Ag-specific CD8+ T cells are central to the study of immunological memory. Although powerful strategies such as MHC tetramers and peptide-induced cytokine production assays exist for identifying Ag-specific CD8+ T cells, alternate strategies that are not dependent upon a priori knowledge of the immunodominant and subdominant antigenic epitopes, as well as the MHC background of the animal are of obvious utility. In this study, we present a transgenic mouse model that uses Cre-loxP recombination to permanently mark all activated CD8+ T cells with beta-galactosidase. We used the lymphocytic choriomeningitis virus infection model to track the dynamics of the antiviral CD8+ T cell responses. We show that in this transgenic mouse model system, all of the antiviral effector and memory CD8+ T cells are contained within the beta-gal-marked CD8+ T cell population.

Animals↗

Chemoprevention of spontaneous intestinal adenomas in the adenomatous polyposis coli Min mouse model with aspirin.

BACKGROUND & AIMS: Colorectal cancer is a significant source of morbidity and mortality in the United States and other Western countries. Epidemiological and experimental data indicate that regular use of aspirin reduces colon cancer risk. This study was designed to determine if aspirin would significantly inhibit gastrointestinal tumor formation in a mouse model of familial adenomatous polyposis. METHODS: Six-week-old male and female C57BL/6J +/+ (control) and C57BL/6J ApcMin/+ (Min) mice were fed either a control AIN-76A diet or one supplemented with 250 or 500 parts per million (ppm) aspirin (n = 6 per group) for 7 weeks. RESULTS: All of the Min mice, but no control mice, developed gastrointestinal tumors. Aspirin significantly reduced tumor multiplicity (number of tumors per mouse) in the small intestine, but not the colon, from an average of 35.8 tumors per mouse (control diet) to 16 and 18.5 tumors per mouse with 250 and 500 ppm aspirin, respectively. Total tumor load (sum of tumor diameters per mouse) was also significantly reduced, from 93.2 mm in total diameter to 40. 4 and 45.0 mm with 250 and 500 ppm aspirin, respectively. Results were not significantly different because of sex or aspirin dose. CONCLUSIONS: High doses of aspirin are effective chemopreventive agents in a mouse model of spontaneous intestinal tumor formation.

Adenoma↗