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Novel pycnodysostosis mouse model uncovers cathepsin K function as a potential regulator of osteoclast apoptosis and senescence.

Pycnodysostosis is a genetic bone disease featuring the unique bone homeostasis disorders of osteolysis and osteopetrosis in the same organism. The pathomechanism for pycnodysostosis has been largely unknown due to the unavailability of a pycnodysostosis mouse model with all the traits of the disease. We generated cathepsin K(-/-) mouse strains in the 129/Sv and C57BL/6J backgrounds and found that, only in the 129/Sv background, cathepsin K(-/-) mice exhibit many characteristics of the human pycnodysostosis-like phenotype. Our data indicated that 129/Sv cathepsin K(-/-) osteoclasts (OCs) lacked normal apoptosis and senescence and exhibited over-growth both in vitro and in vivo. These abnormalities resulted in an unusually high OC number, which is consistent with a recent case study of human pycnodysostosis. Our results show that cathepsin K function has different effects around the skeleton due to site-specific variations in bone homeostasis, such as phenotypes of osteopetrosis in tibiae and osteolysis in calvariae as a result of cathepsin K mutation. Our data demonstrated that the expression levels of p19, p53 and p21 were significantly reduced in 129/Sv cathepsin K(-/-) OCs and forced expression of cathepsin K in pre-OCs induced premature senescence and increased expression of p19, p53 and p21. This is the first evidence that cathepsin K plays a key role in OC apoptosis and senescence, revealing the importance of OC senescence in bone homeostasis. The finding of this novel cathepsin K function provides insight into the pathomechanism of pycnodysostosis and may provide new drug targets for diseases involved in OC-related abnormal bone homeostasis.

Animals↗

Wolbachia-induced neutrophil activation in a mouse model of ocular onchocerciasis (river blindness).

Endosymbiotic Wolbachia bacteria are abundant in the filarial nematodes that cause onchocerciasis (river blindness), including the larvae (microfilariae) that migrate into the cornea. Using a mouse model of ocular onchocerciasis, we recently demonstrated that it is these endosymbiotic bacteria rather than the nematodes per se that induce neutrophil infiltration to the corneal stroma and loss of corneal clarity (Saint Andre et al., Science 295:1892-1895, 2002). To better understand the role of Wolbachia organisms in the pathogenesis of this disease, we examined the fate of these bacteria in the cornea by immunoelectron microscopy. Microfilariae harboring Wolbachia organisms were injected into mouse corneas, and bacteria were detected with antibody to Wolbachia surface protein. Within 18 h of injection, neutrophils completely surrounded the nematodes and were in close proximity to Wolbachia organisms. Wolbachia surface protein labeling was also prominent in neutrophil phagosomes, indicating neutrophil ingestion of Wolbachia organisms. Furthermore, the presence of numerous electron-dense granules around the phagosomes indicated that neutrophils were activated. To determine if Wolbachia organisms directly activate neutrophils, peritoneal neutrophils were incubated with either parasite extracts containing Wolbachia organisms, parasite extracts depleted of Wolbachia organisms (by antibiotic treatment of worms), or Wolbachia organisms isolated from filarial nematodes. After 18 h of incubation, we found that isolated Wolbachia organisms stimulated production of tumor necrosis factor alpha and CXC chemokines macrophage inflammatory protein 2 and KC by neutrophils in a dose-dependent manner. Similarly, these cytokines were induced by filarial extracts containing Wolbachia organisms but not by Wolbachia-depleted extracts. Taken together, these findings indicate that neutrophil activation is an important mechanism by which Wolbachia organisms contribute to the pathogenesis of ocular onchocerciasis.

Animals↗

Knockout mouse model and gametogenic failure.

To evaluate the function of a defined gene in gametogenesis, exciting opportunities are offered by the introduction of techniques to generate knockout mice. In this short article, we briefly describe a few gene knockout mouse models, which show a phenotype that involves impairment of gametogenesis and/or fertility. The focus will be on the mHR6B gene knockout mouse, which shows male infertility. The mHR6B gene encodes an ubiquitin-conjugating enzyme, and the data point to an important role of the ubiquitin pathway in gametogenesis.

Animals↗

Bidirectional ventricular tachycardia and fibrillation elicited in a knock-in mouse model carrier of a mutation in the cardiac ryanodine receptor.

Catecholaminergic polymorphic ventricular tachycardia (CPVT) is an inherited disease characterized by adrenergically mediated polymorphic ventricular tachycardia leading to syncope and sudden cardiac death. The autosomal dominant form of CPVT is caused by mutations in the RyR2 gene encoding the cardiac isoform of the ryanodine receptor. In vitro functional characterization of mutant RyR2 channels showed altered behavior on adrenergic stimulation and caffeine administration with enhanced calcium release from the sarcoplasmic reticulum. As of today no experimental evidence is available to demonstrate that RyR2 mutations can reproduce the arrhythmias observed in CPVT patients. We developed a conditional knock-in mouse model carrier of the R4496C mutation, the mouse equivalent to the R4497C mutations identified in CPVT families, to evaluate if the animals would develop a CPVT phenotype and if beta blockers would prevent arrhythmias. Twenty-six mice (12 wild-type (WT) and 14RyR(R4496C)) underwent exercise stress testing followed by epinephrine administration: none of the WT developed ventricular tachycardia (VT) versus 5/14 RyR(R4496C) mice (P=0.02). Twenty-one mice (8 WT, 8 RyR(R4496C), and 5 RyR(R4496C) pretreated with beta-blockers) received epinephrine and caffeine: 4/8 (50%) RyR(R4496C) mice but none of the WT developed VT (P=0.02); 4/5 RyR(R4496C) mice pretreated with propranolol developed VT (P=0.56 nonsignificant versus RyR(R4496C) mice). These data provide the first experimental demonstration that the R4496C RyR2 mutation predisposes the murine heart to VT and VF in response caffeine and/or adrenergic stimulation. Furthermore, the results show that analogous to what is observed in patients, beta adrenergic stimulation seems ineffective in preventing life-threatening arrhythmias.

Animals↗

Ameliorative effects of follistatin-related protein/TSC-36/FSTL1 on joint inflammation in a mouse model of arthritis.

OBJECTIVE: To clarify the in vivo function of follistatin-related protein (FRP)/TSC-36/FSTL1 in rheumatoid arthritis (RA), we investigated the roles of FRP in a mouse model of arthritis. METHODS: Arthritis was induced in BALB/c mice by injecting anti-type II collagen monoclonal antibody and lipopolysaccharide. Mice were treated with daily intraperitoneal injections of 20 microg of recombinant FRP. Development of arthritis was assessed by the clinical score and footpad swelling. Histologic examination of affected paws was performed on day 21 after the onset of arthritis. The gene expression profiles of affected paws in FRP-treated and untreated mice were compared using commercially available complementary DNA (cDNA) arrays. The difference in gene expression was confirmed by real-time quantitative reverse transcription-polymerase chain reaction. RESULTS: Treatment with recombinant FRP showed significant amelioration of the arthritis severity. Histologic analyses confirmed this finding and revealed the alleviation of cellular infiltration into the synovium as well as cartilage damage. The significant decrease in the amount of urinary deoxypyridinoline also indicated the ameliorative effect of FRP on joint destruction. Moreover, cDNA array analysis of the gene expression profile in FRP-treated arthritic lesions revealed a reduced expression of the c-fos, ets-2, IL6, MMP3, and MMP9 genes, some of which are thought to be associated with synovial inflammation and joint destruction. CONCLUSION: These findings from in vivo experiments suggest that FRP could be one of the key molecules in the treatment of inflammatory joint diseases such as RA.

Animals↗

HUPO BPP Workshop on Mouse Models for Neurodegeneration--Choosing the right models.

The HUPO Brain Proteome Project met during the 4th Dutch Endo-Neuro-Psycho Meeting in Doorwerth, The Netherlands, on June 1, 2005, in order to discuss appropriate (mouse) models for neurodegenerative diseases as well as to conceptualise sophisticated proteomics analyses strategies. Here, the topics of the meeting are summarised.

Animals↗

The effect of treatment with interleukin-1 and tumor necrosis factor on Pseudomonas aeruginosa lung infection in a granulocytopenic mouse model.

The efficacy of treatment with interleukin-1 beta (IL-1 beta) and tumor necrosis factor-alpha (TNF alpha) on Pseudomonas aeruginosa pneumonia was evaluated in a granulocytopenic mouse model. Combined intravenous administration of 2000 U IL-1 beta plus 2000 U TNF alpha significantly diminished mortality from aerosol challenge with P. aeruginosa. Mice treated with IL-1 beta, TNF alpha, or both also exhibited a significant enhancement in pulmonary clearance of P. aeruginosa. Combined cytokine administration induced an increase in the pulmonary content of myeloperoxidase activity. Mature leukocytes were not detected in either circulation or bronchoalveolar lavage fluid from granulocytopenic, cytokine-treated mice. In conclusion, IL-1 beta and TNF alpha treatment exhibited a synergistic protective effect from pulmonary P. aeruginosa challenge in granulocytopenic hosts, probably due to enhancement of nonspecific antibacterial mechanisms.

Agranulocytosis↗

Contrast enhancement in atherosclerosis development in a mouse model: in vivo results at 2 Tesla.

To develop an MRI method for the evaluation of contrast enhancement in early atherosclerotic plaque development in the abdominal aorta of a mouse model. Male apoE-/- mice from three groups, respectively 4 (n = 6), 8 (n = 11) and 16 (n = 4) weeks were included. Axial T1 spin echo images of the abdominal aorta were obtained above and below the renal arteries (90 microm spatial resolution) before and over 1 h after the injection of a macromolecular contrast agent. Signal enhancement was measured in the vessel wall and compared to histological features. Maximal arterial wall signal enhancement was obtained from 16 to 32 min post injection. During this time, the signal-to-noise ratio increased by a factor up to 1.7 in 16 week mice and 2.7 and 2.4 in 8 and 4 weeks mice, respectively. The enhancement of the arterial wall appeared less pronounced in the oldest mice, 16 weeks old, exhibiting more advanced lesions. Using a macromolecular gadolinium agent, contrast uptake in atherogenesis varies with lesion stage and may be related to vessel-wall permeability. Dynamic contrast-enhanced MRI may be useful to evaluate the atherosclerotic plaque activity in mice.

Animals↗

Altered responses to dopaminergic D2 receptor activation and N-type calcium currents in striatal cholinergic interneurons in a mouse model of DYT1 dystonia.

Early-onset torsion dystonia (DYT1) is an autosomal dominant disease caused by a deletion in the gene encoding the protein torsinA. Recently, a transgenic mouse model of DYT1 has been described, expressing either the human wild-type torsinA (hWT) or mutant torsinA (hMT). We recorded the activity of striatal cholinergic interneurons of hWT, hMT, and control mice. In slice preparations, no significant differences were observed in resting membrane potential (RMP), firing activity, action potential duration or Ih current. Quinpirole, a D2-like dopamine receptor agonist, did not produce detectable effects on RMP of cholinergic interneurons in control mice and hWT mice, but in the hMT mice caused membrane depolarization and an increase in the firing rate. D2 receptor activation inhibits N-type high-voltage-activated calcium currents. We found that, in isolated interneurons from hMT mice, the quinpirole-mediated inhibition of N-type currents was significantly larger than in hWT and controls. Moreover, the N-type component was significantly over-represented in hMT mice. The altered sensitivity of N-type channels in hMT mice could account for the paradoxical excitatory effect of D2 stimulation. Our data support the existence of an imbalance between striatal dopaminergic and cholinergic signaling in DYT1 dystonia.

Acetylcholine↗

Pathogenicity of tick-borne encephalitis virus isolated in Hokkaido, Japan in mouse model.

The pathogenic characteristics of tick-borne encephalitis (TBE) virus strain (Oshima 5-10) isolated from a sentinel dog in Hokkaido, Japan, was compared by use of a mouse model with several inoculation routes to other strains of TBE virus (the Far Eastern subtype; Sofjin strain and the Western subtype; Hochosterwitz strain) and TBE complex virus (Langat virus; TP-21 strain). The degree of neuroinvasiveness of the strains in mice subcutaneously (s.c.) inoculated was Sofjin equaled Hochosterwitz which was greater than Oshima and TP-21, respectively. Neurovirulence, as determined after intracerebral inoculation was Sofjin > Oshima = Hochosterwitz > TP-21. Virus replication in the brains of mice s.c. or intracerebrally inoculated with Oshima strain was slower and of lower titer than that of Sofjin strain. Histopathological findings indicated that subarachnoid infiltration of mononuclear cells prior to necrosis of the cerebrum was characteristic in Oshima strain. These findings indicated that the Oshima strain possessed a pathogenic potential common to TBE viruses and is less virulent for mice as compared with the two other TBE strains examined.

Animals↗

Interleukin-4 is not critical to pathogenesis in a mouse model of Pseudomonas aeruginosa corneal infection.

PURPOSE: To determine the contribution of interleukin-4 (IL-4) to the initial host response during corneal infection with Pseudomonas aeruginosa in a mouse model. METHODS: Corneas of 6- to 8-week-old IL-4(-/-) and wild-type mice were topically challenged with P. aeruginosa. Ocular tissue was collected 24 hr and 7 days postchallenge. Viable bacterial counts, myeloperoxidase assays, cytokine levels, and clinical and histological examinations were performed. RESULTS: During challenge with P. aeruginosa, no differences were observed clinically, histologically, or in bacterial load between IL-4(-/-) and wild-type mice at either time point. However, differences in cytokine levels of IL-6, KC, and IL-10 were observed. CONCLUSIONS: The data presented indicate that IL-4, a central Th2 cytokine, may not be critical to the pathogenesis or bacterial clearance in this model of P. aeruginosa bacterial keratitis during the early stages of the infectious process.

Animals↗

Rapid direct method for monitoring antibiotics in a mouse model of bacterial biofilm infection.

We have developed a rapid, continuous method for monitoring the effectiveness of several antibacterial agents in real time, noninvasively, by using a recently described mouse model of chronic biofilm infection (J. L. Kadurugamuwa et al., Infect. Immun. 71:882-890, 2003), which relies on biophotonic imaging of bioluminescent bacteria. To facilitate real-time monitoring of infection, we used a Staphylococcus aureus isolate that was made bioluminescent by inserting a modified lux operon into the bacterial chromosome. This bioluminescent reporter bacterium was used to study the antimicrobial effects of several antibiotics belonging to different molecular families. Treatment with rifampin, tobramycin, and ciprofloxacin was started 7 days after subcutaneous implantation of catheters precolonized with 10(4) CFU of S. aureus. Three different doses of antibiotics were administered twice a day for 4 consecutive days. The number of metabolically active bacteria in untreated mice and the tobramycin- and ciprofloxacin-treated groups remained relatively unchanged over the 4-week observation period, indicating poor efficacies for tobramycin and ciprofloxacin. A rapid dose-dependent decline in metabolic activity in rifampin-treated groups was observed, with almost a 90% reduction after two doses and nearly undetectable levels after three doses. The disappearance of light emission correlated with colony counts. After the final treatment, cell numbers rebounded as a function of concentration in a time-dependent manner. The staphylococci isolated from the catheters of mice treated with rifampin were uniformly resistant to rifampin but retained their in vitro susceptibilities to tobramycin and ciprofloxacin. Since the metabolic activities of viable cells and a postantibiotic effect could be detected directly on the support matrix nondestructively and noninvasively, the methodology is specifically appealing for investigating the effects of antibiotics on biofilms in vivo. Moreover, our study points to the possible use of biophotonic imaging for the detection of the development of resistance to therapeutic agents during treatment of chronic infections in vivo.

Animals↗

Vascular damage in a mouse model of diabetic retinopathy: relation to neuronal and glial changes.

PURPOSE: Lack of information about the development of diabetic retinopathy in mice has greatly hindered the use of genetic mouse models for the study of disease mechanisms and the development of therapeutic strategies. The objective of this study was to characterize the occurrence and pathologic progression of diabetic retinopathy in C57Bl/6J mice. METHODS: Diabetes was induced with five consecutive injections of streptozotocin (STZ). The retinas were collected at different time points (2 weeks to 22 months) after the induction of diabetes and examined by using molecular, histologic, and immunohistochemical techniques and morphometric analysis. RESULTS: There was transient induction of cell apoptosis and caspase-3 activation in retinal neurons of C57Bl/6 mice within days of diabetes induction. Glial fibrillary acidic protein (GFAP), a marker of glial activation, likewise was transiently upregulated, seemingly in astrocytes but not in Müller cells. These abnormalities quickly returned to normal; ultimately, no detectable loss of retinal ganglion cells (RGCs) was noted by any of three independent methods (number of cells in ganglion cell layer of retinal cross-sections, retrograde labeling of retinal ganglion cells with fluorescent dye, or TUNEL staining) after up to a 1-year duration of diabetes. Despite this apparent lack of evidence for progressive damage in neurons and glial cells, diabetic mice developed vascular disease characteristic of the early stage of diabetic retinopathy beginning at 6 months after the onset of disease. The vascular damage-formation of acellular capillaries and pericyte ghosts-continued to increase through the 18 months examined. CONCLUSIONS: Diabetic C57Bl/6J mice develop capillary lesion that are characteristic of the early stages of diabetic retinopathy in patients. The data suggest that diabetes-induced degeneration of retinal capillaries can develop independent of neuronal loss or chronic GFAP upregulation in glial cells.

Animals↗

Evidence that elevated glucose causes altered gene expression, apoptosis, and neural tube defects in a mouse model of diabetic pregnancy.

Congenital malformations, including neural tube defects (NTDs), are significantly increased in the offspring of diabetic mothers. We previously reported that in the embryos of a mouse model of diabetic pregnancy, NTDs are associated with reduced expression of the gene Pax-3, which encodes a transcription factor that regulates neural tube development, and that reduced expression of Pax-3 leads to neuroepithelial apoptosis. In this study, we used three approaches to test whether glucose alone could be responsible for these adverse effects of diabetes on embryonic development. First, primary culture of embryo tissue in medium containing 15 mmol/l glucose inhibited Pax-3 expression compared with culture in medium containing 5 mmol/l glucose. Second, inducing hyperglycemia in pregnant mice by subcutaneous glucose administration significantly inhibited Pax-3 expression (P < 0.05), as demonstrated by quantitative reverse transcription-polymerase chain reaction assay of Pax-3 mRNA, and also increased neural tube apoptosis (P < 0.05). NTDs were significantly increased in glucose-injected pregnancies when blood glucose levels were >250 mg/dl (P < 0.002) but not in moderately hyperglycemic pregnancies (150-250 mg/dl, P = 0.37). Third, phlorizin administration to pregnant diabetic mice reduced blood glucose levels and the rate of NTDs. As seen with glucose-injected pregnancies, the rate of NTDs in phlorizin-treated diabetic pregnancies was related to the severity of hyperglycemia, since NTDs were significantly increased in severely hyperglycemic (>250 mg/dl) diabetic pregnancies (P < 0.001) but not in moderately hyperglycemic pregnancies (150-250 mg/dl, P = 0.35). These two findings, that elevated glucose alone can cause the changes in Pax-3 expression observed during diabetic pregnancy and that the NTD rate rises with significant increases in blood glucose levels, suggest that congenital malformations associated with diabetic pregnancy are caused by disruption of regulatory gene expression in the embryo in response to elevated glucose.

Animals↗

Minimal prophylactic concentration of dietary zinc compounds in a mouse model of swine dysentery.

Dietary supplementation with 6000 mg of Zn2+/kg of feed has been shown to modify the clinicopathologic expression of Brachyspira hyodysenteriae infection in a laboratory mouse model of swine dysentery. However, this concentration impaired the body weight gain of the mice. The purpose of the present study was to determine a minimal prophylactic concentration of feed-grade zinc compounds that would not affect the growth of mice challenge-exposed with B. hyodysenteriae. A total of 440, 6- to 8-week-old, C3H/HeN mice were allocated randomly to groups and fed either a defined diet or a defined diet containing either 1000, 2000 or 4000 mg/kg ZnO, ZnSO4 or zinc-methionine for 7 days before intragastric inoculation with B. hyodysenteriae. From days 7 to 35 after inoculation, mice in each group were necropsied at weekly intervals for determination of body weight, presence of B. hyodysenteriae in the cecum, and histological assessment of cecal lesions. Only ZnO fed at 2000 mg/kg had a prophylactic effect against B. hyodysenteriae infection without affecting the body weight gain of the mice. The prophylactic effect of Zn2+ against infection with B. hyodysenteriae was also affected by the relative concentration of Fe2+ and Zn2+/Fe2+ ratio of the diet.

Animal Feed↗

NGF-Tf Conjugate Prevents Degeneration of Substantia Nigra Neurons in a Mouse Model of Parkinson's Disease.

Nerve growth factor(NGF) was purified from Naja naja atra snake venom and conjugated to transferrin(Tf). This conjugate was intravenously injected into a mouse model of Parkinson's disease (PD). Both immunohistochemical staining and pathological detection showed that the NGF-Tf conjugate could prevent the loss of tyrosine hydroxylase-immunoreactive neurons located in substantia nigra and the cell counts of NGF group were 2 330.0+/-260.3, and those of the MPTP group and the control group were 797.0+/-121.4 and 2 381.0+/-158.0, respectively. In addition, electron microscopic examination revealed significant protection against demyelination and vacuolation in subtantia nigra neurons in contrast to the control group. The i.v. injected NGF-Tf conjugate also reversed the neurodegenerative changes such as karyopyknosis, chromatolysis and intracytoplasmic inclusion in diseased neurons.

Journal Article↗

Beta-amyloid mediated nitration of manganese superoxide dismutase: implication for oxidative stress in a APPNLH/NLH X PS-1P264L/P264L double knock-in mouse model of Alzheimer's disease.

Alzheimer's disease is a multifactorial, progressive, age-related neurodegenerative disease. In familial Alzheimer's disease, Abeta is excessively produced and deposited because of mutations in the amyloid precursor protein, presenilin-1, and presenilin-2 genes. Here, we generated a double homozygous knock-in mouse model that incorporates the Swedish familial Alzheimer's disease mutations and converts mouse Abeta to the human sequence in amyloid precursor protein and had the P264L familial Alzheimer's disease mutation in presenilin-1. We observed Abeta deposition in double knock-in mice beginning at 6 months as well as an increase in the levels of insoluble Abeta1-40/1-42. Brain homogenates from 3-, 6-, 9-, 12-, and 14-month-old mice showed that protein levels of manganese superoxide dismutase (MnSOD) were unchanged in the double knock-in mice compared to controls. Genotype-associated increases in nitrotyrosine levels were observed. Protein immunoprecipitation revealed MnSOD as a target of this nitration. Although the levels of MnSOD protein did not change, MnSOD activity and mitochondrial respiration decreased in knock-in mice, suggesting compromised mitochondrial function. The compromised activity of MnSOD, a primary antioxidant enzyme protecting mitochondria, may explain mitochondrial dysfunction and provide the missing link between Abeta-induced oxidative stress and Alzheimer's disease.

Aging↗

Cellular sources of enhanced brain-derived neurotrophic factor production in a mouse model of allergic inflammation.

The aim of this study was to investigate production and cellular sources of brain-derived neurotrophic factor (BDNF) production in allergic asthma. For this purpose a mouse model of chronic and severe ovalbumin (OVA)-induced airway inflammation was developed. Allergen-exposed mice developed elevated immunoglobulin E titers; airway inflammation with influx of lymphocytes, monocytes, and eosinophils; and airway hyperresponsiveness. In addition to an influx of inflammatory cells, interleukin (IL)-4 and IL-5 production were enhanced, macrophages showed morphologic signs of activation, and airway epithelium was thickened and displayed a goblet-cell hyperplasia with a marked mucus production. BDNF was detected using in situ hybridization and enzyme-linked immunosorbent assay. Constitutive expression of BDNF messenger RNA (mRNA) was observed in the respiratory epithelium of sensitized and nonsensitized mouse lungs. In addition, BDNF mRNA was detected in airway inflammatory infiltrations and bronchoalveolar lavage fluid (BALF) cells of OVA-sensitized and aerosol-challenged mice. Highest BDNF protein levels were detected in BALF after long-term allergen aerosol exposure. Analysis of BDNF production by isolated lymphocyte subsets revealed T but not B cells as a cellular source of BDNF. In addition, activated alveolar macrophages were identified as BDNF-positive cells. These data indicate that in allergic airway inflammation BDNF production is upregulated and immune cells serve as a source of BDNF.

Allergens↗