Imaging transgene expression in live animals

In vivo imaging identified efficient antimicrobial treatment against Mycobacterium marinum infection in mouse footpads

Mycobacterium marinum (M. marinum) is the most common causative bacteria of cutaneous non-tuberculous mycobacterial (NTM) infections, including fish tank granuloma. Treating M. marinum-caused infection takes longer than other NTM diseases because M. marinum is less susceptible to antimicrobial agents. A standard treatment regimen for M. marinum infection has not been established yet, and few in vivo experiments have been performed in mammals to evaluate the bactericidal effects of antimicrobials. In this study, we developed a noninvasive in vivo imaging method to assess the therapeutic efficacy of antimicrobials against M. marinum infection. The data obtained using fluorescent protein or bioluminescence from luciferase will offer valuable insights into bacteria visualization across various bacterial infections. Furthermore, through this imaging technique, we demonstrated that combining clarithromycin, rifampicin, ethambutol, and minocycline effectively cleared M. marinum from the footpad. Granulomas with necrotic abscesses formed on the footpad of M. marinum-infected mice, primarily due to neutrophils involved in the host's cell-mediated immune response. Inflammatory cytokine and chemokine levels significantly increased 7 days post-infection, aligning with the footpad swelling and granuloma formation observed in the untreated group. Interestingly, immune mediators and cells induced by M. marinum footpad infection were crucial factors associated with hypersensitivity and granuloma formation, as seen in pulmonary tuberculosis. This novel imaging analysis using a cutaneous NTM mouse model might be a powerful tool for the comprehensive analysis of mycobacterial infections.

Catheter-associated Mycobacterium intracellulare biofilm infection in C3HeB/FeJ mice

Non-tuberculosis mycobacterial (NTM) diseases are steadily increasing in prevalence and mortality worldwide. Mycobacterium avium and M. intracellulare, the two major pathogens of NTM diseases, are resistant to antibiotics, and chlorine, necessitating their capacity to survive in natural environments (e.g. soil and rivers) and disinfected municipal water. They can also form biofilms on artificial surfaces to provide a protective barrier and habitat for bacilli, which can cause refractory systemic disseminated NTM disease. Therefore, preventing biofilm formation by these pathogens is crucial; however, not many in vivo experimental systems and studies on NTM biofilm infection are available. This study develops a mouse model of catheter-associated systemic disseminated disease caused by M. intracellulare that reproduces the pathophysiology of catheter-associated infections observed in patients undergoing peritoneal dialysis. In addition, the bioluminescence system enabled noninvasive visualization of the amount and distribution of bacilli in vivo and conveniently examine the efficacy of antimicrobials. Furthermore, the cellulose-based biofilms, which were extensively formed in the tissue surrounding the catheter insertion site, reduced drug therapy effectiveness. Overall, this study provides insights into the cause of the drug resistance of NTM and may guide the development of new therapies for NTM diseases.

A DNA vaccine (EG95-PT1/2/3-IL2) encoding multi-epitope antigen and IL-2 provokes efficient and long-term immunity to echinococcosis

Echinococcosis is a highly prevalent global zoonosis, and vaccines are required. The commercial vaccine based on a protein-based subunit (EG95), however, is limited by its insufficient cellular immunity, a short protection period, and limited prevention against novel mutant strains. Herein, we applied bioinformatics to develop a DNA vaccine (pEG95-IL2) expressing both multi-epitope-based antigens (EG95-PT1/2/3) and an IL-2 adjuvant to regulate T cell differentiation and memory cell response. EG95-PT1/2/3 was screened with hierarchical structure prediction from the epitope conformation of B cells with high confidence across various species to guarantee immunogenicity. Importantly, cationic arginine-rich lipid nanoparticles (RNP) were utilized as a delivery vehicle to form lipoplexes that had a transfection efficiency of nearly two orders of magnitude greater than that of commercial reagents (Lipofectamine 2000 and polyethyleneimine) with both immune and nonimmune cells (DC2.4 and L929 cells, respectively). RNP/pEG95-IL2 lipoplexes displayed a robust and long-term antigen expression, as well as adjuvant effects during the immunization. Consequently, intramuscular injection of RNP/pEG95-IL2 elicited similar humoral immune responses and significantly greater cellular responses in mice when compared with those of the commercial vaccine. In addition, the inoculation protocol of RNP/pEG95-IL2 with sequential booster further strengthens cellular immunity in comparison with the homologous booster. Those findings provide a promising strategy for improving plasmid vaccine efficacy.

Specific Systems for Evaluation

Fluorescent-based visualization techniques have long been used to monitor biological activity. This chapter explores the delivery of reporter genes as a means to assay and track activity in biological systems. Bioluminescence is the production of light due to biochemical processes. By encoding genes for bioluminescence, biological processes can be visualized based on gene expression. This chapter also discusses the primary applications of bioluminescence as seen through bioluminescent imaging techniques, flow cytometry, and PCR-based methods of gene detection. These techniques are described in terms of researching gene expression, cancer therapy, and protein interactions.

Systematic calibration of an integrated x-ray and optical tomography system for preclinical radiation research

PURPOSE

The cone beam computed tomography (CBCT) guided small animal radiation research platform (SARRP) has been developed for focal tumor irradiation, allowing laboratory researchers to test basic biological hypotheses that can modify radiotherapy outcomes in ways that were not feasible previously. CBCT provides excellent bone to soft tissue contrast, but is incapable of differentiating tumors from surrounding soft tissue. Bioluminescence tomography (BLT), in contrast, allows direct visualization of even subpalpable tumors and quantitative evaluation of tumor response. Integration of BLT with CBCT offers complementary image information, with CBCT delineating anatomic structures and BLT differentiating luminescent tumors. This study is to develop a systematic method to calibrate an integrated CBCT and BLT imaging system which can be adopted onboard the SARRP to guide focal tumor irradiation.

METHODS

The integrated imaging system consists of CBCT, diffuse optical tomography (DOT), and BLT. The anatomy acquired from CBCT and optical properties acquired from DOT serve as a priori information for the subsequent BLT reconstruction. Phantoms were designed and procedures were developed to calibrate the CBCT, DOT/BLT, and the entire integrated system. Geometrical calibration was performed to calibrate the CBCT system. Flat field correction was performed to correct the nonuniform response of the optical imaging system. Absolute emittance calibration was performed to convert the camera readout to the emittance at the phantom or animal surface, which enabled the direct reconstruction of the bioluminescence source strength. Phantom and mouse imaging were performed to validate the calibration.

RESULTS

All calibration procedures were successfully performed. Both CBCT of a thin wire and a euthanized mouse revealed no spatial artifact, validating the accuracy of the CBCT calibration. The absolute emittance calibration was validated with a 650 nm laser source, resulting in a 3.0% difference between simulated and measured signal. The calibration of the entire system was confirmed through the CBCT and BLT reconstruction of a bioluminescence source placed inside a tissue-simulating optical phantom. Using a spatial region constraint, the source position was reconstructed with less than 1 mm error and the source strength reconstructed with less than 24% error.

CONCLUSIONS

A practical and systematic method has been developed to calibrate an integrated x-ray and optical tomography imaging system, including the respective CBCT and optical tomography system calibration and the geometrical calibration of the entire system. The method can be modified and adopted to calibrate CBCT and optical tomography systems that are operated independently or hybrid x-ray and optical tomography imaging systems.

Imaging Approaches in Functional Assessment of Implantable Myogenic Biomaterials and Engineered Muscle Tissue

The fields of tissue engineering and regenerative medicine utilize implantable biomaterials and engineered tissues to regenerate damaged cells or replace lost tissues. There are distinct challenges in all facets of this research, but functional assessments and monitoring of such complex environments as muscle tissues present the current strategic priority. Many extant methods for addressing these questions result in the destruction or alteration of tissues or cell populations under investigation. Modern advances in non-invasive imaging modalities present opportunities to rethink some of the anachronistic methods, however, their standard employment may not be optimal when considering advancements in myology. New image analysis protocols and/or combinations of established modalities need to be addressed. This review focuses on efficacies and limitations of available imaging modalities to the functional assessment of implantable myogenic biomaterials and engineered muscle tissues.

In vivo bioluminescent tracking of mesenchymal stem cells within large hydrogel constructs

The use of multicomponent scaffolds for cell implantation has necessitated sophisticated techniques for tracking of cell survival in vivo. Bioluminescent imaging (BLI) has emerged as a noninvasive tool for evaluating the therapeutic potential of cell-based tissue engineering strategies. However, the ability to use BLI measurements to longitudinally assess large 3D cellular constructs in vivo and the effects of potential confounding factors are poorly understood. In this study, luciferase-expressing human mesenchymal stem cells (hMSCs) were delivered subcutaneously within agarose and RGD-functionalized alginate hydrogel vehicles to investigate the impact of construct composition and tissue formation on BLI signal. Results showed that alginate constructs exhibited twofold greater BLI counts than agarose constructs at comparable hMSC doses. However, each hydrogel type produced a linear correlation between BLI counts and live cell number, indicating that within a given material, relative differences in cell number could be accurately assessed at early time points. The survival efficiency of delivered hMSCs was highest for the lower cell doses embedded within alginate matrix. BLI signal remained predictive of live cell number through 1 week in vivo, although the strength of correlation decreased over time. Irrespective of hydrogel type or initial hMSC seeding dose, all constructs demonstrated a degree of vascularization and development of a fibrotic capsule after 1 week. Formation of tissue within and adjacent to the constructs was accompanied by an attenuation of BLI signal during the initial period of the image acquisition time-frame. In alginate constructs only, greater vessel volume led to a delayed rise in BLI signal following luciferin delivery. This study identified vascular and fibrotic tissue ingrowth as potential confounding variables for longitudinal BLI studies. Further investigation into the complexities of noninvasive BLI data acquisition from multicomponent constructs, following implantation and subsequent tissue formation, is warranted.

Transient overexpression of Pparγ2 and C/ebpα in mesenchymal stem cells induces brown adipose tissue formation

BACKGROUND

Brown adipose tissue plays a pivotal role in mammal metabolism and thermogenesis. It has a great therapeutic potential in several metabolic disorders such as obesity and diabetes. Mesenchymal stem cells (MSCs) are suitable candidates for brown adipose tissue formation de novo. Pparγ2 and C/ebpα are nucleic receptors known to mediate adipogenic differentiation. We hypothesized that overexpression of the Pparγ2 and C/ebpα genes in MSCs would lead to the formation of adipose tissue.

MATERIALS & METHODS

MSCs bearing the Luc reporter gene were transfected to overexpress Pparγ2 and C/ebpα. Differentiation of nucleofected cells was evaluated in vitro and in vivo following ectopic implantation of the cells in C3H/HeN mice.

RESULTS

After implantation, the engineered cells survived for 5 weeks and brown adipose-like tissue was observed in histological samples. Immunostaining and bioluminescent imaging showed new adipocytes expressing Luc and the brown adipose tissue marker, UCP1, in vitro and in vivo.

CONCLUSION

We show that gene delivery of transcription factors into MSCs generates brown adipose tissue in vitro and in vivo.

Combination of imatinib with CXCR4 antagonist BKT140 overcomes the protective effect of stroma and targets CML in vitro and in vivo

Functional role of CXCR4 in chronic myelogenous leukemia (CML) progression was evaluated. Elevated CXCR4 significantly increased the in vitro survival and proliferation in response to CXCL12. CXCR4 stimulation resulted in activation of extracellular signal-regulated kinase (Erk)-1/2, Akt, S6K, STAT3, and STAT5 prosurvival signaling pathways. In accordance, we found that in vitro treatment with CXCR4 antagonist BKT140 directly inhibited the cell growth and induced cell death of CML cells. Combination of BKT140 with suboptimal concentrations of imatinib significantly increased the anti-CML effect. BKT140 induced apoptotic cell death, decreasing the levels of HSP70 and HSP90 chaperones and antiapoptotic proteins BCL-2 and BCL-XL, subsequently promoting the release of mitochondrial factors cytochrome c and SMAC/Diablo. Bone marrow (BM) stromal cells (BMSC) markedly increased the proliferation of CML cells and protected them from imatinib-induced apoptosis. Furthermore, BMSCs elevated proto-oncogene BCL6 expression in the CML cells in response to imatinib treatment, suggesting the possible role of BCL6 in stroma-mediated TKI resistance. BKT140 reversed the protective effect of the stroma, effectively promoted apoptosis, and decreased BCL6 levels in CML cells cocultured with BMSCs. BKT140 administration in vivo effectively reduced the growth of subcutaneous K562-produced xenografts. Moreover, the combination of BKT140 with low-dose imatinib markedly inhibited tumor growth, achieving 95% suppression. Taken together, our data indicate the importance of CXCR4/CXCL12 axis in CML growth and CML-BM stroma interaction. CXCR4 inhibition with BKT140 antagonist efficiently cooperated with imatinib in vitro and in vivo. These results provide the rational basis for CXCR4-targeted therapy in combination with TKI to override drug resistance and suppress residual disease.

Effects of angiotensin II type 2 receptor overexpression on the growth of hepatocellular carcinoma cells in vitro and in vivo

Increasing evidence suggests that the renin-angiotensin system (RAS) plays an important role in tumorigenesis. The interaction between Angiotensin II (AngII) and angiotensin type 1 receptor (AT1R) may have a pivotal role in hepatocellular carcinoma (HCC) and therefore, AT1R blocker and angiotensin I-converting enzyme (ACE) inhibitors may have therapeutic potential in the treatment of hepatic cancer. Although the involvement of AT1R has been well explored, the role of the angiotensin II Type 2 receptor (AT2R) in HCC progression remains poorly understood. Thus, the aim of this study was to explore the effects of AT2R overexpression on HCC cells in vitro and in mouse models of human HCC. An AT2R recombinant adenoviral vector (Ad-G-AT2R-EGFP) was transduced into HCC cell lines and orthotopic tumor grafts. The results indicate that the high dose of Ad-G-AT2R-EGFP–induced overexpression of AT2R in transduced HCC cell lines produced apoptosis. AT2R overexpression in SMMC7721 cells inhibited cell proliferation with a significant reduction of S-phase cells and an enrichment of G1-phase cells through changing expression of CDK4 and cyclinD1. The data also indicate that overexpression of AT2R led to apoptosis via cell death signaling pathway that is dependent on activation of p38 MAPK, pJNK, caspase-8 and caspase-3 and inactivation of pp42/44 MAPK (Erk1/2). Finally, we demonstrated that moderately increasing AT2R expression could increase the growth of HCC tumors and the proliferation of HCC cells in vivo. Our findings suggest that AT2R overexpression regulates proliferation of hepatocellular carcinoma cells in vitro and in vivo, and the precise mechanisms of this phenomenon are yet to be fully determined.

A synthetic oxygen carrier-olfactory ensheathing cell composition system for the promotion of sciatic nerve regeneration

The treatment of lengthy peripheral nerve defects is challenging in the field of the regenerative medicine. Thus far, many nerve scaffolds with seeded cells have been developed, which hold great potential to replace nerve autograft in bridging lengthy nerve defects by providing guiding and bioactive cues. However, low oxygen status has been found within nerve scaffolds after their implantation in vivo, which has been shown to result in death or loss of function of supportive cells, and significantly limit nerve regeneration and functional recovery after nerve injury. In the present study, perfluorotributylamine (PFTBA) was introduced into a collagen-chitosan conduit within which olfactory ensheathing cells (OECs) were seeded to increase oxygen supply to OECs, as well as regenerating axons. The "PFTBA-OECs" enriched scaffolds were then used to bridge a 15-mm-long sciatic nerve defect in rats. Both nerve regeneration and functional recovery were examined at pre-defined time points after surgery. We found that the number of GFP-labeled OECs was significantly higher in the "PFTBA-OECs" scaffold than that in the single OECs scaffold. In addition, PFTBA was found to enhance the beneficial effect of OECs-enriched scaffold on axonal regeneration and functional recovery. All these findings indicate that the "PFTBA-OECs" enriched scaffolds are capable of promoting nerve regeneration and functional recovery, which might be attributable, at least in part, to their beneficial effect on the survival of OECs after their implantation in vivo.

PTH promotes allograft integration in a calvarial bone defect

Allografts may be useful in craniofacial bone repair, although they often fail to integrate with the host bone. We hypothesized that intermittent administration of parathyroid hormone (PTH) would enhance mesenchymal stem cell recruitment and differentiation, resulting in allograft osseointegration in cranial membranous bones. Calvarial bone defects were created in transgenic mice, in which luciferase is expressed under the control of the osteocalcin promoter. The mice were given implants of allografts with or without daily PTH treatment. Bioluminescence imaging (BLI) was performed to monitor host osteprogenitor differentiation at the implantation site. Bone formation was evaluated with the aid of fluorescence imaging (FLI) and microcomputed tomography (μCT) as well as histological analyses. Reverse transcription polymerase chain reaction (RT-PCR) was performed to evaluate the expression of key osteogenic and angiogenic genes. Osteoprogenitor differentiation, as detected by BLI, in mice treated with an allograft implant and PTH was over 2-fold higher than those in mice treated with an allograft implant without PTH. FLI also demonstrated that the bone mineralization process in PTH-treated allografts was significantly higher than that in untreated allografts. The μCT scans revealed a significant increase in bone formation in allograft + PTH treated mice comparing to allograft + PBS treated mice. The osteogenic genes osteocalcin (Oc/Bglap) and integrin binding sialoprotein (Ibsp) were upregulated in the allograft + PTH treated animals. In summary, PTH treatment enhances osteoprogenitor differentiation and augments bone formation around structural allografts. The precise mechanism is not clear, but we show that infiltration pattern of mast cells, associated with the formation of fibrotic tissue, in the defect site is significantly affected by the PTH treatment.

Imaging early stage osteogenic differentiation of mesenchymal stem cells

Stem cells, such as mesenchymal stem cells (MSCs), contribute to bone fracture repair if they are delivered to the injury site. However, it is difficult to assess the retention and differentiation of these cells after implantation. Current options for non-invasively tracking the transplanted stem cells are limited. Cell-based therapies using MSCs would benefit greatly through the use of an imaging methodology that allows cells to be tracked in vivo and in a timely fashion. In this study, we implemented an in vivo imaging methodology to specifically track early events such as differentiation of implanted human MSCs (hMSCs). This system uses the collagen type 1 (Col1α1) promoter to drive expression of firefly luciferase (luc) in addition to a constitutively active promoter to drive the expression of green fluorescent protein (GFP). The resulting dual-promoter reporter gene system provides the opportunity for osteogenic differentiation-specific luc expression for in vivo imaging and constitutive expression of GFP for cell sorting. The function of this dual-promoter reporter gene was validated both in vitro and in vivo. In addition, the ability of this dual-promoter reporter system to image an early event of osteogenic differentiation of hMSCs was demonstrated in a murine segmental bone defect model in which reporter-labeled hMSCs were seeded into an alginate hydrogel scaffold and implanted directly into the defect. Bioluminescence imaging (BLI) was performed to visualize the turn-on of Col1α1 upon osteogenic differentiation and followed by X-ray imaging to assess the healing process for correlation with histological analyses.

Current advances in animal model of chondrosarcoma and related research

Chondrosarcoma is a type of malignant cartilage tumor with a high local recurrence. Due to its resistance to chemo- and radiotherapy, current treatment is limited to surgical resection. Animal model is one of the most important approaches to studying this disease, although systematic reporting on its development is rare. In this review, we summarized the elements involving animal model establishment. On the basis of these elements, we further classified chondrosarcoma animal models into various types. In addition, we compared various measurements for evaluating the animal model. Finally, its specific applications were discussed.

Spatial distribution and survival of human and goat mesenchymal stromal cells on hydroxyapatite and β-tricalcium phosphate

The combination of scaffolds and mesenchymal stromal cells (MSCs) is a promising approach in bone tissue engineering (BTE). Knowledge on the survival, outgrowth and bone-forming capacity of MSCs in vivo is limited. Bioluminescence imaging (BLI), histomorphometry and immunohistochemistry were combined to study the fate of gene-marked goat and human MSCs (gMSCs, hMSCs) on scaffolds with different osteoinductive properties. Luciferase-GFP-labelled MSCs were seeded on hydroxyapatite (HA) or β-tricalcium phosphate (TCP), cultured for 7 days in vitro in osteogenic medium, implanted subcutaneously in immunodeficient mice and monitored with BLI for 6 weeks. The constructs were retrieved and processed for histomorphometry and detection of luciferase-positive cells (LPCs). For gMSCs, BLI revealed doubling of signal after 1 week, declining to 60% of input after 3 weeks and remaining constant until week 6. hMSCs showed a constant decrease of BLI signal to 25% of input, indicating no further expansion. Bone formation of gMSCs was two-fold higher on TCP than HA. hMSCs and gMSCs control samples produced equal amounts of bone on TCP. Upon transduction, there was a four-fold reduction in bone formation compared with untransduced hMSCs, and no bone was formed on HA. LPCs were detected at day 14, but were much less frequent at day 42. Striking differences were observed in spatial distribution. MSCs in TCP were found to be aligned and interconnected on the surface but were scattered in an unstructured fashion in HA. In conclusion, the spatial distribution of MSCs on the scaffold is critical for cell-scaffold-based BTE.

Plasmid DNA is internalized from the apical plasma membrane of the salivary gland epithelium in live animals

Non-viral-mediated gene delivery represents an alternative way to express the gene of interest without inducing immune responses or other adverse effects. Understanding the mechanisms by which plasmid DNAs are delivered to the proper target in vivo is a fundamental issue that needs to be addressed in order to design more effective strategies for gene therapy. As a model system, we have used the submandibular salivary glands in live rats and we have recently shown that reporter transgenes can be expressed in different cell populations of the glandular epithelium, depending on the modality of administration of plasmid DNA. Here, by using a combination of immunofluorescence and intravital microscopy, we have explored the relationship between the pattern of transgenes expression and the internalization of plasmid DNA. We found that plasmid DNA is internalized: (1) by all the cells in the salivary gland epithelium, when administered alone, (2) by large ducts, when mixed with empty adenoviral particles, and (3) by acinar cells upon stimulation of compensatory endocytosis. Moreover, we showed that plasmid DNA utilizes different routes of internalization, and evades both the lysosomal degradative pathway and the retrograde pathway towards the Golgi apparatus. This study clearly shows that in vivo approaches have the potential to address fundamental questions on the cellular mechanisms regulating gene delivery.

Characterization of Ku70(2)-NLS as bipartite nuclear localization sequence for non-viral gene delivery

Several barriers have to be overcome in order to achieve gene expression in target cells, e.g. cellular uptake, endosomal release and translocation to the nucleus. Nuclear localization sequences (NLS) enhance gene delivery by increasing the uptake of plasmid DNA (pDNA) to the nucleus. So far, only monopartite NLS were analysed for non-viral gene delivery. In this study, we examined the characteristics of a novel bipartite NLS like construct, namely NLS Ku70. We synthesized a dimeric structure of a modified NLS from the Ku70 protein (Ku70₂-NLS), a nuclear transport active mutant of Ku70₂-NLS (s1Ku70₂-NLS) and a nuclear transport deficient mutant of Ku70₂-NLS (s2Ku70₂). We examined the transfection efficiency of binary Ku70₂-NLS/DNA and ternary Ku70₂-NLS/PEI/DNA gene vector complexes in vitro by using standard transfection protocols as well as the magnetofection method. The application of Ku70₂-NLS and s1Ku70₂-NLS increased gene transfer efficiency in vitro and in vivo. This study shows for the first time that the use of bipartite NLS compounds alone or in combination with cationic polymers is a promising strategy to enhance the efficiency of non-viral gene transfer.

Restrictions that control herpes simplex virus type 1 infection in mouse brain ex vivo

Elucidating the cellular and molecular factors governing herpes simplex virus type 1 (HSV-1) neurotropism is a prerequisite for understanding HSV-1 encephalitis and for targeting HSV-1-derived vectors for gene transfer to the brain. Earlier we had described an ex vivo system of mouse brain slices and demonstrated a selective and unique infection pattern, mostly around the ventricles. Here, we examined tissue factors controlling HSV-1 infection of brain slices. We demonstrated that heparan sulphate, while an important factor, does not determine the infection pattern. Hyaluronic acid, but not collagen, appears to enhance HSV-1 brain infection. To investigate whether tissue distribution of viral receptors determines the infection pattern, we examined transcription of herpes virus entry mediator and nectin-1 receptor genes in infected and uninfected brain regions. Both the infected and the uninfected regions express the receptors. We also explored the influence of intra-cellular factors. HSV-1 does not preferentially infect proliferating cells in the brain slices, despite its predilection to the ventricular zones. To delineate the step at which the HSV-1 infection cascade is restricted, mRNA was isolated following tissue infection, and transcription of the immediate-early and late viral genes was evaluated. The results indicated that HSV-1 genes are not expressed in regions that do not express a viral reporter gene. Therefore, we conclude that tissue resistance to infection is associated with a block at or prior to the immediate-early mRNA synthesis. Taken together, using the ex vivo system of organotypic culture we describe here extra-cellular and intra-cellular restriction levels of HSV-1 brain infection.

Imaging of alkaline phosphatase activity in bone tissue

The purpose of this study was to develop a paradigm for quantitative molecular imaging of bone cell activity. We hypothesized the feasibility of non-invasive imaging of the osteoblast enzyme alkaline phosphatase (ALP) using a small imaging molecule in combination with ¹⁹Flourine magnetic resonance spectroscopic imaging (¹⁹FMRSI). 6, 8-difluoro-4-methylumbelliferyl phosphate (DiFMUP), a fluorinated ALP substrate that is activatable to a fluorescent hydrolysis product was utilized as a prototype small imaging molecule. The molecular structure of DiFMUP includes two Fluorine atoms adjacent to a phosphate group allowing it and its hydrolysis product to be distinguished using ¹⁹Fluorine magnetic resonance spectroscopy (¹⁹FMRS) and ¹⁹FMRSI. ALP-mediated hydrolysis of DiFMUP was tested on osteoblastic cells and bone tissue, using serial measurements of fluorescence activity. Extracellular activation of DiFMUP on ALP-positive mouse bone precursor cells was observed. Concurringly, DiFMUP was also activated on bone derived from rat tibia. Marked inhibition of the cell and tissue activation of DiFMUP was detected after the addition of the ALP inhibitor levamisole. ¹⁹FMRS and ¹⁹FMRSI were applied for the non-invasive measurement of DiFMUP hydrolysis. ¹⁹FMRS revealed a two-peak spectrum representing DiFMUP with an associated chemical shift for the hydrolysis product. Activation of DiFMUP by ALP yielded a characteristic pharmacokinetic profile, which was quantifiable using non-localized ¹⁹FMRS and enabled the development of a pharmacokinetic model of ALP activity. Application of ¹⁹FMRSI facilitated anatomically accurate, non-invasive imaging of ALP concentration and activity in rat bone. Thus, ¹⁹FMRSI represents a promising approach for the quantitative imaging of bone cell activity during bone formation with potential for both preclinical and clinical applications.

Lung fluorescence imaging to evaluate tumor metastasis induced by AQP5 expression in murine model

Our recent study, by up-regulation of AQP5 expression, showed enhanced proliferation and migration potential in lung cancer. However, so far none of the in vivo study of gene silencing of AQP5 has been tested. In this study, we tested roles of AQP5 on lung cancer metastasis potential by gene silencing of AQP5 in two lung cancer cell lines and tried to monitor lung metastases with EGFP marker. Lungs were imaged at different time points and allowed an accurate evaluation of tumor burden over time. Our results showed significantly decreased metastasis potential in AQP5 gene-silencing cells. Lung imaging confirmed the frequency of metastasis in mice. These data provide more evidence that AQP5 plays important roles in the metastasis potential of lung cancer. Lung fluorescence imaging provides rapid monitoring for tumor growth and metastasis, and it also offers quantitative and sensitive analysis of tumor growth and metastasis, compared to the traditional histology technique.

Evaluation of impaired beta-cell function in nonobese-diabetic (NOD) mouse model using bioluminescence imaging

Insulin-producing pancreatic β cells are functionally impaired or destroyed in diabetes mellitus. The onset of type 1 diabetes (T1D) represents the culmination of a prolonged prediabetic phase of immune-mediated β-cell destruction. To assess the in vivo metabolic status of these cells, we used the ATP-sensitive firefly luciferase bioluminescence imaging approach, as a noninvasive probe to monitor pathological alterations in β-cell function in the nonobese-diabetic (NOD) mouse model of T1D. Hence, we generated the ToIβ-NOD transgenic mice in which doxycycline-inducible luciferase gene is selectively expressed in β cells. A sharp reduction in bioluminescence emitted in vivo from β cells at the early stages, preceded by several weeks of a limited reduction in β-cell mass. Since this decline could be due to the ongoing inflammatory process occurring in vivo, we exposed control islets to inflammatory cytokines and observed a dramatic decrease in luciferase luminescence, which appears to be due in part to a decrease in protein levels and a drop in intracellular ATP levels. This is the first evidence that selective expression of the luciferase gene represents a sensitive method for noninvasive in vivo monitoring of early β-cell dysfunction, subtle metabolic changes, such as endogenous ATP levels, indicative of a pathological condition in a tissue at the cellular level.

Bioluminescent imaging study: FAK inhibitor, PF-562,271, preclinical study in PC3M-luc-C6 local implant and metastasis xenograft models

Focal adhesion kinase (FAK) is essential in regulating integrin signaling pathways responsible for cell survival and proliferation, as well as motility, making FAK a distinctive target in the field of anticancer drug development, especially with regards to metastatic disease.(1) Our objective was to demonstrate tumor growth inhibition by PF-562,271, a selective inhibitor of FAK and FAK2, or Pyk2,(2) in mouse xenograft models, both subcutaneous and metastatic, employing the human prostate cancer cell line PC3M-luc-C6, a modified PC3M cell line that expresses luciferase. After 2 weeks of treatment with PF-562,271, 25 mg/kg PO BID 5x/wk, the subcutaneous model showed a 62% tumor growth inhibition compared to control based on tumor measurements (p < 0.05), with a 88% vs. a 490% increase in bioluminescent signal for treatment and control respectively (p < 0.05). In the metastasis model, the percent change from baseline, after 18 days of treatment, of the treatment group was 2,854 vs. 14,190% for the vehicle (p < 0.01). These results show that PF-562,271 has a potent effect on metastatic prostate cancer growth in vivo.

Bioluminescent imaging: a critical tool in pre-clinical oncology research

Bioluminescent imaging (BLI) is a non-invasive imaging modality widely used in the field of pre-clinical oncology research. Imaging of small animal tumour models using BLI involves the generation of light by luciferase-expressing cells in the animal following administration of substrate. This light may be imaged using an external detector. The technique allows a variety of tumour-associated properties to be visualized dynamically in living models. The increasing use of BLI as a small-animal imaging modality has led to advances in the development of xenogeneic, orthotopic, and genetically engineered animal models expressing luciferase genes. This review aims to provide insight into the principles of BLI and its applications in cancer research. Many studies to assess tumour growth and development, as well as efficacy of candidate therapeutics, have been performed using BLI. More recently, advances have also been made using bioluminescent imaging in studies of protein-protein interactions, genetic screening, cell-cycle regulators, and spontaneous cancer development. Such novel studies highlight the versatility and potential of bioluminescent imaging in future oncological research.

Noninvasive imaging of bone-specific collagen I expression in a luciferase transgenic mouse model

Luciferase transgenic mice are a very promising tool for noninvasive, quantitative, and longitudinal evaluation of gene expression. The aim of this study was to validate the Col(I)-Luc transgenic mouse model in which the luciferase gene is driven by bone-specific regulatory elements from the mouse collagen α1(I) gene for bioluminescent imaging of bone development and remodeling. We observed strong luciferase activity in skeletal tissues of Col(I)-Luc mice, and observed that the light intensity declined with postnatal bone development. Luciferase activity was enhanced in a tail bone repair model and we were able to monitor the process of ectopic bone formation induced by recombinant human bone morphogenetic protein 2 using bioluminescent imaging. We conclude that Col(I)-Luc transgenic mice can be applied in the field of bone tissue engineering for monitoring bone repair processes and for investigating osteoinductive molecules or scaffolds.

Adenovirus encoding human platelet-derived growth factor-B delivered to alveolar bone defects exhibits safety and biodistribution profiles favorable for clinical use

Platelet-derived growth factor (PDGF) gene therapy offers promise for tissue engineering of tooth-supporting alveolar bone defects. To date, limited information exists regarding the safety profile and systemic biodistribution of PDGF gene therapy vectors when delivered locally to periodontal osseous defects. The aim of this preclinical study was to determine the safety profile of adenovirus encoding the PDGF-B gene (AdPDGF-B) delivered in a collagen matrix to periodontal lesions. Standardized alveolar bone defects were created in rats, followed by delivery of matrix alone or containing AdPDGF-B at 5.5 x 10(8) or 5.5 x 10(9) plaque-forming units/ml. The regenerative response was confirmed histologically. Gross clinical observations, hematology, and blood chemistries were monitored to evaluate systemic involvement. Bioluminescence and quantitative polymerase chain reaction were used to assess vector biodistribution. No significant histopathological changes were noted during the investigation. Minor alterations in specific hematological and blood chemistries were seen; however, most parameters were within the normal range for all groups. Bioluminescence analysis revealed vector distribution at the axillary lymph nodes during the first 2 weeks with subsequent return to baseline levels. AdPDGF-B was well contained within the localized osseous defect area without viremia or distant organ involvement. These results indicate that AdPDGF-B delivered in a collagen matrix exhibits acceptable safety profiles for possible use in human clinical studies.

Musculoskeletal molecular imaging: a comprehensive overview

Molecular imaging permits non-invasive visualization and measurement of molecular and cell biology in living subjects, thereby complementing conventional anatomical imaging. Herein, we review the emerging application of molecular imaging for the study of musculoskeletal biology. Utilizing mainly bioluminescence and fluorescence techniques, molecular imaging has enabled in-vivo studies of (i) the activity of osteoblasts, osteoclasts, and hormones, (ii) the mechanisms of pathological cartilage and bone destruction, (iii) skeletal gene and cell therapy with and without biomaterial support, and (iv) the cellular processes in osteolysis and osteomyelitis. In these applications, musculoskeletal molecular imaging demonstrated feasibility for research in a myriad of musculoskeletal conditions ranging from bone fracture and arthritis to skeletal cancer. Importantly, these advances herald great potential for innovative clinical imaging in orthopedics, rheumatology, and oncology.

The ToI-beta transgenic mouse: a model to study the specific role of NF-kappaB in beta-cells

Type 1 diabetes is characterized by the infiltration of inflammatory cells into pancreatic islets of Langerhans, followed by the selective and progressive destruction of insulin-secreting beta-cells. Islet infiltrating leukocytes secrete cytokines including IL-1beta and IFN-gamma, which contribute to beta-cell death. In vitro evidence suggests that cytokine-induced activation of the transcription factor NF-kappaB is an important component of the signal triggering beta-cell apoptosis. To study the role of NF-kappaB in vivo we generated a transgenic mouse line expressing a degradation-resistant NF-kappaB protein inhibitor (DeltaNIkappaBalpha) and the luciferase gene, acting specifically in beta-cells, in an inducible and reversible manner, by using the tet-on regulation system. Using this new mouse model, termed the ToI-beta mouse (for Tet-Ondelta I kappaB in beta-cells) we have previously shown in vitro, that islets expressing the DeltaNIkappaBalpha protein were resistant to the deleterious effects of IL-1beta and IFN-gamma, as assessed by reduced NO production and beta-cell apoptosis. In vivo, a nearly complete protection against multiple low dose streptozocin-induced diabetes was observed, with reduced intra-islet lymphocytic infiltration. In the present study we demonstrate the tight regulated and reversible expression of the DeltaNIkappaBalpha transgene in the ToI-beta mouse model as well as the effect of its overexpression on glucose metabolism and insulin secretion. The results show a lack of effect of transgene induction on both in vivo glucose tolerance tests and in vitro islet insulin secretion and content. Furthermore, to prove the tight control of induction in the model, luciferase mediated light emission was only detected at constant levels in Dox-treated double transgenic mice or islets as well as in a model of islet transplantation. Upon removal of the inducing stimulus, complete reversal of both NF-kappaB inhibition and luciferase activity were observed. Together, our results show the ToI-beta mouse model to be a highly controlled and very accurate model for examining pancreatic beta-cell-specific temporal inhibition of NF-kappaB.

Cancer dormancy: lessons from a B cell lymphoma and adenocarcinoma of the prostate

Cancer dormancy delineates a situation in which residual tumor cells persist in a patient with no apparent clinical symptoms. Although the precise mechanisms underlying cancer dormancy have not been explained, experimental models have provided some insights into the factors that might be involved in the induction and maintenance of a tumor dormant state. The authors of the present chapter studied a murine B cell lymphoma that can be made dormant when interacting with antibodies directed against the idiotype on its immunoglobulin Ig receptor. This experimental model of antibody-induced dormancy enabled the isolation and characterization of dormant lymphoma cells. The results indicated that anti-Ig antibodies activate growth-inhibiting signals that induced cycle arrest and apoptosis. This process appeared to be balanced by the growth of the tumor cells such that the tumor did not expand. In contrast, antibodies against HER-2expressed on prostate adenocarcinoma (PAC) cells were not growth inhibitory. However, an immunotoxin (IT) prepared by conjugating HER-2 to the A-chain of ricin (RTA) was internalized by PAC cells, followed by induction of cycle arrest and apoptotic death. Infusion of HER-2-specific IT into PAC-bearing immunodeficient mice did not eradicate the tumor but retained it dormant over an extended period of time. Hence, certain aspects of signaling receptors expressed on cancer can be manipulated by antibodies to induce and maintain a tumor dormant state.

Expression of plasmid DNA in the salivary gland epithelium: novel approaches to study dynamic cellular processes in live animals

The ability to dynamically image cellular and subcellular structures in a live animal and to target genes to a specific cell population in a living tissue provides a unique tool to address many biological questions in the proper physiological context. Here, we describe a powerful approach that is based on the use of rat submandibular salivary glands, which offer the possibility to easily perform intravital imaging and deliver molecules from the oral cavity, and plasmid DNA, which offers the advantage of rapid manipulations. We show that, under different experimental conditions, a reporter molecule can be rapidly expressed in specific compartments of the glands: 1) in the intercalated ducts, when plasmid DNA is administered alone, and 2) in granular ducts, striated ducts, and, to a lesser extent, acini, when plasmid DNA is mixed with replication-deficient adenovirus subtype 5 particles. Remarkably, we also found that gene expression can be directed to acinar cells when plasmid DNA is administered during isoproterenol-stimulated exocytosis, suggesting a novel mechanism of plasmid internalization regulated by compensatory endocytosis. Finally, as a practical application of these strategies, we show how the expression of fluorescently tagged molecules enables the study of the dynamics of various organelles in live animals at a resolution comparable to that achieved in cell cultures.

The use of a synthetic oxygen carrier-enriched hydrogel to enhance mesenchymal stem cell-based bone formation in vivo

A major hurdle to surmount in bone-tissue engineering is ensuring a sufficient oxygen supply to newly forming tissue to avoid cell death or delayed development of osteogenic features. We hypothesized that an oxygen-enriched hydrogel scaffold would enhance tissue-engineered bone formation in vivo. To test this, we used a well-characterized mesenchymal stem cell (MSC) line, Tet-off BMP2 MSC, whose cells were engineered to express recombinant human bone morphogenetic protein-2. Cells were suspended in hydrogel supplemented with perfluorotributylamine (PFTBA) and implanted subcutaneously in an ectopic site, a radial bone defect, or a lumbar paravertebral muscle (mouse model of spinal fusion) in C3H/HeN mice. For controls, we used cells suspended in the same gel without PFTBA. In the ectopic site, there were significant increases in bone formation (2.5-fold increase), cell survival, and osteocalcin activity in the PFTBA-supplemented groups. PFTBA supplementation significantly increased structural parameters of bone in radial bone defects and triggered a significant 1.4-fold increase in bone volume in the spinal fusion model. We conclude that synthetic oxygen carrier supplementation of tissue-engineered implants enhances ectopic bone formation and yields better bone quality and volume in bone-repair and spinal fusion models, probably due to increased cell survival.

Herpes simplex virus delivery to orthotopic rectal carcinoma results in an efficient and selective antitumor effect

Cancer of the rectum poses a complex therapeutic challenge because of its proximity to adjacent organs and anal sphincters. The addition of radiotherapy before surgical resection has been shown to confer good survival rates while preserving sphincter function. Nevertheless, radiation is associated with significant side effects. On the basis of our previous work showing that herpes simplex virus type-1 (HSV-1) preferentially infects human colon cancer, we set out to examine the oncolytic effect of HSV-1 on orthotopic rectal tumors in mice. Two vectors were compared for oncolytic activity, HSV-1(Gbeta) with wild-type replication and an attenuated HSV-1 vector (HSV-G47Delta). Intratumoral injection of HSV-1(Gbeta) and HSV-G47Delta resulted in a significant reduction or disappearance of the tumors and increased survival of mice. Although the use of HSV-1(Gbeta) was associated with systemic toxicity, HSV-G47Delta appears to possess a selective oncolytic activity. Moreover, infection with HSV-G47Delta resulted in the activation of the double-stranded RNA-dependent protein kinase (PKR) pathway. A significant improvement in viral replication and the antitumor effect was observed when the PKR inhibitor 2-aminopurine was coadministered with HSV-G47Delta to the tumor. In conclusion, the efficacy of local delivery of HSV-G47Delta combined with a specific chemical inhibitor of antiviral activity points to a novel therapeutic modality for rectal cancer and other solid tumors.

T cell survival and function requires the c-Abl tyrosine kinase

C-Abl (Abl) regulates multiple cellular processes, including proliferation, survival, shape determination and motility, and participates in cellular responses to genotoxic and oxidative stress stimuli. Mice lacking Abl exhibit retarded growth, osteoporosis and defects in the immune system resulting in lymphopoenia and susceptibility to infections, leading to early death. To define the role of Abl in the regulation of adult T cells we ablated Abl exclusively in T cells by generating mice with floxed abl alleles and expressing an Lck-Cre transgene (Abl-T(-/-)). These mice exhibited thymic atrophy and abnormally reduced T cell numbers in the periphery. The thymic atrophy was caused by increased susceptibility of thymocytes to cell death. Importantly, Abl deficient T cells displayed abnormally reduced response to mitogenic stimulation in vitro. Consequently, Abl-T(-/-) mice exhibited impaired ability to reject syngeneic tumor, to induce T-mediated tumor cell killing, and to generate anti-tumor antibodies. These results demonstrate a cell-autonomous role for Abl in T cell function and survival.

Molecular-genetic imaging based on reporter gene expression

Molecular imaging includes proteomic, metabolic, cellular biologic process, and genetic imaging. In a narrow sense, molecular imaging means genetic imaging and can be called molecular-genetic imaging. Imaging reporter genes play a leading role in molecular-genetic imaging. There are 3 major methods of molecular-genetic imaging, based on optical, MRI, and nuclear medicine modalities. For each of these modalities, various reporter genes and probes have been developed, and these have resulted in successful transitions from bench to bedside applications. Each of these imaging modalities has its unique advantages and disadvantages. Fluorescent and bioluminescent optical imaging modalities are simple, less expensive, more convenient, and more user friendly than other imaging modalities. Another advantage, especially of bioluminescence imaging, is its ability to detect low levels of gene expression. MRI has the advantage of high spatial resolution, whereas nuclear medicine methods are highly sensitive and allow data from small-animal imaging studies to be translated to clinical practice. Moreover, multimodality imaging reporter genes will allow us to choose the imaging technologies that are most appropriate for the biologic problem at hand and facilitate the clinical application of reporter gene technologies. Reporter genes can be used to visualize the levels of expression of particular exogenous and endogenous genes and several intracellular biologic phenomena, including specific signal transduction pathways, nuclear receptor activities, and protein-protein interactions. This technique provides a straightforward means of monitoring tumor mass and can visualize the in vivo distributions of target cells, such as immune cells and stem cells. Molecular imaging has gradually evolved into an important tool for drug discovery and development, and transgenic mice with an imaging reporter gene can be useful during drug and stem cell therapy development. Moreover, instrumentation improvements, the identification of novel targets and genes, and imaging probe developments suggest that molecular-genetic imaging is likely to play an increasingly important role in the diagnosis and therapy of cancer.

Delivery of DNA into muscle for treating systemic diseases: advantages and challenges

An efficient and safe method to deliver DNA in vivo is a requirement for several purposes, such as the study of gene function and gene therapy applications. Among the different nonviral delivery methods currently under investigation, in vivo DNA electrotransfer has proven to be one of the most efficient and simple methods. This technique is a physical method of gene delivery consisting of a local application of electric pulses after injection of DNA. This technique can be applied to almost any tissue of a living animal, including tumors, skin, liver, kidney, artery, retina, cornea, or even brain, but the focus of this review will be on electrotransfer of plasmid DNA into skeletal muscle and its possible therapeutic uses for systemic diseases. Skeletal muscle is a good target for electrotransfer of DNA because of the following features: a large volume of easily accessible tissue, an endocrine organ capable of expressing several local and systemic factors, and muscle fibers as postmitotic cells have a long lifespan, which allows long-term gene expression. In this review, we will describe the main characteristics of DNA electrotransfer, including toxicity and safety issues related to this technique. We will focus on the important possible therapeutic applications of electrotransfer for systemic diseases demonstrated in animal models in the recent years, in the fields of monogenic diseases, tissue-specific diseases, metabolic disorders, immune-system-related diseases, and cancer. Finally, we will discuss the advantages and challenges of this technique.

The Pharmacology of Radiolabeled Cationic Antimicrobial Peptides

Cationic antimicrobial peptides are good candidates for new diagnostics and antimicrobial agents. They can rapidly kill a broad range of microbes and have additional activities that have impact on the quality and effectiveness of innate responses and inflammation. Furthermore, the challenge of bacterial resistance to conventional antibiotics and the unique mode of action of antimicrobial peptides have made such peptides promising candidates for the development of a new class of antibiotics. This review focuses on antimicrobial peptides as a topic for molecular imaging, infection detection, treatment monitoring and additionally, displaying microbicidal activities. A scintigraphic approach to studying the pharmacokinetics of antimicrobial peptides in laboratory animals has been developed. The peptides were labeled with technetium-99m and, after intravenous injection into laboratory animals, scintigraphy allowed real-time, whole body imaging and quantitative biodistribution studies of delivery of the peptides to the various body compartments. Antimicrobial peptides rapidly accumulated at sites of infection but not at sites of sterile inflammation, indicating that radiolabeled cationic antimicrobial peptides could be used for the detection of infected sites. As the number of viable micro-organisms determines the rate of accumulation of these peptides, radiolabeled antimicrobial peptides enabled to determine the efficacy of antibacterial therapy in animals to be monitored as well to quantify the delivery of antimicrobial peptides to the site of infection. The scintigraphic approach provides to be a reliable method for investigating the pharmacokinetics of small cationic antimicrobial peptides in animals and offers perspective for diagnosis of infections, monitoring antimicrobial therapy, and most important, alternative antimicrobial treatment infections with multi-drug resistant micro-organisms in humans.

Direct, continuous monitoring of air pollution by transgenic sensor mice responsive to halogenated and polycyclic aromatic hydrocarbons

BACKGROUND

The aryl hydrocarbon receptor (AhR, also called the dioxin receptor) plays crucial roles in toxicologic responses of animals to environmental pollutants, especially to halogenated and polycyclic aromatic hydrocarbons. To achieve direct, continuous risk assessment of air pollution using biological systems, we generated transgenic sensor mice that produce secreted alkaline phosphatase (SEAP) under the control of AhR.

METHODS

To characterize responses of the mice to AhR agonists, sensor mice were orally administered 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), 3-methylcholanthrene (3MC), benzo[a]pyrene (B[a]P), or beta-naphthoflavone (BNF), and serum levels of SEAP were evaluated. To monitor air pollution caused by cigarette smoke, we placed the mice each day in an experimental smoking room, and evaluated activity of serum SEAP for up to 4 days. Activation of AhR in individual organs was also examined by reverse transcription-polymerase chain reaction (RT-PCR) analysis of SEAP.

RESULTS

In response to oral exposure to TCDD, sensor mice exhibited dramatic and sustained activation of AhR. The mice also responded sensitively to 3MC, B[a]P, and BNF. Activation of AhR was dose dependent, and the liver was identified as the main responding organ. After exposure to the smoking environment, sensor mice consistently exhibited transient, reversible activation of AhR. RT-PCR analysis of SEAP revealed that activation of AhR occurred predominantly in the lung.

CONCLUSION

We are the first laboratory to demonstrate successfully direct, comprehensive monitoring of air pollution using genetically engineered mammals. The established system would be useful for real risk assessment of halogenated and polycyclic aromatic hydrocarbons in the air, especially in smoking environments.

Carbamoylphosphonate matrix metalloproteinase inhibitors 6: cis-2-aminocyclohexylcarbamoylphosphonic acid, a novel orally active antimetastatic matrix metalloproteinase-2 selective inhibitor--synthesis and pharmacodynamic and pharmacokinetic analysis

cis-2-Aminocyclohexylcarbamoylphosphonic acid ( cis-ACCP) was evaluated in vitro and in two in vivo cancer metastasis models. It reduced metastasis formation in mice by approximately 90% when administered by a repetitive once daily dosing regimen of 50 mg/kg via oral or intraperitoneal routes and was nontoxic up to 500 mg/kg, following intraperitoneal administration daily for two weeks. Pharmacokinetic investigation of cis-ACCP in rats revealed distribution restricted into the extracellular fluid, which is the site of action for the antimetastatic activity and rapid elimination ( t 1/2 approximately 19 min) from blood. Sustained and prolonged absorption ( t 1/2 approximately 126 min) occurred via paracellular mechanism along the small and large intestine with overall bioavailability of 0.3%. The in vivo concentrations of cis-ACCP in the blood in rats was above the minimal concentration for antimetastatic/MMP-inhibitory activity, thus explaining the prolonged action following once daily administration. Finally, 84% of the intravenously administered cis-ACCP to rats was excreted intact in the urine.

Bioluminescent imaging in bone

Monitoring gene expression in vitro and in vivo, is crucial when analyzing osteogenesis and developing effective bone gene therapy protocols. Until recently, molecular analytical tools were only able to detect protein expression either in vitro or in vivo. These systems include histology and immunohistochemistry, fluorescent imaging, PET (micro-PET), CT (micro-CT), and bioluminescent imaging. The last is the only system to date that can enable efficient quantitative monitoring of gene expression both in vitro and in vivo. Effective bioluminescent imaging in bone can be achieved by using transgenic mice harboring the luciferase reporter gene, downstream of an osteogenesis specific promoter. The aim of this chapter is to comprehensively describe the various protocols needed for the detection of bioluminescence in bone development and repair.

In vivo imaging in humanized mice

The radiological modalities that are currently utilized as critical components in clinical medicine have also been adapted to small-animal imaging, among which are ultrasound imaging, X-ray computerized tomography (CT), magnetic resonance imaging (MRI), positron emission tomography (PET), and single-photon emission computed tomography (SPECT). Optical imaging techniques such as bioluminescence imaging (BLI) and fluorescence imaging (FLI) are approaches that are commonly used in small animals. Longitudinal surveys of living (i.e., nonsacrificed) animal models with these modalities provide some clues for the development of clinical applications. The techniques are absolutely essential for translational research. However, there are currently few tools available with sufficient spatial or temporal resolution ideal for all experimental studies. In this chapter, we provide a rationale and techniques for visualizing target cells in living small animals and an overview of the advantages and limitations of current imaging technology. Finally, we introduce a humanized mouse and a novel in vivo imaging system that we have developed. We also discuss real-time observations of reconstructs and clinical manifestations.

Monitoring of disease progression by bioluminescence imaging and magnetic resonance imaging in an animal model of hematologic malignancy

OBJECTIVE

We evaluated disease progression in a mouse model of a hematologic malignancy using a multimodality approach that included bioluminescence imaging (BLI) and magnetic resonance imaging (MRI). We aimed to examine the feasibility and capability of BLI and MRI and to establish techniques for quantitative assessment of disease severity.

METHODS

Mice were inoculated intravenously with Ba/F3 cells transduced with firefly luciferase and p190 BCR-ABL genes. Disease progression in a given mouse was observed longitudinally by in vivo BLI and MRI (n = 5). Imaging studies, including in vivo BLI and MRI of living mice and ex vivo BLI of excised organs, were also performed at various time points (n = 4, 3, 4, and 4 at 1, 2, 3, and 4 weeks after cell inoculation).

RESULTS

Longitudinal studies allowed the assessment of disease progression for each mouse, and an approximately 4-log increase in whole-body BLI signal was shown after initial detection. MRI demonstrated progressive hepatosplenomegaly and growth of hepatic nodules. Ex vivo BLI demonstrated proliferation of the implanted cells in various organs including bone marrow, and the signal for each organ increased with time (Spearman's rank correlation coefficient, R = 0.831-0.914) and as the whole-body signal, observed by in vivo BLI, increased (R = 0.921-0.982). MRI measurements of liver and spleen volumes were shown to have excellent accuracy and volume increases significantly correlated with the BLI organ signal (liver, R = 0.875; spleen, R = 0.971).

CONCLUSION

BLI and MRI allow repeated assessment of disease progression in a mouse model of a hematologic malignancy and provide quantitative markers of disease severity. BLI and MRI measurements reveal different details of disease progression and may play complementary roles in comprehensive assessment.

Ultrasound-based nonviral gene delivery induces bone formation in vivo

Nonviral gene delivery is a promising, safe, therapeutic tool in regenerative medicine. This study is the first to achieve nonviral, ultrasound-based, osteogenic gene delivery that leads to bone tissue formation, in vivo. We hypothesized that direct in vivo sonoporation of naked DNA encoding for the osteogenic gene, recombinant human bone morphogenetic protein-9 (rhBMP-9) would induce bone formation. A luciferase plasmid (Luc), encoding rhBMP-9 or empty pcDNA3 vector mixed with microbubbles, was injected into the thigh muscles of mice. After injection, noninvasive sonoporation was applied. Luc activity was monitored noninvasively, and quantitatively using bioluminescence imaging in vivo, and found for 14 days with a peak expression on day 7. To examine osteogenesis in vivo, rhBMP-9 plasmid was sonoporated into the thigh muscles of transgenic mice that express the Luc gene under the control of a human osteocalcin promoter. Following rhBMP-9 sonoporation, osteocalcin-dependent Luc expression lasted for 24 days and peaked on day 10. Bone tissue was formed in the site of rhBMP-9 delivery, as was shown by micro-computerized tomography and histology. The sonoporation method was also compared with previously developed electrotransfer-based gene delivery and was found significantly inferior in its efficiency of gene delivery. We conclude that ultrasound-mediated osteogenic gene delivery could serve as a therapeutic solution in conditions requiring bone tissue regeneration after further development that will increase the transfection efficiency.

Simian virus 40 vectors for pulmonary gene therapy

Background

Sepsis remains the leading cause of death in critically ill patients. One of the primary organs affected by sepsis is the lung, presenting as the Acute Respiratory Distress Syndrome (ARDS). Organ damage in sepsis involves an alteration in gene expression, making gene transfer a potential therapeutic modality. This work examines the feasibility of applying simian virus 40 (SV40) vectors for pulmonary gene therapy.

Methods

Sepsis-induced ARDS was established by cecal ligation double puncture (2CLP). SV40 vectors carrying the luciferase reporter gene (SV/luc) were administered intratracheally immediately after sepsis induction. Sham operated (SO) as well as 2CLP rats given intratracheal PBS or adenovirus expressing luciferase served as controls. Luc transduction was evaluated by in vivo light detection, immunoassay and luciferase mRNA detection by RT-PCR in tissue harvested from septic rats. Vector abundance and distribution into alveolar cells was evaluated using immunostaining for the SV40 VP1 capsid protein as well as by double staining for VP1 and for the surfactant protein C (proSP-C). Immunostaining for T-lymphocytes was used to evaluate the cellular immune response induced by the vector.

Results

Luc expression measured by in vivo light detection correlated with immunoassay from lung tissue harvested from the same rats. Moreover, our results showed vector presence in type II alveolar cells. The vector did not induce significant cellular immune response.

Conclusion

In the present study we have demonstrated efficient uptake and expression of an SV40 vector in the lungs of animals with sepsis-induced ARDS. These vectors appear to be capable of in vivo transduction of alveolar type II cells and may thus become a future therapeutic tool.

Long term expression of bicistronic vector driven by the FGF-1 IRES in mouse muscle

Background

Electrotransfer of plasmid DNA into skeletal muscle is a promising strategy for the delivery of therapeutic molecules targeting various muscular diseases, cancer and lower-limb ischemia. Internal Ribosome Entry Sites (IRESs) allow co-expression of proteins of interest from a single transcriptional unit. IRESs are RNA elements that have been found in viral RNAs as well as a variety of cellular mRNAs with long 5' untranslated regions. While the encephalomyocarditis virus (EMCV) IRES is often used in expression vectors, we have shown that the FGF-1 IRES is equally active to drive short term transgene expression in mouse muscle. To compare the ability of the FGF-1 IRES to drive long term expression against the EMCV and FGF-2 IRESs, we performed analyses of expression kinetics using bicistronic vectors that express the bioluminescent renilla and firefly luciferase reporter genes. Long term expression of bicistronic vectors was also compared to that of monocistronic vectors. Bioluminescence was quantified ex vivo using a luminometer and in vivo using a CCD camera that monitors luminescence within live animals.

Results

Our data demonstrate that the efficiency of the FGF-1 IRES is comparable to that of the EMCV IRES for long term expression of bicistronic transgenes in mouse muscle, whereas the FGF-2 IRES has a very poor activity. Interestingly, we show that despite the global decrease of vector expression over time, the ratio of firefly to renilla luciferase remains stable with bicistronic vectors containing the FGF-1 or FGF-2 IRES and is slightly affected with the EMCV IRES, whereas it is clearly unstable for mixed monocistronic vectors. In addition, long term expression more drastically decreases with monocistronic vectors, and is different for single or mixed vector injection.

Conclusion

These data validate the use of bicistronic vectors rather than mixed monocistronic vectors for long term expression, and support the use of the FGF-1 IRES. The use of a cellular IRES over one of viral origin is of particular interest in the goal of eliminating viral sequences from transgenic vectors. In addition, the FGF-1 IRES, compared to the EMCV IRES, has a more stable activity, is shorter in length and more flexible in terms of downstream cloning of second cistrons. Finally, the FGF-1 IRES is very attractive to develop multicistronic expression cassettes for gene transfer in mouse muscle.

Review: gene- and stem cell-based therapeutics for bone regeneration and repair

Many clinical conditions require regeneration or implantation of bone. This is one focus shared by neurosurgery and orthopedics. Current therapeutic options (bone grafting and protein-based therapy) do not provide satisfying solutions to the problem of massive bone defects. In the past few years, gene- and stem cell-based therapy has been extensively studied to achieve a viable alternative to current solutions offered by modern medicine for bone-loss repair. The use of adult stem cells for bone regeneration has gained much focus. This unique population of multipotential cells has been isolated from various sources, including bone marrow, adipose, and muscle tissues. Genetic engineering of adult stem cells with potent osteogenic genes has led to fracture repair and rapid bone formation in vivo. It is hypothesized that these genetically modified cells exert both an autocrine and a paracrine effects on host stem cells, leading to an enhanced osteogenic effect. The use of direct gene delivery has also shown much promise for in vivo bone repair. Several viral and nonviral methods have been used to achieve substantial bone tissue formation in various sites in animal models. To advance these platforms to the clinical setting, it will be mandatory to overcome specific hurdles, such as control over transgene expression, viral vector toxicity, and prolonged culture periods of therapeutic stem cells. This review covers a prospect of cell and gene therapy for bone repair as well as some very recent advancements in stem cell isolation, genetic engineering, and exogenous control of transgene expression.