Development of endogenous beta-galactosidase and autofluorescence in rat brain microvessels: implications for cell tracking and gene transfer studies

Embedding of bone samples in methylmethacrylate: a suitable method for tracking LacZ mesenchymal stem cells in skeletal tissues

Considerable research has been focused on the use of bone marrow-derived mesenchymal stem cells (MSCs) for the repair of non-unions and bone defects. To date, the question of whether transplanted MSCs survive and engraft within newly formed tissue remains unresolved. The development of an easy and reliable method that would allow cell fate monitoring in transplant recipients is a pressing concern for the field of tissue engineering. To demonstrate the presence of transplanted cells in newly formed bone, we established a xenograft nude rat model allowing the detection of murine LacZ MSCs in vivo. MSCs were isolated from transgenic lacZ mice, seeded onto bioabsorbable collagen sponges, and transplanted to repair a calvarial defect in nude rats. As a preliminary step, the histological procedure was adapted to optimize the detection of LacZ cells in bone tissue embedded in methylmethacrylate (MMA). Four fixatives and four fixation times were evaluated. Among all the fixatives tested, 2% formaldehyde/0.2% glutaraldehyde at 4C for 4 days gave the best results for X-gal staining at pH 7.4 on both cell cultures and bone explants. All fixatives were effective for immunodetection of beta-gal. In the chimeric LacZ/nude rat animal model, MSCs were detected in vivo for up to 4 weeks after implantation and contributed to the repair and the neovascularization of the bone defect. LacZ is a suitable phenotypic marker to track MSCs in skeletal tissues embedded in MMA.

Percutaneous transplantation of genetically-modified autologous fibroblasts in the rabbit femoral artery: a novel approach for cardiovascular gene therapy

OBJECTIVE

Arterial cell and gene therapies are promising strategies for the treatment of cardiovascular diseases; however, the optimal cell type and delivery technique for such treatment remain to be determined. The aim of the present study was to design a new approach for arterial cell and gene therapy in which genetically modified autologous skin fibroblasts are percutaneously delivered in stented rabbit femoral arteries in vivo.

METHODS

Autologous skin fibroblasts underwent in vitro transfection with the cationic lipid FuGene and plasmids expressing the human form of the tissue inhibitor of metalloproteinase (hTIMP-1) or nls-LacZ reporter genes.

RESULT

Transfection efficiency was about 50% and there were high levels of hTIMP-1 secretion up to 14 days after gene transfer. We demonstrated the feasibility of in vivo percutaneous transplantation of fluorescent fibroblasts in the rabbit femoral artery. Results were confirmed by scanning electron microscopy. In vivo local delivery of hTIMP-1-expressing fibroblasts in stented femoral arteries also resulted in high-levels of hTIMP-1 secretion ex vivo for 7 days. Fibroblast transplantation resulted in a modest increase in intimal hyperplasia at the target site, which was reversed with hTIMP-1-transfected fibroblasts.

CONCLUSION

Percutaneous transplantation of genetically modified autologous fibroblasts could be used as a cellular platform for locoregional secretion of therapeutic proteins to treat either specific arterial diseases or the diseased organ (eg, the heart) supplied by the target artery.

CLINICAL RELEVANCE

Cell and gene therapies are potential new treatments for cardiovascular diseases. We demonstrated that autologous fibroblasts could be easily harvested from a skin biopsy specimen, genetically modified in vitro with nonviral vectors, and percutaneously seeded in vivo in rabbit femoral arteries, leading to locoregional secretion of abundant amounts of recombinant proteins. This new approach has important advantages over alternative approaches that use endothelial cells, viral vectors, and intraoperative cell delivery. Clinical applications may include local treatment of atherosclerotic plaques or aneurysms and also treatment of the diseased organs supplied by the target artery (eg, ischemic or failing heart).

An optimized protocol for detection of E. coli beta-galactosidase in lung tissue following gene transfer

Staining by 5-bromo-4-chloro-3-indolyl-beta-D: -galactopyranoside (X-gal) typically detects activity of E. coli beta-galactosidase (beta-gal) in transduced tissues that express the LacZ reporter gene. In lung tissue from mice that received beta-galactosidase-expressing adeno-associated virus (AAV) vectors via intranasal inhalation, we observed only a low frequency of positive cells after X-gal staining in contrast to other reporter genes, such as alkaline phosphatase or green fluorescent protein. In this study, we systematically tested a number of parameters to improve the sensitivity of X-gal staining in lungs transduced with beta-galactosidase-expressing AAV2/5 vectors. We observed that the use of nuclear-targeted LacZ instead of cytoplasmic LacZ as the reporter gene substantially increases the number of positive cells after X-gal staining. The pH of the staining solution determines staining sensitivity and background staining with pH 7.0 resulting in high sensitivity and no background levels. Glutaraldehyde at 0.2% or 0.5% in PBS as fixative provides optimal results for X-gal staining. The alternative substrate, Bluo-gal, showed no improvement compared with X-gal but instead caused nonspecific background staining. We further stained intact fixed lungs with X-gal and processed them for paraffin embedding or cryosectioning, resulting in equal staining intensities. However, en bloc staining of intact tissues resulted in the absence of positive cells within deeper-located lung areas.

Anti-monocyte chemoattractant protein-1 gene therapy protects against focal brain ischemia in hypertensive rats

Monocyte chemoattractant protein-1 (MCP-1) is expressed in the ischemic cortex after focal brain ischemia and appears to exacerbate ischemic damage. The authors examined the effect of gene transfer of dominant negative MCP-1, called 7ND, 90 minutes after induction of focal brain ischemia in hypertensive rats. Adenoviral vectors encoding mutant MCP-1 (Ad7ND; n = 11), or Escherichia coli beta-galactosidase (AdlacZ; n = 17) as control were injected into the lateral ventricle of male spontaneously hypertensive rats. Both AdlacZ (n = 12) and Ad7ND (n = 6) administration provided transgene expression as early as 6 hours after injection and the expression further increased on day 1, followed by a sustained detection on day 5. Five days after ischemia, infarct volume (75 +/- 13 mm, n = 5, mean +/- SD) significantly reduced to 72% of control (104 +/- 22 mm3, n = 5, P < 0.05) by 7ND gene transfer. Numbers of leukocytes in the vessels (48.3 +/- 32.9/cm2) and macrophage/monocyte infiltration (475.2 +/- 125.5/mm2) of the infarct area in the Ad7ND group were significantly less than those measured in the AdlacZ group (143.8 +/- 72.1/cm2 and 671.8 +/- 125.5/mm2, P < 0.05, respectively). In summary, the postischemic gene transfer of dominant negative MCP-1 attenuated the infarct volume and infiltration of inflammatory cells, suggesting potential usefulness of the anti-MCP-1 gene therapy.

Brain ischemia augments exo-focal transgene expression of adenovirus-mediated gene transfer to ependyma in hypertensive rats

The ependyma is one of the feasible targets for gene transfer to the brain. Using two different replication-deficient recombinant adenoviral vectors, AdCMVbetaGal or AdRSVIL10, we examined effects of cortical brain ischemia on transgene expression in the ependyma after administration of the vector into the lateral ventricle of spontaneously hypertensive rats (SHR). Expression of the reporter gene lacZ at the lateral ventricle was detected by histochemistry for semiquantitative scoring or by biochemical assay for quantitative analysis. Ependymal cells in the ventricles expressed the transgene as early as 6 h after gene transfer in both sham treatment and ischemia treatment. In the sham treatment, the expression peaked at 12 h and slowly decreased toward day 4 and day 7. However, transgene expressions in the ischemic brain on day 4 and day 7 were significantly higher than sham treatment. In the biochemical assay, beta-galactosidase activity detected on day 4 at the periventricular area of the ischemic group (37 +/- 9 mU/mg protein) was significantly greater than that of the sham group (12 +/- 4, P < 0.01). In the enzyme-linked immunosorbent assay for gene transfer of interleukin-10 (IL-10), IL-10 in the cerebrospinal fluid (CSF) of the ischemic group (11,633 +/- 4322 pg/ml) was significantly greater than that in the sham group (2460 +/- 1486, P < 0.05) on day 5. These results suggest that transgene expression in the exo-focal remote area of ependyma is augmented by cortical ischemia, and the ependyma may be a promising target of gene transfer of brain ischemia.

Adenovirus-mediated gene transfer to ischemic brain: ischemic flow threshold for transgene expression

BACKGROUND AND PURPOSE

Gene therapy may be a promising approach for treatment of brain ischemia, although protein synthesis is generally inhibited in ischemic conditions. Our goal in this study was to examine effects of brain ischemia on transgene expression of adenovirus-mediated gene transfer to ischemic brain.

METHODS

Brain ischemia was produced by photochemical occlusion of the distal middle cerebral artery of spontaneously hypertensive rats (n=15). Ninety minutes after ischemia, adenoviral vectors encoding bacterial beta-galactosidase were injected into ipsilateral (nonischemic [I-n], peri-ischemic [I-p], and ischemic core [I-c] areas) and contralateral parietal (C) cortices. Cerebral blood flow before and during ischemia at each injected area was measured by laser-Doppler flowmetry. Expression of transgene was detected by histochemistry for semiquantitative scoring or by biochemical assay for quantitative analysis.

RESULTS

Blood flow to the cortex decreased to 72+/-10% (mean+/-SEM) at I-n, 41+/-6% at I-p, and 23+/-3% at I-c after 10 minutes of ischemia. Expression of the reporter gene was consistently detected at C and I-n at each survival period. The semiquantitative score for transgene expression decreased according to severity of ischemia (C, 2.3; I-n, 2.6; I-p, 1.1; I-c, 0.3; mean values). beta-Galactosidase activity detected by chemiluminescent assay revealed that the values (mean+/-SEM) in the ischemic area (I-p, 15.9+/-9.2 mU/mg protein; I-c, 1.3+/-0.5) were significantly smaller than that of the nonischemic area (C, 45.4+/-6.9). Analysis of cerebral blood flow at I-p revealed that cerebral blood flow threshold for transgene expression was approximately 40% of the resting value.

CONCLUSIONS

Adenovirus-mediated gene transfer into the ischemic brain provided effective expression of transgene at the nonischemic and peri-ischemic areas. Gene transfer to the ischemic brain may be a promising approach for treatment of ischemic penumbra.

The X-gal caution in neural transplantation studies

Cell transplantation into host brain requires a reliable cell marker to trace lineage and location of grafted cells in host tissue. The lacZ gene encodes the bacterial (E. coli) enzyme beta-galactosidase (beta-gal) and is commonly visualized as a blue intracellular precipitate following its incubation with a substrate, "X gal," in an oxidation reaction. LacZ is the "reporter gene" most commonly employed to follow gene expression in neural tissue or to track the fate of transplanted exogenous cells. If the reaction is not performed carefully-with adequate optimization and individualization of various parameters (e.g.. pH, concentration of reagents, addition of chelators, composition of fixatives) and the establishment of various controls--then misleading nonspecific background X-gal positivity can result, leading to the misidentification of cells. Some of this background results from endogenous nonbacterial beta-gal activity in discrete populations of neurons in the mammalian brain; some results from an excessive oxidation reaction. Surprisingly, few articles have empha sized how to recognize and to eliminate these potential confounding artifacts in order to maximize the utility and credibility of this histochemical technique as a cell marker. We briefly review the phenomenon in general, discuss a specific case that illustrates how an insufficiently scrutinized X-gal positivity can be a pitfall in cell transplantation studies, and then provide recommendations for optimizing the specificity and reliability of this histochemical reaction for discerning E. coli beta-gal activity.

Optimizing fluorescent labeling of endothelial cells for tracking during long-term studies of autologous transplantation

BACKGROUND

The fluorescent marker PKH26 has been demonstrated to be useful for the tracking of endothelial cells in short-term studies; however, the optimal labeling conditions for long-term implants have not been determined. This study was designed to evaluate the effects of PKH26 on endothelial cell proliferation and to identify labeling conditions that would yield the greatest fluorescence over time without adversely affecting cell viability.

MATERIALS AND METHODS

Canine jugular vein endothelial cells (CJVECs) were labeled with 0. 04 microM PKH26. Proliferation of labeled and control cells was assessed for 8 consecutive days by [(3)H]thymidine uptake. In a second experiment, CJVECs were labeled at concentrations of 0, 5, 8, 10, and 20 micromol/L. Cells were maintained in culture for 60 days. The fluorescence intensity of each cell population was measured using two techniques. At baseline and at 60 days, fluorescence was measured using a fluorescence-activated cell sorter. On days 14, 28, 45, and 60 fluorescence was measured by constructing gray-scale histograms from photomicrographs taken of each flask under rhodamine illumination. Mean viable cell number for each concentration was determined after 60 days.

RESULTS

In the first experiment, PKH26-labeled and unlabeled CJVECs demonstrated nearly identical growth curves, suggesting that PKH26 had no adverse effect on proliferation. In the second experiment, after 60 days, the 10 and 20 microM groups displayed greater fluorescence by histogram than the 0, 5, or 8 microM groups; however, they were not significantly different from each other (mean intensity 8.2 vs 9.1, P > 0.05, Student-Newman-Keuls test for multiple comparisons). Over 60 days, the cells labeled with 20 microM PKH26 experienced the only significant decrease in viable cells compared to the unlabeled group (5.5 x 10(5) vs 9.6 x 10(5) cells/flask, P < 0.05). Importantly, we observed no significant differences in cell number between the 10 microM group and the lower concentrations compared to the unlabeled cells (P > 0.05).

CONCLUSIONS

We conclude that a concentration of 10 microM PKH26 provides the optimal labeling condition for endothelial cells when long-term tracking is desired.

Pattern of localization of primitive hematopoietic cells in vivo using a novel mouse model

Bone marrow transplantation is increasingly used as a treatment for numerous immunologic, hematologic, and malignant disorders. However, the mechanism by which transplanted hematopoietic stem cells are engrafted is not completely understood. Many traditional techniques have been used to study the engraftment of transplanted stem cells. Most of these methods are ex vivo and, in some cases, donor cells must be modified to enable detection. We describe a novel alternative for identifying unmodified primitive donor cells in a murine host. This mouse model is based on the differential capacity of adenine phosphoribosyltransferase (APRT)-positive and APRT-negative cells to sequester and incorporate radiolabeled adenine. Aprt is the gene encoding the adenine phosphoribosyltransferase purine salvage enzyme and has been ablated in 129sv mice. Following the injection of APRT-positive c-kit-positive enriched hematopoietic cells into syngeneic, sublethally irradiated APRT-deficient mice, engrafted cells and their presumptive progeny were successfully tracked by polymerase chain reaction. Their presence also was visualized by autoradiography of paraffin-embedded tissue sections. APRT-positive c-kit-positive enriched cells were detected in the bone marrow, spleen, lung, and thymus of nonirradiated mice. Donor cells and their progeny were more widely distributed in tissues of sublethally irradiated mice than of their nonirradiated counterparts, demonstrating that the pattern of localization of c-kit-positive enriched cells differs between nonirradiated and sublethally irradiated syngeneic recipients. The Aprt mouse model provides a sensitive method for further studying the mechanism of engraftment of unmodified donor hematopoietic cells in relation to the tissue architecture of the recipient.

Histochemical discrimination of endogenous mammalian beta-galactosidase activity from that resulting from lac-Z gene expression

Minces of several organs from the transgenic mouse ROSAbeta-gal 26 (ROSA-26), which robustly expresses bacterial lac-Z in most tissues, were exposed to 4-bromo-5-chloro-3-indoyl-beta-D-galactopyrosanide (X-gal) at pH ranging from 7.5 to 9.5 to determine the optimal pH for in situ demonstration of bacterial beta-galactosidase activity (neutral pH optimum) while minimizing detection of potentially confounding endogenous mammalian beta-galactosidase (acidic pH optimum). Similar studies were performed with organ minces from C57BL/6 mice, Sprague-Dawley rats, New Zealand white rabbits, and macaques to confirm the effect of pH on minimizing detection of endogenous mammalian beta-galactosidase. In all organs evaluated; heart, liver, spleen, kidney, brain, and skeletal muscle, endogenous beta-galactosidase activity was rarely detected following incubation at pH greater than 7.5. In contrast, bacterial beta-galactosidase activity in the ROSA-26 mice was strongly detected in organ minces following incubation at pH 8.0-9.0. These findings are similar to previous observations we have made in lung minces and confirm that a simple alteration of a commonly used histochemical technique for detecting in situ beta-galactosidase activity, raising the reaction buffer pH to weakly alkaline range, can reliably distinguish between endogenous activity and that resulting from exogenous bacterial gene expression.

Gene transfer in astrocytes: comparison between different delivering methods and expression of the HIV-1 protein Nef

To identify a good system to introduce foreign genes into normal and tumoral astrocytes, we studied the efficiency of two chemical methods, calcium phosphate precipitation and lipofection, and of a viral-mediated transfer by a vector derived from the highly attenuated modified vaccinia virus Ankara (MVA). Using the beta-galactosidase (beta-gal) gene (lacZ) as reporter, we searched for optimal experimental conditions to obtain an efficient gene transfer into human embryonic and neonatal rat astrocytes and into a human astrocytoma cell line (U373 MG). The beta-gal protein production was evaluated by cytochemical staining and enzymatic activity assay. Among chemical methods, lipofection was the most efficient system to transfect astrocytes in providing up to 60% of beta-gal-positive cells in all the cell types analyzed. MVA infection also proved to be an efficient system to introduce heterologous genes into human embryonic astrocytes that appeared 80-100% positive 48-96 hr after an infection at a multiplicity of 1-10. In contrast, only a limited infection was observed with rat astrocytes, human astrocytoma cells, and human leptomeningeal cells. A recombinant MVA vector expressing the human immunodeficiency virus-1 (HIV-1) regulatory protein Nef was used to transfect human embryonic astrocytes, and the resulting Nef expression was compared with that detected after lipofection in the same cells. By Western blot analysis, Nef expression was observed in human astrocytes 24-96 hr after infection and was similar to that present in stably HIV-1-infected astrocytoma cells. Lipofection resulted in lower Nef expression. In spite of these promising results, the negative effects of MVA infection on cell viability and the possibility that a productive infection occurs in human embryonic astrocytes limit the use of this vector for gene delivery in developmentally immature human glial cells.

Improvement of relaxation in an atherosclerotic artery by gene transfer of endothelial nitric oxide synthase

Gene transfer with replication-deficient adenovirus is a useful tool to study vascular biology. We have reported that overexpression of endothelial nitric oxide (NO) in carotid arteries from normal rabbits augments vasorelaxation mediated by NO. In this study, we tested the hypothesis that adenovirus-mediated gene transfer of endothelial nitric oxide synthase (eNOS) improves impaired relaxation of atherosclerotic vessels. We used 2 replication-deficient adenoviruses: AdeNOS, which carries cDNA for eNOS, and Adbetagal, which expresses beta-galactosidase. Common carotid arteries from 10 New Zealand White (NZW; plasma cholesterol, 79+/-13 mg/dL) and 10 Watanabe heritable hyperlipidemic (WHHL; plasma cholesterol, 452+/-39 mg/dL) rabbits were incubated in organ culture with AdeNOS, Adbetagal, or vehicle alone. Carotid arteries from WHHL rabbits had mild to moderate atherosclerotic lesions. Histochemical staining for beta-galactosidase and immunohistochemistry for eNOS indicated transgene expression in the endothelium and adventitia in both NZW and WHHL rabbits. Expression of eNOS determined with Western blot analysis after incubation with AdeNOS tended to be higher in vessels from WHHL rabbits than NZW rabbits. Effects of transgene expression on vascular function were examined by recording isometric tension 1 day after transduction. After precontraction with phenylephrine, acetylcholine produced significantly less relaxation in vessels from WHHL rabbits than in vessels from NZW rabbits. Relaxation in response to acetylcholine was greater in carotid arteries from both NZW and WHHL rabbits that were transfected with AdeNOS than in vessels treated with vehicle or Adbetagal. Vasorelaxation in response to acetylcholine was inhibited by Nomega-nitro-L-arginine. Responses to sodium nitroprusside were similar after treatment with vehicle alone, Adbetagal, or AdeNOS in both groups of rabbits. Thus, overexpression of eNOS with an adenoviral vector improves impaired NO-mediated relaxation in atherosclerotic arteries.

Cationic polymer and lipids enhance adenovirus-mediated gene transfer to rabbit carotid artery

BACKGROUND AND PURPOSE

Improvement of efficiency of gene transfer to endothelium could be useful for several applications. We tested the hypothesis that cationic nonviral molecules augment adenovirus-mediated gene transfer to blood vessels, perhaps by alteration of the surface charge of adenovirus and facilitation of binding to endothelium.

METHODS

Carotid arteries from rabbits were incubated in vitro for 0.5 to 2 hours with an adenoviral vector alone or noncovalent complexes of adenovirus with poly-L-lysine (a cationic polymer) or lipofectin (a cationic lipid). Binding of adenovirus to the vessels was evaluated immediately after incubation with virus, and assay of transgene (ss-galactosidase) activity and histochemistry were performed 24 hours after gene transfer. To determine whether cationic molecules can be used to augment alteration of vascular function by adenovirus-mediated gene transfer, we also examined effects on gene transfer of endothelial nitric oxide synthase.

RESULTS

Assay of ss-galactosidase activity indicated that both cationic molecules increased transgene expression in vessels by approximately 5- to 6-fold. In contrast, when endothelium was removed from the vessels after gene transfer, poly-L-lysine and lipofectin did not significantly increase transgene activity. Histochemistry for ss-galactosidase also suggested that the adenovirus-cationic molecule complexes augmented transgene expression mainly in the endothelium. In addition, we found that complexing adenovirus with cationic molecules increased binding of adenovirus to the vessels. After gene transfer with recombinant adenovirus containing endothelial nitric oxide synthase, calcium ionophore (A23187) produced greater relaxation of vessels treated with adenovirus complexed with poly-L-lysine or lipofectin than those treated with adenovirus alone.

CONCLUSIONS

Cationic molecules improve the efficiency of adenovirus-mediated gene transfer to blood vessels.

Application of recombinant adenovirus for in vivo gene delivery to spinal cord

One strategy for treating spinal cord injury is to supply damaged neurons with the appropriate neurotrophins either by direct delivery or by transfer of the corresponding genes using viral vectors. Here we report the feasibility of using recombinant adenovirus for in vivo gene transfer in spinal cord. After injection of a recombinant adenovirus carrying a beta-galactosidase (beta-gal) reporter gene into the mid-thoracic spinal cord of adult rats, transgene expression occurred not only in several types of cells around the injection site but also in neurons whose axons project to this region from rostral or caudal to the injection site. Among labeled neurons were those of the red nucleus, the vestibular nuclei, reticular formation, locus coeruleus, and Clarke's nucleus. A non-specific immune reaction, which could be blocked by immunosuppression with Cyclosporin A, reduced the number of transduced cells surviving at the injection site by 1 month. In neurons away from the injection site, where the immune response was minimal, transgene expression lasted for at least 2 months. These results support the idea that recombinant adenovirus can be used in the spinal cord for in vivo delivery of therapeutic genes important for supporting neuron survival and axon regeneration.

In situ histochemical detection of beta-galactosidase activity in lung: assessment of X-Gal reagent in distinguishing lacZ gene expression and endogenous beta-galactosidase activity

Bacterial lacZ is one of the most commonly used reporter genes for assessing gene transfer to lung. However, lung contains endogenous beta-galactosidase (beta-Gal), which can confound estimation of exogenous lacZ expression by histochemical techniques (i.e., X-Gal) for in situ demonstration of enzyme activity. We investigated several parameters of the X-Gal reaction, including time and temperature of X-Gal exposure as well as lung tissue processing and fixation techniques, and found that none of these could be used to distinguish between endogenous and exogenous beta-Gal activities. The mammalian and bacterial beta-Gal enzymes, however, have pH optima in the acidic and neutral ranges, respectively. Exposing whole lung, lung minces, or mounted frozen sections of lung to X-Gal at mildly alkaline pH (pH 8.0-8.5), minimized detection of endogenous activity in lungs from a variety of species while preserving that resulting from bacterial enzyme activity in a transgenic mouse expressing lacZ. This technique was also useful in distinguishing endogenous activity from that resulting from adenovirus-mediated lacZ gene transfer to diploid lung fibroblasts in primary culture. An appropriate buffer that maintains the desired pH throughout the duration of X-Gal exposure must be used.

Augmented adenovirus-mediated gene transfer to atherosclerotic vessels

Vascular endothelium is an important target for gene transfer in atherosclerosis. In this study, we examined gene transfer to normal and atherosclerotic blood vessels from two species, using an organ culture method. Using normal aorta, we determined optimal dose, duration of exposure to adenovirus, and duration of incubation of vessels in tissue culture. Aortas from normal and atherosclerotic monkeys were cut into rings and incubated for 2 hours with a recombinant adenovirus, carrying the reporter gene for beta-galactosidase driven by a cytomegalovirus (CMV) promoter. After 20 hours of incubation, transgene expression was assessed with a morphometric method after histochemical staining and a chemiluminescent assay of enzyme activity. Expression of beta-galactosidase after histochemical staining, expressed as percentage of total cells, was similar in adventitial cells of normal monkeys (21 +/- 4%, mean +/- SE%) and atherosclerotic monkeys (25 +/- 12%). Transgene expression in endothelium was higher in atherosclerotic than in normal vessel (53 +/- 3% versus 27 +/- 7%, P < .05). Chemiluminescent assay indicated greater beta-galactosidase activity (2.5 +/- 0.6 mU/mg of protein) in the intima and media of atherosclerotic than normal vessels (0.6 +/- 0.2 mU/mg of protein, P < .05). Aortas from normal (n = 6) and atherosclerotic (n = 5) rabbits also were examined. Transgene expression (after histochemical staining) in endothelium was much greater in atherosclerotic than normal rabbits (39 +/- 3% versus 9 +/- 2%, P < .05) and expression in adventitial cells was similar (normal 23 +/- 2%, atherosclerotic 24 +/- 4%). Chemiluminescent assay indicated greater beta-galactosidase activity (1.2 +/- 0.4 mU/mg of protein) in the intima and media of atherosclerotic than normal vessels (0.2 +/- 0.1 mU/mg protein, P < .05). These findings suggest that an adenoviral vector with a CMV promoter provides similar transgene expression in adventitia of both normal and atherosclerotic vessels. Gene transfer to the endothelium was much more effective in atherosclerotic than in normal vessels. Thus it may be possible to achieve greater transgene expression in atherosclerotic than in normal arteries.

Downregulation of cyclin G1 expression by retrovirus-mediated antisense gene transfer inhibits vascular smooth muscle cell proliferation and neointima formation

BACKGROUND

The contemporary treatment of coronary athero-occlusive disease by percutaneous transluminal coronary angioplasty is hampered by maladaptive wound healing, resulting in significant failure rates. Morbid sequelae include smooth muscle cell (SMC) hyperplasia and restenosis due to vascular neointima formation.

METHODS AND RESULTS

In this study, we examined the inhibitory effects of a concentrated retroviral vector bearing an antisense cyclin G1 gene on aortic SMC proliferation in vitro and on neointima formation in vivo in a rat carotid injury model of restenosis. Retroviral vectors bearing an antisense cyclin G1 construct inhibited the proliferation of transduced aortic SMCs in 2- to 6-day cultures, concomitant with down-regulation of cyclin G1 protein expression and decreased [3H]thymidine incorporation into DNA. Morphological examination showed evidence of cytolysis, giant syncytia formation, and apoptotic changes evidenced by overt cell shrinkage, nuclear fragmentation, and specific immunostaining of nascent 3'-OH DNA ends generated by endonuclease-mediated DNA fragmentation. Pronounced "bystander effects" including neighboring cells were noted in aortic SMCs transduced with the antisense cyclin G1 vector, as determined by quantitative assays and fluorescent labeling of nontransduced cells. In an in vitro tissue injury model, the proliferation and migration of antisense cyclin G1 vector-transduced aortic SMCs were inhibited. Moreover, in vivo delivery of high-titer antisense cyclin G1 vector supernatant to the balloon-injured rat carotid artery in vivo resulted in a significant reduction in neointima formation.

CONCLUSIONS

These findings represent the first demonstration of the inhibitory effects of an antisense cyclin G1 retroviral vector on nonneoplastic cell proliferation. Taken together, these data affirm the potential utility of antisense cyclin G1 constructs in the development of novel gene therapy approaches to vascular restenosis.

Ex vivo adenoviral-mediated gene transfer to lung isografts during cold preservation

BACKGROUND

Although whole-organ gene transfer has been reported in heart and liver transplant models, it has not been well characterized in lung grafts. The aim of this study was to determine the feasibility of ex vivo gene transfer to rat lung isografts during cold preservation using an adenoviral vector.

METHODS

F344 rats, divided into four groups, underwent orthotopic left lung transplantation. In group I, lung grafts were flushed with adenovirus carrying the beta-galactosidase gene. After storage at 10 degrees C, grafts were implanted in recipient animals. Group II underwent the same procedure but graft storage was at 4 degrees C. Groups III (10 degrees C) and IV (4 degrees C) served as controls. On postoperative day 5, recipients were sacrificed, and native and transplanted lungs were examined.

RESULTS

In group I, all animals showed successful, albeit patchy, gene expression. This occurred in 2 of 4 animals in group II, the other 2 showing no expression. Transduced cells were consistent morphologically with endothelial cells and pneumocytes. A minimal mononuclear inflammatory infiltrate was present. Control groups showed no transduction.

CONCLUSIONS

It is feasible to perform ex vivo adenoviral-mediated gene transfer to rat lung isografts during cold preservation.

Gene transfer to cerebral blood vessels after subarachnoid hemorrhage

BACKGROUND AND PURPOSE

Vasospasm remains a major cause of morbidity and mortality after aneurysmal subarachnoid hemorrhage. One step toward gene therapy to prevent spasm of cerebral vessels is to determine whether subarachnoid blood prevents transgene expression.

METHODS

Vasospasm was induced in mongrel dogs using the double-hemorrhage intracranial-injection model. Diameter of the basilar artery was assessed by angiography, and profound vasospasm (> 50% decrease in diameter) was demonstrated at 4 and 7 days. Recombinant adenovirus expressing nuclear-targeted beta-galactosidase (reporter gene) under the control of the cytomegalovirus promoter was injected into the cisterna magna at the same time as (n = 9) or 2 days after (n = 4) injection of blood for induction of vasospasm. Brains were removed and examined histochemically for expression of nuclear beta-galactosidase.

RESULTS

At 2 to 7 days, beta-galactosidase was expressed in leptomeninges over the brain stem, cortex, cerebral arteries, in small vessels in the cerebrum and brain stem, and in the ependymal lining of the ventricles. Transgene expression was observed in adventitia of blood vessels but not in vascular muscle or endothelium. Transgene expression was observed after simultaneous injection of virus and blood or when virus was injected 2 days after blood.

CONCLUSIONS

The findings indicate that intracisternal injection of recombinant adenovirus can be used for gene transfer to cerebral blood vessels and overlying meninges, even in the presence of cisternal blood. We speculate that transfer of genes using recombinant viral vectors that encode for enzymes with vasodilator function to cerebral blood vessels and perivascular tissues may be useful for prevention or treatment of cerebral vasospasm after subarachnoid hemorrhage.

Endothelial cell-based cytokine gene delivery inhibits 9L glioma growth in vivo

Malignant brain neoplasms present great therapeutic challenges due to their extremely aggressive behavior and relative isolation by the blood-brain and blood-tumor barriers. Endothelial cells may be versatile platforms for delivering genes to solid tumors by virtue of their location at blood-tissue interfaces and their proliferation in response to endothelial mitogens produced by tumors. Immortalized rat brain endothelial cells that express the E. coli lacZ reporter gene and the gene for murine interleukin-2 (RBEZ-IL2) were co-inoculated with 9L glioma cells to Fisher rats to examine the effects of endothelial cell-based cytokine delivery on glioma growth in vivo. 9L glioma growth was not affected by the implantation of control RBEZ cells. The growth of subcutaneous and intracranial 9L gliomas was significantly inhibited by RBEZ-IL2 cells (P < 0.005 and P < 0.01, respectively) when compared to control transfected RBEZ cells. Rats receiving intracranial 9L glioma cells with RBEZ-IL2 cells showed increased survival (P < 0.001). Histologic and immunohistologic analysis showed enhanced activation of microglia/macrophages and CD8-positive T lymphocytes and/or natural killer cells within brain at sites of 9L inoculation with RBEZ-IL2 cells. This report establishes that immortalized endothelial cells can be used for cytokine gene delivery and to activate anti-tumor host responses to experimental gliomas within the central nervous system.

Adenovirus-mediated gene transfer to normal and atherosclerotic arteries. A novel approach

Previous studies of gene transfer to blood vessels in vivo have relied on intraluminal, catheter-based methods for delivery of adenoviral and other vectors. In this study, topical application of a replication-deficient adenoviral vector was used as an alternative method of gene transfer to the vessel wall. We administered recombinant adenovirus (1.0 x 1.5 x 10(10) pfu/mL) containing the nuclear targeted bacterial beta-galactosidase gene topically to arteries in normal and atherosclerotic cynomolgus monkeys. Topical administration was achieved by injection of adenoviral suspension within the periarterial sheath. Segments of femoral and carotid arteries were examined histochemically after staining with 5-bromo-4-chloro-3-indolyl-beta-D-galactopyranoside 1 day after treatment with the adenovirus. After topical administration of virus, beta-galactosidase activity was observed in approximately 20% of cells in the adventitia in both normal and atherosclerotic arteries. There was no detectable beta-galactosidase activity in cells of the intima or media. Thus, topical application provides an alternative method for gene transfer to blood vessels in vivo. This approach, which does not require interruption of blood flow and does not disrupt the endothelium, may be useful for studies of vascular biology and perhaps gene therapy in both normal and atherosclerotic vessels.

Adenovirus-mediated gene transfer in vivo to cerebral blood vessels and perivascular tissue

Gene transfer to blood vessels in vivo generally requires interruption of blood flow. Thus, gene transduction to cerebral blood vessels in vivo has not yet been achieved. In this study, we injected replication-deficient adenovirus into cerebrospinal fluid in an attempt to transduce genes to cerebral blood vessels. Recombinant adenovirus (1 x 10(9) infectious units) expressing nuclear-targeted bacterial beta-galactosidase driven by the cytomegalovirus promoter was injected into the cisterna magna of Sprague-Dawley rats. The brains were examined histochemically after staining with 5-bromo-4-chloro-3-indolyl-beta-D-galactopyranoside 1 to 7 days after injection of adenovirus. Leptomeningeal cells overlying the major arteries were efficiently transduced, and adventitial cells of large vessels and smooth muscle cells of small vessels were occasionally stained. beta-Galactosidase was expressed on days 1 and 3 after injection but was undetectable by day 7. Expression of the gene was 'targeted' by altering the position of the head. When viral suspension was injected while the rat was in a nose-down position, the reporter gene was expressed extensively on the ventral surface of the brain, especially along the circle of Willis. When the position was changed to the nose-up or lateral position, the inferior or lateral region of the brain was stained primarily. Administration of the virus into the lateral ventricle provided extensive expression in ependymal cells and leptomeninges with some transduction to cerebral blood vessels. Thus, adenovirus injected into cerebrospinal fluid provides gene transfer in vivo to cerebral blood vessels and, with greater efficiency, to perivascular tissue. Furthermore, cisternal delivery may target specific brain regions by positioning of the head.(ABSTRACT TRUNCATED AT 250 WORDS)

Transplantation to the rat brain of human neural progenitors that were genetically modified using adenoviruses

Transplantations for neurological disorders are limited by the supply of human fetal tissue. To generate larger numbers of cells of appropriate phenotype, we investigated whether human neural progenitors expanded in vitro could be modified with recombinant adenoviruses. Strong expression of beta-galactosidase was obtained in vitro. Two or three weeks after transplantation of engineered cells to the rat brain, we observed a small percentage of surviving neuroblasts strongly expressing beta-galactosidase in four out of 13 rats. Thus human precursor cells that have been genetically modified using adenoviruses are a promising tool for ex vivo gene therapy of neurodegenerative diseases.

Endothelial cell implantation and survival within experimental gliomas

The delivery of therapeutic genes to primary brain neoplasms opens new opportunities for treating these frequently fatal tumors. Efficient gene delivery to tissues remains an important obstacle to therapy, and this problem has unique characteristics in brain tumors due to the blood-brain and blood-tumor barriers. The presence of endothelial mitogens and vessel proliferation within solid tumors suggests that genetically modified endothelial cells might efficiently transplant to brain tumors. Rat brain endothelial cells immortalized with the adenovirus E1A gene and further modified to express the beta-galactosidase reporter were examined for their ability to survive implantation to experimental rat gliomas. Rats received 9L, F98, or C6 glioma cells in combination with endothelial cells intracranially to caudate/putamen or subcutaneously to flank. Implanted endothelial cells were identified by beta-galactosidase histochemistry or by polymerase chain reaction in all tumors up to 35 days postimplantation, the latest time examined. Implanted endothelial cells appeared to cooperate in tumor vessel formation and expressed the brain-specific endothelial glucose transporter type 1 as identified by immunohistochemistry. The proliferation of implanted endothelial cells was supported by their increased number within tumors between postimplantation days 14 and 21 (P = 0.015) and by their expression of the proliferation antigen Ki67. These findings establish that genetically modified endothelial cells can be stably engrafted to growing gliomas and suggest that endothelial cell implantation may provide a means of delivering therapeutic genes to brain neoplasms and other solid tumors. In addition, endothelial implantation to brain may be useful for defining mechanisms of brain-specific endothelial differentiation.