In vivo adenovirus-mediated gene transfer and the expression in ischemic and reperfused rat brain

Adenoviruses-mediated RNA interference targeting cytosolic phospholipase A2α attenuates focal ischemic brain damage in mice

Cerebral ischemia injury is a clinical, frequently occurring disease, which causes a heavy burden on society and families. It has been demonstrated that cytosolic phospholipase A2α (cPLA2α) is significant in neurological injury caused by ischemic brain injury, and inhibition of cPLA2α may reduce stroke injury. In the present study, the role of cPLA2α was investigated in a mouse model of middle cerebral artery occlusion and/or reperfusion (MCAO/R) using an effective cPLA2α inhibitor and adenoviruses-mediated RNA interference. The most effective recombinant adenovirus encoding cPLA2α small interfering RNA (pAd-siRNA-cPLA2α) was constructed and selected. MCAO/R surgery is used to construct the model of focal ischemic brain damage in mice. Adenoviruses-mediated RNA interference targeting cPLA2α was administered by stereotactic surgery 2 h before the MCAO/R. The expression/activity of cPLA2α and cPLA2α-derived injurious lipid mediators was assessed. pAd-siRNA-cPLA2α-treated animals (RNA interference; RNAi group) were compared with pAd-siRNA-control-treated animals (negative group) with regard to neurological deficit, motor function, pathological changes, apoptosis, and infarct volume. The RNAi group animals reduced the expression level of cPLA2α, as determined by western blotting and reverse transcription-quantitative polymerase chain reaction, the improvement of locomotor function was evaluated by rotarod test, and the decrease of apoptosis was evaluated by terminal deoxynucleotidyl transferase dUTP nick end-labeling staining. The decreased infarct areas were evaluated by 2,3,5-triphenyltetrazolium chloride staining. The expression levels of prostaglandin E2, leukotrienes B4, lysophosphatidylcholine and free fatty acids were reduced in the RNAi group when compared with the negative control group. Thus, the data indicates that the expression level of cPLA2α was effectively controlled by pAd-siRNA-cPLA2α treatment. pAd-siRNA-cPLA2α treatment, in reducing the levels of inflammatory factors, neurological deficit and tissue damage, represents an effective potential therapeutic strategy. pAd-siRNA-cPLA2α reduces cPLA2α expression levels with long-term efficacy, thereby improving functional deficits and effectively attenuating ischemic brain damage. Thus, pAd-siRNA-cPLA2α shows potential value for therapeutic evaluation in ischemic brain damage.

Strategies for the Development of Cell Lines for Ex Vivo Gene Therapy in the Central Nervous System

Disorders of the central nervous system (CNS) as a result of trauma or ischemic or neurodegenerative processes still pose a challenge for modern medicine. Due to the complexity of the CNS, and in spite of the advances in the knowledge of its anatomy, pharmacology, and molecular and cellular biology, treatments for these diseases are still limited. The development of cell lines as a source for transplantation into the damaged CNS (cell therapy), and more recently their genetic modification to favor the expression and delivery of molecules with therapeutic potential (ex vivo gene therapy), are some of the techniques used in search of novel restorative strategies. This article reviews the different approaches that have been used and perfected during the last decade to generate cell lines and their use in experimental models of neuronal damage, and evaluates the prospects of applying these methods to treat CNS disorders.

Combining glial cell line-derived neurotrophic factor gene delivery (AdGDNF) with L-arginine decreases contusion size but not behavioral deficits after traumatic brain injury

Our laboratory has previously demonstrated that viral administration of glial cell line-derived neurotrophic factor (AdGDNF), one week prior to a controlled cortical impact (CCI) over the forelimb sensorimotor cortex of the rat (FL-SMC) is neuroprotective, but does not significantly enhance recovery of sensorimotor function. One possible explanation for this discrepancy is that although protected, neurons may not have been functional due to enduring metabolic deficiencies. Additionally, metabolic events following TBI may interfere with expression of therapeutic proteins administered to the injured brain via gene therapy. The current study focused on enhancing the metabolic function of the brain by increasing cerebral blood flow (CBF) with l-arginine in conjunction with administration of AdGDNF immediately following CCI. An adenoviral vector harboring human GDNF was injected unilaterally into FL-SMC of the rat immediately following a unilateral CCI over the FL-SMC. Within 30min of the CCI and AdGDNF injections, some animals were injected with l-arginine (i.v.). Tests of forelimb function and asymmetry were administered for 4weeks post-injury. Animals were sacrificed and contusion size and GDNF protein expression measured. This study demonstrated that rats treated with AdGDNF and l-arginine post-CCI had a significantly smaller contusion than injured rats who did not receive any treatment, or injured rats treated with either AdGDNF or l-arginine alone. Nevertheless, no amelioration of behavioral deficits was seen. These findings suggest that AdGDNF alone following a CCI was not therapeutic and although combining it with l-arginine decreased contusion size, it did not enhance behavioral recovery.

APOE epsilon3 gene transfer attenuates brain damage after experimental stroke

Apolipoprotein E (apoE, protein; APOE, gene) is the major lipid-transport protein in the brain and plays an important role in modulating the outcome and regenerative processes after acute brain injury. The aim of the present study was to determine if gene transfer of the epsilon3 form of APOE improves outcome in a murine model of transient focal cerebral ischaemia. Mice received an intrastriatal injection of vehicle, a second-generation adenoviral vector containing the green fluorescent protein gene (Ad-GFP) or a vector containing the APOE epsilon3 gene (Ad-APOE) 3 days before 60 mins focal ischaemia. Green fluorescent protein expression was observed in cells throughout the striatum and subcortical white matter indicating successful gene transfer and expression. ApoE levels in the brain were significantly increased after Ad-APOE compared with Ad-GFP or vehicle treatment. Ad-APOE treatment reduced the volume of ischaemic damage by 50% compared with Ad-GFP or vehicle treatment (13+/-3 versus 29+/-4 versus 27+/-5 mm(3)). The extent of postischaemic apoE immunoreactivity was enhanced in Ad-APOE compared with Ad-GFP or vehicle treated mice. These results show the ability of APOE gene transfer to markedly improve outcome after cerebral ischaemia and suggest that modulating apoE levels may be a potential strategy in human stroke therapy.

Gene therapy in the nervous system with superoxide dismutase

Neuronal death following necrotic insults involves the generation of reactive oxygen species (ROS). We investigated the effects of antioxidant gene therapy on ROS accumulation after exposure to either sodium cyanide, kainic acid or oxygen glucose deprivation (OGD). Specifically, we generated herpes simplex virus-1 amplicon vector expressing the gene for the antioxidant enzyme CuZnSOD. Overexpression of this gene in primary hippocampal cultures resulted in increased enzymatic activity of the corresponding protein. CuZnSOD significantly protected hippocampal neurons against sodium cyanide insult and the subsequent lipid peroxidation. However, it did not protect against OGD- or kainic-acid-induced toxicity. Moreover, CuZnSOD significantly worsened the toxicity, hydrogen peroxide accumulation and lipid peroxidation induced by kainic acid. As a possible explanation for this surprising worsening, CuZnSOD overexpression increased glutathione peroxidase activity in the presence of sodium cyanide but had no effect on catalase or glutathione peroxidase activity in the presence of kainic acid. Thus, cells were unlikely to be able to detoxify the excess hydrogen peroxide produced as a result of the CuZnSOD overexpression. These studies can be viewed as a cautionary note concerning gene therapy intervention against necrotic insults.

Postischemic administration of Sendai virus vector carrying neurotrophic factor genes prevents delayed neuronal death in gerbils

Sendai virus (SeV) vector-mediated gene delivery of glial cell line-derived neurotrophic factor (GDNF) and nerve growth factor (NGF) prevented the delayed neuronal death induced by transient global ischemia in gerbils, even when the vector was administered several hours after ischemia. Intraventricular administration of SeV vector directed high-level expression of the vector-encoded neurotrophic factor genes, which are potent candidates for the treatment of neurodegenerative diseases. After occlusion of the bilateral carotid arteries of gerbils, SeV vector carrying GDNF (SeV/GDNF), NGF (SeV/NGF), brain-derived neurotrophic factor (SeV/BDNF), insulin-like growth factor-1 (SeV/IGF-1) or vascular endothelial growth factor (SeV/VEGF) was injected into the lateral ventricle. Administration of SeV/GDNF, SeV/NGF or SeV/BDNF 30 min after the ischemic insult effectively prevented the delayed neuronal death of the hippocampal CA1 pyramidal neurons. Furthermore, the administration of SeV/GDNF or SeV/NGF as late as 4 or 6 h after the ischemic insult also prevented the death of these neurons. These results indicate that SeV vector-mediated gene transfer of neurotrophic factors has high therapeutic potency for preventing the delayed neuronal death induced by transient global ischemia, and provides an approach for gene therapy of stroke.

De Novo Neurogenesis and Acute Stroke: Are Exogenous Stem Cells Really Necessary?

RECENT STUDIES DOCUMENTING the phenomenon of de novo neurogenesis within the adult brain have propelled this area of research to the forefront of neuroscience investigations and stroke pathogenesis and treatment. Traditional theories have suggested that the central nervous system is incapable of neural regeneration; hence the emergence of the field of stem cell biology as a discipline devoted to uncovering novel forms of neural repair. However, several recent experimental observations have shown that the adult brain is capable of ongoing neurogenesis in discrete regions of the uninjured brain and additional forms of endogenous neural regeneration in the presence of an inciting event (induction neurogenesis). Induction neurogenesis has the potential for providing new insights into the cause and treatment of acute stroke syndromes.

HSV amplicon delivery of glial cell line-derived neurotrophic factor is neuroprotective against ischemic injury

Direct intracerebral administration of glial cell line-derived neurotrophic factor (GDNF) is neuroprotective against ischemia-induced cerebral injury. Utilizing viral vectors to deliver and express therapeutic genes presents an opportunity to produce GDNF within localized regions of an evolving infarct. We investigated whether a herpes simplex virus (HSV) amplicon-based vector encoding GDNF (HSVgdnf) would protect neurons against ischemic injury. In primary cortical cultures HSVgdnf reduced oxidant-induced injury compared to the control vector HSVlac. To test protective effects in vivo, HSVgdnf or HSVlac was injected into the cerebral cortex 4 days prior to, or 3 days, after a 60-min unilateral occlusion of the middle cerebral artery. Control stroke animals developed bradykinesia and motor asymmetry; pretreatment with HSVgdnf significantly reduced such motor deficits. Animals receiving HSVlac or HSVgdnf after the ischemic insult did not exhibit any behavioral improvement. Histological analyses performed 1 month after stroke revealed a reduction in ischemic tissue loss in rats pretreated with HSVgdnf. Similarly, these animals exhibited less immunostaining for glial fibrillary acidic protein and the apoptotic marker caspase-3. Taken together, our data indicate that HSVgdnf pretreatment provides protection against cerebral ischemia and supports the utilization of the HSV amplicon for therapeutic delivery of trophic factors to the CNS.

Nonviral gene delivery to the central nervous system based on a novel integrin-targeting multifunctional protein

Successful introduction of therapeutic genes into the central nervous system (CNS) requires the further development of efficient transfer vehicles that avoid viral vector-dependent adverse reactions while maintaining high transfection efficiency. The multifunctional protein 249AL was recently constructed for in vitro gene delivery. Here, we explore the capability of this vector for in vivo gene delivery to the postnatal rat CNS. Significant transgene expression was observed both in the excitotoxically injured and noninjured brain after intracortical injection of the DNA-contaning-249AL vector. In the injured brain, a widespread expression occurred in the entire lesioned area and retrograde transport of the vector toward distant thalamic nuclei and transgene expression were observed. Neurons, astrocytes, microglia, and endothelial cells expressed the transgene. No recruitment of leukocytes, demyelination, interleukin-1beta expression, or increase in astrocyte/microglial activation was observed at 6 days postinjection. In conclusion, the 249AL vector shows promising properties for gene therapy intervention in the CNS, including the targeting of different cell populations.

Gene therapy for cerebral vascular disease: update 2003

Gene therapy is a promising strategy for cerebrovascular diseases. Several genes that encode vasoactive products have been transferred via cerebrospinal fluid for the prevention of vasospasm after subarachnoid hemorrhage. Transfer of neuroprotective genes, including targeting of proinflammatory mediators, is a current strategy of gene therapy for ischemic stroke. Stimulation of growth of collateral vessels, stabilization of atherosclerotic plaques, inhibition of thrombosis, and prevention of restenosis are important objectives of gene therapy for coronary and limb arteries, but application of these approaches to carotid and intracranial arteries has received little attention. Several fundamental advances, including development of safer vectors, are needed before gene therapy achieves an important role in the treatment of cerebrovascular disease and stroke.

Targeting of post-ischemic cerebral endothelium in rat by liposomes bearing polyethylene glycol-coupled transferrin

To achieve an efficient delivery targeting to post-ischemic cerebral vascular endothelium, PEG-liposome conjugated with transferrin (Tf) (Tf-PEG-liposome) was intravenously administered to the rats after 90 min of transient middle cerebral occlusion. The expression of Tf receptor (TfR) in the cerebral endothelium increased with a peak at 1 day after the reperfusion and returned to the control level by 6 days. The Tf-PEG fluorescence was marginally detectable in sham control brain, but remarkably increased with a peak at 2 days, showing about 70% of TfR positive vascular endothelium double-labeled with Tf-PEG. These results indicate that the Tf-PEG-liposome could be utilized as an efficient drug delivery tool to the brain after stroke.

Adenovirus-mediated overexpression of a gene prevents hearing loss and progressive inner hair cell loss after transient cochlear ischemia in gerbils

The use of adenoviral vectors has recently provided a novel strategy for direct gene transfer into the cochlea. In this study, we assessed the utility of an adenoviral vector expressing glial-cell-derived neurotrophic factor (GDNF) in ischemia-reperfusion injury of the gerbil cochlea. The vector was injected through the round window 4 days before ischemic insult. The distribution of a reporter transgene was confirmed throughout the cochlea from the basal to the apical turn and Western blot analysis indicated significant upregulation of GDNF protein 11 days following virus inoculation. Hearing ability was assessed by sequentially recording compound action potentials (CAP), and the degree of hair cell loss in the organ of Corti was evaluated in specimens stained with rhodamine-phalloidin and Hoechst 33342. On the seventh day of ischemia, the CAP threshold shift and inner hair cell loss were remarkably suppressed in the Ad-GDNF group compared with the control group. These results suggest that adenovirus-mediated overexpression of GDNF is useful for protection against hair cell damage, which otherwise eventually occurs after transient ischemia of the cochlea.

Enhanced expression of phospho-Akt by electro-acupuncture in normal rat brain

Electro-acupuncture (EA) is an effective curative method for various diseases in oriental medicine. To investigate a detailed molecular mechanism of EA stimulation, an induction of phospho-Akt (p-Akt) was examined in normal adult rat brain after 60 min of EA with acupoints of Baihui (D20) and Renzhong (D26). In the sham control brain, strong neuronal p-Akt expression was found in ventral posterolateral thalamic nucleus (VPL) and medial habenular nuclei (MHb), but moderate to weak in cortex, caudate, CA1 sector and dentate gyrus of hippocampus, and ventral posteromedial thalamic nucleus. EA stimulation generally enhanced and sustained p-Akt expression for at least 24 h especially in the regions listed above, except VPL and MHb where no apparent change was found. Western blot analysis of p-Akt confirmed the enhanced signal intensity after EA at 8 and 24 h. These results suggest that the EA on D20 and D26 acupoints activates the survival Akt signal pathway, which may be maintaining the neural functions such as cell survival and memory formation in normal brain.

Therapeutic time window of adenovirus-mediated GDNF gene transfer after transient middle cerebral artery occlusion in rat

The time dependent influence of adenovirus-mediated glial cell line-derived neurotrophic factor (GDNF) gene (Ad-GDNF) was examined after 90 min of transient middle cerebral artery occlusion (MCAO) in rats. Treatment with Ad-GDNF significantly reduced the infarct volume when immediately administered after the reperfusion, but became insignificant when administered at 1 h after the reperfusion as were the cases treated with vehicle- and adenoviral vector containing the E. coli lacZ gene (Ad-LacZ)-treated groups. The protective effect of GDNF was related to the significant reduction of the number of TUNEL positive cells as well as immunohistochemical positive cells for active caspase-3 but not -9. These results showed that exogenous GDNF gene transfer successfully reduced the infarct size in a time-dependant manner by suppressing active caspase-3 but not active caspase-9. However, the therapeutic time window was shorter than the effect of GDNF protein itself previously reported.

Reduced inflammatory reactions to the inoculation of helper-dependent adenoviral vectors in traumatically injured rat brain

Traumatic brain injury (TBI) causes delayed neuronal deficits that in principle could be prevented by timely intervention with therapeutic genes. However, appropriate vectors for gene transfer to the brain with TBI remain to be developed. First-generation adenoviruses (fgAd) are usually associated with inflammatory and toxic effects when inoculated into brains, despite their high efficiency of gene transfer to these tissues. In this study the authors attempted to determine whether a less immunogenic gene-transfer protocol can be established in the traumatically injured rat brain using helper-dependent adenoviruses (hdAd), a novel adenoviral construct with full deletion of viral coding sequences. Their results show that transgene expression from intrahippocampally inoculated hdAd is maintained for at least 2 months after TBI, in contrast to the much shorter duration of fgAd-mediated gene expression. There was only minimal secretion of proinflammatory IL-1beta and TNF-alpha after inoculation of hdAd. Furthermore, the hdAd-mediated gene expression was associated with less microglial proliferation, astrocytic activation, and macrophage infiltration than observed in fgAd-inoculated brains. There was no additional tissue loss after hdAd inoculation compared with PBS injection. Although both anti-adenoviral and neutralizing antibodies were found in serum after brain inoculation of hdAd, they did not appear to affect transgene expression. The results suggest that hdAd are less immunogenic vectors than conventional adenoviral vectors, and offer improved vehicles for long-term therapeutic transgene transfer to traumatically injured brains.

Adenovirus-mediated glial cell line-derived neurotrophic factor (GDNF) expression protects against subsequent cortical cold injury in rats

We examined whether brain damage after focal cortex trauma may be attenuated by adenoviral delivery of the glial cell line-derived neurotrophic factor (GDNF) gene. For this reason, injections of vehicle, of an adenoviral vector deleted in the E1 region (Ad-dE1) or a vector expressing the GDNF gene from a CMV promoter (Ad-GDNF) were stereotactically placed in the rat sensorimotor cortex, and one day later cold lesions of the cerebral cortex were induced. Lesions were associated with pronounced brain swelling one day after injury. The degree of brain swelling was significantly attenuated by Ad-GDNF delivery (Ad-GDNF: 7.4 +/- 2.2%, Ad-dE1: 21.1 +/- 4.9%, vehicle: 20.9 +/- 5.0% of contralateral; mean +/- SEM, P < 0.05). Furthermore, Ad-GDNF treatment resulted in a significant reduction of the lesion volume seven days after lesioning (Ad-GDNF: 21.8 +/- 2.8 mm3, Ad-dE1: 44.1 +/- 1.6 mm3, vehicle 40.9 +/- 8.6 mm3, P < 0.05). The decrease in the lesion size was associated with a reduction in the number of inducible nitric oxide (iNOS)(+), activated caspase-3(+) and DNA fragmented cells in the perilesion rim, as revealed by immunocytochemistry and terminal transferase biotinylated-dUTP nick end labeling (TUNEL). In Ad-GDNF-treated animals, the number of caspase-3(+) and TUNEL(+) cells was also reduced in the lesion-remote thalamus. The present study shows that adenoviral GDNF delivery is protective in focal cortex trauma.

Impaired retrograde axonal transport of adenovirus-mediated E. coli LacZ gene in the mice carrying mutant SOD1 gene

A replication-defective recombinant adenoviral vector containing E. coli lacZ gene was injected into the gastrocnemius muscles of transgenic mice carrying mutant Cu/Zn superoxide dismutase (SOD1) gene and non-transgenic wild-type mice at 40 weeks of age. After 60 and 90 h of the injection, lacZ staining was observed at the distal ends of the sciatic nerves in both mice groups, with the number and the distances greatly reduced in the transgenic mice. Mean velocities of retrograde transport for lacZ was estimated to be 2.1 and 0.05 mm/24 h in non-transgenic and transgenic mice, respectively. These results indicate that the retrograde axonal transport of foreign gene product is impaired in the mice model for familial amyotrophic lateral sclerosis.

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 future of gene therapy for stroke

New diagnostic and treatment strategies are being developed for stroke. Gene therapy has several potential advantages over classical pharmacologic therapy. Direct administration of DNA into the brain offers the advantage of producing high concentrations of therapeutic agents in a relatively localized environment. Gene transfer also provides longer duration of effect than traditional drug therapy. Recent studies indicate that gene transfer can produce functional proteins in brain parenchyma and cerebral blood vessels after stroke. In animal models, gene transfer may reduce effects of cerebral ischemia or subarachnoid hemorrhage. This review summarizes some current methods of gene transfer to the brain and recent progress that may lead to gene therapy for stroke.

Adenovirus-mediated transfer and expression of beta-gal in injured hippocampus after traumatic brain injury in mice

In models of focal cerebral ischemia, adenoviral gene transfer is often attenuated or delayed versus naive. After controlled cortical impact (CCI)-induced traumatic brain injury in mice, CA1 and CA3 hippocampus exhibit delayed neuronal death by 3 days, with subsequent near complete loss of hippocampus by 21 days. We hypothesized that adenoviral-mediated expression of the reporter gene beta-Galactosidase (beta-Gal) in hippocampus would be attenuated after CCI in mice. C57BL6 mice (n = 16) were subjected to either CCI to left parietal cortex or sham (burr hole). Adenovirus carrying the beta-Gal gene (AdlacZ; 1 x 10(9) plaque-forming units [pfu]/mL) was then injected into left dorsal hippocampus. At 24 or 72 h, beta-Gal expression was quantified (mU/mg protein). Separate mice (n = 10) were used to study beta-Gal spatial distribution in brain sections. Beta-Gal expression in left hippocampus was similar in shams at 24 h (48.4 +/- 4.1) versus 72 h (68.8 +/- 8.8, not significant). CCI did not reduce beta-Gal expression in left hippocampus (68.8 +/- 8.8 versus 88.1 +/- 7.0 at 72 h, sham versus CCI, not significant). In contrast, CCI reduced beta-Gal expression in right (contralateral) hippocampus versus sham (p < 0.05 at both 24 and 72 h). Beta-Gal was seen in many cell types in ipsilateral hippocampus, including CA3 neurons. Despite eventual loss of ipsilateral hippocampus, adenovirus-mediated gene transfer was surprisingly robust early after CCI providing an opportunity to test novel genes targeting delayed hippocampal neuronal death.

Adenovirus-mediated glial cell line-derived neurotrophic factor gene delivery reduces motor neuron injury after transient spinal cord ischemia in rabbits

OBJECTIVE

Glial cell line-derived neurotrophic factor (GDNF) has protective effects on various injuries involving the central and peripheral nervous systems in vitro and vivo. However, the possible protective effect of GDNF on spinal cord ischemia and the exact mechanism involved in the ameliorative effect of GDNF on ischemic spinal cord injuries are not fully understood. Therefore, we investigated the possible protective effect of the adenovirus-mediated GDNF gene delivery on transient spinal cord ischemia in rabbits.

METHODS

The adenoviral vector (lacZ gene as a control or GDNF gene contained) was injected directly into the lumbar spinal cord via a needle inserted into the dorsal spine 2 days before the animal was subjected to 15 minutes of spinal cord ischemia induced by infrarenal aortic occlusion. In situ terminal deoxynucleotidyl transferase (TdT)-mediated dUTP-biotin nick-end labeling (TUNEL staining) was performed, and temporal profiles of the GDNF and caspase-3 (caspase-3 is the marker of apoptotic change) immunoreactivity were investigated.

RESULTS

In the control rabbit, the majority of motor neurons showed selective cell death at 7 days of reperfusion. Immunocytochemistry showed that in situ TUNEL staining was selectively detected at 2 days of reperfusion in motor neuron nuclei. GDNF and caspase-3 were selectively induced in the motor neuron cells at 8 hours of reperfusion. In the GDNF-treated group, a large population of motor neuron cells was still surviving at 7 days after having been subjected to 15 minutes of ischemia. Unlike the control group, the GDNF-treated group expressed GDNF persistently. Induction of TUNEL staining and immunoreactivity for caspase-3 were greatly reduced by the GDNF treatment.

CONCLUSION

These results suggest that the reduction in motor neuron death by GDNF was greatly associated with a reduction in DNA fragmentation and apoptotic signals of the caspase-3 cascade; they further suggest a great potential for gene therapy for paraplegic patients in the future.

Therapeutic potential of neurotrophic factors and neural stem cells against ischemic brain injury

Development of neuronal and glial cells and their maintenance are under control of neurotrophic factors (NTFs). An exogenous administration of NTFs protects extremely sensitive brain tissue from ischemic damage. On the other hand, it is now known that neural stem cells are present in normal adult brain, and have a potential to compensate and recover neural functions that were lost due to ischemic stroke. These stem cells are also under control of NTFs to differentiate into a certain species of neural cells. Thus, the purpose of this review is to summarize the present understanding of the role of NTFs in normal and ischemic brain and the therapeutic potential of NTF protein itself or gene therapy, and then to summarize the role of NTFs in stem cell differentiation and a possible therapeutic potential with the neural stem cells against ischemic brain injury.

Adenovirus-mediated gene transfer of glial cell line-derived neurotrophic factor prevents ischemic brain injury after transient middle cerebral artery occlusion in rats

To examine a possible protective effect of exogenous glial cell line-derived neurotrophic factor (GDNF) gene expression against ischemic brain injury, a replication-defective adenoviral vector containing GDNF gene (Ad-GDNF) was directly injected into the cerebral cortex at 1 day before 90 minutes of transient middle cerebral artery occlusion (MCAO) in rats. 2,3,5-Triphenyltetrazolium chloride staining showed that infarct volume of the Ad-GDNF-injected group at 24 hours after the transient MCAO was significantly smaller than that of vehicle- or Ad-LacZ-treated group. Enzyme-linked immunosorbent assay (ELISA) for immunoreactive GDNF demonstrated that GDNF gene products in the Ad-GDNF-injected group were higher than those of vehicle-treated group at 24 hours after transient MCAO. Immunoreactive GDNF staining was obviously detected in the cortex around the needle track just before or 24 hours after MCAO in the Ad-GDNF group, whereas no or slight GDNF staining was detected in the vehicle group. The numbers of TUNEL, immunoreactive caspase-3, and cytochrome c-positive neurons induced in the ipsilateral cerebral cortex at 24 hours after transient MCAO were markedly reduced by the Ad-GDNF group. These results suggest that the successful exogenous GDNF gene transfer ameliorates ischemic brain injury after transient MCAO in association with the reduction of apoptotic signals.

In vivo adenovirus-mediated gene transfer and expression in ischemic rabbit spinal cord

PURPOSE

In an attempt to study whether ischemic spinal cord expresses a foreign gene in vivo, a replication-defective adenoviral vector containing the Escherichia coli lacZ gene was directly injected into the ischemic spinal cord of rabbits, and temporal and spatial profiles of the exogenous gene expression were compared with that of the control spinal cord.

METHODS

Thirty-nine Japanese domesticated white rabbits weighing 2 to 3 kg were used in this study and were divided into two subgroups, a 15-minute ischemia group and a sham control group. The adenoviral vector was directly injected into lumbar spinal cord by a needle from dorsal spine just after the infrarenal aortic occlusion in the case of ischemia. Animals were allowed to recover at ambient temperature and were killed at 1, 2, 4, and 7 days after reperfusion (n = 3 at each time point).

RESULTS

In the control rabbit, adenoviral vector was transferred into the spinal cord, and the lacZ gene was expressed at dorsal astroglia and anterior motor neurons at 1 to 7 days of reperfusion. After 15 minutes of ischemia, the lacZ gene was expressed at 2 and 4 days of reperfusion in dorsal astroglia and anterior motor neurons, which were positive for Fas antigen.

CONCLUSION

This result suggests that it is possible to transfer and express the lacZ gene in ischemic motor neurons, which eventually show apoptotic change with induction of Fas antigen, and also suggests a great potential of gene therapy for paraplegic patients in the future.

Hypoxia-inducible factor-1alpha mediates hypoxia-induced delayed neuronal death that involves p53

Hypoxia-induced delayed neuronal death is known to require de novo gene expression; however, the molecular mediators that are involved remain undefined. The transcription factor hypoxia-inducible factor-1alpha (HIF-1alpha), in addition to promoting the expression of adaptive genes under conditions of hypoxia, has been implicated as being a necessary component in p53-mediated cell death in tumors. Using herpes amplicon-mediated gene transfer in cortical neuronal cultures, we demonstrate that delivery of a dominant-negative form of HIF-1alpha (HIFdn), capable of disrupting hypoxia-dependent transcription, reduces delayed neuronal death that follows hypoxic stress. In contrast, hypoxia-resistant p53-null primary cultures are not protected by HIFdn expression. These data indicate that, in hypoxic neurons, HIF-1alpha and p53 conspire to promote a pathological sequence resulting in cell death.

Inflammatory responses and their impact on beta-galactosidase transgene expression following adenovirus vector delivery to the primate caudate nucleus

An E1, E3 deleted adenovirus vector, serotype 5, carrying the marker gene LacZ was bilaterally microinfused into the caudate nuclei of 10 St Kitts green monkeys. The location and number of cells expressing transgene and host immunologic response were evaluated at 1 week (n = 2) and 1 month (n = 8) following vector infusion. A large number of cells expressed beta-galactosidase in some monkeys, exceeding 600000 in one monkey, but no expression was seen in three of 10. All monkeys had positive adenoviral antibody titers before vector infusion, indicating the possibility of previous exposure to some adenovirus, but only one showed a significant increase in titer afterwards. Inflammatory cell markers revealed an inverse correlation between transgene expression and the extent of inflammatory response. Dexamethasone administered immediately before and for 8 days following vector delivery, however, had no effect on transgene expression. The demonstration of significant inflammatory responses in the brain of some individual primates, including demyelination, indicates the need for new generations of adenovirus vectors, or the successful suppression of inflammatory responses, before this vector is suitable for non-cytotoxic clinical applications in the CNS.

Gene therapy for cerebrovascular disease

OBJECTIVE

To review the principles of and the experimental and clinical results of gene therapy for cerebrovascular disease.

METHODS

Literature review.

RESULTS

Vectors for gene transfer into the brain or into the cerebral vasculature include naked plasmid deoxyribonucleic acid, cationic liposomes, and viruses such as adenovirus, retrovirus, adeno-associated virus, and herpes simplex virus. Experiments using these vectors showed that intra- or perivascular application to systemic arteries can lead to transfection and expression of a foreign transgene in the adventitia and the endothelium. Intrathecal administration can lead to transfection and foreign transgene expression in leptomeningeal cells as well as in fibroblasts of blood vessel adventitia. Biological effects demonstrated thus far include increased nitric oxide production by transfection of cerebral arterial adventitia with adenovirus expressing nitric oxide synthase. Adenoviruses carrying foreign genes have been used to decrease neuronal damage in cerebral ischemia and to decrease blood pressure in spontaneously hypertensive rats. Vectors and therapeutic applications for gene therapy are evolving rapidly.

CONCLUSION

Gene therapy for cerebrovascular disease is likely to have clinical application in the near future and will have a major impact on neurosurgery. Neurosurgeons will need to be aware of the literature in this area.

Induction of DNA fragmentation and HSP72 immunoreactivity by adenovirus-mediated gene transfer in normal gerbil hippocampus and ventricle

Foreign genes have been successfully transferred and expressed in experimental animal brains using adenoviral vectors. However, it is not fully understood whether adenovirus-mediated gene transfer causes stressful or cytotoxic injury in brain. A replication-defective adenoviral vector containing the Escherichia coli lacZ gene (AdCMVnLacZ) was directly injected into right hippocampus and lateral ventricle of normal gerbil brains. Temporal and spatial profiles of the expression of lacZ gene products, DNA fragmentation detected by terminal deoxynucleotidyl d-UTP nick end labeling (TUNEL) staining, and heat shock protein 72 (HSP72) immunoreactivity were examined until 21 days after the injection. In the ventricle, lacZ gene was immediately and strongly expressed at 8 hr after the injection of AdCMVnLacZ, with a peak at 1-3 days, and disappeared by 21 days. Although a small number of choroid plexus cells were TUNEL positive at 3 and 7 days, no HSP72 immunostaining was observed in the ventricle. Small-to-moderate expression of lacZ gene was found in the needle route from 8 hr to 3 days after the injection, and a small number of TUNEL-positive cells were detected at the needle track at 1-3 days. In the hippocampus, lacZ gene was markedly expressed around the dentate gyrus (DG) at 8 hr to 3 days with a peak at 1 day. Large number of TUNEL or moderate-to-dense HSP70 staining cells were also detected in the same area. CA1 neuronal cells just adjacent to the needle route showed TUNEL positivity at 1 to 3 days. However, the TUNEL staining was not associated with lacZ gene expression. The majority of lacZ-expressing cells were discriminated from the TUNEL-positive cells, whereas some were double-positive with HSP72 staining in DG. Cellular loss was observed in the CA1 layer around the needle route. An apoptotic change was morphologically observed in the marginal region of the DG at 1-3 days and in the ventricle at 3-7 days. In the sham control group, TUNEL-positive or HSP72-staining cells were only detected around the needle track including CA1 cells adjacent to the needle route. These data suggest that adenoviral gene transfer may induce direct traumatic injury in the CA1 sector near the needle route, indirect apoptotic cell loss in the DG and ventricle, and stressful effect on the dentate granule cells in association with adenovirus infection in normal gerbil brain.

DNA fragmentation and HSP72 gene expression by adenovirus-mediated gene transfer in postischemic gerbil hippocampus and ventricle

A replication defective adenoviral vector containing the E. coli lacZ gene (AdCMVnLacZ) was directly injected into right hippocampus and lateral ventricle immediately after 5 min of transient global ischemia in gerbils. The relations between the lacZ gene expression and DNA fragmentation or heat shock protein 72 (HSP72) immunoreactivity were examined up to 21 days post ischemia. The lacZ gene was transiently expressed at 1 day in the hippocampus except around the CA1 region, while a large number of the periventricular cells strongly expressed the lacZ gene from 8 h to 7 days. In CA1 layer, terminal deoxynucleotidyl dUTP nick end labeling (TUNEL) positive cells, which were present only adjacent to the needle track at 8 h to 1 day, became more extensive in the whole CA1 layer at 3 to 7 days. TUNEL-positive cells were also detected around the DG at 1 day, around the needle track at 8 h to 3 days, and in the choroid plexus cells at 7 days. HSP72 staining was detected in the subiculum at 1 to 3 days, the dentate granule cells at 8 h to 1 day, and in the CA3 or CA4 pyramidal cells at 1 to 3 days. Some lacZ expressing cells were double-positive with HSP72 in DG, while the majority of those were distinguished from the TUNEL-positive cells. Pyramidal neurons were almost completely lost in the CA1 sector at 7 days after the ischemia. The present study demonstrates the successful LacZ gene transfer into the hippocampus and ventricle of postischemic gerbil brain except in the vulnerable CA1 layer by adenoviral vector injection. However, adenovirus-mediated gene transfer may induce indirect apoptotic cell death in the DG and ventricle, in addition to direct traumatic injury around the needle track.

Expression of adenovirus-mediated E. coli lacZ gene in skeletal muscles and spinal motor neurons of transgenic mice with a mutant superoxide dismutase gene

A replication-defective recombinant adenoviral vector containing E. coli lacZ gene was injected into the right biceps brachii muscles of transgenic mice carrying mutant human Cu/Zn superoxide dismutase (SOD1) gene and non-transgenic wild-type mice at 27 weeks of age. Although the transgenic mice showed remarkable neurogenic muscular changes and a marked motor neuron loss in the anterior horn of spinal cord, the lacZ gene was widely expressed in all the injected muscles of transgenic mice as well as of wild-type mice at 7 days after the injection. In one transgenic and two wild-type mice, the lacZ gene expression was first detected in a few motor neurons of right lower cervical cord (C5-C6). These results demonstrate that an adenovirus-mediated foreign gene is transferred and expressed in skeletal muscles both of normal and transgenic mice model for familial amyotrophic lateral sclerosis (FALS), and also, in the spinal motor neurons, may be transferred by retrograde transport from innervated muscles.