Acute cerebral ischemia causes hypoxic neuronal cell death by necrosis and apoptosis. Expression of anti-apoptotic transgenes in ischemic brainThrombotic vessel occlusion in the brain causes acute hypoxia in the respective vascular territory and subsequently induces neuronal death in the core and the penumbra of the ischemic lesion which is caused by necrosis and apoptosis. 1,2 The anti-apoptotic protein bcl-2 is known to protect most eukaryotic cells from apoptotic or necrotic cell death. 3 Bcl-2 also protects human neurons in cell culture against apoptosis induced by withdrawal of nerve growth factor (NGF) and by amyloid ␤-peptide, as well as against oxidative and hypoxic insults. [4][5][6] Delivery of the bcl-2 gene and expression of transgenic bcl-2 in ischemic brain tissue results in neuroprotection and may inhibit hypoxic cell death in vivo. [7][8][9][10] Most of the previous studies on neuroprotective gene transfer used genetically engineered virus vectors, such as herpes-simplex type I virus (HSV), adenovirus (AV), or adeno-associated virus (AAV). 8,9,11

Green fluorescent protein (GFP) is an effective marker for retrovirus and herpes virus vector-mediated gene transfer into various central nervous system-derived cells, both proliferative and non-proliferative, in culture and in vivo. Retrovirus vectors were used to stably transduce several rat and human glioma lines, and a multipotent mouse neural progenitor line in culture. Implantation of selected pools of transduced glioma cells into rodent brain allowed clear visualization of the tumor and the invading tumor edge. Helper virus-free HSV-1 amplicon vectors successfully transferred gfp into non-dividing primary neural cells in culture and in the rat brain. This study describes the versatility of GFP for: (i) labelling of glioma cells in experimental brain tumor models and neural progenitor cells by retrovirus vectors, and (ii) efficient, non-toxic delivery of genes to post mitotic cells of the nervous system using helper-virus free HSV-1 amplicon vectors.

Expression of anti-apoptotic or neurotrophic transgene proteins in hypoxic neurons may provide a novel therapeutic strategy for neuroprotection and alleviation of damage to ischemic brain areas. NT2, a human neoplastic cell line which terminally differentiates into postmitotic neuronsIschemia of the brain due to major vessel thrombosis causes hypoxia in the respective vascular territory and subsequently induces neuronal death which is at least in part caused by apoptosis, especially in the penumbra of the lesion. 1,2 Hypoxia-inducible expression of anti-apoptotic or neurotrophic transgenes in hypoxic neurons may provide a novel therapeutic strategy for neuroprotection and alleviation of damage to ischemic brain areas.Hypoxia has been known as a potent inducer of a large number of genes including those encoding erythropoietin, vascular endothelial growth factor (VEGF), and some glycolytic enzymes, eg phosphoglycerate kinase. These genes have specific regulatory sequences in their promoter regions, known as hypoxia responsive elements (HRE). 3 Under hypoxic conditions, the upregulated hypoxia-inducible transcription factor 1 (HIF-1) binds to the HRE and initiates transcription of 3Ј sequences. This physiological mechanism has been utilized for develop- ment of hypoxia-responsive gene transfer vectors with HRE-based promoters. Hypoxia-inducible expression of transgenes has been reported in tumor cells and in cardiac myocytes. [4][5][6][7][8][9] Recently, new hypoxia-responsive vectors for tumor-specific gene therapy were developed. 10

A 73-year-old female treated with clopidogrel for vascular disease presented with sudden onset of back pain, urinary retention and paraplegia. MRI scans demonstrated a thoracolumbar epidural hematoma and the patient underwent emergency laminectomy for evacuation of the hematoma. A possible causal link between clopidogrel and occurrence of the hemorrhage is discussed and the literature on spontaneous spinal hematomas is reviewed.

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