Genetically Modified Pc 12 Brain Grafts: Survivability and Inducible Nerve Growth Factor Expression

Neural transplantation of genetically modified cells has been successfully employed to reverse functional deficits in animal models of neurodegenerative disorders, including Parkinson's disease. While implanted PC12 cells secrete dopamine in vivo and can ameliorate dopamine deficiency in parkinsonian rat model systems, these cells either degenerate within 2-3 wk postimplantation (presumably due to the lack of neural trophic factor support at the site of implantation), or in some cases, form a tumor mass leading to the death of the host animal. To address these limitations, we have developed a genetically modified PC12 cell line that can synthesize nerve growth factor (NGF) under the control of a zinc-inducible metallothionein promoter. When implanted in the rat striatum and under in vivo zinc stimulation, these cells will neurodifferentiate, express tyrosine hydroxylase, and will undergo survival through potential autocrine trophic support. This regulatable cell line and general approach may provide additional insight on the potential utilization of cell transplants for treatment of Parkinson's disease and other neurodegenerative disorders.

Download Full-text

Local protective effects of nerve growth factor-secreting fibroblasts against excitotoxic lesions in the rat striatum

Journal of Neurosurgery ◽

10.3171/jns.1993.78.2.0267 ◽

1993 ◽

Vol 78 (2) ◽

pp. 267-273 ◽

Cited By ~ 98

Author(s):

David M. Frim ◽

M. Priscilla Short ◽

William S. Rosenberg ◽

Joseph Simpson ◽

Xandra O. Breakefield ◽

...

Keyword(s):

Nerve Growth Factor ◽

Growth Factor ◽

Corpus Callosum ◽

Cell Line ◽

Neuronal Survival ◽

Delivery Systems ◽

Rat Striatum ◽

Protective Effects ◽

Nerve Growth ◽

Excitotoxic Lesion

✓ Neurotrophic factors, such as nerve growth factor (NGF), in addition to their role in neuronal development, have protective effects on neuronal survival. Intracerebral implantation of cells genetically altered to secrete high levels of NGF is also found to promote neuronal survival in experimental lesioning models of the brain. The range of activity for such biological delivery systems has not yet been well described either spatially or temporally. Therefore, the authors chose to study the local and distant protective effects of an NGF-secreting rat fibroblast cell line implanted in an excitotoxic lesion model of Huntington's disease. They found that preimplantion of NGF-secreting fibroblasts placed within the corpus callosum reduced the maximum crosssectional area of a subsequent excitotoxic lesion in the ipsilateral striatum by 80% when compared to the effects of a non-NGF-secreting fibroblast graft, and by 83% when compared to excitotoxic lesions in ungrafted animals (p < 0.003). However, NGF-secreting cells placed in the contralateral corpus callosum failed to affect striatal lesion size significantly when compared to contralateral or ipsilateral non-NGF-secreting cell implants. Of note, fibroblasts were clearly visible within the graft site at 7 and 18 days after implantation; however, few cells within the grafts stained positively for NGF peptide or for the messenger ribonucleic acid (mRNA) encoding the transfected NGF gene-construct at either time point. These results show that biological delivery systems for NGF appear to have a profound but local effect on neuronal excitotoxicity, which will necessitate careful neurosurgical placement for maximum effect. Furthermore, the ability of this genetically altered cell line to synthesize NGF mRNA and peptide appears to decrease spontaneously in vivo, a characteristic that will need to be addressed before this method of biological delivery can be utilized as a treatment for chronic degenerative diseases.

Download Full-text