Lesion-induced increase in survival and migration of human neural progenitor cells releasing GDNF.

The use of human neural progenitor cells (hNPC) has been proposed to provide neuronal replacement or astrocytes delivering growth factors for brain disorders such as Parkinson's and Huntington's disease. Success in such studies likely requires migration from the site of transplantation and integration into host tissue in the face of ongoing damage. In the current study, hNPC modified to release glial cell line-derived neurotrophic factor (hNPCGDNF) were transplanted into either intact or lesioned animals. GDNF release itself had no effect on the survival, migration, or differentiation of the cells. The most robust migration and survival was found using a direct lesion of striatum (Huntington's model) with indirect lesions of the dopamine system (Parkinson's model) or intact animals showing successively less migration and survival. No lesion affected differentiation patterns. We conclude that the type of brain injury dictates migration and integration of hNPC, which has important consequences when considering transplantation of these cells as a therapy for neurodegenerative diseases.

GDNF delivery using human neural progenitor cells in a rat model of ALS.

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by progressive loss of spinal cord, brainstem, and cortical motor neurons. In a minority of patients, the disease is caused by mutations in the copper (2+)/zinc (2+) superoxide dismutase 1 (SOD1) gene. Recent evidence suggests that astrocytes are dysfunctional in ALS and may be a critical link in the support of motor neuron health. Furthermore, growth factors, such as glial cell line-derived neurotrophic factor (GDNF), have a high affinity for motor neurons and can prevent their death following various insults, but due to the protein's large size are difficult to directly administer to brain. In this study, human neural progenitor cells (hNPC) isolated from the cortex were expanded in culture and modified using lentivirus to secrete GDNF (hNPC(GDNF)). These cells survived up to 11 weeks following transplantation into the lumbar spinal cord of rats overexpressing the G93A SOD1 mutation (SOD1 (G93A)). Cellular integration into both gray and white matter was observed without adverse behavioral effects. All transplants secreted GDNF within the region of cell survival, but not outside this area. Fibers were seen to upregulate cholinergic markers in response to GDNF, indicating it was physiologically active. We conclude that genetically modified hNPC can survive, integrate, and release GDNF in the spinal cord of SOD1 (G93A) rats. As such, they provide an interesting source of cells for both glial replacement and trophic factor delivery in future human clinical studies.

Combining growth factors, stem cells, and gene therapy for the aging brain.

Stem cells have been suggested as a possible "fountain of youth" for replacing tissues lost during aging. In the brain, replacing lost neurons is a challenge, as they have to then be reconnected with their appropriate targets. Perhaps a more realistic and practical strategy for affecting the aging process would be to prevent the loss of neurons from occurring, thus retaining intact circuitry. Glial cell line-derived neurotrophic factor (GDNF) can reverse some aspects of aging in the monkey. Additionally, we have recently shown that GDNF directly infused into the human brain has significant effects on the symptoms of Parkinson disease. Human neural stem cells can be cultured, genetically modified, and transplanted. As such, these cells are ideal for ex vivo gene therapy, and may be used in the future as "minipumps" to release GDNF in vivo to protect aging neurons. Using such an approach could delay the effects of aging in the brain, giving a better quality of life. Stem cells might not be the fountain of youth, but provide a fountain of youth through the release of growth factors such as GDNF.

Human neural stem cell transplants improve motor function in a rat model of Huntington's disease.

The present study investigated the neuroanatomical and behavioral effects of human stem cell transplants into the striatum of quinolinic acid (QA)-lesioned rats. Twenty-four rats received unilateral QA (200 nM/microl) injections into the striatum. One week later, rats were transplanted with stem cells derived from human fetal cortex (12 weeks postconception) that were either 1) pretreated in culture media with the differentiating cytokine ciliary neurotrophic factor (CNTF; n = 9) or 2) allowed to grow in culture media alone (n=7). Each rat was injected with a total of 200,000 cells. A third group of rats (n=8) was given a sham injection of vehicle. Rats transplanted with human stem cells performed significantly better over the 8 weeks of testing on the cylinder test compared with those treated with vehicle (P < or = 0.001). Stereological striatal volume analyses performed on Nissl-stained sections revealed that rats transplanted with CNTF-treated neurospheres had a 22% greater striatal volume on the lesioned side compared with those receiving transplants of untreated neurospheres (P = 0.0003) and a 26% greater striatal volume compared with rats injected with vehicle (P < or = 0.0001). Numerous human nuclei-positive cells were visualized in the striatum in both transplantation groups. Grafted cells were also observed in the globus pallidus, entopeduncular nucleus, and substantia nigra pars reticulata, areas of the basal ganglia receiving striatal projections. Some of the human nuclei-positive cells coexpressed glial fibrillary acidic protein and NeuN, suggesting that they had differentiated into neurons and astrocytes. Taken together, these data demonstrate that striatal transplants of human fetal stem cells elicit behavioral and anatomical recovery in a rodent model of Huntington's disease.