Parkinson's disease (PD) is a neurodegenerative disease characterized by progressive degeneration of nigrostriatal dopaminergic (DA) neurons. The therapeutic potential of glial cell line-derived neurotrophic factor (GDNF), the most potent neurotrophic factor for DA neurons, has been demonstrated in many experimental models of PD. However, chronic delivery of GDNF to DA neurons in the brain remains an unmet challenge. Here, we report the effects of GDNF-releasing Notch-induced human bone marrow-derived mesenchymal stem cells (MSC) grafted into striatum of the 6-hydroxydopamine (6-OHDA) progressively lesioned rat model of PD. Human MSC, obtained from bone marrow aspirates of young, healthy adult volunteers, were transiently transfected with the intracellular domain of the Notch1 gene (NICD) to generate SB623 cells. SB623 cells expressing GDNF and/or humanized Renilla green fluorescent protein (hrGFP) following lentiviral transduction or nontransduced cells were stereotaxically placed into rat striatum 1 week after a unilateral partial 6-OHDA striatal lesion. At 4 weeks, rats that had received GDNF-transduced SB623 cells had significantly decreased amphetamine-induced rotation compared with control rats, although this effect was not observed in rats that received GFP-transduced or nontransduced SB623 cells. At 5 weeks, rejuvenated tyrosine hydroxylase-immunoreactive (TH-IR) fibers that appeared to be host DA axons were observed in and around grafts. This effect was more prominent in rats that received GDNF-secreting cells and was not observed in controls. These observations suggest that human bone-marrow derived MSC, genetically modified to secrete GDNF, hold potential as an allogeneic or autologous stem cell therapy for PD.

Parkinson's disease (PD) is a common neurodegenerative disease characterized by the selective loss of dopaminergic (DA) neurons in the midbrain. Various types of stem cells that have potential to differentiate into DA neurons are being investigated as cellular therapies for PD. Stem cells also secrete growth factors and therefore also may have therapeutic effects in promoting the health of diseased DA neurons in the PD brain. To address this possibility in an experimental model of PD, bone marrow-derived neuroprogenitor-like cells were generated from bone marrow procured from healthy human adult volunteers and their potential to elicit recovery of damaged DA axons was studied in a partial lesion rat model of PD. Following collection of bone marrow, mesenchymal stem cells (MSC) were isolated and then genetically modified to create SB623 cells by transient transfection with the intracellular domain of the Notch1 gene (NICD), a modification that upregulates expression of certain neuroprogenitor markers. Ten deposits of 0.5 µl of SB623 cell suspension adjusted from 6,000 to 21,000 cells/µl in PBS or PBS alone were stereotaxically placed in the striatum 1 week after the nigrostriatal projection had been partially lesioned in adult F344 rats by injection of 6-hydroxydopamine (6-OHDA) into the striatum. At 3 weeks, a small number of grafted SB623 cells survived in the lesioned striatum as visualized by expression of the human specific nuclear matrix protein (hNuMA). In rats that received SB623 cells, but not in control rats, dense tyrosine hydroxylase immunoreactive (TH-ir) fibers were observed around the grafts. These fibers appeared to be rejuvenated host DA axons because no TH-ir in soma of surviving SB623 cells or coexpression of TH and hNuMA-ir were observed. In addition, dense serotonin immunoreactive (5-HT-ir) fibers were observed around grafted SB623 cells and these fibers also appeared to be of the host origin. Also, in some SB623 grafted rats that were sacrificed within 2 h of dl-amphetamine injection, hot spots of c-Fos-positive nuclei that coincided with rejuvenated dense TH fibers around the grafted SB623 cells were observed, suggesting increased availability of DA in these locations. Our observations suggest that NICD-transfected MSC hold potential as a readily available autologous or allogenic cellular therapy for ameliorating the degeneration of DA and 5-HT neurons in PD patients.

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