The colayer method as an efficient way to genetically modify mesencephalic progenitor cells transplanted into 6-OHDA rat model of Parkinson's disease.

Exogenous cell replacement represents a potent treatment option for Parkinson's disease. However, the low survival rate of transplanted dopaminergic neurons (DA) calls for methodological improvements. Here we evaluated a method to combine transient genetic modification of neuronal progenitor cells with an optimized cell culture protocol prior to intrastriatal transplantation into 6-hydroxydopamine (6-OHDA) unilateral lesioned rats. Plasmid-based delivery of brain-derived neurotrophic factor (BDNF) increases the number of DA neurons, identified by tyrosine hydroxylase immunoreactivity (TH-ir), by 25% in vitro, compared to enhanced green fluorescence protein (EGFP)-transfected controls. However, the nucleofection itself, especially the cell detachment and reseeding procedure, decreases the TH-ir neuron number to 40% compared with nontransfected control cultures. To circumvent this drawback we established the colayer method, which contains a mix of nucleofected cells reseeded on top of an adherent sister culture in a ratio 1:3. In this setup TH-ir neuron number remains high and could be further increased by 25% after BDNF transfection. Comparison of both cell culture procedures (standard and colayer) after intrastriatal transplantation revealed a similar DA neuron survival as seen in vitro. Two weeks after grafting TH-ir neuron number was strongly reduced in animals receiving the standard EGFP-transfected cells (271 ± 62) compared to 1,723 ± 199 TH-ir neurons in the colayer group. In contrast to the in vitro results, no differences in the number of grafted TH-ir neurons were observed between BDNF, EGFP, and nontransfected colayer groups, neither 2 nor 13 weeks after transplantation. Likewise, amphetamine and apomorphine-induced rotational behavior improved similarly over time in all groups. Nevertheless, the colayer protocol provides an efficient way for neurotrophic factor release by transplanted progenitor cells and will help to study the effects of candidate factors on survival and integration of transplanted DA neurons.

Topology of intrastriatal dopaminergic grafts determines functional and emotional outcome in neurotoxin-lesioned rats.

Many Parkinson's disease (PD) patients suffer from anxiety disorders, which often precede the onset of classical motor symptoms. So far, there is no evidence from randomized, placebo-controlled trials for successful treatment of anxiety in patients with PD. Grafts of fetal nigral neurons are currently explored as a restorative cell therapy for PD. In PD animal models, intrastriatal transplantations of embryonic dopaminergic neurons have been shown to ameliorate behavioral defects. In our previous study we showed that expanded and differentiated neural progenitors improved drug-induced rotation behavior and posture balance as a more complex motor task. However, it is not clear whether grafting of these cells affected spontaneous locomotor activity and anxiety-like behavior in 6-OHDA lesioned rats. Therefore, we analyzed behavior of control, lesioned, sham-transplanted, and transplanted rats using open field (OF) and elevated plus maze (EPM). After unilateral 6-OHDA lesion of the medial forebrain bundle, we observed reduced locomotor activity in the EPM (wall-rearing, entries in closed arms) in lesioned and sham-transplanted rats, which correlated with the loss of dopaminergic neurons and apomorphine-induced rotation behavior. Furthermore, anxiety-like behavior in the EPM (entries and time in open arms) was increased in lesioned and sham-transplanted rats. Although exogenous cell replacement improved apomorphine-induced rotation behavior, locomotor activity and anxiety-like behavior was not reconstituted in transplanted rats. However, we provided evidence for an interaction of locomotor activity/anxiety-like behavior with graft localization in the host striatum. These results emphasize the crucial role of graft localization for benefit of restorative cell therapy for PD.

Characterization and differentiation potential of rat ventral mesencephalic neuronal progenitor cells immortalized with SV40 large T antigen.

Neuronal progenitor cells (NPCs) possess high potential for use in regenerative medicine. To overcome their limited mitotic competence, various immortalization strategies have been applied that allow their prolonged maintenance and expansion in vitro. Such immortalized cells can be used for the design and discovery of new cell-based therapies for neurodegenerative diseases, such as Parkinson's disease. We immortalized rat ventral mesencephalic NPCs by using SV40 large T antigen (SV40Tag). All cell clones displayed a two- to three-fold higher proliferation rate compared with the primary cells. In order to induce dopaminergic differentiation of generated cell clones, both glial-derived neurotrophic factor and di-butyryl cyclic adenosine monophosphate were applied. Treated cells were then characterized regarding the expression of dopaminergic lineage markers, differentiation of various cell populations, calcium imaging in the presence of kainate, and immunohistochemistry after intrastriatal transplantation. Treated cells displayed morphological maturation, and calcium imaging revealed neuronal properties in the presence of kainate. These cells also expressed low mRNA levels of the dopamine transporter and tyrosine hydroxylase (TH), although no TH-immunopositive neurons were found. Intrastriatal transplantation into the neurotoxin-lesioned rats did not induce further differentiation. As an alternative approach, we silenced SV40Tag with short interfering RNA, but this was not sufficient to trigger differentiation into dopaminergic neurons. Nevertheless, neuronal and glial cells were detected as shown by beta-tubulin type III and glial fibrillary acidic protein staining, respectively. SV40Tag cells are suitable for carrying out controlled genetic modifications as shown by overexpression of enhanced green fluorescence protein after efficient non-viral transfection.