Reduced Anxiety-Like Behavior and Altered Hippocampal Morphology in Female p75NTR(exon IV-/-) Mice.

The presence of the p75 neurotrophin receptor (p75NTR) in adult basal forebrain cholinergic neurons, precursor cells in the subventricular cell layer and the subgranular cell layer of the hippocampus has been linked to alterations in learning as well as anxiety- and depression- related behaviors. In contrast to previous studies performed in a p75NTR(exon III-/-) model still expressing the short isoform of the p75NTR, we focused on locomotor and anxiety-associated behavior in p75NTR(exon IV-/-) mice lacking both p75NTR isoforms. Comparing p75NTR(exon IV-/-) and wildtype mice for both male and female animals showed an anxiolytic-like behavior as evidenced by increased central activities in the open field paradigm and flex field activity system as well as higher numbers of open arm entries in the elevated plus maze test in female p75NTR knockout mice. Morphometrical analyses of dorsal and ventral hippocampus revealed a reduction of width of the dentate gyrus and the granular cell layer in the dorsal but not ventral hippocampus in male and female p75NTR(exon IV-/-) mice. We conclude that germ-line deletion of p75NTR seems to differentially affect morphometry of dorsal and ventral dentate gyrus and that p75NTR may play a role in anxiety-like behavior, specifically in female mice.

Expression of early developmental markers predicts the efficiency of embryonic stem cell differentiation into midbrain dopaminergic neurons.

Dopaminergic neurons derived from pluripotent stem cells are among the best investigated products of in vitro stem cell differentiation owing to their potential use for neurorestorative therapy of Parkinson's disease. However, the classical differentiation protocols for both mouse and human pluripotent stem cells generate a limited percentage of dopaminergic neurons and yield a considerable cellular heterogeneity comprising numerous scarcely characterized cell populations. To improve pluripotent stem cell differentiation protocols for midbrain dopaminergic neurons, we established extensive and strictly quantitative gene expression profiles, including markers for pluripotent cells, neural progenitors, non-neural cells, pan-neuronal and glial cells, neurotransmitter phenotypes, midbrain and nonmidbrain populations, floor plate and basal plate populations, as well as for Hedgehog, Fgf, and Wnt signaling pathways. The profiles were applied to discrete stages of in vitro differentiation of mouse embryonic stem cells toward the dopaminergic lineage and after transplantation into the striatum of 6-hydroxy-dopamine-lesioned rats. The comparison of gene expression in vitro with stages in the developing ventral midbrain between embryonic day 11.5 and 13.5 ex vivo revealed dynamic changes in the expression of transcription factors and signaling molecules. Based on these profiles, we propose quantitative gene expression milestones that predict the efficiency of dopaminergic differentiation achieved at the end point of the protocol, already at earlier stages of differentiation.

Cell fate analysis of embryonic ventral mesencephalic grafts in the 6-OHDA model of Parkinson's disease.

Evidence from carefully conducted open label clinical trials suggested that therapeutic benefit can be achieved by grafting fetal dopaminergic (DAergic) neurons derived from ventral mesencephalon (VM) into the denervated striatum of Parkinson's disease (PD) patients. However, two double-blind trials generated negative results reporting deleterious side effects such as prominent dyskinesias. Heterogeneous composition of VM grafts is likely to account for suboptimal clinical efficacy.We consider that gene expression patterns of the VM tissue needs to be better understood by comparing the genetic signature of the surviving and functioning grafts with the cell suspensions used for transplantation. In addition, it is crucial to assess whether the grafted cells exhibit the DAergic phenotype of adult substantia nigra pars compacta (SNpc). To investigate this further, we used a GFP reporter mouse as source of VM tissue that enabled the detection and dissection of the grafts 6 weeks post implantation. A comparative gene expression analysis of the VM cell suspension and grafts revealed that VM grafts continue to differentiate post-implantation. In addition, implanted grafts showed a mature SNpc-like molecular DAergic phenotype with similar expression levels of TH, Vmat2 and Dat. However, by comparing gene expression of the adult SNpc with dissected grafts we detected a higher expression of progenitor markers in the grafts. Finally, when compared to the VM cell suspension, post-grafting there was a higher expression of markers inherent to glia and other neuronal populations.In summary, our data highlight the dynamic development of distinctive DAergic and non-DAergic gene expression markers associated with the maturation of VM grafts in vivo. The molecular signature of VM grafts and its functional relevance should be further explored in future studies aimed at the optimization of DAergic cell therapy approaches in PD.

Striatal transplantation in a rodent model of multiple system atrophy: effects on L-Dopa response.

Progressive degeneration of striatal projection neurons is thought to account for the loss of L-Dopa response observed in the majority of patients with the parkinsonian variant of multiple system atrophy (MSA-P). Here we have investigated the effects of E14 embryonic striatal allografts on dopaminergic responsiveness in the unilateral double-lesion rat model of MSA-P by using tests of complex motor behavior. Both sham and graft animals showed an increase in apomorphine-induced rotations as well as an improvement in cylinder test performance following surgical intervention. In contrast, L-Dopa responsiveness of stepping behavior was improved only in grafted animals. The restoration of apomorphine-induced rotation correlated with the P-zone volume of grafts. Our findings indicate that transplantation of embryonic striatal grafts might, at least to some extent, restore responsiveness to L-Dopa in tasks of complex motor behavior. Therefore, striatal transplantation should be further defined preclinically as a possible therapeutic option for patients with MSA-P and a failing L-Dopa response.

Evidence for dopaminergic re-innervation by embryonic allografts in an optimized rat model of the Parkinsonian variant of multiple system atrophy.

Embryonic transplantation has been considered as an alternative treatment strategy for drug resistant parkinsonian symptoms in multiple system atrophy. So far our group has created a number of animal models of striatonigral degeneration, the core pathology underlying progressive Parkinsonism associated with multiple system atrophy, as testbed for neurorestaurative and neuroprotective approaches. Using embryonic allografts of either nigral, striatal, or combined nigro-striatal tissue we were able to consistently show graft survival in a denervated and lesioned striatum as well as improvement of rotational behaviour. However, due to severe lesions of the striatum and the chosen time window of 3-6 weeks between lesion and grafting, severe gliosis led to demarcation of the graft and prevented re-innervation of the remaining adult striatum. The aim of the present study was to modify our "double toxin-double lesion" rat model by reducing the dose of quinolinic acid injected into the striatum from 150 to 75 nmol and shortening the interval between lesion and grafting to 1-2 weeks. Injection of 75 nmol quinolinic acid still led to a significant reduction of DARPP-32 positive neurons and volume in the striatum. Analysis of embryonic mesencephalic grafts revealed survival of dopaminergic neurons and outgrowth of fibres re-innervating the adult striatum. Rotation behaviour was improved in the graft group. Considering embryonic transplantation a possible future antiparkinson therapeutic intervention in multiple system atrophy patients our data stress the necessity of optimal patient selection, i.e. early stage disease with limited striatal dysfunction.

Neuropathological and behavioral changes induced by various treatment paradigms with MPTP and 3-nitropropionic acid in mice: towards a model of striatonigral degeneration (multiple system atrophy).

We characterized two models of dual nigral and striatal lesions replicating the lesion pattern of striatonigral degeneration, the neuropathological hallmark of parkinsonism associated with multiple system atrophy (SND/MSA-P). For this purpose, we used systemic administration of 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP) and 3-nitropropionic acid (3-NP) in C57BL mice. One group of animals was first injected with MPTP followed by 3NP (MPTP+3-NP model). In the second group 3-NP was injected first, followed by MPTP (3-NP+MPTP model). The behavioral and neuropathological characteristics of these two models were compared to those observed after single 3-NP or MPTP intoxication. Results showed that, compared to control mice, spontaneous nocturnal locomotor activity was preserved in the MPTP+3-NP model, whereas it was reduced by 27% ( P<0.05) in the 3-NP+MPTP model and in animals treated with either 3-NP (27%, P<0.05) or MPTP (23%, P<0.05) alone. Quantitative histological evaluation based on Nissl staining and DARPP-32 immunohistochemistry revealed that 3-NP alone and 3-NP+MPTP treatment produced a marked (greater than 50%) loss of striatal neurons, whereas MPTP+3-NP treatment attenuated loss of striatal neurons by 43%. Further, loss of tyrosine hydroxylase-positive neurons in substantia nigra pars compacta (SNc) was attenuated after 3-NP+MPTP treatment compared to that observed after MPTP (40% vs 74%, P<0.001) and MPTP+3NP treatment (55% vs 74%, P<0.01). Our results show that MPTP-induced nigral lesions attenuate 3-NP toxicity and, reciprocally, that 3-NP-induced striatal lesions reduce MPTP toxicity. This suggests that complex integrative mechanisms are likely to regulate the vulnerability of the striatum and SNc to cell death in SND/MSA-P.