Sox-2 Positive Neural Progenitors in the Primate Striatum Undergo Dynamic Changes after Dopamine Denervation.

The existence of endogenous neural progenitors in the nigrostriatal system could represent a powerful tool for restorative therapies in Parkinson's disease. Sox-2 is a transcription factor expressed in pluripotent and adult stem cells, including neural progenitors. In the adult brain Sox-2 is expressed in the neurogenic niches. There is also widespread expression of Sox-2 in other brain regions, although the neurogenic potential outside the niches is uncertain. Here, we analyzed the presence of Sox-2+ cells in the adult primate (Macaca fascicularis) brain in naïve animals (N = 3) and in animals exposed to systemic administration of 1-methyl-4-phenyl-1,2,3,6 tetrahydropyridine to render them parkinsonian (N = 8). Animals received bromodeoxyuridine (100 mg/kg once a day during five consecutive days) to label proliferating cells and their progeny. Using confocal and electron microscopy we analyzed the Sox-2+ cell population in the nigrostriatal system and investigated changes in the number, proliferation and neurogenic potential of Sox-2+ cells, in control conditions and at two time points after MPTP administration. We found Sox-2+ cells with self-renewal capacity in both the striatum and the substantia nigra. Importantly, only in the striatum Sox-2+ was expressed in some calretinin+ neurons. MPTP administration led to an increase in the proliferation of striatal Sox-2+ cells and to an acute, concomitant decrease in the percentage of Sox-2+/calretinin+ neurons, which recovered by 18 months. Given their potential capacity to differentiate into neurons and their responsiveness to dopamine neurotoxic insults, striatal Sox-2+ cells represent good candidates to harness endogenous repair mechanisms for regenerative approaches in Parkinson's disease

Chronic levodopa administration followed by a washout period increased number and induced phenotypic changes in striatal dopaminergic cells in MPTP-monkeys.

In addition to the medium spiny neurons the mammalian striatum contains a small population of GABAergic interneurons that are immunoreactive for tyrosine hydroxylase (TH), which dramatically increases after lesions to the nigrostriatal pathway and striatal delivery of neurotrophic factors. The regulatory effect of levodopa (L-Dopa) on the number and phenotype of these cells is less well understood. Eleven macaques (Macaca fascicularis) were included. Group I (n = 4) received 1-methyl-4-phenyl-1,2,3,6 tetrahydropyridine (MPTP) and L-Dopa; Group II (n = 4) was treated with MPTP plus vehicle and Group III (n = 3) consist of intact animals (control group). L-Dopa and vehicle were given for 1 year and animals sacrificed 6 months later. Immunohistochemistry against TH was used to identify striatal and nigral dopaminergic cells. Double and triple labeling immunofluorescence was performed to detect the neurochemical characteristics of the striatal TH-ir cells using antibodies against: TH, anti-glutamate decarboxylase (GAD(67)) anti-calretinin (CR) anti-dopa decarboxylase (DDC) and anti-dopamine and cyclic AMP-regulated phosphoprotein (DARPP-32). The greatest density of TH-ir striatal cells was detected in the striatum of the L-Dopa treated monkeys and particularly in its associative territory. None of the striatal TH-ir cell expressed DARPP-32 indicating they are interneurons. The percentages of TH-ir cells that expressed GAD67 and DDC was approximately 50%. Interestingly, we found that in the L-Dopa group the number of TH/CR expressing cells was significantly reduced. We conclude that chronic L-Dopa administration produced a long-lasting increase in the number of TH-ir cells, even after a washout period of 6 months. L-Dopa also modified the phenotype of these cells with a significant reduction of the TH/CR phenotype in favor of an increased number of TH/GAD cells that do not express CR. We suggest that the increased number of striatal TH-ir cells might be involved in the development of aberrant striatal circuits and the appearance of L-Dopa induced dyskinesias

Double immunofluorescence images of the striatal TH-ir cells showing one TH-ir cell that also express dopa-decarboxilase (DDC) (A), absence of TH-ir cells immunolabeled with the dopamine and cyclic AMP-regulated phosphoprotein (DARPP-32) (B) TH-ir interneurons expressing calretinin (CR) (C) and glutamate decarboxylase (GAD67) (D).

<p>Scale bars 20 µm.</p

Experimental study design, treatments and group assignments.

<p>Experimental study design, treatments and group assignments.</p

Correction: Sox-2 Positive Neural Progenitors in the Primate Striatum Undergo Dynamic Changes after Dopamine Denervation.

[This corrects the article on p. e66377 in vol. 8.]

Triple immunofluorescence images showing the different 4 phenotypes of the TH-ir cells here described.

<p>A) TH-ir cell labeled with CR and GAD67, B) two TH-ir cells that do not express either CR or GAD67, C) TH-ir cell expressing GAD67 but not CR and D) two TH-ir cells expressing CR but not for GAD67. Scale bars 20 µm.</p

General characteristics of the animals and TH-ir cell counting in the striatum and substantia nigra.

*<p>: <i>P</i>≤0.05 compared to vehicle or L-Dopa with control group.</p><p>#: <i>P</i>≤0.05 compared to L-Dopa with vehicle group. The data show the mean and its corresponding SEM.</p

Graphic representation of the distribution of striatal TH-ir neurons in each experimental group.

<p>Note that L-Dopa group has the highest number of TH-ir cells, particularly in the more rostral areas. The delineation of territory boundaries based on anatomical assessments is also showed. Sensorimotor (SM), Associative (ASS) and Limbic (Lim) territories of the caudate (Cd), Putamen (Pu) and part of nucleus accumbens (Acc) are included. The distances from the anterior commissure (AC) are indicated.</p

Striatal coronal sections immunostained with TH and counterstained with Nissl showing the morphology of the striatal dopaminergic cells.

<p>Control monkey (A) vehicle-treated monkey (B) and L-Dopa-treated monkey (C). Scale bar, 100 µm (A-C) and 20 µm (A’–C’).</p