Self-Assembling Peptide Nanofiber Scaffolds Enhance Dopaminergic Differentiation of Mouse Pluripotent Stem Cells in 3-Dimensional Culture

<div><p>Dopaminergic differentiation of embryonic stem cells (ESCs) gains more and more attention worldwide owing to its potential use for neurorestorative therapy for the treatment of Parkinson’s disease. The conventional 2D cell culture on petri dishes with various animal derived substrata such as collagen gels, laminin, and Matrigel is widely used to induce dopaminergic differentiation and it may limit the efficiency in the generation of dopaminergic neurons from ESCs and prevent their application for human therapies. Here, we reported that a self-assembling peptide made from natural amino acids has a property to generate a true 3D environment for dopaminergic differentiation. Mouse ESCs (R1) and mouse iPSCs (TTF-1) embedded in RADA16-I peptide-derived nanofiber scaffolds led to a marked increase in dopaminergic differentiation compared to the laminin-coated 2D culture or Matrigel-encapsulated 3D culture. These differentiated neurons expressed specific dopaminergic markers and produced appropriate patterns of action potential firing. Consistent with the increase in the number of dopaminergic neurons differentiated from R1 or TTF-1 in the self-assembling peptide nanofiber scaffold (SAPNS), both the expression levels of genes that involve in dopaminergic differentiation and maturation and the dopamine release in SAPNS culture were significantly elevated. The results of the study suggest that SAPNS provides a promising 3D culture system for dopaminergic differentiation.</p> </div

Relative mRNA expression levels of dopaminergic differentiation markers (<i>Lmx1a</i>, <i>Foxa2</i>, En1, <i>Aadc</i>, <i>Nurr1</i>, Th, <i>Vmat2</i>, and <i>Dat</i>) in laminin-2D culture, Matrigel-3D culture and SAPNS-3D culture respectively.

<p>Quantitative real-time RT-PCR demonstrated that a 4-fold increase for <i>Lmx1a</i> (A), 5-fold increase for <i>Nurr1</i> (E), <i>Vmat2</i> (G), and <i>Dat</i> (H), 6-fold increase for En1 (C) and <i>Aadc</i> (D), and 7-fold increase for <i>Foxa2</i> (B) and Th (F) were found in both R1 and TTF-1 differentiation when cultured in SAPNS as compared to their expressions in Matrigel or on laminin.</p

Dopaminergic differentiation of R1 cells was significantly improved in SAPNS-3D culture.

<p>(A) Immunocytochemistry for TH and Tuj1 revealed the dopaminergic differentiation of R1 in Laminin-2D culture. (B) Immunocytochemistry for TH and Tuj1 revealed the dopaminergic differentiation of R1 in Matrigel-3D culture. (C) Immunocytochemistry for TH and Tuj1 revealed the dopaminergic differentiation of R1 in SAPNS-3D culture. (D) The percentage of TH-positive cells of total Tuj1-positive cells was 41.5% ± 3.4% in SAPNS-3D culture, which was significantly higher than 8.3% ± 1.4% in the laminin-2D culture and 7.9% ± 1.6% in Matrigel-3D culture. *P<0.001. Scale bar: 150 µm.</p

Derivation of neural progenitors from R1 and TTF-1 cells.

<p>(A) and (D) Phase contrast image shows that R1 and TTF-1 cells grew as colonies on mitomycin-treated MEF feeder cells. (B) and (E) Phase contrast image shows neural rosettes derived from R1 and TTF-1 cells. (C) and (F) Immunostaining reveals that predominantly cells in rosettes R1 and TTF-1 cells were Nestin positive. Scale bar: 200 µm in A and D; 150 µm in B, C, E, and F.</p

The majority of TH positive neurons co-expressed specific midbrain dopaminergic neuron markers.

<p>(A-C) Characterization of R1-derived TH positive neurons in SAPNS. (A) Double immunostaining showed that R1-derived TH positive neurons were co-labeled with Nurrl; (B) Double immunostaining showed that R1-derived TH positive neurons were co-labeled with Dat; (C) The majority of R1-derived TH positive neurons co-expressed Nurr1 or Dat. (D-F) Characterization of TTF-1-derived TH positive neurons in SAPNS. (D) Double immunostaining showed that TTF-1-derived TH positive neurons were co-labeled with Nurrl; (E) Double immunostaining showed that TTF-1-derived TH positive neurons were co-labeled with Dat; (F) The majority of TTF-1-derived TH positive neurons co-expressed Nurr1 or Dat. Scale bar: 100 µm.</p

Behavioral Stress Fails to Accelerate the Onset and Progression of Plaque Pathology in the Brain of a Mouse Model of Alzheimer's Disease

<div><p>Conflicting findings exist regarding the link between environmental factors and development of Alzheimer's disease (AD) in a variety of transgenic mouse models of AD. In the present study, we investigated the effect of behavioral stress on the onset and progression of Aβ pathology in the brains of TgCRND8 mice, a transgenic mouse model of AD. One group of TgCRND8 mice was subjected to restraint stress starting at 1 month of age until they were 3 months old, while restraint stress in the second group started at 4 months of age until they were 6 months old. After 2 months of treatment, no differences in the soluble, formic acid extracted, or histologically detected Aβ deposition in the cortical and hippocampal levels were found between non-stressed and stressed mice. These results showed that restraint stress alone failed to aggravate amyloid pathology when initiated either before or after the age of amyloid plaque deposition in TgCRND8 mice, suggesting that if stress aggravated AD phenotype, it may not be via an amyloid-related mechanism in the TgCRND8 mice. These findings are indicative that plaque load per se may not be used as a significant criterion for evaluating the effect of stress on AD patients.</p></div

Restraint stress activated hypothalamic neurons in TgCRND8 mice.

<p>A–D: Cross sections of the brains stained with c-fos immunohistochemical staining in PVN (A and C) and SON (B and D) of TgCRND8 mice at the age of 4 months undergone restraint stress (A and B) and non-stress treatment (C and D). E: Quantitative analysis of number of c-fos immunoreactive nuclei in SON of stressed and non-stressed TgCRND8 mice. * indicates statistical differences when compared with their age-matched non-stressed controls at <i>p</i><0.01. Scale bar = 150 µm.</p

The number of Thioflavin S-positive plaques/section in the brains of TgCRND8 mice at the age of 1, 3 or 6 month-old.

<p>The number of Thioflavin S-positive plaques/section in the brains of TgCRND8 mice at the age of 1, 3 or 6 month-old.</p

Plasma corticosterone levels in the stressed TgCRND8 mice increased compared with that in their non-stressed controls at the age of 3 and 6 month-old.

<p>* indicates statistical differences when compared with their age-matched non-stressed controls at <i>p</i><0.01.</p

Cross sections of the brains were stained with Thioflavin S staining in TgCRND8 mice at the age of 1 (A), 3 (B) and 6 (C) months.

<p>Scale bar = 100 µm.</p