Experimental study using multiple strains of prion disease in cattle reveals an inverse relationship between incubation time and misfolded prion accumulation, neuroinflammation and autophagy

Proteinopathies result from aberrant folding and accumulation of specific proteins. Currently, there is a lack of knowledge about the factors that influence disease progression making this a key challenge for the development of therapies for proteinopathies. Due to the similarities between transmissible spongiform encephalopathies (TSEs) and other protein misfolding diseases, TSEs can be used to understand other proteinopathies. Bovine spongiform encephalopathy (BSE) is a TSE that occurs in cattle and can be subdivided into three strains: classical BSE, and atypical BSEs (H-type and L-type) that have shorter incubation periods. The NLRP3 inflammasome is a critical component of the innate immune system that leads to release of IL-1β (Interlukin-1β). Macroautophagy is an intracellular mechanism that plays an essential role in protein clearance. In this study, we use the retina as a model to investigate the relationship between disease incubation period, prion protein (PrPSc) accumulation, neuroinflammation, and changes in macroautophagy. We demonstrate that atypical BSEs present with increased PrPSc accumulation and neuroinflammation, and decreased autophagy. Our work suggests a relationship between disease time course, neuroinflammation, and the autophagic stress response. This work may help identify novel therapeutic biomarkers that can delay or prevent the progression of proteinopathies

Xenotransplantation of adult hippocampal neural progenitors into the developing zebrafish for assessment of stem cell plasticity

Adult stem cells are considered multipotent, restricted to differentiate into a few tissue-specific cell types. With the advent of technologies which can dedifferentiate and transdifferentiate cell types, assumptions about the process of cell fate determination must be reconsidered, including the role of extrinsic versus intrinsic factors. To determine the plasticity of adult neural progenitors, rat hippocampal progenitor cells were xenotransplanted into embryonic zebrafish. These animals allow for easy detection of transplanted cells due to their external development and transparency at early stages. Adult neural progenitors were observed throughout the zebrafish for the duration of the experiment (at least five days post-transplantation). While the majority of transplanted cells were observed in the central nervous system, a large percentage of cells were located in superficial tissues. However, approximately one-third of these cells retained neural morphology and expression of the neuronal marker, Class III β-tubulin, indicating that the transplanted adult neural progenitors did not adapt alternate fates. A very small subset of cells demonstrated unique, non-neural flattened morphology, suggesting that adult neural progenitors may exhibit plasticity in this model, though at a very low rate. These findings demonstrate that the developing zebrafish may be an efficient model to explore plasticity of a variety of adult stem cell types and the role of external factors on cell fate

Adult neural stem cell plasticity

Stem cells derived from adult tissues have long been considered multipotent, able to differentiate into a limited number of cell types found in their tissue of origin. Embryonic stem cells, in contrast, are pluripotent, which may differentiate into almost all cell types. With the ability to create induced pluripotent stem cells from somatic cells now available, the properties of multipotent stem cells are being re-evaluated. If adult cells may be reverted to pluripotent stem cells, can multipotent stem cells also be manipulated towards pluripotency? Advancements in biotechnology now allow for better methods to investigate stem cell plasticity, such as the relative influence of external versus intrinsic factors on cell fate. Recent studies indicate that adult neural stem cells (NSCs) demonstrate greater plasticity under certain conditions, resulting in the derivation of a variety of cell types including muscle, hematopoietic, and epithelial cells. This suggests that NSCs may provide a potential source of rare cell types for clinical application as an alternative to embryonic stem cells. Producing rare cell types from NSCs rather than embryonic stem cells avoids the ethical issues surrounding the use of this cell type. Further, NSCs may be an advantageous source compared to induced pluripotent stem cells, which are difficult to create, expensive, and time-consuming to develop. Adult NSCs have the ability to form neurons, astrocytes, and oligodendrocytes in vitro. More recently, evidence has arisen which indicates adult NSCs may have extended plasticity. Studies have demonstrated differentiation into cell types of all three germ layers through a variety of methods

Soluble factors from neocortical astrocytes enhance neuronal differentiation of neural progenitor cells from adult rat hippocampus on micropatterned polymer substrates

Rat adult hippocampal progenitor cells (AHPCs) are self-renewing, multipotent neural progenitors that have the ability to differentiate into neurons and glia. Previously, we demonstrated that coculture of AHPCs with postnatal day two, type 1 cortical astrocytes on laminin-coated micropatterned polymer substrates facilitates selective neuronal differentiation of the AHPCs 1. Under this condition, multi-dimensional cell-cell and/or cell-extracellular matrix interactions, as well as possible soluble factors released from astrocytes provided spatial and temporal control selectively enhancing neuronal differentiation and neurite alignment on topographically different regions of the same substrate. To investigate the potential role of astrocyte-derived soluble factors as cues involved in neuronal differentiation, a non-contact co-culture system was used. Under control conditions, approximately 14% of the AHPCs were immunoreactive (IR) for the neuronal marker, class III β-tubulin (TUJ1-IR). When co-cultured in physical contact with astrocytes, neuronal differentiation increased significantly to about 25%, consistent with our previous results. Moreover, under non-contact co-culture conditions using Transwell insert cultures, neuronal differentiation was dramatically increased to approximately 64%. Furthermore, neurite outgrowth from neuronal cell bodies was considerably greater on the patterned substrate, compared to the non-patterned planar substrate under non-contact co-culture conditions. Taken together, our results demonstrate that astrocyte-derived soluble factors provide cues for specific neuronal differentiation of AHPCs cultured on micropatterned substrates. In addition, a suppressive influence on neuronal differentiation appears to be mediated by contact with co-cultured astrocytes. These results provide important insights into mechanisms for controlling neural progenitor/stem cell differentiation and facilitate development of strategies for CNS repair

Polycaprolactone Microfibrous Scaffolds to Navigate Neural Stem Cells

Fibrous scaffolds have shown promise in tissue engineering due to their ability to improve cell alignment and migration. In this paper, poly(ε-caprolactone) (PCL) fibers are fabricated in different sizes using a microfluidic platform. By using this approach, we demonstrated considerable flexibility in ability to control the size of the fibers. It was shown that the average diameter of the fibers was obtained in the range of 2.6–36.5 μm by selecting the PCL solution flow rate from 1 to 5 μL min–1 and the sheath flow rate from 20 to 400 μL min–1 in the microfluidic channel. The microfibers were used to create 3D microenvironments in order to investigate growth and differentiation of adult hippocampal stem/progenitor cells (AHPCs) in vitro. The results indicated that the 3D topography of the PCL substrates, along with chemical (extracellular matrix) guidance cues supported the adhesion, survival, and differentiation of the AHPCs. Additionally, it was found that the cell deviation angle for 44–66% of cells on different types of fibers was less than 10°. This reveals the functionality of PCL fibrous scaffolds for cell alignment important in applications such as reconnecting serious nerve injuries and guiding the direction of axon growth as well as regenerating blood vessels, tendons, and muscle tissue