The effect of SARS-CoV-2 on the nervous system: a review of neurological impacts caused by human coronaviruses.

The COVID-19 pandemic has affected millions of people worldwide. While coronaviruses typically have low rates of neurotropic effects, the massive transmission of SARS-CoV-2 suggests that a substantial population will suffer from potential SARS-CoV-2-related neurological disorders. The rapid and recent emergence of SARS-CoV-2 means little research exists on its potential neurological effects. Here we analyze the effects of similar viruses to provide insight into the potential effects of SARS-CoV-2 on the nervous system and beyond. Seven coronavirus strains (HCoV-OC43, HCoV-HKU1, HCoV-229E, HCoV-NL63, SARS-CoV, MERS-CoV, SARS-CoV-2) can infect humans. Many of these strains cause neurological effects, such as headaches, dizziness, strokes, seizures, and critical illness polyneuropathy/myopathy. Certain studies have also linked coronaviruses with multiple sclerosis and extensive central nervous system injuries. Reviewing these studies provides insight into the anticipated effects for patients with SARS-CoV-2. This review will first describe the effects of other coronaviruses that have caused severe disease (SARS-CoV, MERS-CoV) on the nervous system, as well as their proposed origins, non-neurological effects, and neurological infection mechanisms. It will then discuss what is known about SARS-CoV-2 in these areas with reference to the aforementioned viruses, with the goal of providing a holistic picture of SARS-CoV-2.

Indirect 3D bioprinting and characterization of alginate scaffolds for potential nerve tissue engineering applications.

Low-concentration hydrogels have favorable properties for many cell functions in tissue engineering but are considerably limited from a scaffold fabrication point of view due to poor three-dimensional (3D) printability. Here, we developed an indirect-bioprinting process for alginate scaffolds and characterized the potential of these scaffolds for nerve tissue engineering applications. The indirect-bioprinting process involves (1) printing a sacrificial framework from gelatin, (2) impregnating the framework with low-concentration alginate, and (3) removing the gelatin framework by an incubation process, thus forming low-concentration alginate scaffolds. The scaffolds were characterized by compression testing, swelling, degradation, and morphological and biological assessment of incorporated or seeded Schwann cells. For comparison, varying concentrations of alginate scaffolds (from 0.5% to 3%) were fabricated and sterilized using either ultraviolet light or ethanol. Results indicated that scaffolds can be fabricated using the indirect-bioprinting process, wherein the scaffold properties are affected by the concentration of alginate and sterilization technique used. These factors provide effective means of regulating the properties of scaffolds fabricated using the indirect-bioprinting process. Cell-incorporated scaffolds demonstrated better cell viability than bulk gels. In addition, scaffolds showed better cell functionality when fabricated with a lower concentration of alginate compared to a higher concentration. The indirect-bioprinting process that we implemented could be extended to other types of low-concentration hydrogels to address the tradeoffs between printability and properties for favorable cell functions.

3D Printing of Neural Tissues Derived from Human Induced Pluripotent Stem Cells Using a Fibrin-Based Bioink.

3D bioprinting offers the opportunity to automate the process of tissue engineering, which combines biomaterial scaffolds and cells to generate substitutes for diseased or damaged tissues. These bioprinting methods construct tissue replacements by positioning cells encapsulated in bioinks into specific locations in the resulting constructs. Human induced pluripotent stem cells (hiPSCs) serve as an important tool when engineering neural tissues. These cells can be expanded indefinitely and differentiated into the cell types found in the central nervous systems, including neurons. One common method for differentiating hiPSCs into neural tissue requires the formation of aggregates inside of defined diameter microwells cultured in chemically defined media. However, 3D bioprinting of such hiPSC-derived aggregates has not been previously reported in the literature, as it requires the development of specialized bioinks for supporting cell survival and differentiation into mature neural phenotypes. Here we detail methods including preparing base material components of the bioink, producing the bioink, and the steps involved in printing 3D neural tissues derived from hiPSC-derived neural aggregates using Aspect Biosystems' novel RX1 printer and their lab-on-a-printer (LOP) technology.