Supplementary MaterialsPEER-REVIEW REPORT 1. than embryonic stem cells avoids the honest issues surrounding the use of this cell type. Further, NSCs may be an advantageous resource compared to induced pluripotent stem cells, which are hard to create, expensive, and time-consuming to develop. Adult NSCs have the ability to form neurons, astrocytes, and oligodendrocytes version of this Cast assay, adult cells are injected into a blastula, embryoid body, or are co-cultured with embryonic stem cells. This method, while simpler than carrying out experiments with live animals, does not allow for observation of the full developmental process due to the current limitations of organism development technology. However, it does permit close observation of cell behavior immediately following transplantation and direct measurement of fate-determining factors. Open in a separate window Number 1 Methods for assessing adult stem cell plasticity. (A) The chimera assay checks the full differentiation capacity of stem cells. The stem cells of interest (dark gray) are transplanted into the early developing embryo. Mice, chicks, swine, and now zebrafish have been utilized in this model. Plasticity is shown when the transplanted cells are found with fresh TG-101348 inhibition phenotypes functioning outside of their cells of source. (B) Adult stem cells have been injected into specific cells of adult mice to test for TG-101348 inhibition plasticity toward a particular fate. (C) Co-culture of adult stem cells with somatic cells or secreted factors also checks for differentiation toward a specific cell type. Adult neural stem cell plasticity shown from the chimera assay was first exhibited in 2000. Adult mouse neural progenitors were transplanted into mouse blastocysts, generating chimeric animals. Characterization by immunohistochemistry shown differentiation into cardiac muscle mass cells, hepatocytes, and epithelial cells. The neural progenitors were also injected into chick embryos, a process called xenotransplantation (xeno referring to cross-species). Adult neural progenitor-derived cells were observed, forming chimeric ectodermal, endodermal, and mesodermal cells (Clarke et al., 2000). A following study published in 2004 found contradicting results. Transplantation of fetal mouse neural progenitor cells into mouse blastocysts did not result in chimeric animals. Further investigation following blastula development identified the progenitors rapidly differentiated into glial cells, preventing assessment of plasticity (Grco et al., 2004). Fetal TG-101348 inhibition porcine neural progenitor cells transplanted into 4- and 9-cell stage embryos of the same varieties did not form chimeras, as well (Zhao et al., 2012). Checks for adult neural stem cell plasticity using the chimera assay have been performed using embryonic zebrafish, as well. Xenotransplantation of mammalian cells into zebrafish has recently been developed as TG-101348 inhibition a rapid method for the study of cell behavior and fate. The fate of transplanted cells may be observed in real-time as zebrafish are transparent at early stages. development avoids the need for embryo implantation into surrogate mothers, further aiding observation. The immature zebrafish immune system at this stage also helps prevent donor cell rejection. Similar to the results in mice, findings of plasticity following xenotransplantation into zebrafish are variable. Fetal mouse neural progenitor cells transplanted into blastula-stage zebrafish by Xiao et al. (2016) were later found in multiple locations, including mesodermally-derived cells such as heart and blood, epithelial, and endodermal cells. Although no immunohistochemical characterization of these cells was performed, cells in the epidermis did display an epithelial morphology. Subsequent co-culture of the neural progenitor cells with mouse pores and skin cells resulted in the formation of keratin1-positive cells (Xiao et al., 2016). A recent study published by Sandquist and colleagues in 2018 also shown chimerism following transplantation of adult rat neural progenitors into embryonic zebrafish. The majority of cells found outside the CNS were located in the epidermis, with cells also observed in skeletal, cardiac muscle mass and facial cartilage. However, immunohistochemical analysis indicated that the majority of transplanted cells retained their neural phenotypes despite their locations outside the central nervous system, with positive immunolabeling for class III.