Reprogramming cell fates by small molecules

ABSTRACT Reprogramming cell fates towards pluripotent stem cells and other cell types has revolutionized our understanding of cellular plasticity. During the last decade, transcription factors and microRNAs have become powerful reprogramming factors for modulating cell fates. Recently, many efforts are focused on reprogramming cell fates by non-viral and non-integrating chemical approaches. Small molecules not only are useful in generating desired cell types in vitro for various applications, such as disease modeling and cell-based transplantation, but also hold great promise to be further developed as drugs to stimulate patients’ endogenous cells to repair and regenerate in vivo. Here we will focus on chemical approaches for generating induced pluripotent stem cells, neurons, cardiomyocytes, hepatocytes and pancreatic β cells. Significantly, the rapid and exciting advances in cellular reprogramming by small molecules will help us to achieve the long-term goal of curing devastating diseases, injuries, cancers and aging

A field study on heavy metals phytoattenuation potential of monocropping and intercropping of maize and/or legumes in weakly alkaline soils

<p>The study focused on the phytoattenuation effects of monocropping and intercropping of maize (<i>Zea mays</i>) and/or legumes on Cu, Zn, Pb, and Cd in weakly alkaline soils. Nine growth stages of monocropping maize were chosen to study the dynamic process of extraction of heavy metals. The total content of heavy metals extracted by the aerial part of monocropped maize increased in a sigmoidal pattern over the effective accumulative temperature. The biggest biomass, highest extraction content, and lowest heavy metals bioaccumulation level occurred at physiological maturity. Among the different planting patterns, including monocropping and intercropping of maize and/or soybean (<i>Glycine max</i>), pea (<i>Pisum sativum</i>), and alfalfa (<i>Medicago sativa</i>), the extraction efficiency of Cu, Zn, Pb, and Cd varied greatly. Only intercropping of maize and soybean yielded relatively higher extraction efficiency for the four metals with no significant difference in the total biomass. Moreover, the heavy metals concentrations in dry biomass from all the planting patterns in the present study were within China's national legal thresholds for fodder use. Therefore, slightly polluted alkaline soils can be safely used through monocropping and intercropping of maize and/or legumes for a range of purposes. In particular, this study indicated that intercropping improves soil ecosystems polluted by heavy metals compared with monocropping.</p

Pharmacological Reprogramming of Fibroblasts into Neural Stem Cells by Signaling-Directed Transcriptional Activation

Cellular reprogramming using chemically defined conditions, without genetic manipulation, is a promising approach for generating clinically relevant cell types for regenerative medicine and drug discovery. However, small-molecule approaches for inducing lineage-specific stem cells from somatic cells across lineage boundaries have been challenging. Here, we report highly efficient reprogramming of mouse fibroblasts into induced neural stem cell-like cells (ciNSLCs) using a cocktail of nine components (M9). The resulting ciNSLCs closely resemble primary neural stem cells molecularly and functionally. Transcriptome analysis revealed that M9 induces a gradual and specific conversion of fibroblasts toward a neural fate. During reprogramming specific transcription factors such as Elk1 and Gli2 that are downstream of M9-induced signaling pathways bind and activate endogenous master neural genes to specify neural identity. Our study provides an effective chemical approach for generating neural stem cells from mouse fibroblasts and reveals mechanistic insights into underlying reprogramming processes

Using Flow Cytometry to Compare the Dynamics of Photoreceptor Outer Segment Phagocytosis in iPS-Derived RPE Cells

PURPOSE. Retinal pigment epithelium (RPE) autologous grafts can be readily derived from induced pluripotent stem (iPS) cells. It is critical to stringently characterize iPS-RPE using standardized and quantifiable methods to be confident that they are safe and adequate replacements for diseased RPE before utilizing them in clinical settings. One important and required function is that the iPS-RPE phagocytose photoreceptor outer segments (POS). METHODS. We developed a flow cytometry-based assay to monitor binding and internalization of FITC labeled POS by ARPE-19, human fetal RPE (hfRPE), and two types of iPS-RPE. Expression and density of α(v)β(5) integrin, CD36, and MerTK receptors, which are required for phagocytosis, were compared. RESULTS. Trypsinization of treated RPE cells results in the release of bound POS. The number of freed POS, the percentage of cells that internalized POS, the brightness of the FITC signal from the cells, and the surface density of the phagocytosis receptors on single RPE cells were measured using flow cytometry. These assays reveal that receptor density is dynamic during differentiation and this can affect the binding and internalization dynamics of the RPE cells. Highly differentiated iPS-RPE phagocytose POS more efficiently than hfRPE. CONCLUSIONS. Caution should be exercised to not use RPE grafts until demonstrating that they are fully functional. The density of the phagocytosis receptors is dynamic and may be used as a predictor for how well the iPS-RPE cells will function in vivo. The phagocytosis dynamics observed between iPS-RPE and primary RPE is very encouraging and adds to mounting evidence that iPS-RPE may be a viable replacement for dysfunctional or dying RPE in human patients

Using Flow Cytometry to Compare the Dynamics of Photoreceptor Outer Segment Phagocytosis in iPS-Derived RPE CellsPhagocytosis in iPS-Derived RPE Cells

PurposeRetinal pigment epithelium (RPE) autologous grafts can be readily derived from induced pluripotent stem (iPS) cells. It is critical to stringently characterize iPS-RPE using standardized and quantifiable methods to be confident that they are safe and adequate replacements for diseased RPE before utilizing them in clinical settings. One important and required function is that the iPS-RPE phagocytose photoreceptor outer segments (POS).MethodsWe developed a flow cytometry-based assay to monitor binding and internalization of FITC labeled POS by ARPE-19, human fetal RPE (hfRPE), and two types of iPS-RPE. Expression and density of α(v)β₅ integrin, CD36, and MerTK receptors, which are required for phagocytosis, were compared.ResultsTrypsinization of treated RPE cells results in the release of bound POS. The number of freed POS, the percentage of cells that internalized POS, the brightness of the FITC signal from the cells, and the surface density of the phagocytosis receptors on single RPE cells were measured using flow cytometry. These assays reveal that receptor density is dynamic during differentiation and this can affect the binding and internalization dynamics of the RPE cells. Highly differentiated iPS-RPE phagocytose POS more efficiently than hfRPE.ConclusionsCaution should be exercised to not use RPE grafts until demonstrating that they are fully functional. The density of the phagocytosis receptors is dynamic and may be used as a predictor for how well the iPS-RPE cells will function in vivo. The phagocytosis dynamics observed between iPS-RPE and primary RPE is very encouraging and adds to mounting evidence that iPS-RPE may be a viable replacement for dysfunctional or dying RPE in human patients