A Synthetic Hybrid Molecule for the Selective Removal of Human Pluripotent Stem Cells from Cell Mixtures

Sorting differentiated mammalian cells using deterministic lateral displacement microfluidic devices

Separation of differentiated and undifferentiated cells without labeling is required for cell analyses and clinical application of cultured differentiated cells in vitro. To proceed with the passive separation of differentiated cells inside a clean bench, we developed a system of deterministic lateral displacement (DLD) microfluidic devices and applied this system to sort differentiated cells in vitro. The fluid flow is driven by compressed air to the buffer. Priming and sorting can be completed by air pressure control. We use this system to separate C2C12 mononuclear myocytes from multinuclear myotubes. Additionally, using a DLD microfluidic channel of Dc = 20 μm, multinuclear myotubes can be effectively sorted as larger particles. We prepared differentiated adipocytes from mouse embryonic fibroblast (MEF) cells and sorted those containing lipid droplets. The diameters of these sorted adipocytes considered larger particles, exceeded 20 μm, similar to the Dc of the DLD microfluidic channel. Differentiated cell sorting by cell size will contribute to single-cell analyses and in vitro tissue model preparation for drug discovery.

Structural Modification Endows Small-Molecular SN38 Derivatives with Multifaceted Functions

As a camptothecin derivative, 7-ethyl-10-hydroxycamptothecin (SN38) combats cancer by inhibiting topoisomerase I. SN38 is one of the most active compounds among camptothecin derivatives. In addition, SN38 is also a theranostic reagent due to its intrinsic fluorescence. However, the poor water solubility, high systemic toxicity and limited action against drug resistance and metastasis of tumor cells of SN38 indicates that there is great space for the structural modification of SN38. From the perspective of chemical modification, this paper summarizes the progress of SN38 in improving solubility, increasing activity, reducing toxicity and possessing multifunction and analyzes the strategies of structure modification to provide a reference for drug development based on SN38.

A Simplified and Effective Approach for the Isolation of Small Pluripotent Stem Cells Derived from Human Peripheral Blood

Pluripotent stem cells are key players in regenerative medicine. Embryonic pluripotent stem cells, despite their significant advantages, are associated with limitations such as their inadequate availability and the ethical dilemmas in their isolation and clinical use. The discovery of very small embryonic-like (VSEL) stem cells addressed the aforementioned limitations, but their isolation technique remains a challenge due to their small cell size and their efficiency in isolation. Here, we report a simplified and effective approach for the isolation of small pluripotent stem cells derived from human peripheral blood. Our approach results in a high yield of small blood stem cell (SBSC) population, which expresses pluripotent embryonic markers (e.g., Nanog, SSEA-3) and the Yamanaka factors. Further, a fraction of SBSCs also co-express hematopoietic markers (e.g., CD45 and CD90) and/or mesenchymal markers (e.g., CD29, CD105 and PTH1R), suggesting a mixed stem cell population. Finally, quantitative proteomic profiling reveals that SBSCs contain various stem cell markers (CD9, ITGA6, MAPK1, MTHFD1, STAT3, HSPB1, HSPA4), and Transcription reg complex factors (e.g., STAT5B, PDLIM1, ANXA2, ATF6, CAMK1). In conclusion, we present a novel, simplified and effective isolating process that yields an abundant population of small-sized cells with characteristics of pluripotency from human peripheral blood.

Highly Sensitive Detection of Human Pluripotent Stem Cells by Loop-Mediated Isothermal Amplification

For safe regenerative medicines, contaminated or remaining tumorigenic undifferentiated cells in cell-derived products must be rigorously assessed through sensitive assays. Although in vitro nucleic acid tests offer particularly sensitive tumorigenicity-associated assays, the human pluripotent stem cell (hPSC) detectability is partly constrained by the small input amount of RNA per test. To overcome this limitation, we developed reverse transcription loop-mediated isothermal amplification (RT-LAMP) assays that are highly gene specific and robust against interfering materials. LAMP could readily assay microgram order of input sample per test and detected an equivalent model of 0.00002% hiPSC contamination in a simple one-pot reaction. For the evaluation of cell-derived total RNA, RT-LAMP detected spiked-in hPSCs among hPSC-derived trilineage cells utilizing multiple pluripotency RNAs. We also developed multiplex RT-LAMP assays and further applied for in situ cell imaging, achieving specific co-staining of pluripotency proteins and RNAs. Our attempts uncovered the utility of RT-LAMP approaches for tumorigenicity-associated assays, supporting practical applications of regenerative medicine.

Principles and Protocols For Post-Cryopreservation Quality Evaluation of Stem Cells in Novel Biomedicine

Stem cell therapy is a thriving topic of interest among researchers and clinicians due to evidence of its effectiveness and promising therapeutic advantage in numerous disease conditions as presented by novel biomedical research. However, extensive clinical application of stem cells is limited by its storage and transportation. The emergence of cryopreservation technology has made it possible for living organs, tissues, cells and even living organisms to survive for a long time at deep low temperatures. During the cryopreservation process, stem cell preparations are subject to three major damages: osmotic damage, mechanical damage, and peroxidative damage. Therefore, Assessing the effectiveness and safety of stem cells following cryopreservation is fundamental to the quality control of stem cell preparations. This article presents the important biosafety and quality control parameters to be assessed during the manufacturing of clinical grade stem cell products, highlights the significance of preventing cryodamage. and provides a reference for protocols in the quality control of stem cell preparations.

Enzymatically Forming Intranuclear Peptide Assemblies for Selectively Killing Human Induced Pluripotent Stem Cells

Tumorigenic risk of undifferentiated human induced pluripotent stem cells (iPSCs), being a major obstacle for clinical application of iPSCs, requires novel approaches for selectively eliminating undifferentiated iPSCs. Here, we show that an l-phosphopentapeptide, upon the dephosphorylation catalyzed by alkaline phosphatase (ALP) overexpressed by iPSCs, rapidly forms intranuclear peptide assemblies made of α-helices to selectively kill iPSCs. The phosphopentapeptide, consisting of four l-leucine residues and a C-terminal l-phosphotyrosine, self-assembles to form micelles/nanoparticles, which transform into peptide nanofibers/nanoribbons after enzymatic dephosphorylation removes the phosphate group from the l-phosphotyrosine. The concentration of ALP and incubation time dictates the morphology of the peptide assemblies. Circular dichroism and FTIR indicate that the l-pentapeptide in the assemblies contains a mixture of an α-helix and aggregated strands. Incubating the l-phosphopentapeptide with human iPSCs results in rapid killing of the iPSCs (=<2 h) due to the significant accumulation of the peptide assemblies in the nuclei of iPSCs. The phosphopentapeptide is innocuous to normal cells (e.g., HEK293 and hematopoietic progenitor cell (HPC)) because normal cells hardly overexpress ALP. Inhibiting ALP, mutating the l-phosphotyrosine from the C-terminal to the middle of the phosphopentapeptides, or replacing l-leucine to d-leucine in the phosphopentapeptide abolishes the intranuclear assemblies of the pentapeptides. Treating the l-phosphopentapeptide with cell lysate of normal cells (e.g., HS-5) confirms the proteolysis of the l-pentapeptide. This work, as the first case of intranuclear assemblies of peptides, not only illustrates the application of enzymatic noncovalent synthesis for selectively targeting nuclei of cells but also may lead to a new way to eliminate other pathological cells that express a high level of certain enzymes.

Kyoto probe-1 reveals phenotypic differences between mouse ES cells and iTS-P cells

Kyoto probe 1 (KP-1) rapidly distinguishes between human ES/iPS (hES/iPS) cells and their differentiated cells. Recently, we generated induced tissue-specific stem cells from pancreas (iTS-P cells) using reprogramming factors and tissue-specific selection. The iTS-P cells have self-renewal potential, and subcutaneously transplanting them into immunodeficient mice did not generate teratomas. In this study, we applied KP-1 to analyze mouse ES (mES) cells and mouse iTS-P (miTS-P) cells. KP-1 completely stained mES cells in colonies, but only miTS-P cells at the edge of a colony. This difference was caused by cell type-specific expression of different ABC transporters. These finding suggest that KP-1 will be useful for distinguishing between iPS and iTS-P cells.

Chemical decontamination of iPS cell-derived neural cell mixtures

This report describes the design and evaluation of phosphorylated 7-ethyl-10-hydroxycamptothecin (SN38-P), which selectively eliminates tumor-forming proliferative stem cells, including human induced pluripotent stem cells (hiPSCs) and neural stem cells, from iPSC-derived neural cell mixtures. Results of the present study demonstrate that simple phosphorylation of an anticancer drug can provide a safe, cost-effective, and chemically-defined tool for decontaminating hiPSC-derived neuron.

Selective Elimination of Human Induced Pluripotent Stem Cells Using Medium with High Concentration of L-Alanine

Human pluripotent stem cells, including human induced pluripotent stem cells (hiPSCs), serve as highly valuable sources for both cell-based therapies and basic research, owing to their abilities to self-renew and differentiate into any cell type of the human body. However, tumorigenic risks of residual undifferentiated stem cells limit the clinical application of hiPSCs, necessitating methods to eliminate undifferentiated hiPSCs from differentiated cells. Here, we found that undifferentiated hiPSCs were more sensitive to the treatment with a medium supplemented with high concentration of L-alanine than human fibroblasts (hFBs), human skeletal muscle cells (hSkMCs), hiPSC-derived cardiomyocytes (iCMs) or hiPSC-derived fibroblast-like cells (iFLCs), which were used as differentiated cells. Undifferentiated hiPSCs co-cultured with differentiated cells were selectively eliminated following treatment. In addition, we found that the medium supplemented with high concentration of D-alanine or β-alanine also induced cell death of hiPSCs and the treatment at 4 °C didn't induce cell death of hiPSCs. The cell death induced would be associated partly with high osmotic pressure of the medium supplemented with L-alanine. As L-alanine is a component of proteins in human body and popular ingredient of cell culture media, treatment with high concentration of L-alanine may be useful for eliminating tumorigenic residual hiPSCs for stem cell-based therapies.