High-efficiency derivation of human embryonic stem cell lines using a culture system with minimized trophoblast cell proliferation

Pluripotent stem cells: Basic biology or else differentiations aimed at translational research and the role of flow cytometry

Pluripotent stem cell research has revolutionized the modern era for the past 14 years with the advent of induced pluripotent stem cells. Before this time, scientists had access to human and mouse embryonic stem cells primarily for basic research and an attempt towards lineage-specific differentiations for cell therapy applications. Regarding pluripotent stem cells, expression of bonafide marker proteins such as Oct4, Nanog, Sox2, Klf4, c-Myc, and Lin28 have been considered giving a perfect readout for pluripotent stem cells and assessed using an analytical flow cytometer. In addition to the intracellular markers, surface markers such as stage-specific embryonic antigen-1 for mouse cells and SSEA-4 for human cells are needed to sort pure populations of stem cells for further downstream applications for cell therapy. The surface marker SSEA-4 is the most appropriate for obtaining pure populations of human pluripotent stem cells. When differentiated in a controlled manner using growth factors or small molecules, it is mandatory to assess the downregulation of pluripotency markers (Oct4, Nanog, Sox2, and Klf4) with subsequent up-regulation of stage-specific differentiation markers. Such assessments are done using flow cytometry. Pluripotent stem cells have a high teratoma-forming potential in vivo. Small amounts of undifferentiated PSCs might lead to dangerous teratomas upon transplantation if leftover in the pool of differentiated cells. Hence, flow cytometry is essential for sorting out PSC populations with teratoma-forming potential. The pure populations of differentiated progenitors need to be flow-sorted before differentiating them further for cell therapy applications. For example, Glycoprotein 2 is a specific cell-surface marker for pancreatic progenitors that enables one to sort the pancreatic progenitors differentiated from human PSCs. Taken together, analytical flow cytometry, and cell sorting provide indispensable tools in PSC research and cell therapy.

Generation of RUNX1c-eGFP induced pluripotent stem cell, MUSIi012-A-4, using CRISPR/Cas9

Runt-Related Transcription Factor 1c (RUNX1c) plays an important role in regulating the development of hematopoietic stem cells (HSC). Using CRISPR/Cas9 gene editing technology, we established a RUNX1c-eGFP reporter cell line from the MUSIi012-A cell line. The MUSIi012-A-4 cell line has normal stem cell morphology and karyotype, expresses pluripotency markers, and can be differentiated into all three germ layers in vitro and in vivo. This cell line serves as a valuable model to observe the expression of RUNX1c via eGFP tracking during human hematopoietic development.

CRISPR/Cas9 mediated approach to generate YAP-depleted human embryonic stem cell line (MUSIe002-A-1)

Yes-associated protein (YAP), an important effector protein of the Hippo signaling pathway, acts as a molecular switch in controlling cell proliferation and apoptosis. In this study, a YAP-targeted isogenic sub-clone of the MUSIe002-A was generated, designated as MUSIe002-A-1. The MUSIe002-1 cell line had normal pluripotent stem cell characteristics and karyotype. Its ability to differentiate into three germ layers was confirmed. As reduction of YAP does not disturb the pluripotency of hESCs, this cell line serves as a valuable model to extrapolate the functional role of YAP in stem cell biology and its applications.

Role of YAP as a Mechanosensing Molecule in Stem Cells and Stem Cell-Derived Hematopoietic Cells

Yes-associated protein (YAP) and WW domain-containing transcription regulator protein 1 (WWTR1, also known as TAZ) are transcriptional coactivators in the Hippo signaling pathway. Both are well-known regulators of cell proliferation and organ size control, and they have significant roles in promoting cell proliferation and differentiation. The roles of YAP and TAZ in stem cell pluripotency and differentiation have been extensively studied. However, the upstream mediators of YAP and TAZ are not well understood. Recently, a novel role of YAP in mechanosensing and mechanotransduction has been reported. The present review updates information on the regulation of YAP by mechanical cues such as extracellular matrix stiffness, fluid shear stress, and actin cytoskeleton tension in stem cell behaviors and differentiation. The review explores mesenchymal stem cell fate decisions, pluripotent stem cells (PSCs), self-renewal, pluripotency, and differentiation to blood products. Understanding how cells sense their microenvironment or niche and mimic those microenvironments in vitro could improve the efficiency of producing stem cell products and the efficacy of the products.

Derivation of the MUSIe002-A human embryonic stem cell line

The MUSIe002-A cell line was established from in vitro fertilization of human sperm and oocytes donated for research with informed consent. This cell line exhibited normal human embryonic stem cell (hESC) characteristics, including typical cell morphology, expression of all pluripotent stem cell markers, and potential to differentiate into three germ layers. A karyotyping analysis revealed 46 XY chromosome and cells that did not have mycoplasma contamination. MUSIe002-A represents a valuable unlimited cell source and is of potential interest for human in vitro stem cell based-models, genetic modifications, and stem cell-based therapy of human disease.

YAP-depleted iPSC MUSIi012-A-2 maintained all normal stem cell characteristics

Yes-associated protein (YAP) is an important transcriptional coactivator in the Hippo signaling pathway. Using CRISPR/Cas9 technology, we established a stable YAP-knockdown (YAP-KD) induced pluripotent stem cell (iPSC) from the MUSIi012-A cell line. The YAP-KD iPSC MUSIi012-A-2 maintained the pluripotent phenotype, the ability to differentiate into all three embryonic germ layers, and it maintained the normal karyotype.

Derivation of human embryonic stem cell line MUSIe001-A from an embryo with homozygous α0-thalassemia (SEA deletion)

MUSIe001-A cell line was derived from a Southeast Asian (SEA) type deletion α⁰-thalassemia embryo. The SEA deletion embryo was donated for research with informed consent. This cell line shows normal hESC morphology, expresses all pluripotent markers, and has the potential to differentiate into all three germ layers in vitro and in vivo. The MUSIe001-A line has normal karyotype and is free from mycoplasma contamination. PCR analysis confirmed the MUSIe001-A cell line to be a SEA type deletion. MUSIe001-A is a valuable proof of principle model for gene therapy that will facilitate the development of new treatments for affected foetuses.

Derivation of new human embryonic stem cell lines (Yazd1-3) and their vitrification using Cryotech and Cryowin tools: A lab resources report

Background

Cell banking of initial outgrowths from newly derived human embryonic stem cells (hESCs) requires an efficient freezing method. Vitrification is used for the preservation of gametes and early embryos in assisted reproduction techniques (ART). Moreover, vitrification was applied for cryopreservation of hESCs using open pulled straws.

Objective

To derive and characterize new hESC lines and then use Cryotech and Cryowin tools for their vitrification.

Materials and Methods

Human ESC lines were generated in a microdrop culture system using mouse embryonic fibroblasts (MEFs) as the feeder layer; this was later scaled up using both MEFs and Yazd human foreskin fibroblasts batch 8 (YhFF#8). To bank the cell lines, master cell banks of 100 Cryotech and Cryowin tools were produced for each individual cell line using the vitrification method; flasks of hESC lines were also cryopreserved using a conventional slow-freezing method.

Results

The pluripotency of cell lines was assessed by their expression of pluripotency-associated genes (OCT4/POU5F1, NANOG, and SOX2) and markers such as SSEA4, TRA-1-60, and TRA-2-49. Their in vitro capacity to differentiate into germ layers and germ cells using embryoid body (EB) formation and monolayer culture was assessed by screening the expression of differentiation-associated genes. The chromosomal constitution of each hESC line was assessed by G-banding karyotyping.

Conclusion

Cryotech and Cryowin tools used to vitrify new hESCs at an early stage of derivation is an efficient method of preserving hESCs.