Generation of hematopoietic stem cells from human embryonic stem cells using a defined, stepwise, serum-free, and serum replacement-free monolayer culture method

Human Embryonic Stem Cells as a Model for Hematopoietic Stem Cell Differentiation and Viral Infection

Pluripotent human embryonic stem cell (hESC) lines are a valuable in vitro tool to differentiate specific cell lineages, including cells from all three germ layers, i.e., neuronal cells, myocytes, and hematopoietic cells, including progenitors (described here), lymphoid cells, and myeloid cells. However, dramatically different cell subtypes and functional properties of specific cells can arise depending on the differentiation technique used. We previously optimized hematopoietic stem cell differentiation from two different NIH-approved hESC lines to generate CD34+ hematopoietic progenitor cells (HPCs). Infection of these HPCs with a common herpesvirus (human cytomegalovirus) results in maintenance of viral latency, capability of viral reactivation, recapitulation of viral mutant phenotypes, and virus-induced myelosuppression of hematopoietic differentiation. However, different HPC subpopulations support different viral latency and reactivation phenotypes, and different hESC-to-HPC differentiation methods alter the ratio of stem cell subsets. In addition, differences in differentiation methods are dependent on both protocol/reagents and user techniques. Here, we report a simplified and optimized method to generate large numbers of CD34+ HPCs with consistent phenotypes and demonstrate a comparison of several common methods that can be used to control the ratio of available HPC subpopulations. A key aspect of this approach is that we achieve consistency in differentiation across users in different laboratories and, importantly, among newly trained individuals. © 2022 The Authors. Current Protocols published by Wiley Periodicals LLC. Basic Protocol 1: Maintenance of human embryonic stem cells (hESCs) Basic Protocol 2: Differentiation of hESCs to hematopoietic progenitor cells (HPCs) Basic Protocol 3: Downstream functional differentiation of hESC-derived HPCs to mature lineages Support Protocol 1: Freezing and testing frozen batches of hESCs Support Protocol 2: Counting hESCs Support Protocol 3: Phenotyping by flow cytometry.

Human induced pluripotent stem cell line banking for the production of rare blood type erythrocytes

Background

The in vitro production of mature human red blood cells (RBCs) from induced pluripotent stem cells (iPSCs) has been the focus of research to meet the high demand for blood transfusions. However, limitations like high costs and technological requirements restrict the use of RBCs produced by iPSC differentiation to specific circumstances, such as for patients with rare blood types or alloimmunized patients. In this study, we developed a detailed protocol for the generation of iPSC lines derived from peripheral blood of donors with O D-positive blood and rare blood types (D–and Jr(a-)) and subsequent erythroid differentiation.

Methods

Mononuclear cells separated from the peripheral blood of O D-positive and rare blood type donors were cultured to produce and expand erythroid progenitors and reprogrammed into iPSCs. A 31-day serum-free, xeno-free erythroid differentiation protocol was used to generate reticulocytes. The stability of iPSC lines was confirmed with chromosomal analysis and RT-PCR. Morphology and cell counts were determined by microscopy observations and flow cytometry.

Results

Cells from all donors were successfully used to generate iPSC lines, which were differentiated into erythroid precursors without any apparent chromosomal mutations. This differentiation protocol resulted in moderate erythrocyte yield per iPSC.

Conclusions

It has previously only been hypothesized that erythroid differentiation from iPSCs could be used to produce RBCs for transfusion to patients with rare blood types or who have been alloimmunized. Our results demonstrate the feasibility of producing autologous iPSC-differentiated RBCs for clinical transfusions in patients without alternative options.

Establishment of a feeder and serum-free culture system for human embryonic stem cells

Stem cells are an immortal cell population capable of self-renewal; they are essential for human development and ageing and are a major focus of research in regenerative medicine. Despite considerable progress in differentiation of stem cells in vitro, culture conditions require further optimization to maximize the potential for multicellular differentiation during expansion. The aim of this study was to develop a feeder-free, serum-free culture method for human embryonic stem cells (hESCs), to establish optimal conditions for hESC proliferation, and to determine the biological characteristics of the resulting hESCs. The H9 hESC line was cultured using a homemade serum-free, feeder-free culture system, and growth was observed. The expression of pluripotency proteins (OCT4, NANOG, SOX2, LIN28, SSEA-3, SSEA-4, TRA-1-60, and TRA-1-81) in hESCs was determined by immunofluorescence and western blotting. The mRNA expression levels of genes encoding nestin, brachyury and α-fetoprotein in differentiated H9 cells were determined by RT-PCR. The newly developed culture system resulted in classical hESC colonies that were round or elliptical in shape, with clear and neat boundaries. The expression of pluripotency proteins was increased, and the genes encoding nestin, brachyury, and α-fetoprotein were expressed in H9 cells, suggesting that the cells maintained in vitro differentiation capacity. Our culture system containing a unique set of components, with animal-derived substances, maintained the self-renewal potential and pluripotency of H9 cells for eight passages. Further optimization of this system may expand the clinical application of hESCs.

Hematopoietic stem cells from induced pluripotent stem cells - considering the role of microRNA as a cell differentiation regulator

Although hematopoietic stem cell (HSC) therapy for hematological diseases can lead to a good outcome from the clinical point of view, the limited number of ideal donors, the comorbidity of patients and the increasing number of elderly patients may limit the application of this therapy. HSCs can be generated from induced pluripotent stem cells (iPSCs), which requires the understanding of the bone marrow and liver niches components and function in vivo iPSCs have been extensively applied in several studies involving disease models, drug screening and cellular replacement therapies. However, the somatic reprogramming by transcription factors is a low-efficiency process. Moreover, the reprogramming process is also regulated by microRNAs (miRNAs), which modulate the expression of the transcription factors OCT-4 (also known as POU5F1), SOX-2, KLF-4 and MYC, leading somatic cells to a pluripotent state. In this Review, we present an overview of the challenges of cell reprogramming protocols with regard to HSC generation from iPSCs, and highlight the potential role of miRNAs in cell reprogramming and in the differentiation of induced pluripotent stem cells.