Well-defined differentiation of hesc-derived hemangioblasts by embryoid body formation without enzymatic treatment

Gene Expression Patterns of Royan Human Embryonic Stem Cells Correlate with Their Propensity and Culture Systems

OBJECTIVE

Human embryonic stem cells (hESCs) have the potential to give rise to all types of cells in the human body when appropriately induced to differentiate. Stem cells can differentiate spontaneously into the three-germ layer derivatives by embryoid bodies (EBs) formation. However, the two-dimensional (2D) adherent culture of hESCs under defined conditions is commonly used for directed differentiation toward a specific type of mature cells. In this study, we aimed to determine the propensity of the Royan hESC lines based on comparison of expression levels of 46 lineage specific markers.

MATERIALS AND METHODS

In this experimental study, we have compared the expression of lineage-specific markers in hESC lines during EB versus adherent-based spontaneous differentiation. We used quantitative real-time polymerase chain reaction (qRT-PCR) to assess expressions of 46 lineage-specific markers in 4 hESC lines, Royan H1 (RH1), RH2, RH5, and RH6, during spontaneous differentiation in both EB and adherent cultures at 0, 10, and 30 days after initiation of differentiation.

RESULTS

Based on qRT-PCR data analysis, the liver and neuronal markers had higher expression levels in EBs, whereas skin-specific markers expressed at higher levels in the adherent culture. The results showed differential expression patterns of some lineage-specific markers in EBs compared with the adherent cultures.

CONCLUSION

According to these results, possibly the spontaneous differentiation technique could be a useful method for optimization of culture conditions to differentiate stem cells into specific cell types such ectoderm, neuron, endoderm and hepatocyte. This approach might prove beneficial for further work on maximizing the efficiency of directed differentiation and development of novel differentiation protocols.

Definitive Erythropoiesis from Pluripotent Stem Cells: Recent Advances and Perspectives

Derivation of functional and mature red blood cells (RBCs) with adult globin expression from renewable source such as induced pluripotent stem cells (iPSCs) is of importance from the clinical point of view. Definitive RBC generation can only be succeeded through production of true hematopoietic stem cells (HSCs). There has been a great effort to obtain definitive engraftable HSCs from iPSCs but the results were mostly unsatisfactory due to low, short-term and linage-biased engraftment in mouse models. Moreover, ex vivo differentiation approaches ended up with RBCs with mostly embryonic and fetal globin expression. To establish reliable, standardized and effective laboratory protocols, we need to expand our knowledge about developmental hematopoiesis/erythropoiesis and identify critical regulatory signaling pathways and transcription factors. Once we meet these challenges, we could establish differentiation protocols for massive RBC production for transfusion purposes in the clinical setting, performing drug screening and disease modeling in ex vivo conditions, and investigating the embryological cascade of erythropoiesis. More interestingly, with the introduction of relatively efficient and facile genome editing tools, genetic correction for inherited RBC disorders such as sickle cell disease (SCD) would become possible through iPSCs that can subsequently generate definitive HSCs, which then give rise to definitive RBCs producing β-globin after transplantation.

Superior Red Blood Cell Generation from Human Pluripotent Stem Cells Through a Novel Microcarrier-Based Embryoid Body Platform

In vitro generation of red blood cells (RBCs) from human embryonic stem cells and human induced pluripotent stem cells appears to be a promising alternate approach to circumvent shortages in donor-derived blood supplies for clinical applications. Conventional methods for hematopoietic differentiation of human pluripotent stem cells (hPSC) rely on embryoid body (EB) formation and/or coculture with xenogeneic cell lines. However, most current methods for hPSC expansion and EB formation are not amenable for scale-up to levels required for large-scale RBC generation. Moreover, differentiation methods that rely on xenogenic cell lines would face obstacles for future clinical translation. In this study, we report the development of a serum-free and chemically defined microcarrier-based suspension culture platform for scalable hPSC expansion and EB formation. Improved survival and better quality EBs generated with the microcarrier-based method resulted in significantly improved mesoderm induction and, when combined with hematopoietic differentiation, resulted in at least a 6-fold improvement in hematopoietic precursor expansion, potentially culminating in a 80-fold improvement in the yield of RBC generation compared to a conventional EB-based differentiation method. In addition, we report efficient terminal maturation and generation of mature enucleated RBCs using a coculture system that comprised primary human mesenchymal stromal cells. The microcarrier-based platform could prove to be an appealing strategy for future scale-up of hPSC culture, EB generation, and large-scale generation of RBCs under defined and xeno-free conditions.

Directing human embryonic stem cells towards functional endothelial cells easily and without purification

Hemangioblasts or blood islands only arise in early development thereby the sources to obtain these bi-potential cells are limited. While previous studies have isolated both lineages in vitro through the hemangioblast, derivation efficiency was rather low due to cellular damage attributed by enzyme usage and fluorescent activated cell sorting (FACS). This study focused on avoiding the use of damaging factors in the derivation of endothelial cells (ECs). Single cell H9-human embryonic stem cells (hESCs) were obtained by using a mild dissociation protocol then human embryoid body (hEB) formation was performed under hemangioblast differentiation conditions. The hEBs were subjected to a two-stage cytokine treatment procedure. Subsequent culture of the adhesive cells in day 4 hEBs gave arise to a seemingly pure population of ECs. The hESC-derived ECs were characterized by identifying signature endothelial gene and protein markers as well as testing for in vitro functionality. Furthermore, in vivo functionality was also confirmed by transplanting the cells in hindlimb ischemic murine models. We demonstrate that the genetic change required for EC derivation precedes blast colony formation. Furthermore, cell damage was prevented by abating enzyme usage and FACS, resulting in a high yield of ECs upon adhesion. Under this method, confluent cultures of ECs were obtainable 4 days after hEB formation which is significantly faster than previous protocols.