Bcl2 enhances induced hematopoietic differentiation of murine embryonic stem cells

Key genes and integrated modules in hematopoietic differentiation of human embryonic stem cells: a comprehensive bioinformatic analysis

Background

The generation of hematopoietic stem cells (HSCs) and blood cells from human embryonic stem cells (hESCs) is a major goal for regenerative medicine; however, the differentiation mechanisms are largely undefined. Here, we aimed to identify the regulated genes and functional modules related to the early differentiation of the endothelial-to-hematopoietic transition (EHT) using comprehensive bioinformatics analyses.

Methods

Undifferentiated hESCs (hESC-H9), CD34⁺ cells from 10-day differentiated hESC-H9 cells, and CD34⁺ cells from umbilical cord cells were isolated and collected. Cells from these three groups were subjected to RNA extraction and microarray analysis by which differentially expressed genes (DEGs) and time-series profiles were analyzed by significance analysis of microarray (SAM) and short time-series expression miner (STEM) algorithms. Gene enrichment analysis was performed by ClusterProfiler Package in Rstudio, while a protein-protein interaction (PPI) network was constructed by search tool for the retrieval of interacting genes (STRING) and visualized in Cytoscape. Hub genes were further identified with the MCODE algorithm in Cytoscape.

Results

In the present study, we identified 11,262 DEGs and 16 time-series profiles that were enriched in biological processes of chromosome segregation, cell cycle, and leukocyte activation and differentiation, as well as hematopoiesis. Analysis using the MCODE algorithm further identified six integrated modules that might play an important role in the EHT process, including mitosis/cell cycle, mitochondrial process, splicing, ubiquitination, ribosome, and apoptosis.

Conclusions

The study identified potential genes and integrated functional modules associated with the hematopoietic and endothelial differentiation of human ESCs.

Electronic supplementary material

The online version of this article (10.1186/s13287-018-1050-7) contains supplementary material, which is available to authorized users.

In vivo selection with lentiviral expression of Bcl2T69A/S70A/S87A mutant in hematopoietic stem cell-transplanted mice

Current in vivo selections for hematopoietic stem cell (HSC)-based gene therapy are drug dependent and not without risk of cytotoxicity or tumorigenesis. We developed a new in vivo selection system with the non-phosphorylatable Bcl2 mutant Bcl2^{T69A/S70A/S87A} (Bcl2^AAA), which makes in vivo selection drug independent and without risk of cytotoxicity or tumorigenesis. We demonstrated in HSC-transplanted mice that Bcl2^AAA facilitated efficient in vivo selection in the absence of any exogenously applied drugs under both myeloablative and non-myeloablative conditioning. In mice transplanted with retrovirally transduced sca-1-positive bone marrow cells, the marked cell level increased from 26.38% of input transduced cells to 92.61 ± 0.95% of peripheral blood cells for myeloablative transplantation or to 37.82 ± 6.35% for non-myeloablative transplantation 6 months after transplantation. Bcl2^AAA did not induce tumorigenesis and does not influence hematopoiesis and the function of the reconstituted blood system. However, the high-level constitutive expression of Bcl2^AAA mediated by retroviral vector induced exhaustion of the marked cells after tertiary transplantation. Fortunately, low-level constitutive expression of Bcl2^AAA driven by an internal promoter in lentiviral vector could both maintain the marked cell level (24.13 ± 5.27%, 27.17 ± 5.51%, 24.33 ± 5.08%, and 22.07 ± 4.44% for primary, secondary, tertiary, and quaternary recipients) and avoid the exhaustion of the marked cells even in quaternary recipients. Importantly, the low-level constitutive expression of Bcl2^AAA did not induce tumorigenesis. Thus, the in vivo selection employing the low-level constitutive expression of Bcl2^AAA provides a general platform which is relevant for widespread applications of gene therapy.

Improved Survival and Hematopoietic Differentiation of Murine Embryonic Stem Cells on Electrospun Polycaprolactone Nanofiber

OBJECTIVE

Three-dimensional (3D) biomimetic nanofiber scaffolds have widespread ap- plications in biomedical tissue engineering. They provide a suitable environment for cel- lular adhesion, survival, proliferation and differentiation, guide new tissue formation and development, and are one of the outstanding goals of tissue engineering. Electrospinning has recently emerged as a leading technique for producing biomimetic scaffolds with mi- cro to nanoscale topography and a high porosity similar to the natural extracellular matrix (ECM). These scaffolds are comprised of synthetic and natural polymers for tissue engi- neering applications. Several kinds of cells such as human embryonic stem cells (hESCs) and mouse ESCs (mESCs) have been cultured and differentiated on nanofiber scaffolds. mESCs can be induced to differentiate into a particular cell lineage when cultured as em- bryoid bodies (EBs) on nano-sized scaffolds.

MATERIALS AND METHODS

We cultured mESCs (2500 cells/100 µl) in 96-well plates with knockout Dulbecco's modified eagle medium (DMEM-KO) and Roswell Park Memorial Institute-1640 (RPMI-1640), both supplemented with 20% ESC grade fetal bovine serum (FBS) and essential factors in the presence of leukemia inhibitory factor (LIF). mESCs were seeded at a density of 2500 cells/100 µl onto electrospun polycaprolactone (PCL) nanofibers in 96-well plates. The control group comprised mESCs grown on tissue cul- ture plates (TCP) at a density of 2500 cells/100 µl. Differentiation of mESCs into mouse hematopoietic stem cells (mHSCs) was performed by stem cell factor (SCF), interleukin-3 (IL-3), IL-6 and Fms-related tyrosine kinase ligand (Flt3-L) cytokines for both the PCL and TCP groups. We performed an experimental study of mESCs differentiation.

RESULTS

PCL was compared to conventional TCP for survival and differentiation of mESCs to mHSCs. There were significantly more mESCs in the PCL group. Flowcyto- metric analysis revealed differences in hematopoietic differentiation between the PCL and TCP culture systems. There were more CD34+(Sca1+) and CD133+cells subpopulations in the PCL group compared to the conventional TCP culture system.

CONCLUSION

The nanofiber scaffold, as an effective surface, improves survival and differentiation of mESCs into mHSCs compared to gelatin coated TCP. More studies are necessary to understand how the topographical features of electrospun fibers af- fect cell growth and behavior. This can be achieved by designing biomimetic scaffolds for tissue engineering.

PKR negatively regulates leukemia progression in association with PP2A activation, Bcl-2 inhibition and increased apoptosis

Reduced expression and activity of the proapoptotic, double-stranded RNA-dependent protein kinase, PKR (protein kinase R) is observed in breast, lung and various leukemias, suggesting that loss of PKR potentiates transformation. Now we report that decreased PKR activity inhibits chemotherapy-induced apoptosis of leukemia cells both in vitro and in vivo. Inhibition of PKR expression or activity reduces protein phosphatase 2A (PP2A) activity, a B-cell lymphoma 2 (Bcl-2) phosphatase, resulting in enhanced Bcl-2 phosphorylation. Thus, inhibition of PKR activity leads to hyperphosphorylation of Bcl-2, stabilization of Bcl-2/Bax interaction and decreased Bax insertion into the outer mitochondrial membrane. Treatment with the PP2A activator, FTY720, restores Bcl-2 dephosphorylation and apoptosis in cells with reduced PKR expression following stress. Significantly, xenografts of REH leukemic cells with reduced PKR display significantly increased tumor volume, increased resistance to doxorubicin treatment and shorter survival. Importantly, FTY720 treatment restores sensitivity to chemotherapy and prolongs overall survival of these mice. Collectively, these findings suggest that PP2A activation is a downstream target of PKR and the PKR/PP2A signaling axis is required for rapid and potent stress-induced apoptosis. Importantly, loss of PKR promotes leukemia progression and may serve as a biomarker for predicting chemosensitivity.

Enhancing in vivo survival of adipose-derived stromal cells through Bcl-2 overexpression using a minicircle vector

Tissue regeneration using progenitor cell-based therapy has the potential to aid in the healing of a diverse range of pathologies, ranging from short-gut syndrome to spinal cord lesions. However, there are numerous hurdles to be overcome prior to the widespread application of these cells in the clinical setting. One of the primary barriers to effective stem cell therapy is the hostile environment that progenitor cells encounter in the clinical injury wound setting. In order to promote cellular survival, stem cell differentiation, and participation in tissue regeneration, relevant cells and delivery scaffolds must be paired with strategies to prevent cell death to ensure that these cells can survive to form de novo tissue. The Bcl-2 protein is a prosurvival member of a family of proteins that regulate the mitochondrial pathway of apoptosis. Using several strategies to overexpress the Bcl-2 protein, we demonstrated a decrease in the mediators of apoptosis in vitro and in vivo. This was shown through the use of two different clinical tissue repair models. Cells overexpressing Bcl-2 not only survived within the wound environment at a statistically significantly higher rate than control cells, but also increased tissue regeneration. Finally, we used a nonintegrating minicircle technology to achieve this in a potentially clinically applicable strategy for stem cell therapy.

Getting away with murder: how does the BCL-2 family of proteins kill with immunity?

The adult human body produces approximately one million white blood cells every second. However, only a small fraction of the cells will survive because the majority is eliminated through a genetically controlled form of cell death known as apoptosis. This review places into perspective recent studies pertaining to the BCL-2 family of proteins as critical regulators of the development and function of the immune system, with particular attention on B cell and T cell biology. Here we discuss how elegant murine model systems have revealed the major contributions of the BCL-2 family in establishing an effective immune system. Moreover, we highlight some key regulatory pathways that influence the expression, function, and stability of individual BCL-2 family members, and discuss their role in immunity. From lethal mechanisms to more gentle ones, the final portion of the review discusses the nonapoptotic functions of the BCL-2 family and how they pertain to the control of immunity.

Effect of low dose bisphenol A on the early differentiation of human embryonic stem cells into mammary epithelial cells

It has been previously reported that bisphenol A (BPA) can disturb the development of mammary structure and increase the risk of breast cancer in experimental animals. In this study, an in vitro model of human embryonic stem cell (hESC) differentiation into mammary epithelial cells was applied to investigate the effect of low dose BPA on the early stages of mammogenesis. A newly established hESC line was directionally differentiated into mammary epithelial cells by a well-established three-dimensional (3D) culture system. The differentiated mammary epithelial cells were characterized by immunofluorescence and western blotting assay, and were called induced differentiated mammary epithelial cells (iDMECs) based on these data. The hESCs were treated with low doses of BPA range 10(-9)-10(-6)M during the differentiation process, with DMSO as the solvent control and 17-β-estrodiol (E2) as the estrogen-positive control. Our results showed that low dose BPA and E2 could influence the mammosphere area of iDMECs and upregulate the expression level of Oct4 and Nanog proteins, while only BPA could downregulate the expression of E-cadherin protein. Taken together, this study provides some insights into the effects of low dose BPA on the early differentiation stage of mammary epithelial cells and suggests an easier canceration status of iDMECs under the effect of low dose BPA during its early differentiation stage.

Cyclic AMP induces IPC leukemia cell apoptosis via CRE-and CDK-dependent Bim transcription

The IPC-81 cell line is derived from the transplantable BNML model of acute myelogenic leukemia (AML), known to be a reliable predictor of the clinical efficiency of antileukemic agents, like the first-line AML anthracycline drug daunorubicin (DNR). We show here that cAMP acted synergistically with DNR to induce IPC cell death. The DNR-induced death differed from that induced by cAMP by (1) not involving Bim induction, (2) being abrogated by GSK3β inhibitors, (3) by being promoted by the HSP90/p23 antagonist geldanamycin and truncated p23 and (4) by being insensitive to the CRE binding protein (CREB) antagonist ICER and to cyclin-dependent protein kinase (CDK) inhibitors. In contrast, the apoptosis induced by cAMP correlated tightly with Bim protein expression. It was abrogated by Bim (BCL2L11) downregulation, whether achieved by the CREB antagonist ICER, by CDK inhibitors, by Bim-directed RNAi, or by protein synthesis inhibitor. The forced expression of BimL killed IPC-81_WT cells rapidly, Bcl2-overexpressing cells being partially resistant. The pivotal role of CREB and CDK activity for Bim transcription is unprecedented. It is also noteworthy that newly developed cAMP analogs specifically activating PKA isozyme I (PKA-I) were able to induce IPC cell apoptosis. Our findings support the notion that AML cells may possess targetable death pathways not exploited by common anti-cancer agents.

RNA interference reveals a requirement for both p18INK4c and p27Kip1 in B lymphopoiesis

Cyclin-dependent kinase inhibitors (CKIs) p18(INK4c) (p18) and p27(Kip1) (p27) were reported to be able to modulate self-renewal and differentiation of hematopoietic stem cells (HSCs) and hematopoietic progenitor cells, and regulate the lineage cell proliferation and maturation into the terminal elements; however, whether p18 and p27 in HSCs affect the development of lineage cells, especially B lymphocytes, in the reconstituted blood is unknown. Here we employed small-interference RNA (siRNA) technique, which provides a powerful tool for tissue-targeted knockdown of genes, to evaluate the biological functions of the p18 and p27 in the hematopoiesis process. We knocked down the expression of p18, p27 alone or both in the isolated sca-1(+) bone marrow cells by lentiviral vector-based siRNA system, and transplanted these cells into lethally irradiated C57BL/6J mice to evaluate the effect of these two genes on reconstituted lymphocyte development. The knockdown of p18 or p27 alone or both was proved to be effective as verified by western blotting. FACS analysis results showed that compared with the control group, the B lymphocytes were both significantly lower in p18, p27 alone and especially in both p18 and p27 knockdown group in reconstituted peripheral blood; and the B lymphocytes showed similar trend in bone marrow. Interestingly, the differentiation to T cells was not greatly changed, only with the dramatic decrease of the CD4/CD8 ratio. Overexpression of the antiapoptotic protein Bcl2 could not rescue the B lymphopoiesis. All these results demonstrate that p18 and p27 are collaboratively involved in B lymphopoiesis, and simultaneous knockdown of p18 and p27 probably blocks the differentiation from HSCs to B lymphocytes, but not triggers apoptosis of B cell precursors.

Enhanced generation of myeloid lineages in hematopoietic differentiation from embryonic stem cells by silencing transcriptional repressor Twist-2

The self-renewal and multilineage differentiation of embryonic stem cells (ESC) is largely governed by transcription factors or repressors. Extensive efforts have focused on elucidating critical factors that control the differentiation of specific cell lineages, for instance, myeloid lineages in hematopoietic development. In this study, we found that Twist-2, a basic helix-loop-helix (bHLH) transcription factor, plays a critical role in inhibiting the differentiation of ESC. Murine ES cells, in which Twist-2 expression is silenced by lentivirally delivered shRNA, exhibit an enhanced formation of primary embryoid bodies (EB) and enhanced differentiation into mesodermally derived hematopoietic colonies. Furthermore, Twist-2 silenced (LV-siTwist-2) ESC display significantly increased generation of myeloid lineages (Gr-1(+) and F4/80(+) cells) during in vitro hematopoietic differentiation. Treatment with the Toll-like receptor (TLR) 4 ligand synergistically stimulates the generation of primary EB formation as well as of hematopoietic progenitors differentiated from LV-siTwist-2 ES cells. Thus, this study reveals the critical role of the transcriptional repressor Twist-2 in regulating the development of myeloid lineage in hematopoietic differentiation from ESC. This study also suggests a potential strategy for directional differentiation of ESC by inhibiting a transcriptional repressor.

Sera from children with autism alter proliferation of human neuronal progenitor cells exposed to oxidation

Altered brain development during embryogenesis and early postnatal life has been hypothesized to be responsible for the abnormal behaviors of people with autism. The specific genetic background that alters vulnerability to some environmental insults has been suggested in the etiology of autism; however, the specific pathomechanisms have not been identified. Recently, we showed that sera from children with autism alter the maturation of human neuronal progenitor cells (NPCs) in culture. Results suggest that pre-programmed neurogenesis, i.e., neuronal proliferation, migration, differentiation, growth, and circuit organization, can be affected differently by factors present in autistic sera. In this report, we tested the effect of autistic sera on the vulnerability of NPCs to oxidative stress-a recognized risk factor of autism. We found that mild oxidative stress reduced proliferation of differentiating NPCs but not immature NPCs. This decrease of proliferation was less prominent in cultures treated with sera from children with autism than from age-matched controls. These results suggest that altered response of NPCs to oxidative stress may play a role in the etiology of autism.