高山 直也

The underlying mechanisms of atherosclerosis, the second leading cause of death among Werner syndrome (WS) patients, are not fully understood. Here, we establish an in vitro co-culture system using macrophages (iMφs), vascular endothelial cells (iVECs), and vascular smooth muscle cells (iVSMCs) derived from induced pluripotent stem cells. In co-culture, WS-iMφs induces endothelial dysfunction in WS-iVECs and characteristics of the synthetic phenotype in WS-iVSMCs. Transcriptomics and open chromatin analysis reveal accelerated activation of type I interferon signaling and reduced chromatin accessibility of several transcriptional binding sites required for cellular homeostasis in WS-iMφs. Furthermore, the H3K9me3 levels show an inverse correlation with retrotransposable elements, and retrotransposable element-derived double-stranded RNA activates the DExH-box helicase 58 (DHX58)-dependent cytoplasmic RNA sensing pathway in WS-iMφs. Conversely, silencing type I interferon signaling in WS-iMφs rescues cell proliferation and suppresses cellular senescence and inflammation. These findings suggest that Mφ-specific inhibition of type I interferon signaling could be targeted to treat atherosclerosis in WS patients.

Abstract We recently achieved the first-in-human transfusion of induced pluripotent stem cell-derived platelets (iPSC-PLTs) as an alternative to standard transfusions, which are dependent on donors and therefore variable in supply. However, heterogeneity characterized by thrombopoiesis-biased or immune-biased megakaryocytes (MKs) continues to pose a bottleneck against the standardization of iPSC-PLT manufacturing. To address this problem, here we employ microRNA (miRNA) switch biotechnology to distinguish subpopulations of imMKCLs, the MK cell lines producing iPSC-PLTs. Upon miRNA switch-based screening, we find imMKCLs with lower let-7 activity exhibit an immune-skewed transcriptional signature. Notably, the low activity of let-7a-5p results in the upregulation of RAS like proto-oncogene B (RALB) expression, which is crucial for the lineage determination of immune-biased imMKCL subpopulations and leads to the activation of interferon-dependent signaling. The dysregulation of immune properties/subpopulations, along with the secretion of inflammatory cytokines, contributes to a decline in the quality of the whole imMKCL population.

Ex-vivo expansion of human hematopoietic stem/progenitor cells (HSPCs) represents a promising technology for investigating HSPCs' function and overcoming donor shortage for transplantation. HSPCs appropriately regulate self-renewal and differentiation, relying on hematopoietic supporting cells within the bone marrow microenvironment. Notably, various strategies employing primary mesenchymal stem cells (MSCs) as hematopoietic supporting cells have demonstrated successful HSPC expansion (De Lima, et al, N. Engl. J. Med. 2012). However, the preparation of primary MSCs includes harmful procedures, hindering the stable supply of high-quality hematopoietic supporting cells, thereby limited expansion capability and enhancement of clone variation. To overcome these issues, we have established the high-quality type of an immortalized MSCs (imMSCs) cell line derived from human induced pluripotent cells (iPSCs) with knockdown of p53 gene. The imMSCs exhibited exponential proliferation over 2 months, while retaining their MSC phenotype and functionality. To examine the supporting capability of imMSCs on HSPC expansion, we performed coculture experiments with cord blood-derived CD34 + cells in the presence or absence of combination of small compounds StemRegenin-1 and UM171 (SU). We compared four distinct culture conditions, i.e., i) the basic culture with cytokines (SCF, THPO, and FLT3L), as a control; ii) cocultured with imMSCs (imMSC condition); iii) SU alone (SU condition); and iv) cocultured with imMSC and SU (imMSC+SU condition). After a 7-day culture period, we observed a 2 to 3-fold expansion of the CD34 +CD45RA -CD90 + (phenotypic HSC) population in the imMSC condition compared to control. Moreover, the addition of SU (imMSC+SU condition) demonstrated a synergistical effect in promoting HSC expansion (up to 9-fold). Meanwhile, to evaluate the functional potential of expanded HSPCs in vivo, we conducted a xenotransplantation assay using NOG mice as recipients. The expanded HSPCs obtained from the initial 1,000 CD34 + cells were transplanted into the femoral bone of sub-lethally irradiated mice (2Gy). After 12 weeks, mice were sacrificed, and the proportion of human CD45 + cells in the murine bone marrow were analyzed with flow cytometer. All experimental conditions (ii, iii, and iv in the above) enabled to increase chimerism levels compared to the control (i). Notably, the imMSC+SU condition showed a significantly higher chimerism level compared to that of the freshly isolated CD34 + cells, highlighting the efficacy of our expanded HSPCs. Furthermore, a limiting dilution assay using immunodeficient mice revealed that the imMSC, SU, and imMSC+SU conditions showed 3.5-fold, 7.4-fold, and 20-fold expansion of functional HSCs, respectively, in comparison to the control. To elucidate the underlying mechanism how intervention promote HSPC expansion, we employed RNA sequencing analysis. We found that interferon signaling genes (ISGs) were significantly elevated in HSPCs from either imMSC or imMSC+SU compared to other conditions. This finding of elevated ISGs was recapitulated by freshly isolated CB-derived HSCs (uncultured), indicating that ISGs may contribute to the self-renewal ability of both uncultured HSC and those cocultured with imMSCs. While multiple roles of inflammatory signaling, including ISGs, have been identified in hematopoiesis, its role in the fate decision of cord blood-derived HSCs remains poorly understood. To gain further insights, we examined the role of the IFN pathway through shRNA-mediated knockdown of IRF3/7 in CD34 + HSPCs. Our results revealed that the knockdown of IRF3/7 in HSPCs led to a significant reduction in the phenotypic HSC population in all conditions, suggesting the critical role of interferon signaling in HSC expansion. In this context, we attempted to recapitulate the effects of imMSCs by administering recombinant IFN-2α with various doses. However, IFN-2α administration at any doses failed to promote HSC expansion, suggesting transcript of ISGs-dependent but not IFN protein-dependent mechanism might be crucial for the HSC self-renewal. Taken together, our new co-culture system using imMSCs should contribute to a better understanding of the regulatory networks governing HSPC biology as well as the future clinical application of HSPC expansion.

Platelet-rich plasma (PRP) promotes bone union through osteoinduction. We investigated whether adding demineralized bone matrix (DBM), derived naturally from biomaterial and with various growth factors, for osteoconductivity and bone marrow fluid for osteogenesis results in different bone unions. Eight-week-old male Sprague-Dawley rats were divided into four groups of five based on transplantation material: sham control (C group); DBM alone (D group); DBM + PRP (DP group); and DBM + PRP + bone marrow fluid (DPB group). After posterolateral fusion at L3-5, postoperative weekly CT imaging determined average number of bone union in facet joints (4 joints × 5 animals = 20 joints) and bone formation. Pathological evaluation and bone strength were assessed using 3-point bending two weeks postoperatively. Facet joint bone union at four weeks postoperatively was 4/20 (20%, DP group) and 8/20 (40%, DPB group) joints. Six weeks postoperatively, it was 7/20 (35%, D group), 12/20 (60%, DP group), and 16/20 (80%, DPB group). Eight weeks postoperatively, it was 13/20 (65%, D group), 17/20 (85%, DP group), and 20/20 (100%, DPB group), suggesting that DPB > DP > D > C. Bone formation and bone strength showed a similar DPB > DP > D > C group trend. Adding PRP and bone marrow fluid to DBM promotes bone union and strength.

Hematopoietic stem cells (HSCs) exhibit considerable cell-intrinsic changes with age. Here, we present an integrated analysis of transcriptome and chromatin accessibility of aged HSCs and downstream progenitors. Alterations in chromatin accessibility preferentially take place in HSCs with aging, which gradually resolve with differentiation. Differentially open accessible regions (open DARs) in aged HSCs are enriched for enhancers and show enrichment of binding motifs of the STAT, ATF, and CNC family transcription factors that are activated in response to external stresses. Genes linked to open DARs show significantly higher levels of basal expression and their expression reaches significantly higher peaks after cytokine stimulation in aged HSCs than in young HSCs, suggesting that open DARs contribute to augmented transcriptional responses under stress conditions. However, a short-term stress challenge that mimics infection is not sufficient to induce persistent chromatin accessibility changes in young HSCs. These results indicate that the ongoing and/or history of exposure to external stresses may be epigenetically inscribed in HSCs to augment their responses to external stimuli.

Obesity is a worldwide epidemic that predisposes individuals to many age-associated diseases, but its exact effects on organ dysfunction are largely unknown1. Hair follicles-mini-epithelial organs that grow hair-are miniaturized by ageing to cause hair loss through the depletion of hair follicle stem cells (HFSCs)2. Here we report that obesity-induced stress, such as that induced by a high-fat diet (HFD), targets HFSCs to accelerate hair thinning. Chronological gene expression analysis revealed that HFD feeding for four consecutive days in young mice directed activated HFSCs towards epidermal keratinization by generating excess reactive oxygen species, but did not reduce the pool of HFSCs. Integrative analysis using stem cell fate tracing, epigenetics and reverse genetics showed that further feeding with an HFD subsequently induced lipid droplets and NF-κB activation within HFSCs via autocrine and/or paracrine IL-1R signalling. These integrated factors converge on the marked inhibition of Sonic hedgehog (SHH) signal transduction in HFSCs, thereby further depleting lipid-laden HFSCs through their aberrant differentiation and inducing hair follicle miniaturization and eventual hair loss. Conversely, transgenic or pharmacological activation of SHH rescued HFD-induced hair loss. These data collectively demonstrate that stem cell inflammatory signals induced by obesity robustly represses organ regeneration signals to accelerate the miniaturization of mini-organs, and suggests the importance of daily prevention of organ dysfunction.

Adult progeria, Werner syndrome (WS), is an autosomal recessive disorder that develops accelerated aging-associated symptoms after puberty. Refractory skin ulcer of limbs, which is one of the symptoms specific to WS, is seriously painful and sometimes results in amputation. In recent years, cell therapy using mesenchymal stem cells (MSCs) has been attracting attention; however, the effect of WS-derived MSCs on skin ulcers is still unclear. In this study, we generated iPS cells from a patient with WS and a normal subject, differentiated them into MSCs (WS- and NM-iMSC, respectively), and performed cell therapy to a refractory skin ulcer mouse model. As a result, WS-iMSC recapitulated premature senescence phenotypes in vitro. Upon subcutaneous injection around the wounds of mice, WS-iMSC was significantly inferior in wound healing effect compared to NM-iMSC. Proteome and transcriptome analysis revealed altered expression of genes related to angiogenesis, inflammation, and proliferation in WS-iMSC with remarkable downregulation of VEGF, a potent angiogenic factor. In addition, simultaneous administration of recombinant human VEGF and WS-iMSC improved the wound healing effect in vivo. These results indicate that the expression of angiogenic factors is reduced in WS-iMSC, and its supplementation restores the wound healing ability. This finding may pave the way to develop the treatment of intractable skin ulcers of WS.

Adult progeria Werner syndrome (WS), a rare autosomal recessive disorder, is characterized by accelerated aging symptoms after puberty. The causative gene, WRN, is a member of the RecQ DNA helicase family and is predominantly involved in DNA replication, repair, and telomere maintenance. Here, we report the generation of iPS cells from a patient with WS and correction of the WRN gene by the CRISPR/Cas9-mediated method. These iPSC lines would be a valuable resource for deciphering the pathogenesis of WS.

Different dynamics of gene expression are observed during cell differentiation. In T cells, genes that are turned on early or turned off and stay off have been thoroughly studied. However, genes that are initially turned off but then turned on again after stimulation has ceased have not been defined; they are obviously important, especially in the context of acute versus chronic inflammation. Using the Th1/Th2 differentiation paradigm, we found that the Cxxc1 subunit of the Trithorax complex directs transcription of genes initially down-regulated by TCR stimulation but up-regulated again in a later phase. The late up-regulation of these genes was impaired either by prolonged TCR stimulation or Cxxc1 deficiency, which led to decreased expression of Trib3 and Klf2 in Th1 and Th2 cells, respectively. Loss of Cxxc1 resulted in enhanced pathogenicity in allergic airway inflammation in vivo. Thus, Cxxc1 plays essential roles in the establishment of a proper CD4+ T cell immune system via epigenetic control of a specific set of genes.

Werner syndrome (WS), also known as adult progeria, is characterized by accelerated aging symptoms from a young age. Patients with WS experience painful intractable skin ulcers with calcifications in their extremities, subcutaneous lipoatrophy, and sarcopenia. However, there is no significant abnormality in the trunk skin, where the subcutaneous fat relatively accumulates. The cause of such differences between the limbs and trunk is unknown. To investigate the underlying mechanism behind these phenomena, we established and analyzed dermal fibroblasts from the foot and trunk of two WS patients. As a result, WS foot-derived fibroblasts showed decreased proliferative potential compared to that from the trunk, which correlated with the telomere shortening. Transcriptome analysis showed increased expression of genes involved in osteogenesis in the foot fibroblasts, while adipogenic and chondrogenic genes were downregulated in comparison with the trunk. Consistent with these findings, the adipogenic and chondrogenic differentiation capacity was significantly decreased in the foot fibroblasts in vitro. On the other hand, the osteogenic potential was mutually maintained and comparable in the foot and trunk fibroblasts. These distinct phenotypes in the foot and trunk fibroblasts are consistent with the clinical symptoms of WS and may partially explain the underlying mechanism of this disease phenotype.

Introduction: Platelet-rich plasma (PRP) is drawing attention as a substance that can promote bone formation. The growth factors present in PRP are stable for a long time after freeze-drying. However, the effects of PRP are inconsistent, and its effects on bone union in spinal surgery remain controversial. The immortalized megakaryocyte cell lines (imMKCLs) derived from human-induced pluripotent stem cells (hiPSCs) have been developed to produce numerous stable and clinically functional platelets. In this study, growth factors present in freeze-dried hiPSC-derived imMKCLs and platelets (iPS-MK/Plts) were evaluated, and their ability to promote bone formation was examined using a rat lumbar artificial bone grafting model. Methods: We prepared freeze-dried iPS-MK/Plts and quantified their growth factors by enzyme-linked immunosorbent assays. Surgical grafting of artificial bone to the lumbar transverse processes was performed in 8-week-old female rats, which were divided into two groups: artificial bone graft (control) and artificial bone graft plus freeze-dried iPS-MK/Plts (iPS group). Transplantation was performed only on the left side. Eight weeks after the surgery, we captured computed tomography images and compared bilateral differences in the bone volume of the graft site in each rat. We also compared the left side/right side bone volume ratio between the two groups. Results: The freeze-dried iPS-MK/Plts contained numerous growth factors. While there was no significant increase in bone volume on the transplanted side than that on the non-grafted side in the control group, bone volume significantly increased on the transplanted side in the iPS group, as evidenced by augmented mean left/right bone volume ratio of the iPS group compared with that of the control group. But the new bone observed in the iPS group was histologically normal. Conclusions: Freeze-dried hiPSC-derived MKCLs and platelets contain several stable growth factors and have the potential for promoting new bone formation.

Atherosclerosis is a major cause of various fatal diseases, such as myocardial infarction, stroke, and ischemic heart failure worldwide. The risk factors of atherosclerosis are well known, including hypertension, diabetes mellitus, dyslipidemia, smoking and obesity. Growing evidence also suggests that aging is the strongest determinant of stroke, which is less common before 40 years old (Soler and Ruiz 2010). Werner syndrome (WS) is a rare human inherited disorder characterized by the appearance of premature aging followed by early onset of aging-associated diseases including atherosclerosis. Myocardial infarction and cancer are being the most common causes of death in patients with WS (Oshima et al. 1993). However, despite being one of the most common causes of death, the etiology of atherosclerosis in WS patients have not been well documented yet. Therefore, the aim of the study was to assess in vitro model of atherosclerosis using WS patient-derived induced pluripotent stem cells (iPSC) to better understand the etiology and pathogenesis of atherosclerosis in WS patients. Atherosclerosis is a chronic inflammatory disease in which vascular endothelial cells (VEC), vascular smooth muscle cells (VSMC) and macrophages (Mφ) play interactive roles in the progression of the disease. To obtain these cells in vitro, we induced VEC, VSMC and Mφ from the progenitor cell populations, KDR+/CD34+/TRA-1-60-, KDR+/CD34-/TRA-1-60- and CD43+/CD34+ cells respectively, derived from iPSCs by the iPS-sac method we developed previously (Takayama et al. 2008, 2010). We found by co-culture with C3H10T1/2 mouse mesenchymal stromal cell line, KDR+/CD34+ and KDR+/CD34- cell populations were able to efficiently induce VEC and VSMC respectively on day 17. Especially, VEC induction efficiency was ~ 4 and ~ 21 fold as compared with the previously established method with collagen IV and laminin-411 respectively (Ohta et al. 2016; Sone et al. 2007; Taura et al. 2009). Furthermore, to induce Mφ, iPS-sac-like structures in culture were maintained for two weeks to get CD43+ hematopoietic cells. CD43+ cells were then cultured for an additional 7 days with a cytokine cocktail on C3H10T1/2 feeder layer. After 3 weeks of initiating culture, ~ 54% of CD11b+/CD33+ Mφ-like cells were obtained. To examine the responses of the induced VEC- and Mφ-like cells in atherosclerotic conditions, we applied oxidized low-density lipoprotein (Ox-LDL) at the concentration of 10, 50 and 100 μg/mL, and performed qRT-PCR analysis. It is well known that inflammatory response is triggered with the uptake of LDL both in VEC and Mφ, thereby contribute to local inflammation, cell necrosis, apoptosis, VSMC proliferation and fibrosis. Accordingly, in Ox-LDL treated iPSC-derived VEC and Mφ, mRNA expression of IL-1β, IL-6 and TNF-α were increased in a dose dependent manner. A critical event in the early stages of atherosclerosis is the internalization of lipid particles by VEC, and then, these lipids particles are oxidized to form Ox-LDL in the endothelium, leading to an increase in inflammatory cell adhesion molecules (ICAM-1 and VCAM-1) on the endothelium. Subsequently, monocytes are then recruited and differentiated into Mφ and start to uptake Ox-LDL particles ultimately forming foam-cells (Wu et al. 2017). Next, we were enthusiastic to compare the effect of Ox-LDL for inflammatory response in WS iPSC-derived VEC and Mφ with healthy iPSC-derived VEC and Mφ. Although no differences were observed in the induction efficiency, cell proliferation and mean fluorescent intensity of Ox-LDL uptake between WS- and healthy-iPSC-derived VEC and Mφ, qRT-PCR analysis revealed that, VEC derived from WS-iPSC shows much higher mRNA expression of cell adhesion molecule gene (ICAM-1; 2.5 fold and VCAM-1; 3.6 fold), inflammatory cytokine gene (IL-6; 12.5 fold and TGF-β; 4.3 fold) and endothelial dysfunction related gene (ET-1; 5.9 fold and PAI-1; 25.2 fold) compared with healthy-iPSC-derived VEC. Consequently, our results suggest that the higher risk of atherosclerosis in WS patients might be due to excessive inflammation response against Ox-LDL in WS-iPSC-derived cells, which is independent of other risk factors frequently observed in WS, such as diabetes and hyperlipidemia, and might be implicated to understand the pathogenesis and therapeutic strategy against WS and general atherosclerosis. Disclosures Eto: Megakaryon Co. Ltd.: Equity Ownership, Membership on an entity's Board of Directors or advisory committees.

Recurrent inactivating mutations have been identified in the X-linked PHF6 gene, encoding a chromatin-binding transcriptional regulator protein, in various hematological malignancies. However, the role of PHF6 in normal hematopoiesis and its tumor suppressor function remain largely unknown. We herein generated mice carrying a floxed Phf6 allele and inactivated Phf6 in hematopoietic cells at various developmental stages. The Phf6 deletion in embryos augmented the capacity of hematopoietic stem cells (HSCs) to proliferate in cultures and reconstitute hematopoiesis in recipient mice. The Phf6 deletion in neonates and adults revealed that cycling HSCs readily acquired an advantage in competitive repopulation upon the Phf6 deletion, while dormant HSCs only did so after serial transplantations. Phf6-deficient HSCs maintained an enhanced repopulating capacity during serial transplantations; however, they did not induce any hematological malignancies. Mechanistically, Phf6 directly and indirectly activated downstream effectors in TNFα signaling. The Phf6 deletion repressed the expression of a set of genes associated with TNFα signaling, thereby conferring resistance against the TNFα-med

Mutations in the isocitrate dehydrogenase-1 gene (IDH1) are common drivers of acute myeloid leukemia (AML) but their mechanism is not fully understood. It is thought that IDH1 mutants act by inhibiting TET2 to alter DNA methylation, but there are significant unexplained clinical differences between IDH1- and TET2-mutant diseases. We have discovered that mice expressing endogenous mutant IDH1 have reduced numbers of hematopoietic stem cells (HSCs), in contrast to Tet2 knockout (TET2-KO) mice. Mutant IDH1 downregulates the DNA damage (DD) sensor ATM by altering histone methylation, leading to impaired DNA repair, increased sensitivity to DD, and reduced HSC self-renewal, independent of TET2. ATM expression is also decreased in human IDH1-mutated AML. These findings may have implications for treatment of IDH-mutant leukemia.

To investigate miRNA function in human acute myeloid leukemia (AML) stem cells (LSC), we generated a prognostic LSC-associated miRNA signature derived from functionally validated subpopulations of AML samples. For one signature miRNA, miR-126, high bioactivity aggregated all in vivo patient sample LSC activity into a single sorted population, tightly couplingmiR-126 expression to LSC function. Through functional studies, miR-126 was found to restrain cell cycle progression, prevent differentiation, and increase self-renewal of primary LSC in vivo. Compared with prior results showing miR-126 regulation of normal hematopoietic stem cell (HSC) cycling, these functional stem effects are opposite between LSC and HSC. Combined transcriptome and proteome analysis demonstrates that miR-126 targets the PI3K/AKT/MTOR signaling pathway, preserving LSC quiescence and promoting chemotherapy resistance.

In a classical view of hematopoiesis, the various blood cell lineages arise via a hierarchical scheme starting with multipotent stem cells that become increasingly restricted in their differentiation potential through oligopotent and then unipotent progenitors. We developed a cell-sorting scheme to resolvemyeloid (My), erythroid (Er), and megakaryocytic (Mk) fates from single CD34(+) cells and then mapped the progenitor hierarchy across human development. Fetal liver contained large numbers of distinct oligopotent progenitors with intermingled My, Er, and Mk fates. However, few oligopotent progenitor intermediates were present in the adult bone marrow. Instead, only two progenitor classes predominate, multipotent and unipotent, with Er-Mk lineages emerging from multipotent cells. The developmental shift to an adult "two-tier" hierarchy challenges current dogma and provides a revised framework to understand normal and disease states of human hematopoiesis.

Mutations in the histone 3 variant H3.3 have been identified in one-third of pediatric glioblastomas (GBMs), but not in adult tumors. Here we show that H3.3 is a dynamic determinant of functional properties in adult GBM. H3.3 is repressed by mixed lineage leukemia 5 (MLL5) in self-renewing GBM cells. MLL5 is a global epigenetic repressor that orchestrates reorganization of chromatin structure by punctuating chromosomes with foci of compacted chromatin, favoring tumorigenic and self-renewing properties. Conversely, H3.3 antagonizes self-renewal and promotes differentiation. We exploited these epigenetic states to rationally identify two small molecules that effectively curb cancer stem cell properties in a preclinical model. Our work uncovers a role for MLL5 and H3.3 in maintaining self-renewal hierarchies in adult GBM.

The existence of progenitor/mesenchymal stem cells (MSCs) was demonstrated previously in human primary/deciduous teeth. In this study, we examined dental pulp cells from root portion (root cells) of primary teeth without discernible root resorption and compared them with pulp cells from the crown portion (crown cells). Root cells and crown cells were characterized and compared to each other based on progenitor/MSC characteristics and on their generation efficiency of induced pluripotent stem (iPS) cells. Root cells and crown cells included cells manifesting typical progenitor/MSC properties such as osteogenic and adipogenic differentiation potential and clonogenicity. Interestingly, root cells showed a higher expression level of embryonic stem cell marker, KLF4, than crown cells. Moreover, the number of colony-forming unit-fibroblast and cell proliferation rate were higher for root cells than crown cells, and the efficiency of generating iPS cells from root cells was approximately four times higher than that from crown cells. Taken together, these results suggest that root cells from primary teeth show the MSC-like properties and thus could be a potent alternative source for iPS cell generation and the subsequent transplantation therapy.

Induced pluripotent stem cells (iPS) derived from disease cells are expected to provide a new experimental material, especially for diseases from which samples are difficult to obtain. In this study, we generated iPS from samples from patients with primary and secondary myelofibrosis. The primary myelofibrosis cells had chromosome 13q deletions, and the secondary myelofibrosis (SMF) cells had JAK2V617F mutations. The myelofibrosis patient cell-derived iPS (MF-iPS) were confirmed as possessing these parental disease-specific genomic markers. The capacity to form three germ layers was confirmed by teratoma assay. By co-culture with specific feeder cells and cytokines, MF-iPS can re-differentiate into blood progenitor cells and finally into megakaryocytes. We found that mRNA levels of interleukin-8, one of the candidate cytokines related to the pathogenesis of myelofibrosis, was elevated predominantly in megakaryocytes derived from MF-iPS. Because megakaryocytes from myelofibrosis clones are considered to produce critical mediators to proliferate fibroblasts in the bone marrow and iPS can provide differentiated cells abundantly, the disease-specific iPS we established should be a good research tool for this intractable disease. (C) 2014 ISEH - International Society for Experimental Hematology. Published by Elsevier Inc.

Adult hemoglobin composed of alpha- and beta-globin reflects a change from expression of embryonic epsilon- and fetal gamma-globin to adult beta-globin in human erythroid cells, so-called globin switching. Human pluripotent stem cells (hPSCs) are a potential source for in vitro erythrocyte production, but they show prominent expression of gamma-globin with little beta-globin expression, which indicates incomplete globin switching. To examine the mechanism of this impaired globin switching, we optimized multicolor flow cytometry to simultaneously follow expression of different globin subtypes using different immunofluorescent probes. This enabled us to detect upregulation of beta-globin and the corresponding silencing of gamma-globin at the single-cell level during cord blood CD34(+) cell-derived erythropoiesis, examined as an endogenous control. Using this approach, we initially characterized the heterogeneous beta-globin expression in erythroblasts from several hPSC clones and confirmed the predominant expression of gamma-globin. These hPSC-derived erythroid cells also displayed reduced expression of BCL11A-L. However, doxycycline-induced overexpression of BCL11A-L in selected hPSCs promoted gamma-globin silencing. These results strongly suggest that impaired gamma-globin silencing is associated with downregulated BCL11A-L in hPSC-derived erythroblasts and that multicolor staining of globin subtypes is an effective approach to studying globin switching in vitro.