The RUNX1 gene is a critical transcription factor for the generation and maintenance of hematopoietic stem cells. RUNX1 is also one of the most frequently mutated gene in sporadic leukemias. Heterozygous loss-of-function mutations of the RUNX1 gene in the germline cause a rare autosomal dominant disorder called familial platelet disorder with propensity to acute myelogenous leukemia (FPD/AML). Besides the preexisting platelet disorder in FPD/AML patients, AML also develops in 20-60% of affected individuals. Since its discovery by the Gilliland group in 1999, RUNX1 mutation in the germline has been extensively investigated in the field. The past two decades of research have taught us three important lessons: 1) patients with FPD/AML display atypical symptoms and they have a widened clinical spectrum of FPD, such as eczema and syndromic thrombocytopenia, 2) the elucidation of variant of uncertain significance (VUS) of RUNX1 have revealed their role in epigenetic functions and involvement in the Fanconi anemia DNA repair pathway, and 3) non-coding mutations of RUNX1 also causes FPD/AML. In three distinct familial cases, an enhancer for RUNX1, eR1, was either lost or disconnected from the promoter through genetic deletion or chromosomal translocation abnormalities. This experience, with congenital mutations of RUNX1, will be very useful for future research for a series of other leukemia-causing germline mutations that have been recently identified.

Genetic predisposition is a major cause of childhood cancer. Multiple cancer-predisposing syndromes have been identified, including Li-Fraumeni syndrome (LFS), neurofibromatosis type 1, APC-related adenomatous polyposis, Beckwith-Wiedemann syndrome, multiple endocrine neoplasia 1, ataxia telangiectasia, RUNX1 deficiency, Fanconi anemia, Bloom syndrome, and PTEN hamartoma tumor syndrome. LFS is a prototypical genetically predisposing condition. Accordingly, individualized therapy, surveillance, risk reduction, and family counseling are needed when a patient is diagnosed with LFS. More ethically important problems are encountered in a pediatric LFS patient, including the identification of patients requiring screening, the age at screening, the process of obtaining informed consent from children, and the responsibility of following a pediatric patient with a genetic predisposition. Therefore, it is crucial to determine whether planned genetic testing has direct benefits for pediatric patients. In this context, TP53 testing may be justified in a pediatric cancer patient with suspected LFS, given the importance of decisions such as the use of radiotherapy and the screening of family members as hematopoietic stem cell transplantation donors, the surveillance of subsequent cancers, and counseling for family members. In this review article, I have discussed these issues and indicated some consensus among various clinicians, including adult hematologists.

Hematopoietic stem cells (HSCs) are maintained in steady state in the bone marrow (BM); these cells are capable of continuous self-renewal and have the potential for multilineage-differentiation into all blood cell lineages. The BM has long been considered as an immune-privilege organ with little immunological reactions. However, recent findings have revealed that immunological/hematopoietic challenges such as infection or inflammation induce broad spectrum of immune and inflammatory responses in BM. While these responses play a beneficial role to boost immune activation and blood production, chronic challenge might lead to BM pathology and dysregulation, including hematopoietic aplasia or neoplasia. We will introduce recent findings focused on hematopoietic activation induced by existing outside of our body or co-existing with us, and discuss to what degree and how function of HSCs and progenitors is regulated and altered by bacterial insult.

Since induced pluripotent stem (iPS) cell-derived blood products can be produced from any individual, they are expected to complement current transfusion products. However, a main problem is how to produce 10 U platelet preparations. Therefore, we established an immortalized megakaryocyte cell line (imMKCL) from iPS cells. We also found that turbulent flow was an essential physical factor for platelet generation in vivo. This knowledge enabled us to obtain 100 billion functional platelets from imMKCL using an 8 L bioreactor. We propose that the enhanced platelet production in the bioreactor occurs due to the turbulent flow that promoted the release of stress-induced cytokines.

Graft-versus-host disease (GVHD) is a potentially fatal complication of allogeneic hematopoietic stem cell transplantation. The gastrointestinal tract is a major target organ of GVHD, and disruption of the barrier function of the intestinal mucosa leads to an influx of danger signals derived from intestinal microbiota, which may further exaggerate GVHD. We have shown that the recombinant human R-spondin1 protects intestinal stem cells against GVHD, improves intestinal dysbiosis, and ameliorates GVHD. However, the endogenous R-spondin-producing cells in the small intestine remained to be studied in greater detail. This study clarified that R-spondin3 is the predominant R-spondin protein produced in the mouse small intestine. We also found that R-spondin3 is predominantly produced by lymphatic endothelial cells. Furthermore, we found that GVHD targets lymphatic endothelial cells in the small intestine, leading to decreased R-spondin3 production. GVHD-induced reduction of endogenous R-spondin3 could delay intestinal epithelial regeneration, possibly resulting in GVHD deterioration.

Functional food material, polyamines are considered to be essential for growth factors in virtually all cells. The polyamines putrescine, spermidine and spermine are low molecular weight organic polycations, well known as mediators involved in cell homeostasis. The proposed functions of polyamines are the regulation of ion channels, nucleic acid packaging, signal transduction, cell proliferation, and differentiation, as well as gene expression. In skeletal muscle, regulation of polyamine levels is associated with muscle hypertrophy and atrophy, yet detailed studies are remained to be undergoing. Here, we studied how polyamines may affect the proliferation and/or differentiation of murine myoblast progenitor C2C12 cell line. Upon polyamine treatment of C2C12 cells during induction of myogenic differentiation, the number of myotubes significantly increased. Morphologically, polyamine-treated myotubes exhibited elongated cell body and contained larger amount of nuclei in the cell. On the other hand, the polyamine did not have influence on myoblasts proliferation. Furthermore, compensatory muscle hypertrophy of C57BL6 mice that underwent sciatic nerve transection of the left hindlimb was enhanced by administration of polyamines. Therefore, our study demonstrates that polyamines may play an important role in regulating myogenic differentiation rather than myoblasts proliferation.

Morphological analysis of the blood smear is an essential element of diagnosing a disease hematologically and has been performed by conventional manual light microscopy for several decades. Although this method is the gold standard, it is labor-intensive, requires continuous training of the personnel, and is subject to relatively large interobserver variability. The artificial intelligence (AI)-based automated methods for the digital morphological analysis of blood smears have recently been developed. In this review, our recently developed convolutional neural network (CNN)-based digital morphology hematology analysis system is introduced. AI-based digital morphology hematology analysis system is firstly needed to incorporate digital imaging of blood cells into the analysis system. It is essential to establish a digital platform, which was already established in the radiological diagnosis, for the dissemination of CNN-based automated digital morphology hematology analyzer in the near future.

Cardiac safety assessments play a key role in drug development. New non-clinical cardiac safety risk assessments, such as the use of iPSC-derived cardiomyocytes, have been validated by several consortiums both in Japan and abroad. The emerging multidisciplinary field of cardio-oncology has been recognized more important. The success of new cancer therapies has improved life expectancy of cancer patients, hence more attention has been paid to cardiotoxicities associated with existing and new anti-cancer therapies, such as cardiomyocyte injury and heart failure, vascular injury and hypertension or thrombosis, which accelerated coronary artery disease. In addition to the well-studied proarrhythmia risk, some cardiotoxicities, such as contractility impairment, are expected to be evaluated by iPSC-derived cardiomyocytes. Here we developed a novel imaging-based in vitro contractility assay using iPSC-derived cardiomyocytes. In the review, we would like to discuss the current status and future perspectives in the assessment of cardiac contractile function by anti-cancer agents.

Biomarkers, which include cells, cytokines/chemokines, and genes, present in patient blood, urine, or tissues, are considered objective indicators of disease progression or treatment response. Recipients of allogeneic hematopoietic cell transplantation often develop acute and/or chronic graft-versus-host disease (GVHD). Biomarkers that could provide precise assessment of temporal inflammatory conditions in transplant recipients could help us to identify recipients at an increased risk of GVHD, determine the severity of GVHD, and decide upon treatment strategies. The current review article summarizes several established biomarkers for acute and chronic GVHD, as well as interesting and novel viewpoints. Biomarkers could be categorized as those associated with an abnormal immune reconstitution, organ damage, or poor wound healing, including inflammation and fibrosis. The investigation of biomarkers for GVHD would shed light on the complicated networks underlying allo-immune responses and is necessary for further advances in our understanding of GVHD pathophysiology. Clinical trials of preemptive interventions or novel drugs based on GVHD biomarkers are warranted. Research on potential biomarkers of GVHD would lead to further progress in diagnosis, treatment, and drug discovery.

By intensive efforts of sequencing a large number of genomes from patients with myelodysplastic syndromes (MDS), a comprehensive registry of driver mutations repeatedly found in MDS patients has been identified, providing us with a virtually complete spectrum of driver mutations in this disease. Importantly, significant correlations between driver mutations have been revealed, suggesting that some combinations of genetic events confer strong selective advantages on mutated stem cells. Next-generation sequencing technology has also revealed that clonal hematopoiesis is a common, age-related process, in which a somatically mutated hematopoietic precursor gives rise to a genetically distinct subpopulation in the blood. Furthermore, novel germline mutations have been identified, indicating that mutated stem cells appear long before MDS presentation. Such founding mutations are thought to be acquired and positively selected for in a well-organized manner to allow expansion of the initiating clone to compromise normal hematopoiesis, ultimately resulting in MDS and subsequent transformation into acute myeloid leukemia in many patients.

For more than two decades, the leukemia stem cell (LSC) model has received considerable attention following the identification of rare engrafting cell subpopulations in patient-derived xenograft assays. LSCs are thought to induce leukemogenesis and recurrence and are considered excellent targets in the development of curative therapies. Experimental support for this model in human malignancy was first achieved for acute myeloid leukemia (AML). Subsequent studies of AML stem cells have revealed a dormant state and enrichment of the CD34+CD38- subpopulation. These cells express specific antigens (e.g., CD123, CD47, TIM-3) and depend on several signaling pathways (e.g., WNT/β-catenin and PI3K/AKT/FOXO pathways) and mitochondrial respiration for growth and survival. More recently, genetic and immunological studies revealed that LSCs are genetically heterogenous and can escape host antitumor immunity. This article summarizes the current knowledge about LSCs and discusses future challenges involving the translation of research findings into real-time benefits for AML patients.

Gilteritinib is an FMS-like tyrosine kinase 3 (FLT3) inhibitor that has shown efficacy in patients with refractory or recurrent adult acute myeloid leukemia (AML) with FLT3 mutations. However, there are limited data for pediatric patients treated with this drug. Herein, we report the clinical courses of two children with FLT3-mutated recurrent AML who received gilteritinib. Case 1: An 11-year-old boy with secondary relapsed AML presented with an FLT3 internal tandem duplication (ITD) since the first recurrence. One week after gilteritinib initiation, blasts, which had comprised 90% of the white blood cells before treatment, almost disappeared from the peripheral blood without tumor lysis syndrome. The patient developed multiple adverse effects and died from the disease 2.5 months after gilteritinib initiation. Case 2: A 12-year-old girl diagnosed with AML was positive for FLT3 ITD. She received gilteritinib during her first relapse post-stem cell transplantation. After the drug was administered, the recipient cell counts increased, as determined by molecular tests (i.e., FISH), whereas microscopically, there was a complete response for 5 months with good performance status. Gilteritinib treatment in children with FLT3-mutated recurrent AML is feasible and effective. As a patient experienced several adverse effects with gilteritinib treatment, clinical trials are required to determine the appropriate pediatric dose of this medication.

Blood vessels supply oxygen and nutrients to all the cells in a living body, and provide essential transport routes for collecting waste products. For these functions, blood vessel networks should be appropriately formed in each tissue. Therefore, blood vessels are one of the earliest organs formed during the developmental process. Development of the blood vessel system promotes tissue differentiation and organ morphogenesis, allowing each organ to maintain its unique functions under changing metabolic conditions. Blood vessels have a relatively simple structure, consisting of endothelial cells covering the inner layer, and pericytes or smooth muscle cells surrounding the outside. The structure of the vascular network is extremely diverse, with blood vessels uniquely organized depending on the tissues they serve, to create tissue-specific microenvironments. How are such tissue-specific vascular environments generated? Over the years, anatomical findings have accumulated to confirm this vascular diversity. However, the molecular basis for this diversity has remained unclear. In the present article, we review the mechanisms of coordinated developmental control of the vascular and neural systems in the cerebral cortex from the viewpoint of the accurate expression control of vascular endothelial growth factor (VEGF) signaling, and describe future perspectives.

Retinitis pigmentosa (RP) is a group of hereditary diseases that involve loss of photoreceptors. There has been no established treatment for RP, and it is now the 2nd leading cause of blindness in Japan. Previous clinical researches using human fetal retina transplantation suggested some functional recovery in vision, but it did not become a standard therapy because of ethical concerns for using fetus tissues. Invention of induced pluripotent stem cells (iPSC) in 2006 and the establishment of retinal organoids induction protocol from ES/iPS cells have paved a way of cell therapy for RP without ethical concerns. Our team has shown that mouse iPSC derived retinas can survive and mature after subretinal transplantation to the end-stage retinal degeneration model mice. Further, human ESC derived retinas survived and matured in retinal degeneration monkey models. Recently, we have established a qualitative and quantitative evaluation tool for photoreceptor synapses, QUANTOS, and showed that photoreceptors in mouse iPSC derived retina can form photoreceptor synapses in a time dependent manner after transplantation. We are now moving toward 1st in human clinical trial using iPSC derived retina for RP.

Pericytes stabilize microvessels by wrapping them with their processes. They are located within the neurovascular unit between endothelial cells, astrocytes, and neurons, and interact with neighboring cells to generate diverse functional responses that are critical for central nerve system (CNS) function in health and disease. Recent evidence suggests that brain pericytes play crucial roles in regulating microvascular functions, such as blood-brain barrier properties, capillary blood flow, angiogenesis, and the entry of leukocytes into the brain. Pericytes also take part in tissue repair after CNS injury and may have stem cell-like properties. In addition, recent reports suggest that peripheral nerve pericytes, forming the blood-nerve barrier (BNB), regulate BNB function and basement membrane maintenance. Microvascular dysfunction due to pericyte degeneration initiates secondary neurodegenerative changes in the nervous system. In this review, we will first describe the origin, heterogeneity, and the physiological characteristics of pericytes. We next review possible pathological mechanisms and consequences of pericyte impairment in nervous system diseases including Alzheimer's diseases, diabetes, vascular dementia, and stroke. Finally, we will discuss how pericytes can be targeted for developing novel therapeutic approaches for treating patients with neurological disorders.

There are few reports of a patient presenting with combined follicular lymphoma (FL) and classical Hodgkin lymphoma (cHL). A 37-year-old Japanese man was diagnosed with FL with generalized lymphadenopathy and treated with R-CHOP. Four months later, he presented with fever, elevated lactic acid dehydrogenase (LDH), and pancytopenia. Consequently, he was diagnosed with cHL in the bone marrow. Identical clonality of FL and cHL tumor cells suggested identical immunoglobulin heavy chain gene rearrangements. He was treated with salvage chemotherapy and high-dose chemotherapy with autologous hematopoietic stem cell transformation (HDT-ASCT), which has led to complete remission and no recurrence for more than two years after transplantation. Our case suggests that HDT-ASCT may be an effective treatment for this rare clinical condition.

Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disease characterized by progressive muscle wasting and weakness. Riluzole was the sole drug available for treating ALS until 2015, when edaravone was approved as a new anti-ALS drug. Recent discoveries of the disease-causal genes and proteins, as well as the rapid advancement of induced pluripotent stem (iPS) cell manipulations, drug deliveries, and molecular modifications have provided diverse and promising drug candidates. In particular, antisense-oligonucleotide therapy appears to significantly prevent disease progression when introduced early. Moreover, the in vitro modeling of ALS using patients' own iPS cells enables effective screening of approved drugs. Drug repositioning is a robust short-cut to bedside use in patients with ALS, due to the availability of data for safety concerns. Currently, five investigator-initiated drug trials are underway in Japan. These include trials of hepatocyte growth factor, perampanel, ultra-high-dose methylcobalamin, ropinirole, and bosutinib. This is a review of new ALS drugs that are either currently available or in on-going trials. We additionally review the pathogenic pathways that these drugs target.

The rare chromosomal translocation t(16;21) has been associated with CD56 expression and extramedullary lesions in acute myeloid leukemia (AML). We herein report the first case of the development of isolated pericardial relapse after HLA-haploidentical peripheral blood stem cell transplantation (haplo-PBSCT). A 42-year-old male AML patient with t(16;21)(p11.2;q22) received haplo-PBSCT at partial remission, and he exhibited dyspnea due to massive pericardial effusion 11 months later. The effusion analysis revealed CD56+ leukemic cells, and G-banded karyotyping of the cells demonstrated t(16;21)(p11.2;q22). Salvage chemotherapy was administered, but only a transient improvement of the effusion was achieved. Moreover, the pleural effusion developed without bone marrow relapse.

Human induced pluripotent stem (iPS) cell-derived hepatocyte-like cells (iPS-HLCs) are expected to be applicable to large-scale in vitro hepatotoxicity screening systems. Accordingly, methods for generating HLCs from human iPS cells have been improved over the past decade. However, although human hepatocytes have zone-specific characteristics in vivo, there is currently no technique to generate zone-specific HLCs from human iPS cells. Therefore, to generate HLCs with zone-specific properties from human iPS cells, we cultured iPS-HLCs using a parenchymal or nonparenchymal cell-conditioned medium (CM). The results showed that urea production and gluconeogenesis capacity in iPS-HLCs were increased by culturing with cholangiocyte-CM, and glutamine production and drug metabolism capacity in iPS-HLCs were increased by culturing with hepatocyte-CM. It was thus clarified that iPS-HLCs acquire zone 1 hepatocyte-like properties by culturing with cholangiocyte-CM and that iPS-HLCs acquire zone 3 hepatocyte-like properties by culturing with hepatocyte-CM. In addition, we found that WNT inhibitory factor-1 secreted from cholangiocytes, and WNT7B and WNT8B secreted from hepatocytes play important roles in the zone-specific conversion of iPS-HLCs. We hope that our findings will facilitate the application of iPS-HLCs to drug discovery research.

In the tumor immunotherapy field, the adoptive immunotherapies, in which patient-derived T cells are strengthened ex vivo by activation or genetic modification, have been shown to be effective. However, some issues still remain to be solved. For example, it is not easy to efficiently expand tumor antigen-specific T cells, since they easily get exhausted during ex vivo culture. Moreover, these strategies are costly and time-consuming, because they are mainly conducted in autologous settings. To address these issues, we have been utilizing the induced pluripotent stem(iPS)cell technology. When iPS cells are established from tumor antigen-specific T cells, T cells regenerated from these iPS cells are expected to express the same T cell receptor(TCR)as the original T cells. In line with this concept, we succeeded in regenerating tumor antigen-specific cytotoxic T cells in 2013. We subsequently succeeded in developing a method by which very potent cytotoxic T lymphocytes are regenerated. We are now developing a strategy where non-T derived iPSCs are transduced with exogenous TCR gene efficacy and safety of which have been clinically tested. We plan to apply this approach to HLA haplotype-homozygous iPS cell stock lines, expecting that it will become possible to establish "off-the-shelf T cell" bank against various types of tumors.