Our laboratory previously established spinal motor neurons (MN) from induced-pluripotent stem cells (iPSCs) prepared from both sporadic and familial ALS patients, and successfully recapitulated disease-specific pathophysiological processes. We next searched for effective drugs capable of slowing the progression of ALS using a drug library of 1232 existing compounds and discovered that ropinirole hydrochloride prevented MN death. In December 2018, we started an investigator-initiated clinical trial testing ropinirole hydrochloride extended-release tablets in ALS patients. This is an on-going phase I/IIa randomized, double-blind, placebo-controlled, single-center, open-label continuation clinical trial (UMIN000034954). The primary aim is to assess the safety and tolerability of ropinirole hydrochloride in patients with ALS. We will also perform an efficacy evaluation using patient-derived iPSCs/MN. Major inclusion criteria were as follows: 1) 'clinically possible and laboratory-supported ALS', 'clinically probable ALS' or 'clinically definite ALS', according to the criteria for the diagnosis of ALS (El Escorial revised) and within 60 months after disease onset; 2) change in ALSFRS-R score of -2 to -5 points during the 12-week run-in period. Finally, 15 patients will be assigned to the active drug and 5 patients to the placebo. Our trial will be a touchstone trial for iPSC-based drug development strategies.

Amyotrophic lateral sclerosis (ALS) is the most rapidly progressive motor neuron disease (MND) in adults, characterized by the selective death of motor neurons in the motor cortex, brainstem, and spinal cord. Riluzole and edaravone are the only approved drugs available in Japan to date. Approximately 10% of ALS cases are familial in rature, defined as the existence of disease-causing mutation. SOD1 is the most frequent causative gene for ALS among Japanese individuals, while C9orf72 mutation is more prevalent in Western countries. Genotype-phenotype correlation described in the literature of familial ALS enables to establish models of the disease. This review article describes the clinical characteristics of familial ALS based on each disease-causing mutation. The pathomechanism of ALS including proteostasis, RNA metabolism, and axonal pathology are discussed in detail. We also reviewed the status of development of therapeutic strategies for familial ALS based on analysis of animal models and induced pluripotent stem cells.

A 64-year-old woman was diagnosed with diffuse large B-cell lymphoma (DLBCL) in 2013. After eight courses of R-CHOP therapy followed by local irradiation of the remaining retroperitoneal soft tissue shadow, complete response was confirmed on 18F-2-fluoro-2-deoxyglucose-positron emission tomography/computed tomography (FDG-PET/CT). Early in 2016, patient's serum LDH and soluble IL-2 receptor levels elevated. With suspected recurrence of DLBCL, FDG-PET/CT was performed that showed no lymphadenopathy or abnormal FDG uptake. By the end of July 2016, the patient developed fever and night sweating. Intravascular large B-cell lymphoma (IVLBCL) was suspected, and the patient underwent random skin biopsies, which revealed large atypical cells infiltrating peripheral and intravascular regions of the subcutaneous adipose tissue. Cell morphology, immunostaining, and PCR analysis of the immunoglobulin heavy chain gene suggested the recurrence of DLBCL. Despite salvage chemotherapy and autologous peripheral stem cell transplantation with high-dose chemotherapy, approximately 15 months later, DLBCL recurred and involved the lungs. The patient again received chemotherapy and achieved a second remission. Because DLBCL may recur like intravascular lymphoma, the same tests used for IVLBCL diagnosis are required in cases of suspected recurrence of DLBCL based on clinical and laboratory findings.

A 12-year-old boy was diagnosed with aplastic anemia. He was followed as an outpatient without medication, and his cytopenia improved after several years. When he was 26 years old, an annual medical checkup revealed leukocytopenia, and at the age of 31 years, he was diagnosed with myelodysplastic syndrome (MDS), refractory cytopenia with multilineage dysplasia. Chromosomal analysis of his bone marrow cells revealed trisomy 8. Ten months after being diagnosed with MDS, he developed refractory stomatitis. Two months later, he experienced abdominal pain and bloody stool, and simple punched-out ulcers similar to intestinal Behçet's disease (BD) were noted in the terminal ileum on colonoscopy. Steroids, mesalazine, and adalimumab were ineffective. Nineteen months after the MDS diagnosis, he underwent cord blood transplantation from an HLA 1-locus mismatched unrelated donor in accordance with a non-myeloablative pretransplant conditioning regimen. The patient's stomatitis and ileocecal ulcers improved following the transplantation. Currently, both MDS and BD-like symptoms are in complete remission at 36 months post transplantation, and the patient continues to take low-dose oral tacrolimus for chronic skin GVHD. Allogeneic hematopoietic stem cell transplantation could become a therapeutic choice for MDS associated with BD, even if refractory intestinal BD symptoms are present.

It is well known that acute lymphoblastic leukemia (ALL) cells can invade the central nervous system (CNS), but the underlying mechanism of such invasion is still unclear. We discovered the direct routes taken by ALL cells when migrating into CNS in ALL model mice. We observed that ALL cells migrate along the external surface of vessels that pass directly between the vertebral or calvarial bone marrow and the subarachnoid space. The basement membrane of these bridging vessels is enriched in laminin. The laminin is recognized by integrin α6, which is expressed by ALL cells. The interaction between integrin α6 and laminin mediated the invasion of ALL cells. Furthermore, the expression of integrin α6 depends on PI3Kδ activity. Mice with ALL xenografts were treated with a PI3Kδ inhibitor, which decreased integrin α6 expression on ALL cells. This resulted in significant reductions in blast counts in the cerebrospinal fluid and in CNS disease symptoms. Our data suggest that the PI3Kδ inhibitor has potential to prevent CNS involvement in ALL.

The 8p11 myeloproliferative syndrome (EMS) is a relatively rare hematological malignancy defined by the presence of chromosomal abnormalities associated with fibroblast growth factor-1 gene, located in the 8p11-12.1 chromosomal locus. To date, only around a hundred cases have been reported in the literature. Patients with EMS present with various forms of myeloid/lymphoid malignancies, such as myeloproliferative neoplasms, acute myeloid leukemia, and T- or B-linage lymphoblastic lymphoma, which are frequently associated with eosinophilia. Prognosis of EMS is poor and a standard treatment strategy has not yet been established. In contrast to myeloid/lymphoid neoplasms associated with PDGFR-A or PDGFR-B rearrangement, the tyrosine kinase inhibitor (TKI) imatinib is not an effective therapeutic option for EMS patients. Other types of TKI, i.e., PKC412, sorafenib, ponatinib, dasatinib, and dovitinib, show growth-inhibitory effects against the cells harboring several types of FGFR-1 fusion genes in in vitro studies; however, the usefulness of either drug has not been confirmed by clinical trials. Therefore, at present, allo-hematopoietic stem cell transplantation is the only curative methods for EMS. Very recently, a phase-2 study with pemigatinib, an inhibitor for FGFR1, showed clinical benefits for EMS patients, including major cytogenetic response, suggesting a new therapeutic option for EMS.

The median survival time in myelofibrosis is about 5 years, and allogeneic hematopoietic stem cell transplantation is the only curative treatment. Because the clinical course and prognosis of myelofibrosis is not uniform, transplantation-related death or long-term prognosis should be evaluated by varied prognostic prediction systems. This includes assessing gene mutation information in each patient, and the indication and timing of transplantation should be decided based on this information. Previous reports have shown that transplanted hematopoietic stem cells can be engrafted despite marked fibrosis in the bone marrow, and allogeneic hematopoietic stem cell transplantation is a curative treatment for myelofibrosis. However, the transplant-related mortality rate is 30-50%, and the overall survival rate is only around 50%. Future work should focus on methods to decrease transplant-related mortality, including the selection of stem cell source, the development of optimal pre-transplant treatment, and how to best incorporate JAK2 inhibitors before transplantation.

The mechanism underlying production of various types of blood cells from hematopoietic stem and progenitor cells has been a central theme in hematology. Conventionally, hematopoietic cell populations are analyzed by cell surface markers to judge cell types and differentiation stages, and by transplantation assays to assess differentiation potential. Recently, however, next-generation sequencing technology has enabled single-cell transcriptome and epigenome analyses and cell barcoding-based lineage tracing during unperturbed hematopoiesis. These innovative assays revealed that each cell population is extensively heterogenous. Many cells within hematopoietic stem cell populations may not be multipotent, and conversely, hematopoietic progenitor cells often display self-renewal capacity. Moreover, cells tend to make their lineage choice much earlier than previously thought. Altogether, these results challenge the current hierarchical differentiation models and propose new continuous models. Single-cell analyses are expected to greatly contribute to our understanding of normal and abnormal hematopoiesis and to the development of new therapies for blood disorders.

The hematopoietic stem cells, defined as blood stem cells with self-replication ability and multipotency, are key to successful hematopoietic stem cell transplantation. With the history of transplantation in the past 60 years and advances in stem cell technologies, our understanding of the hematopoietic system has deepened. However, the molecular mechanisms of self-renewal and pluripotency, which are the essence of the hematopoietic stem cells, remain poorly understood. One reason is that the identification/purification methods of the hematopoietic stem cells, particularly the long-term hematopoietic stem cells capable of lifelong self-renewal, is technically difficult owing to their scarcity in the bone marrow and has not been established to this date. Considering that a long-lasting blood production after hematopoietic stem cell transplantation is crucial, it is essential to understand the biology of the long-term hematopoietic stem cells not only scientifically but also clinically. This review describes the scientific and clinical significance of the long-term hematopoietic stem cells by showing the results of the latest researches in the introduction of hematopoietic stem cell identification/purification history.

Human iPS cells are somatic cells reprogrammed to the pluripotent state. Because of their pluripotent nature, iPS cells are now commonly used to model several developmental processes including hematopoiesis in vitro. The in vitro models can be used to study the mechanisms regulating not only normal hematopoiesis but also hematological diseases ranging from monogenic congenital disorders to genetically multifactorial malignancies. Those disease models can also be used to investigate novel treatments through procedures including high throughput drug screening. The possible clinical applications of iPS cell-derived hematopoietic cells include immunotherapy with T lymphocytes, NK cells and macrophages, and transfusion therapy with platelets and red blood cells. Platelets have now been produced from iPS cells in quantities sufficient for clinical use. By developing expandable immortalized megakaryocyte cell lines (imMKCLs), several novel drugs and turbulence-incorporated bioreactors, efficient and scalable generation of platelets was achieved. This review summarizes the current status of iPS cell research in hematopoiesis with details on iPS cell-derived platelets.

A 51-year-old man complaining of exertional dyspnea and syncope was admitted to our hospital. Computed tomography(CT) and transesophageal echocardiography demonstrated a mobile tumor-like lesion in the right atrium. Surgical resection was performed under cardioplegic arrest, which revealed an organized thrombus. Pathological examination revealed amyloid deposition in the myocardium, and bone marrow biopsy revealed CD138 (+) stem cells. Therefore, the patient was diagnosed with amyloid light-chain (AL) amyloidosis associated with multiple myeloma. Although he required percutaneous cardiopulmonary support for postoperative right heart failure for 3 days, he recovered well and was discharged from the hospital on day 44, in a good condition. He was treated with bortezomib for multiple myeloma after surgery. Thus, despite the maintenance of sinus rhythm, intra-cardiac thrombus could be formed with amyloidosis.

The liver is a major organ responsible for maintaining the body's homeostasis and xenobiotic metabolism. Liver transplantation is essential for the alleviation of many severe liver diseases. However, there are many patients who cannot receive liver transplants because of donor shortage. Therefore development of effective therapeutic drugs that can replace the need for liver transplantation is desired. To this end, model cells that faithfully reproduce hepatic functions are essential. It is expected that human induced pluripotent stem cell (iPS)-derived hepatocyte-like cells, which faithfully reproduce hepatic functions, would be a valuable tool for drug discovery. Hepatic differentiation from human iPS cells has been performed using growth factors, but the hepatic differentiation efficiency was quite low and liver functions of human iPS cell-derived hepatocyte-like cells were lower than those of primary human hepatocytes. Therefore we tried to improve the hepatic differentiation technology using gene transfer, genome editing, three-dimensional culture, and extracellular matrix technologies. As a result, the purity of human iPS cell-derived hepatocyte-like cells was improved into 90% or more, and the liver functions of human iPS cell-derived hepatocyte-like cells were improved to a level comparable to primary human hepatocytes. In this article, we introduce the research results we have acquired over the last decade.

We performed drug screening using motor neurons derived from disease-specific induced pluripotent stem cells (iPSCs) for amyotrophic lateral sclerosis (ALS) and found that ropinirole hydrochloride prevented motor neuron death. We have started a randomized clinical trial testing ropinirole hydrochloride in ALS patients in December 2018. This is a phase I/IIa randomized, double-blind, placebo-controlled, single-center, open-label continuation clinical trial. The primary aim is to assess the safety and tolerability of ropinirole hydrochloride in patients with ALS. Secondary aims include the following effectiveness evaluations: ALSFRS-R, quantitative muscle strength by a hand-held dynamometer, muscle volume by CT scan, forced vital capacity, physical activity by an activity tracker, survival, ALSAQ40 scale, and a Zarit Caregiver Burden Interview. Moreover, we will perform an efficacy evaluation using subjects-derived iPSCs/motor neurons and assess plasma/CSF biomarkers (TDP-43, and ALS-related RNA/micro RNA) as exploratory research questions. Ropinirole hydrochloride potentially targets multiple mechanisms of ALS pathology (i.e., oxidative stress, mitochondrial dysfunction, and abnormal aggregation of TDP-43/FUS protein, which is representative of the ALS phenotype), with promising preclinical study results based on iPSC research. The availability of the drug suggests that rapid translation to daily clinical use might be possible. Our trial will provide reliable and important data for further potential trials. The results will appear in March 2021.

POEMS syndrome is a rare paraneoplastic disorder characterized by polyneuropathy, organomegaly, endocrinopathy, λ-type monoclonal protein derived from only two germlines (IGLV1-40 or IGLV1-44), skin changes, extravascular volume overload, and serum vascular endothelial growth factor elevation. To understand the molecular pathophysiology of the disease, comprehensive genetic analyses of bone marrow plasma cells was performed in 20 patients with the syndrome. Although a median of 14.5 mutated genes were identified per patient, none of the driver gene mutations frequently found in multiple myeloma were detected. RNA sequencing revealed a transcription profile specific to POEMS syndrome, which suggested that the genetic and transcriptional profiles of plasma cells in POEMS syndrome are distinct from multiple myeloma and monoclonal gammopathy of undetermined significance. Treatment strategies for the devastating disease have been developed by targeting monoclonal plasma cells with novel agents, mainly thalidomide, followed by autologous stem cell transplantation (ASCT). Moreover, the 5-year overall survival after ASCT has improved to as high as 90% with dramatic improvement in symptoms and activities of daily living. However, the 5-year progression-free survival during long-term follow-up has dropped to 60%. Therefore, identifying novel therapeutic targets are imperative for further improvement of disease outcomes.

Adult T-cell leukemia-lymphoma (ATL) is a peripheral T-cell lymphoma caused by human T-cell lymphotropic virus type I. Patients with aggressive ATL exhibit poor outcomes, even with dose-dense intensive chemotherapy. Thus, allogeneic hematopoietic stem cell transplantation (allo-HSCT) is considered in all patients eligible for transplant. However, patients with aggressive ATL often have chemo-refractoriness or experience early relapse during chemotherapy. Allo-HSCT is often ineffective in patients with active disease status. Mogamulizumab (Moga) was approved in 2012 in Japan as a potent treatment option for patients with relapsed or refractory ATL. However, there is a major concern that the use of Moga before allo-HSCT could increase the risk of post-transplant complications, such as graft-versus-host disease (GVHD), because Moga depletes regulatory T cells. Here, we would like to describe the possible effects of pre-transplant Moga on post-transplant complications, such as acute GVHD, and to discuss how Moga could be efficiently incorporated in the treatment regimen of patients with aggressive ATL to maximize the expected clinical benefit.

Myelodysplastic syndromes (MDS) constitute a group of heterogeneous disorders of hematopoietic stem cells, characterized by defective hematopoiesis and multilineage dysplasia. While low-risk subtypes normally exhibit a relatively chronic clinical course, high-risk subtypes harbor unfavorable prognosis in which hematopoietic stem cell transplantation (HCT) is the only curative therapy. Nevertheless, transplantation-related mortality is relatively high and should be weighed against the potential benefits of HCT. Hence, it is vital to precisely stratify the prognostic risks before HCT for predicting and enhancing their prognosis. Recently, our understanding of the genetic basis of MDS has substantially advanced, through which a full spectrum of major mutational targets was delineated. Moreover, its effects in the setting of HCT have also been assessed besides the conventional predictive factors. While clinical factors account for as much as 70% of the total hazard of MDS cases treated with HCT, the remaining 30% is explicated by genetic factors. The integration of genetic test and conventional clinical factors could be useful for precise stratification of the prognostic risks and, therefore, treatment decision in MDS.

Chronic active Epstein-Barr virus infection (CAEBV) presents with mononucleosis-like symptoms such as chronic persistent or recurrent pyrexia, lymphadenopathy, and hepatosplenomegaly because of the reactivation of Epstein-Barr virus (EBV) as demonstrated by the recurrence of EBV-infected cells. The mechanism of CAEBV remains obscure, and CAEBV can lead to fatal conditions such as hemophagocytic syndrome and malignant lymphoma by clonal expansion of EBV-infected T- or NK-cells. Without hematopoietic stem cell transplantation, CAEBV has a poor prognosis. CAEBV is listed in the revised 2016 World Health Organization classification as a chronic active EBV infection of T- and NK-cell types, systemic form, among EBV-positive T- and NK-cell lymphoproliferative diseases of childhood. However, similar clinical conditions have been reported in adult patients. Therefore, we investigated the clinical features of adult patients with CAEBV-like features (adult-onset CAEBV) in a relatively small number of cases. Additionally, genetic alterations related to CAEBV development have also been reported. Along with these results, we reviewed the clinical characteristics of adult-onset CAEBV.

In drug disposition, the liver and small intestine are very important as tissues involving in drug metabolism, absorption, and excretion. Thus, in drug development studies, it is necessary to evaluate the pharmacokinetics in these tissues accurately including the contributions of drug-metabolizing enzymes and drug transporters. Currently, all kinds of evaluation systems have been used for the pharmacokinetic prediction; however, there are some issues in these systems. Therefore, the researches for the development of human induced pluripotent stem (iPS) cell-derived hepatocytes and enterocytes, as novel systems besides existing ones, are being advanced. Because human iPS cells have abilities of pluripotency and almost infinite proliferation, it is thought to be possible to stably provide the high-quality cells that have similar characteristics to human normal tissue cells by using human iPS cells. In this review, we describe current status of differentiation studies of human iPS cell-derived hepatocytes and enterocytes and the functional characteristics of these cells centered on pharmacokinetic functions.

Bone marrow (BM), the tissue specializing in the production of hematopoietic cells, consists of multiple components (e.g., extracellular matrixes, vasculatures, and stromal cells) that generate a complex three-dimensional network and several localized microenvironment. These microenvironments regulate hematopoietic stem and progenitor cells, including megakaryocyte lineage cells. In this review, we first provide an overview of the microenvironment for hematopoietic stem cells as an introduction to bone marrow microenvironment and subsequently summarize the microenvironment for megakaryocyte differentiation and maturation (megakaryopoiesis). In the last portion, we describe megakaryocyte regulation by podoplanin-positive peri-arteriolar stromal cells in the mouse bone marrow.

Aplastic anemia (AA), a hematopoietic disorder characterized by hypocellular bone marrow, is caused by immunologically-mediated hematopoietic stem cell injury. Viral infection is hypothesized as the underlying cause of hepatitis-associated AA, although its mechanism is still unclear. This report describes a case of AA following suspected drug-induced liver injury (DILI). An 18-year-old man developed severe liver dysfunction after taking oral over-the-counter drugs. The patient was diagnosed with suspected DILI based on drug-induced lymphocyte stimulation test and liver biopsy results. Although liver dysfunction improved after a course of steroid pulse therapy and liver supporting therapy, the man gradually developed pancytopenia within 3 months of DILI diagnosis, prompting the diagnosis of AA following DILI. Paroxysmal nocturnal hemoglobinuria-type cells were detected by high-sensitivity flow cytometry. Immunosuppressive therapy with antithymocyte globulin and cyclosporin was administered, with pancytopenia improvement. To the best of our knowledge, this is the first report in the literature with a case of AA following DILI, and we believe it is important for evaluating the pathogenesis of drug-induced and hepatitis-associated AA.