Human induced pluripotent stem cells derived cardiomyocytes (hiPSC-CMs) can recapitulate the properties of human cardiomyocyte and exhibit disease phenotypes in vitro, attributable to their healthy- or patient-specific genetic backgrounds. Therefore, hiPSC-CMs are a crucial tool for developing therapeutic agents for cardiovascular diseases, and regenerative medicine using hiPSC-CMs is expected to be an alternative therapy to heart transplantation. Moreover, the development of organoid models has been advanced to replicate the complex structure of heart tissue in vitro, thereby effectively facilitating drug discovery. On the other hand, current methods for advancing drug discovery using hiPSC-CMs face limitations, including the difficulty of quantifying characteristics such as cell structure and predicting the risk and efficacy of candidate drug in clinical practice. In the field of regenerative medicine, challenges include quality control and the verification of safety of transplanted cells in human. In silico model, including artificial intelligence (AI) and simulation, have been developed in the field of drug discovery using hiPSC-CMs. These advancements encompass phenotype scoring via AI and risk prediction through simulations. This review outlines the current status and challenges of drug discovery using hiPSC-CMs and in silico model, based on the published reports.

Tacrolimus is widely recognized as an anti-rejection agent due to its immunosuppressive characteristics. It binds to the immunophilin FK506-binding protein (FKBP) and thus to calcineurin, and inhibits its activity. Tacrolimus' therapeutic concentration range in blood is narrow, and its pharmacokinetics are highly variable among individuals. First, because tacrolimus primarily distributes to red blood cells (RBCs), anemia and blood transfusions can cause fluctuations in tacrolimus blood concentrations. Variations in blood tacrolimus concentration significantly correlated with variations in RBC count, hemoglobin level, and hematocrit value, but not with variations in white blood cell or platelet counts. Interestingly, FKBP played an important role in tacrolimus distribution to RBCs. The effects of intracellular and extracellular FKBP levels on RBC distribution of tacrolimus in circulating blood were substantial. Secondly, proteins affecting pharmacokinetics can differ at the genetic level in their expression and functional potency. Genetic polymorphisms that influence tacrolimus pharmacokinetics have been reported. A polymorphism in the gene encoding the metabolic enzyme cytochrome P450 (CYP) 3A5 is a particularly influential factor affecting tacrolimus pharmacokinetics in Japanese patients. CYP3A5 polymorphisms correlated with individual differences in tacrolimus blood concentration changes after starting continuous infusion in allogeneic hematopoietic stem cell transplantation (HSCT) recipients. In addition, CYP3A5*3 polymorphism also correlated with differences in the frequency of acute graft-versus-host disease (GVHD) development in allogeneic HSCT recipients.

Advanced cell culture systems including human induced pluripotent stem (iPS) cells and organoids enable the generation of intricate structural and functional organ models in vitro. Application of these advanced cell culture systems to research on a wide range of diseases including infectious diseases is underway. Due to the impact of the coronavirus disease 2019 (COVID-19) pandemic, advanced cell culture systems in the virus research field are rapidly becoming popular. Respiratory models generated using human iPS cells and organoid technology are useful for analyzing respiratory cell responses caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. However, there is still room for the development of an apical-out model, which is essential for simple virus infection experiments, and a model that can analyze host responses in the alveoli and airways. In this study, we developed human iPS cell-derived alveolar and airway models with an apical-out structure by using a micropatterning plate. In the alveolar model, we confirmed that this model contains abundant type II alveolar epithelial (AT2) cells, which are the target cells of SARS-CoV-2 in the alveoli. In the airway model, we confirmed that this model contains abundant ciliated cells, which are the target cells of SARS-CoV-2 in the airway. Using our alveolar and airway models, we can analyze the differences in infection efficiency and host response of each SARS-CoV-2 variant. We hope that the human iPS cell-derived alveolar and airway models generated using a micropatterning plate will be used to analyze not only SARS-CoV-2 but also a wide range of respiratory viruses.

Bone marrow (BM) failure is a condition characterized by peripheral pancytopenia resulting from decreased hematopoiesis in the BM. It includes congenital disorders such as Fanconi anemia (FA), as well as acquired conditions such as acquired aplastic anemia (AA), myelodysplastic syndrome (MDS), and paroxysmal nocturnal hemoglobinuria (PNH). AA presents with pancytopenia and BM hypoplasia, primarily triggered by an autoimmune mechanism involving T cells that damage hematopoietic stem cells (HSCs). Genomic investigations utilizing next-generation sequencing or SNP arrays have revealed that clonal hematopoiesis by HSCs with genetic aberrations, including PIGA, DNMT3A, ASXL1, BCOR/BCORL1, copy-number neutral LOH of chromosome 6p (6pLOH), and somatic mutations in HLA class I alleles are prevalent in AA patients. Recent studies have identified somatic mutations in genes associated with the JAK-STAT and MAPK pathways in T cells of AA patients. Genomic abnormalities in AA differ from those observed in MDS and age-related clonal hematopoiesis. Notably, the presence of PNH-type cells and HLA class I allele-lacking cells represent two major instances of escape hematopoiesis, which indicate the presence of HSCs evading autoimmune T cell attacks. These findings provide crucial insights into the immune pathophysiology of BM failure.

Mitochondrial metabolic dependencies characteristic of acute myeloid leukemia (AML) have recently been identified, demonstrating that metabolic enzymes regulate AML gene expression and control cell differentiation and stemness. These mitochondrial metabolic adaptations occur independently of underlying genomic abnormalities and contribute to chemotherapy resistance and relapse. Mitochondrial alterations also lead to metabolic vulnerability of AML cells, whose metabolism is characterized by dependence on oxidative phosphorylation, fatty acid oxidation, reactive oxygen species (ROS) production, and mitochondrial dynamics. Currently, mitochondrial properties of AML cells and leukemia stem cells are being investigated, focusing on metabolism, signal transduction, mitochondrial respiration, ROS generation, and mitophagy. In addition, mitochondria-targeted agents have shown promising results in clinical trials. This paper outlines recent findings from preclinical and clinical trials on the utility of agents targeting mitochondria-related molecules and metabolic pathways and their efficacy in combination with existing chemotherapies.

EVI1 is a zinc finger transcription factor encoded by the MECOM locus and is essential for the development and maintenance of hematopoietic stem cells. However, overexpression of EVI1 in various myeloid malignancies is associated with aggressive clinical behavior and poor outcome. The locus encodes multiple isoforms that are differentially acting and independently regulated. EVI1 interacts with a variety of transcription and epigenetic factors via different domains. It also regulates cell survival, differentiation, and proliferation through a variety of mechanisms, including transcriptional activation and repression, regulation of other transcription factors' activity, and chromatin remodeling. While the mechanism by which 3q26 translocation leads to high EVI1 expression through enhancer hijacking of genes active in myeloid development is now better understood, regulation of EVI1 expression in the absence of chromosomal translocations and in normal hematopoiesis remains unclear. Recent studies have provided insight into the regulatory mechanisms of EVI1 expression and action, which may lead to development of targeted therapies in the near future.

Sustaining lifelong hematopoiesis requires maintenance, proliferation, and differentiation of hematopoietic stem cells. Thrombopoietin is a cytokine essential for regulation of hematopoietic stem cells as well as differentiation and maturation of megakaryocytes required for platelet production. Due to these properties, thrombopoietin agonists have been used to treat bone marrow failure syndromes such as aplastic anemia. Through analysis of thrombopoietin gene-deficient mice, my colleagues and I have demonstrated the mechanism of action of thrombopoietin receptor agonists in hematopoietic stem cell maintenance and differentiation. This review focuses on governance of homeostasis in the hematopoietic system by thrombopoietin signaling.

Age-related clonal hematopoiesis and myeloid malignancies arise from hematopoietic stem cells and progenitors with genetic abnormalities. Advances in next-generation sequencing technology have led to the identification of a wide variety of genetic alterations involved in disease onset. However, it remains unclear how diverse genetic alterations, lacking disease specificity, lead to the development of myeloid malignancies and the progression of clonal hematopoiesis. Mitochondrial abnormalities and their roles in various pathological conditions such as aging, inflammation, neurological diseases, cardiac diseases, and cancer have recently been revealed, and have garnered attention as new therapeutic targets. This review focuses on regulation of mitochondrial dynamics and outlines the role of mitochondria in myeloid malignancies and clonal hematopoiesis.

Hematopoietic stem cell (HSC)-targeted gene therapy is curative for various genetic blood diseases, and its efficacy has been demonstrated in recent clinical trials. HSCs have self-renewal and hematopoietic multipotency; therefore, repairing pathological mutations or defects in HSCs allows for a lifelong cure with a single treatment. Autologous HSC gene therapy has been developed by lentiviral gene addition or gene editing, and is an option for most patients because it does not require a compatible donor. Current HSC gene therapy is based on ex vivo methods, in which patient HSCs are harvested, genetically modified ex vivo, and autologously transplanted into patients. However, the complexity of this process and the high cost of treatment are hindering the spread of gene therapy. Therefore, in vivo HSC gene therapy is being developed to deliver gene therapy tools directly into bone marrow HSCs by administration without ex vivo culture.

Methods in which patient-derived T cells are genetically modified in vitro and administered to patients have been demonstrated effective in the area of cancer immunotherapy. However, these methods have some unresolved issues such as cost, time, and unstable quality. Several groups have developed strategies to overcome these barriers by regenerating T cells from iPSCs. We have been developing a method in which specific TCR genes are introduced into iPSCs and T cells are regenerated from these iPSCs (TCR-iPSC method). We are now using starting iPSCs from the iPSC stock lines provided by CiRA-F, as the iPSC stock cells are less likely to be rejected. A study aimed at application to solid tumors demonstrated the therapeutic effect of regenerated T cells in a patient tissue xenograft model of WT1 antigen-positive renal cell carcinoma. This article will also discuss strategies by other groups to regenerate various types of T cells from iPSCs.

Prediction of intestinal drug absorption and drug-induced intestinal toxicity is critical for the development of orally-administered drugs. However, it is difficult to accurately predict these events because of large species differences and a lack of appropriate in vitro assay. Then, we proposed the use of human crypt-derived intestinal cells for the prediction of intestinal absorption and the risk of intestinal toxicity. 3D human intestinal spheroids were established from fresh surgical specimens of proximal jejunum and terminal ileum using the conditioned media containing Wnt3a, R-spondin 3, and noggin. To generate 2D monolayer, spheroids were enzymatically dissociated into single cells and plated onto Matrigel-precoated culture plates/inserts. We have confirmed the activities of typical drug-metabolizing enzymes and uptake/efflux transporters in human jejunal spheroid-derived differentiated cells. Intestinal availability (Fg) estimated from the apical-to-basal permeation clearance across the jejunal monolayer showed a good correlation with in vivo human Fg values for five CYP3A substrate drugs. As for the prediction of intestinal toxicity, we found that the degree of ATP decreases in intestinal spheroids incubated with different EGFR-TKIs varied greatly depending on the drugs and the rank order of the extent of ATP decrease corresponded with that of frequency of clinically-observed diarrhea. We also constructed enterochromaffin (EC) cell-rich spheroids and quantified serotonin release from EC cells upon exposure to drugs for the prediction of drug-induced nausea and vomiting. As a result, we found that the serotonin release was related to the high/low risk of nausea and vomiting of each ALK/ROS1 kinase inhibitors.

Drug discovery research takes many years and tons of effort, and the success rate is extremely low. In order to overcome this situation, pharmaceutical companies struggle to improve the probability of success drug research and development with multiple approaches. Recently, it is important to predict the clinical effects of the candidates as early as possible in drug discovery stage, to stratify patients with diseases, and to provide appropriate readouts for evaluation of pharmacological efficacy for increasing the success rate. In this environment, the importance of non-clinical research that actively utilizes human-derived samples including patient-derived samples is increasing. In this article, author describes the use of human-derived samples in non-clinical research, especially focusing on the utilization of induced pluripotent stem cells. Human-derived samples are valuable experimental materials that have, at least in part, human-specific characteristics that experimental animals do not possess. In particular, patient-derived samples are thought to have the genetic predisposition and at least some disease characteristics that cause the disease, and are useful from the perspective of elucidating the pathogenesis, disease modeling, and predictability of clinical effects. This is also valuable for drug discovery research in diseases that are difficult to reproduce in experimental animals such as mice. Whereas, human-derived samples have some limitations, and we need ethical procedures and consideration when researchers use them. Author will provide an overview of the use of human-derived samples in non-clinical research based on the perspectives as described above and introduce our research group cases, and future research prospects using them.

Myelodysplastic syndrome (MDS) is a refractory cancer that arises from hematopoietic stem cells and predominantly affects elderly adults. In addition to driver gene mutations, which are also found in clonal hematopoiesis in healthy elderly people, systemic inflammation caused by infection or collagen disease has long been known as an extracellular factor in the pathogenesis of MDS. Wild-type HSCs have an "innate immune memory" that functions in response to infection and inflammatory stress, and my colleagues and I used an infection stress model to demonstrate that the innate immune response by the TLR-TRIF-PLK-ELF1 pathway is similarly critical in impairment of hematopoiesis and dysregulation of chromatin in MDS stem cells. This revealed that not only are MDS stem cells expanded by the TRAF6-NF-kB pathway, the innate immune response is also involved in generating MDS stem cells. In this review, I will present research findings related to "innate immune memory," one of the pathogenic mechanisms of blood cancer, and discuss future directions for basic pathological research and potential therapeutic development.

Chimeric antigen receptor-transduced autologous T (CAR-T) cell therapy targeting CD19 has revolutionized the treatment of CD19-positive hematological tumors, including acute lymphoblastic leukemia and large B-cell lymphoma. However, despite the high response rate, many problems such as exceedingly high cost, complex logistics, insufficient speed, and manufacturing failures have become apparent. One solution for these problems is to use an allogeneic cell as an effector cell for genetic modification with CAR. Allogeneic, or "off-the-shelf", CAR-expressing immune-effector cells include 1) genome-edited, T-cell receptor (TCR) gene-deleted CAR-T cells generated using healthy adult donor T cells, 2) induced pluripotent stem cell-derived CAR-T cells, and 3) CAR NK cells. NK cells are notorious for their poor ex-vivo expansion and low susceptibility to genetic modification. In this article, I will review the current state and future prospects of allogeneic CAR cell therapies, with special reference to CAR NK cells.

A 62-year-old woman with adult T-cell leukemia/lymphoma (ATL) received umbilical cord blood transplantation (CBT) in first complete remission. However, relapse of ATL was detected on day 74 post-transplantation, as evidenced by the rapid growth of lymphoma cells in peripheral blood and an increase in soluble interleukin-2 receptor (sIL2R) levels. Discontinuation of immunosuppressant therapy alone did not improve ATL findings, but treatment with lenalidomide caused lymphoma cells to disappear from the peripheral blood and sIL2R levels to return to normal. Pancytopenia was observed as a lenalidomide-associated adverse effect, but lymphocyte counts were not reduced. The patient was judged to be in complete remission based on results of Southern blot analysis and human T-cell leukemia virus 1 (HTLV-1)-infected cell analysis using flow cytometry (HAS-Flow). Flow cytometric analysis of peripheral blood and FISH analysis of X and Y chromosomes revealed that the therapeutic effect of lenalidomide was associated with an increase in the number of donor-derived peripheral natural killer cells. ATL relapse was not observed at 13 months into lenalidomide treatment. Our results suggest that lenalidomide is an effective option for the treatment of post-transplant relapsed ATL.

Allogeneic hematopoietic stem cell transplantation (allo-SCT) is a curative treatment option for multiple myeloma (MM), but few patients are eligible due to its high risk of treatment-related toxicity and relapse. Here, we report the feasibility and efficacy of allo-SCT after myeloablative conditioning with 8 Gy of total body irradiation (TBI) for reducing relapse of MM. We retrospectively analyzed data from 30 consecutive patients who received allo-SCT for MM after 8 Gy of TBI at Japanese Red Cross Medical Center between 2012 and 2021. Median age at allo-SCT was 47 (range 31-61) years. Stem-cell sources were peripheral blood from an HLA-matched related donor (MRD, n=5), bone marrow from an HLA-matched unrelated donor (MUD, n=5), bone marrow from an HLA-mismatched unrelated donor (MMUD, n=13), and cord blood (n=7). All patients received conditioning with 8 Gy of TBI combined with Flu/Mel (n=28) or others (n=2). Five-year PFS and 5-year OS were 36.7% and 46.2%, respectively. Sixteen patients died during the observation period (12 of primary disease and 4 of treatment-related toxicity). Patients with VGPR or better before allo-SCT had significantly better PFS (p=0.009) and OS (p=0.01) than others. Patients who received MMUD cells tended to have better PFS than those with other cell sources. Our report showed that allo-SCT for MM after 8 Gy of TBI is feasible, and the better PFS of MMUD suggests graft-versus-myeloma effects.

Aplastic anemia is a syndrome characterized by reduced hematopoietic stem cells, bone marrow hypoplasia, and pancytopenia, and is often considered a T-cell-mediated autoimmune disease. It is predominantly treated with hematopoietic stem cell transplantation and immunosuppressive therapy with anti-human thymocyte immunoglobulin (ATG) and cyclosporine. Only rabbit ATG was previously available in Japan, but equine ATG was recently approved for use in 2023. Thrombopoietin receptor agonists available in Japan are oral eltrombopag and injectable romiplostim. In hematopoietic stem cell transplantation for aplastic anemia, a conditioning regimen of reduced-dose cyclophosphamide and fludarabine has been used to reduce cardiotoxicity. Human leukocyte antigen haploidentical stem cell transplants have also been developed, and their use in patients without a donor is increasingly reported. Future advancements in novel drugs and transplantation therapies could revolutionize the management of aplastic anemia.

Chronic graft-versus-host disease (cGVHD) negatively impacts long-term survival and quality of life (QOL) after allogeneic hematopoietic cell transplantation. Corticosteroids are the first-line treatment for cGVHD, but approximately 30% to 70% of patients develop steroid-refractory cGVHD (SR-cGVHD), which has an extremely poor prognosis. The pathophysiology of cGVHD is more complicated than acute GVHD, but recent advances using murine models in conjunction with human studies indicate three major phases: 1) acute inflammation, 2) chronic inflammation with loss of immune tolerance, and 3) disrupted target organ homeostasis and fibrosis. Strategies that help prevent cGVHD include optimal donor selection and choice of conditioning regimen as well as pharmacologic and graft manipulation strategies. The key cellular mediators of SR-cGVHD are T cells, B cells, antigen-presenting cells, and fibroblasts. T cells and B cells are now targetable with the inhibitors ibrutinib and ruxolitinib, respectively. Recently, promising results have been obtained by modulating pathologic T cell responses with Rock2 inhibitors and targeting fibrosis with CSF-1R inhibitors. To optimize the use of these medications, a better understanding of the biological and target organ-specific mechanisms of cGVHD is needed. Here we review recent advances in cGVHD pathogenesis and discuss how best to implement recently approved biology-driven treatments for cGVHD.

There is growing recognition of post-transplant cyclophosphamide (PTCy) as the new standard prophylaxis for graft-versus-host disease (GVHD) in HLA-matched peripheral blood stem cell transplants with reduced intensity conditioning, based on recent results of randomized phase III trials of PTCy. Allogeneic hematopoietic cell transplantation (HCT) with PTCy is thought to have GVHD-dependent and -independent graft-versus-tumor (GVT) effects. Its GVHD-dependent effects may be attenuated by PTCy-induced alloreactive T cell dysfunction and preferential recovery of regulatory T cells after HCT, but its GVT effects do not appear to be significantly impaired in patients in remission or with indolent disease. As patients not in remission are often also candidates for transplantation in Japan, it will be necessary to use PTCy as a platform to establish a strategy that could also be effective in patients not in remission and to revise the donor selection algorithm.

Health surveys to assess adverse events after peripheral blood stem cell harvest (PBSCH) have conventionally been conducted by phone, but phone calls are suboptimal for conducting frequent surveys. We developed a web-based application (donor app) that enables donors to inform healthcare professionals (HCPs) of their health status as an electronic patient-reported outcome (ePRO). In this prospective observational study, we compared the usefulness of this donor app to phone calls for conducting health surveys. App users reported ePRO daily, and patients called by HCPs reported their health status at least once a week when called. The observation period was from the first administration of granulocyte colony-stimulating factor to the first follow-up visit after PBSCH, excluding the hospitalization period. Each group consisted of eight donors with a median age of 32 years (range: 19-58). Nine (56.3%) were female. There were eight related donors in the phone call group and four in the donor app group. During the observation period, HCPs obtained health status reports more frequently from app users than from phone call recipients (mean proportion of days with reports made during the observation period, 27.0% vs 53.5%; p<0.05). Average time spent by the HCPs for one follow-up and total follow-ups were both significantly shorter when the donor app was used. There were no differences in donor burden or satisfaction with donation. Our study suggests that use of a donor app could provide more detailed health survey data without increasing the burden on donors and HCPs.