CAR-T therapy has shown excellent therapeutic efficacy in B-cell malignancy. Nevertheless, manufacturing stability, quality control, and CAR T-cell availability are still challenging because current CAR T-cell therapy is a personalized product derived from patient peripheral T-cells. However, allogeneic T-cells have emerged as a novel source to overcome this issue. Because induced pluripotent stem (iPS) cells are pluripotent stem cells derived from somatic cells and have in vitro self-renewal ability and pluripotency, they are expected to be a source of many regenerative medicinal products. Recently, it has become possible to generate CD8 killer T cells from iPS cells, and efforts have been made to generate CAR-CD8 killer T-cells from allogeneic iPS cells. This review discusses the induction of CD8 killer T-cells from iPS cells, efforts to improve the safety and certainty of the induction process for clinical use, and the utility of gene editing to reduce allogeneic antigenicity of iPS T-cells.

This study focused on amnion-derived mesenchymal stem cells (MSCs), which have immune- and inflammation-regulating properties, 1) a large number of stem cells, 2) high proliferative potential, and 3) are non-invasive to harvest. Based on the general research reported in many immune- and inflammation-related disease models, research on their commercial and therapeutic application was conducted. We have successfully manufactured a clinical trial product of amnion MSCs for the first time worldwide (clinical trial product name: AM01) and conducted physician-led clinical trials for acute graft versus host disease and Crohn's disease. Furthermore, CTEX Corporation, the first certified venture from Hyogo College of Medicine, was launched to further accelerate the clinical trial progression to obtain the manufacturing and marketing approval for amnion MSC AM01 to be used as a regenerative medical product at early stage.

The COVID-19 pandemic has cast a shadow over transfusion medicine based on the blood donation system. However, managing alloimmune platelet transfusion refractoriness (allo-PTR) has already been difficult. As a first step toward resolving this issue using induced pluripotent stem cell-derived platelet products (iPSC-PLTs), a clinical trial of autologous products (iPLAT1) was conducted in a patient with allo-PTR caused by anti-HPA-1a antibodies who had no compatible donor, and safety was confirmed. To produce iPSC-PLTs, a master cell bank (MCB) of expandable megakaryocyte lines (imMKCLs) is established from iPSCs. From this MCB, iPSC-PLTs are manufactured using a newly developed turbulent-type bioreactor and various compounds. Their quality, safety, and efficacy are confirmed by extensive preclinical studies. Based on the findings of the iPLAT1 study, a clinical trial of allo-transfusion of HLA homozygous iPSC-PLTs is currently ongoing and HLA class I-deficient O-type universal iPSC-PLTs are also being developed. iPSC-PLTs are expected to solve various problems, including allo-PTR in platelet transfusion, and greatly contribute to the advancement of transfusion medicine.

Hematopoietic stem cells (HSC) have self-renewal as well as multilineage differentiation capacity and maintain hematopoiesis throughout life. HSC transplantation (HSCT) is performed as a curative therapy for hematopoietic malignancies and nonmalignant hematopoietic disorders. Furthermore, bone marrow, mobilized peripheral blood, and cord blood are available sources for HSCT. HLA compatibility is the most critical factor for a successful HSCT. The HSC number in a graft is also invaluable for engraftment. Moreover, it is challenging to obtain an abundant number of HSC for patients with obesity, particularly, in cord blood. HSC ex vivo expansion is an appropriate solution for this problem. Extrinsic factors to expand and maintain HSCs, such as cytokines are identified from analysis of HSCs and their niche. Thus, HSC ex vivo expansion is improved by adding them in culture medium; however, it is still difficult for therapeutic applications. Recently, several small molecular compounds have been reported to facilitate ex vivo expansion of HSC. Clinical trials that transplant ex vivo expanded cord blood have been already expanded, and some trials demonstrate reduction of time to hematopoietic recovery. Thus, we anticipate that ex vivo expanded cord blood transplantation will be applied widely in the future.

Magnetic nanoparticle-incorporated liposomes (magnetic liposomes) are considered a promising site-specific drug delivery carrier. Although there are many reports on the development of magnetic liposomes, most of them focus on the characteristics of magnetic nanoparticles, rather than liposomes. Therefore, we first evaluated the effect of the physicochemical properties of magnetic liposomes on their interaction with cells. The highest cellular uptake and retention under a magnetic field was observed using small magnetic cationic liposomes. However, magnetic cationic liposomes exhibited strong cytotoxicity. Based on these results, we constructed complexes of less toxic magnetic anionic liposomes (Mag-AL) and atelocollagen (ATCOL), a biocompatible cationic biomaterial. The cellular associated amount of Mag-AL under a magnetic field was significantly increased when Mag-AL was complexed with ATCOL, and it was comparable to that of magnetic cationic liposomes. Additionally, Mag-AL/ATCOL complexes produced no cytotoxic effect. Moreover, liver accumulation of Mag-AL/ATCOL complexes was significantly increased at a magnetic field-exposed region after intravenous injection in rats. These results indicate that Mag-AL/ATCOL complexes may be a safe and efficient magnetic responsive drug carrier. Next, we applied Mag-AL/ATCOL complexes to prepare magnetized cells for effective cell therapy. Mesenchymal stem cells (MSCs), which have the capacity to suppress tissue inflammation, were efficiently magnetized by incubation with Mag-AL/ATCOL complexes under a magnetic field. Intramuscularly injected magnetized MSCs were significantly retained in mouse skeletal muscle in the presence of a magnetic field and modulated tissue inflammatory responses. These results suggest that magnetized MSCs are useful for muscle regeneration.

Hematopoietic stem cells (HSCs) are defined as cells present in the bone marrow that are capable of both self-renewal and multilineage differentiation. The differentiation pathway from HSCs to mature blood cells and HSC self-renewal and differentiation mechanisms still remain unclear and require further elucidation. However, HSCs are a highly diverse population with analysis limitations at the population level. Moreover, molecular and cell biological single-cell analysis has been attracting tremendous attention recently. Herein, we introduce a cell biological single-cell analysis method (single-cell transplantation and cell lineage tracing experiments using genetic techniques) in the field of HSCs.

The nervous system is distributed throughout all body organs and unconsciously maintains homeostasis. The peripheral nervous system, which comprises autonomic and sensory nerves, is distributed in the bone marrow, which controls hematopoiesis, and the surrounding bone tissue, which is also closely associated with hematopoiesis regulation. Recent advances in research techniques have revealed that the peripheral nervous system affects normal hematopoiesis, hematopoiesis under stress, and the regulation of hematopoietic aging. The peripheral nervous system also affects the development and progression of malignant tumors, including hematopoietic tumors and normal tissue, making the peripheral nerve regulation a potential new therapeutic target.

Hematopoietic stem cells are one of the most sensitive tissues to radiation exposure. Epidemiological studies of atomic bomb survivors in Nagasaki and Hiroshima revealed a radiation dose-response relationship for acute myeloid leukemia, acute lymphoblastic leukemia, and Chronic myelogenous leukemia. In our study of myelodysplastic syndrome (MDS) in Nagasaki, the relative risk was higher in the proximal-exposed group. Additionally, the frequency of chromosome abnormalities associated with poor prognosis was higher in the proximal-exposed group than in the non-exposed group. However, no association between the exposure distance and prognosis was observed. We used next-generation sequencing to analyze the role of genetic abnormalities in the development of MDS. The results indicated that genetic mutations related to DNA methylation pathways, which are frequently observed in de novo MDS, were considerably less frequent in the proximal-exposed than in the distal-exposed group. These results suggest that the pathogenesis of MDS in atomic bomb survivors may be different from that of treatment-related and de novo MDS.

Epstein-Barr virus (EBV)-associated lymphomas are common in Asia and exhibit a poor prognosis. As EBV antigens LMP1 and LMP2 are often expressed in EBV-associated lymphomas, these lymphomas should be a good target for antigen-specific cytotoxic T lymphocyte (CTL) therapy. However, CTLs continuously exposed to viral or tumor antigens often become exhausted. Antigen-specific CTLs generated from induced pluripotent stem cells are functionally rejuvenated, showing a strong antitumor effect on EBV-associated lymphomas and persistence in vivo. For feasible "off-the-shelf" therapy, we generated allogeneic EBV-specific CTLs in the cell processing center and prepared them for actual use in clinical settings.

Based on the progress of gene-modification technologies, bispecific antibodies that possess antigen-binding sites with two different specificities have been developed. After the success of blinatumomab for treating refractory B-cell leukemia, series of clinical trials using bispecific antibodies for relapsed and refractory hematological malignancies are being conducted. Several bispecific antibodies target an antigen expressed by tumor cells and the CD3 molecule where binding of bispecific antibodies can generate artificial immunological synapses between tumor cells and human T cells. Therefore, fine tuning of binding affinity and/or structural conformation concomitant with bispecific antibodies may be required to induce antitumor effects and regulate immune-related adverse events, such as cytokine release syndrome. In the future, combination therapy of conventional chemotherapy and/or allogeneic stem-cell transplantation with bispecific antibody therapy will be necessary. Furthermore, molecular target therapy with bispecific antibody therapy is expected to pave the way for next-generation target therapy, resulting in the development of a further effective and safe treatment strategy for hematological malignancies.

The efficacy of T-cell therapy depends on the maintenance of antigen specificity, memory phenotype, longterm viability, and proliferative capacity of T cells in vivo. Personalized autologous T-cell therapies pose a few manufacturing challenges, in terms of quality, and supply stability. Recently, it has become possible to derive CD8 killer T cells from induced pluripotent stem cells (iPSCs) and develop CAR-CD8 killer T cells from allogeneic iPSCs. This article reviews CD8 killer T-cell induction from iPSCs, attempts to enhance process safety and reliability, and discusses the use of gene-editing technology for reducing allogeneic antigenicity.

Graft-versus-host disease (GVHD) is a potentially life-threatening complication of allogeneic hematopoietic stem cell transplantation (allo-SCT). Recent advances in understanding the GVHD pathophysiology promoted development of novel therapeutic agents for GVHD. In acute GVHD, emerging evidence suggested that it targets tissue stem cells in the skin, liver, and gut, resulting in treatment refractoriness. Furthermore, antimicrobial peptide deficiency, nutritional status alteration of the gut microbiota, and antibiotic administration lead to gut dysbiosis, which is related to GVHD onset and treatment-related mortality after allo-SCT. In this review, recent advances in understanding the GVHD pathophysiology are summarized, and novel agents for the treatment and prophylaxis of acute and chronic GVHD are introduced.

Several types of nonhematopoietic cells, including mesenchymal stem or progenitor cells, mature mesenchymal cells, and endothelial cells, and mature hematopoietic cells such as monocytes, macrophages, NK cells, T cells, and B cells regulate the proliferation and survival of myeloma cells. The cell functions adjacent to myeloma cells is specialized by the location of these cells, called a niche. This review focuses on the role and interaction of cellular components of the myeloma-specific niche revealed by studies that utilized the recently developed experimental techniques of single-cell RNA sequencing and high-parameter cytometry. In the myeloma niche, immune cells and mesenchymal cells regulate tumor proliferation. Bone marrow inflammation induced by multiple myeloma, tumor cells, mesenchymal stromal cells, and immune cells interact, results in the dysregulation of anti-tumor immunity. This complex network could affect tumorigenesis, disease progression, and treatment resistance of multiple myeloma.

Treatment outcomes for multiple myeloma (MM) have improved due to the introduction of autologous stem cell transplantation and novel drugs. However, many patients develop resistance to existing therapies; hence, novel treatment strategies for these patients must be established. Therapeutic antibodies, including daratumumab and isatuximab targeting CD38 and elotuzumab targeting SLAMF7, have been introduced as immunotherapies for MM. These antibodies exert cytotoxic effects on myeloma cells through the activation of effectors such as natural killer cells and complement, and induction of phagocytosis by macrophages. Suppressed anti-tumor immunity may be related to acquisition of drug resistance by myeloma cells in patients with MM. It has been reported that the effect of therapeutic antibodies is through the stimulation of anti-tumor immunity. Thus, as each therapeutic antibody displays its own mechanism of action, therapy based on this mechanism of action should be introduced. Furthermore, chimeric antigen receptor (CAR) T-cell therapy, antibody drug conjugates (ADC), and bispecific antibodies (BsAbs) are gradually being introduced as novel immunotherapies for MM. CAR T-cells with high proliferation levels and persistence in recipients to improve the duration of therapeutic response are currently being developed.

It is well documented that multiple myeloma (MM) originates in a single plasma cell transformed by chromosome 14q translocations or chromosomal hyperdiploidy and evolves with the accumulation of point mutations of driver genes and/or cytogenetic abnormalities. Furthermore, disease progression is accomplished by branching patterns of subclonal evolution from reservoir clones with a propagating potential and/or the emergence of minor clones, which already exist at premalignant stages and outcompete other clones through selective pressure mainly by therapeutic agents. Each subclone harbors novel mutations and distinct phenotypes, including drug sensitivities. Generally, mature clones are highly sensitive to proteasome inhibitors (PIs), whereas immature clones are resistant to PIs although could be eradicated by immunomodulatory drugs (IMiDs). The branching evolution is a result of the fitness of different clones to the microenvironment and their evasion of immune surveillance; therefore, IMiDs are effective for MM with this pattern of evolution. In contrast, ∼20% of MM evolve neutrally in the context of strong oncogenic drivers, including high-risk IgH translocations, and are relatively resistant to IMiDs. Treatment strategies considering the genomic landscape and the pattern of clonal evolution may further improve the treatment outcome of MM.

Malignant lymphomas are a group of diseases in which epigenomic abnormalities are fundamental to the pathogenesis and pathophysiology and are characterized by a high frequency of abnormalities in DNA methylation regulators and histone modifiers. These epigenomic abnormalities directly amplify malignant clones. They also originated from a cell lineage differentiated from hematopoietic stem cells through epigenomic changes. These characteristics are associated with their high affinity for epigenomic therapies. Hematology has been a leader in the basic, clinical, and drug discovery areas of disease epigenetics. However, the epigenomic regulation is generally recognized as a complex system, and gaps are observed between basic and clinical studies. To overview the status and importance of "epigenomic abnormalities in malignant lymphoma," this review first summarizes the concept and essential importance of the epigenome and then outlines the current status and future perspective of epigenomic abnormalities in malignant lymphomas.

Acute myeloid leukemia (AML) is a heterogeneous cell population comprising genetically diverse sub-clones with significant differences in properties that vary from one patient to another. Since AML properties are similar to those of hematopoietic stem and myeloid cells, bone marrow as an organ responsible for the survival of AML-initiating cells has been proposed to be able to cause relapse following chemotherapy. Therefore, establishing in vivo experimental systems is critical for understanding the properties of AML cells and developing therapeutic strategies. In this review, the history, advantages, and disadvantages of mouse leukemia models wherein mouse cells are transformed by oncogenic events, including xenograft mice in which human AML cells are transplanted into immunodeficient mice, were introduced. Following which I described the development of chimeric antigen receptor cell therapy using human cytokines expressing the AML xenograft mice.

The novel coronavirus disease 2019 (COVID-19) is caused by acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Hematopoietic stem cell transplant (HSCT) recipients are at increased risk of mortality and morbidity with COVID-19 due to severe immune dysfunction. Recombinant adenovirus vector-based vaccine, such as AstraZeneca ChAdOx1, and mRNA-based vaccines, such as Pfizer BNT162b2 and Moderna mRNA-1273 have been used in Japan. COVID-19 vaccine administration to HSCT recipients was reported to result in a 68-96.5% seroconversion for the spike protein. Factors associated with the absence of humoral responses were the time-interval from HSCT to vaccination, absolute lymphocyte count, systemic immunosuppressive treatments, graft versus host disease (GVHD), B-cell count, and hypogammaglobulinemia. New onset and exacerbation of chronic GVHD have been reported as an adverse events associated with vaccination. COVID-19 vaccination of HSCT recipients is relatively safe, and recipients should be vaccinated against COVID-19 6 months after transplantation. In the future, it is necessary to consider passive immunotherapy for HSCT patients who do not benefit from COVID1-19 vaccination.

Protein production is tightly regulated in cells because the accumulation of un-/misfolded proteins triggers cellular responses, particularly in the endoplasmic reticulum (ER). Recently, several studies have reported the implications of unfolded protein response (UPR) and ER stress in hematopoiesis, particularly in hematopoietic stem cells (HSCs). The majority of HSCs are maintained in a dormant state under physiological conditions in the adult body, and their protein synthesis rate is also maintained at a low level. Once HSC proliferation is activated, the protein synthesis rate is elevated, and therefore, newly synthesized peptides have to be efficiently folded to prevent the induction of UPR. Importantly, UPR can expand the ER capacity that enables increased protein production and eliminates cells accumulating abnormal proteins; thus, blocking the UPR signal could rather be hazardous for the cells. Thus, understanding how protein quality control is properly controlled and developing methods to manipulate the regulatory mechanisms are imperative to maximize the potential role of HSC.

We have performed extensive basic and preclinical research to investigate the role of human induced pluripotent cell-derived neural stem/progenitor cell (hiPSC-NS/PC) grafts in spinal cord injury (SCI) models, and evidence obtained from animal experiments confirms the safety and effectiveness of this approach. We have initiated a first-in-human clinical trial of hiPSC-NS/PC transplantation in patients with subacute SCI. Research on the therapeutic mechanism underlying stem cell transplantation therapy is ongoing worldwide; this paper outlines the current knowledge of the therapeutic mechanism.