Macrophages have been discovered more than 100 years ago. Recent studies indicated that monocytes and macrophages can be categorized into several distinct phenotypes and their respective differentiation mechanisms are known. We also reported that the Jmjd3 is critical for the macrophage subtype activated by allergic stimuli and that the tissue resident macrophage subtype in adipose tissue, which is controlled by Trib1, is responsible for maintaining homeostasis of peripheral tissues such as adipocyte. Thus, it is considered that various macrophage/monocyte subtypes corresponding to certain disorders were existed in our body. Furthermore, in order to investigate the relationship between macrophage subtype and disease, we focused on fibrosis as the next target disease. Its pathogenesis is poorly understood, and there are few effective therapies. Previously we found that a new macrophage/monocyte subtype, which their markers are Msr1⁺Ceacam1⁺Ly6C⁻Mac1⁺F4/80⁻monocyte and share granulocyte characteristics, involved in development of fibrosis was accumulated in the affected area in the lungs at the beginning of fibrosis. We termed the monocyte/ macrophage subtype segregated-nucleus-containing atypical monocytes (SatM). Towards understanding the mechanism of fibrosis onset, we next focused on investigation of non-haematopoietic cells involved in activation of immune cell such as SatM during fibrotic phase.

As the brain is a prime immune privileged organ, immune responses in it were not studied as intensively as other peripheral organs in the past. However, the brain is studded with immune cells called microglia, which play important roles particularly in diseased conditions. In addition, from recent descriptive works, we have learned a lot about immune cells in neighboring tissues. Recent progress has rather made it clearer that the immune responses in and around the brain are complicated reactions with both positive and negative effects. And we still have not identified the way(s) we should pursue for clinical applications. Here we introduce microglia and macrophages in the steady state. We also discuss their roles in stroke, a major cause of death and disability in Japan, and Alzheimer’s disease, which account for 60 to 70% of dementia.

The central nervous system (CNS) is a highly complex collection of various cell-types, such as neurons, glial cells, vascular cells, and immune cells, and their complex and dynamic interactions enable to achieve highly sophisticated functions of the CNS. Among such CNS cells are microglia, which are well-known primary CNS macrophages localized in the CNS parenchyma and play a pivotal role in the maintenance of tissue homeostasis. Besides microglia, there are anatomically distinct macrophage populations at the border of the CNS, such as meninge, and perivascular space, called CNS-associated macrophages (CAMs). Recent studies have given novel insights into the nature of CAMs. In this review, I will discuss our current knowledge of the origins, the cellular properties of CNS macrophages.

Genetics and gut microbiota contribute to the development of autoimmune diseases. SKG mice, which harbor a point mutation in the ZAP70 gene, develop autoimmune arthritis in BALB/c background and systemic lupus erythematosus in C57BL/6 background. Defective TCR signaling by ZAP70 mutation alters thymic selection thresholds and allows the positive selection of otherwise negatively selected self-reactive T cells. On the other hand, defective TCR signaling attenuates the positive selection of certain microbiota-reactive T cells, which lead to impaired IgA synthesis at mucosal site and gut dysbiosis. Gut dysbiosis, in turn, promotes autoimmunity via driving Th17 differentiation. Thus, defective TCR signaling leads to autoimmunity by altering thymic selection thresholds of self-reactive T cells and microbiota-reactive T cells. In this review, genomics-microbiota interactions for the development of autoimmunity will be discussed with the special focus on the recent finding obtained from animal models of autoimmunity with defective TCR signaling.

Diabetic kidney disease is a major cause of renal failure that urgently necessitates a breakthrough in disease management. Specific remedies are needed for preventing Type 2 diabetes which causes significant changes in an array of plasma metabolites. By untargeted metabolome analysis, phenyl sulfate (PS) increased with the progression of diabetes. In experimental diabetes models, PS administration induces albuminuria and podocyte damage due to the mitochondrial dysfunction. By clinical diabetic kidney disease (DKD) cohort analysis, it was also confirmed that the PS levels significantly correlate with basal and predicted 2-year progression of albuminuria. Phenol is synthesized from dietary tyrosine by gut bacterial-specific tyrosine phenol-lyase (TPL), and absorbed phenol is metabolized into PS in the liver. Inhibition of TPL reduces not only the circulating PS level but also albuminuria in diabetic mice. TPL inhibitor did not significantly alter the major composition, showing the non-lethal inhibition of microbial-specific enzymes has a therapeutic advantage, with lower selective pressure for the development of drug resistance. Clinically, 362 patients in a multi-center clinical study in diabetic nephropathy cohort (U-CARE) were analyzed with full data. The basal plasma PS level significantly correlated with ACR, eGFR, age, duration, HbA1c and uric acid, but not with suPAR. Multiple regression analysis revealed that ACR was the only factor that significantly correlated with PS. By stratified logistic regression analysis, in the microalbuminuria group, PS was the only factor related to the amount of change in the 2-year ACR in all models. PS is not only an early diagnosis marker, but also a modifiable cause and therefore a target for the treatment of DKD. Reduction of microbiota-derived phenol by the inhibitor should represent another aspect for developing drugs of DKD prevention.

With the advent of next-generation sequencers and subsequent large national projects by the U.S. and Europe, scientific information and knowledge have been dramatically accumulated on the microbiome and data associated with various diseases. Ever since the surprising highly successful efficacy of refractory C. difficile infectious disease by fecal microbiota transplantation is reported, microbiome modulation has been expected as a new approach for drug discovery. Therefore, lots of microbiome drug discovery ventures have sprung up and clinical pipelines in late-stage clinical development have already been created especially in U.S. and Europe. Unfortunately, Japan is lagging behind U.S. and Europe., as is often the case with other modalities such as the genome-based drug discovery. However, since pioneering research on gut microbiota began in Japan and has since been highly successful, the establishment of a domestic microbiome drug discovery infrastructure is long overdue. Under this environment, the Japan Microbiome Consortium, a general incorporated association established in 2017 to promote the industrial application of microbiome research, has been promoting pre-competitive collaborative activities with the participation of more than 30 domestic companies, including pharmaceutical companies, to build the microbiome drug discovery infrastructure. The consortium has been working on the construction of a drug discovery ecosystem that will lead to (1) a reliable measurement platform, (2) microbiome data in the healthy gut, and (3) microbiome drug discovery, by utilizing government projects. In this paper, we introduce the consortium and its activities to promote industrialization through pre-competitive collaborative activities.

In a series of drug development processes from basic research to non-clinical and clinical trials, genome editing technologies have been making innovative breakthroughs. Genome editing using CRISPR/Cas9 system, which was awarded the Novel Prize in Chemistry in 2020, has greatly streamlined the production of genetically modified mice and cells, which have been used in a variety of drug discovery research and non-clinical trials. Setsuro Tech Inc. (Setsurotech) established in 2017 is a biotech startup originated in Tokushima University. In this paper, we will briefly review genome editing technology using CRISPR/Cas9 system, and then introduce our company, our fundamental technologies; GEEP method (Genome Editing by Electroporation of Cas9 Protein) developed by Takemoto et al., and VIKING method (Versatile NHEJ-based Knock-in using Genome Editing) established by Sawatsubashi et al. Also, we will introduce our contribution to the field of drug discovery research and industrial application of genome editing technology.