高山 直也

The underlying mechanisms of atherosclerosis, the second leading cause of death among Werner syndrome (WS) patients, are not fully understood. Here, we establish an in vitro co-culture system using macrophages (iMφs), vascular endothelial cells (iVECs), and vascular smooth muscle cells (iVSMCs) derived from induced pluripotent stem cells. In co-culture, WS-iMφs induces endothelial dysfunction in WS-iVECs and characteristics of the synthetic phenotype in WS-iVSMCs. Transcriptomics and open chromatin analysis reveal accelerated activation of type I interferon signaling and reduced chromatin accessibility of several transcriptional binding sites required for cellular homeostasis in WS-iMφs. Furthermore, the H3K9me3 levels show an inverse correlation with retrotransposable elements, and retrotransposable element-derived double-stranded RNA activates the DExH-box helicase 58 (DHX58)-dependent cytoplasmic RNA sensing pathway in WS-iMφs. Conversely, silencing type I interferon signaling in WS-iMφs rescues cell proliferation and suppresses cellular senescence and inflammation. These findings suggest that Mφ-specific inhibition of type I interferon signaling could be targeted to treat atherosclerosis in WS patients.

INTRODUCTION: Platelet-rich plasma obtained by centrifuging peripheral blood can promote osteogenesis owing to its abundant growth factors but has drawbacks, including rapid growth factor loss and inconsistent effects depending on donor factors. To overcome these issues, we were the first in the world to use freeze-dried human induced pluripotent stem cell-derived megakaryocytes and platelets (S-FD-iMPs) and found that they have osteogenesis-promoting effects. Since turbulence was found to activate platelet biogenesis and iPS cell-derived platelets can now be produced on a clinical scale by a device called VerMES, this study examined the osteogenesis-promoting effect and safety of clinical-scale FD-iMP (V-FD-iMPs) for future human clinical application. METHOD: We administered either S-FD-iMPs, V-FD-iMPs, or saline along with artificial bone to the lumbar spine of 8-week-old male Sprague-Dawley rats (n = 4 each) and evaluated bone formation by computed tomography (CT) and pathology. Next, we administered V-FD-iMPs or saline along with artificial bone to the lumber spines of 5-week-old male New Zealand White rabbits (n = 4 each) and evaluated the bone formation by CT and pathology. Rats (n = 10) and rabbits (n = 6) that received artificial bone and V-FD-iMPs in the lumbar spine were also observed for 6 months for adverse events, including infection, tumor formation, and death. RESULTS: Both V-FD-iMPs and S-FD-iMPs significantly enhanced osteogenesis in the lumber spines of rats in comparison with the controls 8 weeks postoperatively, with no significant differences between them. Furthermore, V-FD-iMPs vigorously promoted osteogenesis in the lumber spines of rabbits 8 weeks postoperatively. In rats and rabbits, V-FD-iMPs showed no adverse effects, including infection, tumor formation, and death, over 6 months. CONCLUSION: These results suggest that V-FD-iMPs promote safe osteogenesis.

Abstract We recently achieved the first-in-human transfusion of induced pluripotent stem cell-derived platelets (iPSC-PLTs) as an alternative to standard transfusions, which are dependent on donors and therefore variable in supply. However, heterogeneity characterized by thrombopoiesis-biased or immune-biased megakaryocytes (MKs) continues to pose a bottleneck against the standardization of iPSC-PLT manufacturing. To address this problem, here we employ microRNA (miRNA) switch biotechnology to distinguish subpopulations of imMKCLs, the MK cell lines producing iPSC-PLTs. Upon miRNA switch-based screening, we find imMKCLs with lower let-7 activity exhibit an immune-skewed transcriptional signature. Notably, the low activity of let-7a-5p results in the upregulation of RAS like proto-oncogene B (RALB) expression, which is crucial for the lineage determination of immune-biased imMKCL subpopulations and leads to the activation of interferon-dependent signaling. The dysregulation of immune properties/subpopulations, along with the secretion of inflammatory cytokines, contributes to a decline in the quality of the whole imMKCL population.