Modified application of Kawamoto’s film method for super‐resolution imaging of megakaryocytes in undecalcified bone marrow

Abstract Background Super‐resolution microscopy has enabled high‐resolution imaging of the actin cytoskeleton in megakaryocytes and platelets. These technologies have extended our knowledge of thrombopoiesis and platelet spreading using megakaryocytes and platelets cultured in vitro on matrix proteins. However, for better understanding of megakaryocytopoiesis and platelet production, high‐resolution imaging of cells in an in vivo bone marrow microenvironment is required. Development of Kawamoto’s film method greatly advanced the techniques of thin cryosectioning of hard tissues such as undecalcified bones. One obstacle that remains is the spherical aberration that occurs due to the difference in the refractive index for the light path, limiting the usage of Kawamoto’s film method to lower magnification observation. Objectives To overcome the weakness of the conventional Kawamoto’s film method for higher magnification observation of undecalcified bone marrow. Methods We have modified the original method with a very simple method: flipping the film at the step of mounting the sections on the glass. Results and Conclusions This new method successfully led to the adjustment of the refractive index and enabled super‐resolution imaging of megakaryocytes in undecalcified mouse femurs. Our modified method will expand the application of Kawamoto’s film method and enable precise analysis of megakaryocytopoiesis and platelet production in the bone marrow microenvironment under pathophysiological conditions

Extracellular tyrosyl-tRNA synthetase cleaved by plasma proteinases and stored in platelet α-granules: Potential role in monocyte activation.

BackgroundTyrosyl-tRNA synthetase (YRS) belongs to the family of enzymes that catalyzes the tRNA aminoacylation reaction for protein synthesis, and it has been recently shown to exert noncanonical functions. Although database results indicate extremely low levels of YRS mRNA in platelets, YRS protein is abundantly present. The source of YRS in platelets, as well as the physiological role of platelet-stored YRS, remains largely unknown.ObjectivesTo clarify how YRS accumulates in platelets and determine the potential role of platelet-stored YRS.MethodsRecombinant YRS proteins with epitope tags were prepared and tested in vitro for proteolytic cleavage in human plasma. Fluorescent-labeled YRS was examined for uptake by platelets, as demonstrated by western blotting and confocal microscopy analysis. Using RAW-Dual reporter cells, Toll-like receptor and type I interferon activation pathways were analyzed after treatment with YRS.ResultsFull-length YRS was cleaved by both elastase and matrix metalloproteinases in the plasma. The cleaved, N-terminal YRS fragment corresponds to the endogenous YRS detected in platelet lysate by western blotting. Both full-length and cleaved forms of YRS were taken up by platelets in vitro and stored in the α-granules. The N-terminal YRS fragment generated by proteolytic cleavage had monocyte activation comparable to that of the constitutive-active mutant YRS (YRSY341A) previously reported.ConclusionPlatelets take up both full-length YRS and the active form of cleaved YRS fragment from the plasma. The cleaved, N-terminal YRS fragment stored in α-granules may have potential to activate monocytes

Extracellular tyrosyl-tRNA synthetase cleaved by plasma proteinases and stored in platelet α-granules: Potential role in monocyte activation.

BackgroundTyrosyl-tRNA synthetase (YRS) belongs to the family of enzymes that catalyzes the tRNA aminoacylation reaction for protein synthesis, and it has been recently shown to exert noncanonical functions. Although database results indicate extremely low levels of YRS mRNA in platelets, YRS protein is abundantly present. The source of YRS in platelets, as well as the physiological role of platelet-stored YRS, remains largely unknown.ObjectivesTo clarify how YRS accumulates in platelets and determine the potential role of platelet-stored YRS.MethodsRecombinant YRS proteins with epitope tags were prepared and tested in vitro for proteolytic cleavage in human plasma. Fluorescent-labeled YRS was examined for uptake by platelets, as demonstrated by western blotting and confocal microscopy analysis. Using RAW-Dual reporter cells, Toll-like receptor and type I interferon activation pathways were analyzed after treatment with YRS.ResultsFull-length YRS was cleaved by both elastase and matrix metalloproteinases in the plasma. The cleaved, N-terminal YRS fragment corresponds to the endogenous YRS detected in platelet lysate by western blotting. Both full-length and cleaved forms of YRS were taken up by platelets in vitro and stored in the α-granules. The N-terminal YRS fragment generated by proteolytic cleavage had monocyte activation comparable to that of the constitutive-active mutant YRS (YRSY341A) previously reported.ConclusionPlatelets take up both full-length YRS and the active form of cleaved YRS fragment from the plasma. The cleaved, N-terminal YRS fragment stored in α-granules may have potential to activate monocytes

Antagonism of VEGF by genetically engineered dendritic cells is essential to induce antitumor immunity against malignant ascites

Malignant ascitis (MA) is a highly intractable and immunotherapy-resistant state of advanced gastro-intestinal and ovarian cancers. Using a murine model of MA with CT26 colon cancer cells, we here determined that the imbalance between the VEGF-A/vascular permeability factor and its decoy receptor, soluble fms-like tryrosine kinase receptor-1 (sFLT-1), was a major cause of MA resistance to dendritic cell (DC)-based immunotherapy. We found that the ratio of VEGF-A/sFLT-1 was increased not only in murine but also in human MA, and F-gene-deleted recombinant Sendai virus (rSeV/dF)-mediated secretion of human sFLT-1 by DCs augmented not only the activity of DCs themselves, but also dramatically improved the survival of tumor-bearing animals associated with enhanced CTL activity and its infiltration to peritoneal tumors. These findings were not seen in immunodeficient mice, indicating that a VEGF-A/sFLT-1 imbalance is critical for determining the antitumor immune response by DC-vaccination therapy against MA

Nanomedicines Eradicating Cancer Stem-like Cells <i>in Vivo</i> by pH-Triggered Intracellular Cooperative Action of Loaded Drugs

Nanomedicines capable of control over drug functions have potential for developing resilient therapies, even against tumors harboring recalcitrant cancer stem cells (CSCs). By coordinating drug interactions within the confined inner compartment of core–shell nanomedicines, we conceived multicomponent nanomedicines directed to achieve synchronized and synergistic drug cooperation within tumor cells as a strategy for enhancing efficacy, overcoming drug resistance, and eradicating CSCs. The approach was validated by using polymeric micellar nanomedicines co-incorporating the pan-kinase inhibitor staurosporine (STS), which was identified as the most potent CSC inhibitor from a panel of signaling-pathway inhibitors, and the cytotoxic agent epirubicin (Epi), through rationally contriving the affinity between the drugs. The micelles released both drugs simultaneously, triggered by acidic endosomal pH, attaining concurrent intracellular delivery, with STS working as a companion for Epi, down-regulating efflux transporters and resistance mechanisms induced by Epi. These features prompted the nanomedicines to eradicate orthotopic xenografts of Epi-resistant mesothelioma bearing a CSC subpopulation