Impaired formation of neutrophil extracellular traps in patients with MDS

Analyzing Blood Cells of High-Risk Myelodysplastic Syndrome Patients Using Interferometric Phase Microscopy and Fluorescent Flow Cytometry

Myelodysplastic syndromes (MDSs) are a group of potentially deadly diseases that affect the morphology and function of neutrophils. Rapid diagnosis of MDS is crucial for the initiation of treatment that can vastly improve disease outcome. In this work, we present a new approach for detecting morphological differences between neutrophils isolated from blood samples of high-risk MDS patients and blood bank donors (BBDs). Using fluorescent flow cytometry, neutrophils were stained with 2',7'-dichlorofluorescin diacetate (DCF), which reacts with reactive oxygen species (ROS), and Hoechst, which binds to DNA. We observed that BBDs possessed two cell clusters (designated H and L), whereas MDS patients possessed a single cluster (L). Later, we used FACS to sort the H and the L cells and used interferometric phase microscopy (IPM) to image the cells without utilizing cell staining. IPM images showed that H cells are characterized by low optical path delay (OPD) in the nucleus relative to the cytoplasm, especially in cell vesicles containing ROS, whereas L cells are characterized by low OPD in the cytoplasm relative to the nucleus and no ROS-containing vesicles. Moreover, L cells present a higher average OPD and dry mass compared to H cells. When examining neutrophils from MDS patients and BBDs by IPM during flow, we identified ~20% of cells as H cells in BBDs in contrast to ~4% in MDS patients. These results indicate that IPM can be utilized for the diagnosis of complex hematological pathologies such as MDS.

Neutrophil hitchhiking nanoparticles enhance bacteria-mediated cancer therapy via NETosis reprogramming

Bacteria have shown great potential in anti-tumor treatment, and an attenuated strain of Salmonella named VNP20009 has been shown to be safe in clinical trials. However, colonized bacteria recruit neutrophils into the tumor, which release NETs to capture and eliminate bacteria, compromising bacterial-based tumor treatment. In this study, we report a neutrophil hitchhiking nanoparticles (SPPS) that block the formation of NET to enhance bacteria-mediated tumor therapy. In the 4 T1 tumor-bearing mouse model, following 24 h of bacterial therapy, there was an approximately 3.0-fold increase in the number of neutrophils in the bloodstream, while the amount of SPPS homing to tumor tissue through neutrophil hitchhiking increased approximately 2.0-fold. It is worth noting that the NETs in tumors significantly decreased by approximately 2.0-fold through an intracellular ROS scavenging-mediated NETosis reprogramming, thereby increasing bacterial vitality by 1.9-fold in tumors. More importantly, the gene drug (siBcl-2) loaded in SPPS can be re-encapsulated in apoptotic bodies by reprogramming neutrophils from NETosis to apoptosis, and enable the redelivery of drugs to tumor cells, further boosting the antitumor efficacy with a synergistic effect, resulting in about 98% tumor inhibition rate and 90% survival rate.

Infectious Complications in Patients with Myelodysplastic Syndromes: A Report from the Düsseldorf MDS Registry

Despite notable advancements in infection prevention and treatment, individuals with hematologic malignancies still face the persistent threat of frequent and life-threatening complications. Those undergoing chemotherapy or other disease-modifying therapies are particularly vulnerable to developing infectious complications, increasing the risk of mortality. Myelodysplastic syndromes (MDS) predominantly affect the elderly, with the incidence rising with age and peaking at around 70 years. Patients with MDS commonly present with unexplained low blood-cell counts, primarily anemia, and often experience varying degrees of neutropenia as the disease progresses. In our subsequent retrospective study involving 1593 patients from the Düsseldorf MDS Registry, we aimed at outlining the incidence of infections in MDS patients and identifying factors contributing to heightened susceptibility to infectious complications in this population.

No indication of aberrant neutrophil extracellular trap release in indolent or advanced systemic mastocytosis

In disease states with chronic inflammation, there is a crosstalk between mast cells and neutrophil granulocytes in the inflamed microenvironment, which may be potentiated by tryptase. In systemic mastocytosis (SM), mast cells are constitutively active and tryptase is elevated in blood. Mast cell activation in SM leads to symptoms from various organs depending on where the active mast cells reside, for example, palpitations, flush, allergic symptoms including anaphylactic reactions, and osteoporosis. Whether neutrophil function is altered in SM is not well understood. In the current study, we assessed nucleosomal citrullinated histone H3 (H3Cit-DNA) as a proxy for neutrophil extracellular trap release in plasma from 55 patients with indolent and advanced SM. We observed a strong trend towards a correlation between leukocyte count, eosinophil count and neutrophil count and H3Cit-DNA levels in patients with advanced SM but not in indolent SM; however, no differences in H3Cit-DNA levels in SM patients compared with healthy controls. H3Cit-DNA levels did not correlate with SM disease burden, tryptase levels, history of anaphylaxis or presence of cutaneous mastocytosis; thus, there is no evidence of a general neutrophil extracellular trap release in SM. Interestingly, H3Cit-DNA levels and leukocyte counts were elevated in a subgroup of SM patients with aberrant mast cell CD2 expression, which warrants further investigation. In conclusion, we found no evidence of global increase in neutrophil extracellular trap release in SM.

Myelodysplastic neoplasm-associated U2AF1 mutations induce host defense defects by compromising neutrophil chemotaxis

Myelodysplastic neoplasm (MDS) is a hematopoietic stem cell disorder that may evolve into acute myeloid leukemia. Fatal infection is among the most common cause of death in MDS patients, likely due to myeloid cell cytopenia and dysfunction in these patients. Mutations in genes that encode components of the spliceosome represent the most common class of somatically acquired mutations in MDS patients. To determine the molecular underpinnings of the host defense defects in MDS patients, we investigated the MDS-associated spliceosome mutation U2AF1-S34F using a transgenic mouse model that expresses this mutant gene. We found that U2AF1-S34F causes a profound host defense defect in these mice, likely by inducing a significant neutrophil chemotaxis defect. Studies in human neutrophils suggest that this effect of U2AF1-S34F likely extends to MDS patients as well. RNA-seq analysis suggests that the expression of multiple genes that mediate cell migration are affected by this spliceosome mutation and therefore are likely drivers of this neutrophil dysfunction.