CD62L expression level determines the cell fate of myeloid progenitors

Clustering analyses of murine bone marrow-derived neutrophils reveal a phenotypic heterogeneity that can respond differentially to stimulation

Neutrophils are granulocytic cells produced in the bone marrow from a granulocytic progenitor cell. During infection, the production of chemokines and cytokines induces the recruitment of neutrophils to the infected tissue to promote the clearance of microbial pathogens. Several studies have shown that different subpopulations of neutrophils can be identified during infection. However, no previous studies evaluated subpopulations of neutrophils purified from the bone marrow (BM), which are typically used to study the biology of these cells based on the assumption that the neutrophil population is homogeneous. In the present study, responses of purified BM-derived neutrophils to various stimuli such as PMA, LPS, and Streptococcus pneumoniae were evaluated using flow cytometry and bh-SNE analyses. Further, neutrophil population heterogeneity was assessed by clustering analyses. Our data suggest that purified BM-derived neutrophils were not a homogeneous cell population and were clustered into 12 subsets, each displaying a unique marker profile, where CD11b and CD62L emerged as pivotal markers for neutrophil function. Importantly, the subsets responded differentially to each stimulus, suggesting a nuanced activation pattern. Changes in biomarker expression were analyzed via Ingenuity Pathway Analysis (IPA) to unravel functional implications of the identified clusters, revealing subsets associated with different neutrophil functions, such as "Migration of neutrophils" or "Phagocytosis in neutrophils". This study contributes to understanding the diversity of purified BM-derived neutrophils and the implications of using these cellular preparations to raise conclusions about the functionality of these cells in various infection models.

The effects of immune cell phenotypes and plasma metabolomes on diabetic foot ulcer: a Mendelian randomization study and mediation analysis

This study investigates the causal relationships between plasma metabolites, immune cell phenotypes, and diabetic foot ulcer (DFU). A Mendelian randomization (MR) study was conducted, which included 731 immune cell phenotypes, 1400 metabolites, and DFU. The primary analytical approach was the inverse variance-weighted method. Sensitivity analyses were performed to assess heterogeneity and pleiotropy, and MR analyses in the reverse direction were conducted to examine the possibility of reverse causation. In addition, a mediation analysis was performed to reveal how metabolites mediate the impact of immune cells on DFU. Through MR, reverse MR and sensitivity analysis, the casualty was found in 17 immune cell phenotypes and 18 metabolites. A total of 15 mediating relationships were identified through mediation analysis, including 9 metabolites and 10 immune cell phenotypes. Among them, the highest mediation proportion was citrulline levels mediating CD24+ CD27+ AC (absolute count, B cell panel) to DFU, with a proportion of 11.60%. In conclusion, the study identified causal relationships between 10 immune cell phenotypes mediated by 9 metabolites. These discoveries offered fresh perspectives on the processes behind DFU and laid the groundwork for subsequent studies to create specific treatments for DFU.

Long non-coding RNA Malat1 fine-tunes bone homeostasis and repair by orchestrating cellular crosstalk and β-catenin-OPG/Jagged1 pathway

The IncRNA Malat1 was initially believed to be dispensable for physiology due to the lack of observable phenotypes in Malat1 knockout (KO) mice. However, our study challenges this conclusion. We found that both Malat1 KO and conditional KO mice in the osteoblast lineage exhibit significant osteoporosis. Mechanistically, Malat1 acts as an intrinsic regulator in osteoblasts to promote osteogenesis. Interestingly, Malat1 does not directly affect osteoclastogenesis but inhibits osteoclastogenesis in a non-autonomous manner in vivo via integrating crosstalk between multiple cell types, including osteoblasts, osteoclasts, and chondrocytes. Our findings substantiate the existence of a novel remodeling network in which Malat1 serves as a central regulator by binding to β-catenin and functioning through the β-catenin-OPG/Jagged1 pathway in osteoblasts and chondrocytes. In pathological conditions, Malat1 significantly promotes bone regeneration in fracture healing. Bone homeostasis and regeneration are crucial to well-being. Our discoveries establish a previous unrecognized paradigm model of Malat1 function in the skeletal system, providing novel mechanistic insights into how a lncRNA integrates cellular crosstalk and molecular networks to fine tune tissue homeostasis, remodeling and repair.

Long non-coding RNA Malat1 fine-tunes bone homeostasis and repair by orchestrating cellular crosstalk and the β-catenin-OPG/Jagged1 pathway

The IncRNA Malat1 was initially believed to be dispensable for physiology due to the lack of observable phenotypes in Malat1 knockout (KO) mice. However, our study challenges this conclusion. We found that both Malat1 KO and conditional KO mice in the osteoblast lineage exhibit significant osteoporosis. Mechanistically, Malat1 acts as an intrinsic regulator in osteoblasts to promote osteogenesis. Interestingly, Malat1 does not directly affect osteoclastogenesis but inhibits osteoclastogenesis in a non-autonomous manner in vivo via integrating crosstalk between multiple cell types, including osteoblasts, osteoclasts and chondrocytes. Our findings substantiate the existence of a novel remodeling network in which Malat1 serves as a central regulator by binding to β-catenin and functioning through the β-catenin-OPG/Jagged1 pathway in osteoblasts and chondrocytes. In pathological conditions, Malat1 significantly promotes bone regeneration in fracture healing. Bone homeostasis and regeneration are crucial to well-being. Our discoveries establish a previous unrecognized paradigm model of Malat1 function in the skeletal system, providing novel mechanistic insights into how a lncRNA integrates cellular crosstalk and molecular networks to fine tune tissue homeostasis, remodeling and repair.

Neutrophil-like Monocytes Increase in Patients with Colon Cancer and Induce Dysfunctional TIGIT+ NK Cells

Myeloid-derived suppressor cells (MDSCs) are a heterogeneous family of immune cells including granulocytic (CD14neg/CD15+/HLA-DRneg) and monocytic subtypes (CD14+/CD15neg/HLA-DRneg). In the present study, we found a population of monocytes expressing the granulocyte marker CD15 that significantly increased in both peripheral blood (PB) and tumoral tissues of patients with colorectal cancer (CRC). Further phenotypical analysis confirmed the granulocytic-like features of this monocyte subpopulation that is associated with an increase in granulocyte-monocyte precursors (GMPs) in the PB of these patients (pts). Mechanistically, this granulocyte-like monocyte population suppressed NK cell activity by inducing TIGIT and engaging NKp30. Accordingly, an increased frequency of TIGIT+ NK cells with impaired functions was found in both the PB and tumoral tissue of CRC pts. Collectively, we provided new mechanistic explanations for tumor immune escape occurring in CRC by showing the increase in this new kind of MDSC, in both PB and CRC tissue, which is able to significantly impair the effector functions of NK cells, thereby representing a potential therapeutic target for cancer immunotherapy.

C/EBPβ-induced lymphoid-to-myeloid transdifferentiation emulates granulocyte-monocyte progenitor biology

CCAAT/enhancer-binding protein beta (C/EBPβ) induces primary v-Abl immortalized mouse B cells to transdifferentiate (BT, B cell transdifferentiation) into granulocyte-macrophage progenitor-like cells (GMPBTs). GMPBTs maintain cytokine-independent self-renewal, lineage choice, and multilineage differentiation. Single-cell transcriptomics demonstrated that GMPBTs comprise a continuum of myelomonopoietic differentiation states that seamlessly fit into state-to-fate maps of normal granulocyte-macrophage progenitors (GMPs). Inactivating v-Abl kinase revealed the dependence on activated CSF2-JAK2-STAT5 signaling. Deleting IRF8 diminished monopoiesis and enhanced granulopoiesis while removing C/EBPβ-abrogated self-renewal and granulopoiesis but permitted macrophage differentiation. The GMPBT culture system is easily scalable to explore the basics of GMP biology and lineage commitment and largely reduces ethically and legislatively debatable, labor-intensive, and costly animal experiments.

An aging-related immune landscape in the hematopoietic immune system

BACKGROUND

Aging is a holistic change that has a major impact on the immune system, and immunosenescence contributes to the overall progression of aging. The bone marrow is the most important hematopoietic immune organ, while the spleen, as the most important extramedullary hematopoietic immune organ, maintains homeostasis of the human hematopoietic immune system (HIS) in cooperation with the bone marrow. However, the overall changes in the HIS during aging have not been described. Here, we describe a hematopoietic immune map of the spleen and bone marrow of young and old mice using single-cell sequencing and flow cytometry techniques.

RESULTS

We observed extensive, complex changes in the HIS during aging. Compared with young mice, the immune cells of aged mice showed a marked tendency toward myeloid differentiation, with the neutrophil population accounting for a significant proportion of this response. In this change, hypoxia-inducible factor 1-alpha (Hif1α) was significantly overexpressed, and this enhanced the immune efficacy and inflammatory response of neutrophils. Our research revealed that during the aging process, hematopoietic stem cells undergo significant changes in function and composition, and their polymorphism and differentiation abilities are downregulated. Moreover, we found that the highly responsive CD62L + HSCs were obviously downregulated in aging, suggesting that they may play an important role in the aging process.

CONCLUSIONS

Overall, aging extensively alters the cellular composition and function of the HIS. These findings could potentially give high-dimensional insights and enable more accurate functional and developmental analyses as well as immune monitoring in HIS aging.

Characteristics of immune cells and causal relationship with chondromalacia: A two-sample, bidirectional mendelian randomization study

Chondromalacia, characterized by the softening of cartilage, is a prevalent condition affecting joint health with complex etiology. The immune system's role in its pathogenesis has been implicated but remains to be fully elucidated. To address a critical knowledge gap, we conducted a two-sample Mendelian randomization analysis of 731 immune cell phenotypes, assessing parameters like fluorescence, cell count, and morphology. After sensitivity and pleiotropy checks, and applying a false discovery rate correction, our study linked 17 phenotypes to chondromalacia (p < .05). Among them, seven immune cell phenotypes were found to have a protective effect against chondromalacia (IVW: p < .05, OR <1), while 10 were considered risk factors (IVW:p < .05, OR >1). Despite the constraints of sample size and possible genetic differences among populations, our research has identified a notable genetic correlation between specific immune cell indicators and chondromalacia. This breakthrough sheds light on the pathophysiological mechanisms of the condition. The identification of protective and risk-associated immune cell phenotypes provides a foundation for further exploration of immunological mechanisms in chondromalacia and may pave the way for targeted interventions. Future research is warranted to validate these findings and explore their clinical implications.

CD62L as target receptor for specific gene delivery into less differentiated human T lymphocytes

Chimeric antigen receptor (CAR)-expressing T cells are a complex and heterogeneous gene therapy product with variable phenotype compositions. A higher proportion of less differentiated CAR T cells is usually associated with improved antitumoral function and persistence. We describe in this study a novel receptor-targeted lentiviral vector (LV) named 62L-LV that preferentially transduces less differentiated T cells marked by the L-selectin receptor CD62L, with transduction rates of up to 70% of CD4+ and 50% of CD8+ primary T cells. Remarkably, higher amounts of less differentiated T cells are transduced and preserved upon long-term cultivation using 62L-LV compared to VSV-LV. Interestingly, shed CD62L neither altered the binding of 62L-LV particles to T cells nor impacted their transduction. The incubation of 2 days of activated T lymphocytes with 62L-LV or VSV-LV for only 24 hours was sufficient to generate CAR T cells that controlled tumor growth in a leukemia tumor mouse model. The data proved that potent CAR T cells can be generated by short-term ex vivo exposure of primary cells to LVs. As a first vector type that preferentially transduces less differentiated T lymphocytes, 62L-LV has the potential to circumvent cumbersome selections of T cell subtypes and offers substantial shortening of the CAR T cell manufacturing process.

Recombinant Human Interleukin-2 Corrects NK Cell Phenotype and Functional Activity in Patients with Post-COVID Syndrome

Post-COVID syndrome develops in 10–20% of people who have recovered from COVID-19 and it is characterized by impaired function of the nervous, cardiovascular, and immune systems. Previously, it was found that patients who recovered from infection with the SARS-CoV-2 virus had a decrease in the number and functional activity of NK cells. The aim of the study was to assess the effectiveness of recombinant human IL-2 (rhIL-2) administered to correct NK cell phenotype and functional activity in patients with post-COVID syndrome. Patients were examined after 3 months for acute COVID-19 of varying severity. The phenotype of the peripheral blood NK cells was studied by flow cytometry. It was found that disturbances in the cell subset composition in patients with post-COVID syndrome were characterized by low levels of mature (p = 0.001) and cytotoxic NK cells (p = 0.013), with increased release of immature NK cells (p = 0.023). Functional deficiency of NK cells in post-COVID syndrome was characterized by lowered cytotoxic activity due to the decreased count of CD57+ (p = 0.001) and CD8+ (p < 0.001) NK cells. In the treatment of patients with post-COVID syndrome with recombinant IL-2, peripheral blood NK cell count and functional potential were restored. In general, the effectiveness of using rhIL-2 in treatment of post-COVID syndrome has been proven in patients with low levels of NK cells.