Project description:Background—Diabetes is a prevalent public health problem that affects about one third of the U.S. population and leads to serious vascular complications with increased risk for coronary artery disease. How bone marrow hematopoiesis contributes to diabetes complications is incompletely understood. We thus investigated the role of bone marrow endothelial cells in diabetic regulation of inflammatory myeloid cell production. Methods and Results—In three types of mouse diabetes, we observed enhanced proliferation of hematopoietic stem and progenitor cells (HSPC) leading to augmented circulating myeloid cell numbers. Analysis of bone marrow niche cells revealed that endothelial cells in diabetic mice expressed less Cxcl12, a retention factor promoting HSPC quiescence. Transcriptome-wide analysis of bone marrow endothelial cells demonstrated enrichment of genes involved in epithelial growth factor receptor (EGFR) signaling in mice with diet-induced diabetes. To explore whether endothelial EGFR plays a functional role in myelopoiesis, we generated mice with endothelial-specific deletion of EGFR (Cdh5Cre EGFRfl/fl). Unexpectedly, we found enhanced HSPC proliferation and increased myeloid cell production in Cdh5Cre EGFRfl/fl mice compared to wild type mice with diabetes. Disrupted EGFR signaling in endothelial cells decreased their expression of the HSPC retention factor angiopoietin-1. We tested the functional relevance of these findings for wound healing and atherosclerosis, both implicated in complications of diabetes. Inflammatory myeloid cells accumulated more in skin wounds of diabetic Cdh5Cre EGFRfl/fl mice, significantly delaying wound closure. Atherosclerosis accelerated in Cdh5Cre EGFRfl/fl mice, leading to larger and more inflamed atherosclerotic lesions in the aorta. Conclusions—In diabetes, bone marrow endothelial cells participate in the dysregulation of bone marrow hematopoiesis and promote cardiovascular complications via leukocyte overproduction. Specifically, diabetes reduces endothelial production of Cxcl12, a quiescence-promoting niche factor that reduces stem cell proliferation. We also describe a previously unknown counter-regulatory pathway, in which protective endothelial EGFR signaling curbs HSPC proliferation and myeloid cell production via angiopoietin-1.

Project description:BackgroundDiabetes mellitus is a prevalent public health problem that affects about one-third of the US population and leads to serious vascular complications with increased risk for coronary artery disease. How bone marrow hematopoiesis contributes to diabetes mellitus complications is incompletely understood. We investigated the role of bone marrow endothelial cells in diabetic regulation of inflammatory myeloid cell production.MethodsIn 3 types of mouse diabetes mellitus, including streptozotocin, high-fat diet, and genetic induction using leptin-receptor-deficient db/db mice, we assayed leukocytes, hematopoietic stem and progenitor cells (HSPC). In addition, we investigated bone marrow endothelial cells with flow cytometry and expression profiling.ResultsIn diabetes mellitus, we observed enhanced proliferation of HSPC leading to augmented circulating myeloid cell numbers. Analysis of bone marrow niche cells revealed that endothelial cells in diabetic mice expressed less Cxcl12, a retention factor promoting HSPC quiescence. Transcriptome-wide analysis of bone marrow endothelial cells demonstrated enrichment of genes involved in epithelial growth factor receptor (Egfr) signaling in mice with diet-induced diabetes mellitus. To explore whether endothelial Egfr plays a functional role in myelopoiesis, we generated mice with endothelial-specific deletion of Egfr (Cdh5Cre Egfrfl/fl). We found enhanced HSPC proliferation and increased myeloid cell production in Cdh5Cre Egfrfl/fl mice compared with wild-type mice with diabetes mellitus. Disrupted Egfr signaling in endothelial cells decreased their expression of the HSPC retention factor angiopoietin-1. We tested the functional relevance of these findings for wound healing and atherosclerosis, both implicated in complications of diabetes mellitus. Inflammatory myeloid cells accumulated more in skin wounds of diabetic Cdh5Cre Egfrfl/fl mice, significantly delaying wound closure. Atherosclerosis was accelerated in Cdh5Cre Egfrfl/fl mice, leading to larger and more inflamed atherosclerotic lesions in the aorta.ConclusionsIn diabetes mellitus, bone marrow endothelial cells participate in the dysregulation of bone marrow hematopoiesis. Diabetes mellitus reduces endothelial production of Cxcl12, a quiescence-promoting niche factor that reduces stem cell proliferation. We describe a previously unknown counterregulatory pathway, in which protective endothelial Egfr signaling curbs HSPC proliferation and myeloid cell production.

Project description:Myeloid cells, in particular monocytes and macrophages, are well-described to suppress the antitumor immune response. However, the molecular mechanisms controlling immunosuppressive myeloid cell states are ill- defined, hampering the development of myeloid-targeted therapies for cancer1,2. Here, we transcriptionally profiled over 500,000 tumor infiltrating leukocytes in non-small cell lung cancer (NSCLC) patients and in the KrasG12DTp53-/- (KP) murine lung adenocarcinoma model. In both species, the Type 2 cytokine IL-4 was predicted to be the primary driver of tumor infiltrating monocyte-derived macrophage (mo-mac) phenotype, despite the fact that lung tumors were largely devoid of IL-4 producing cells. Using a panel of conditional knockout mice, we found that only deletion of IL-4Ra within early myeloid progenitors in bone marrow (BM) reduced lung tumor burden, while deletion of this receptor in downstream mature myeloid cells had no effect. Detailed transcriptional analysis followed by mechanistic studies in vivo revealed an essential role for local BM IL-4 signaling in reprograming myelopoiesis in cancer. Mechanistically, basophils and eosinophils within BM upregulated IL4 production upon sensing distal tumor cues; local BM IL-4 acted on granulocyte-monocyte progenitors to transcriptionally program the development of immunosuppressive myeloid cells, which then homed to the tumor and promoted tumor growth. Consequentially, specific depletion of basophils, which were enriched in BM but absent from the tumor, profoundly reduced tumor burden and normalized myelopoiesis in experimental lung tumors. Prompted by these results, we designed and initiated the first clinical trial of dupilumab, a humanized IL- 4Ra blocking antibody commonly used for atopic disease, given in conjunction with PD-(L)1 blockade in relapsed/refractory NSCLC patients who had progressed on standard chemoimmunotherapy combinations. Consistent with our preclinical mouse data, dupilumab drove a reduction in circulating monocytes. This was coupled with an expansion of circulating and tumor-infiltrating CD8 T cells. Notably, one out of the six patients who enrolled in Phase 1b of this trial exhibited significant decrease in his tumor burden after two months of dupilumab treatment, and the clinical response deepened further to a near complete response even after cessation of dupilumab, suggestive of successful reprogramming of the antitumor response. Collectively, our study defines a role for IL-4 signaling in lung tumor progression, identifies a central axis controlling immunosuppressive myelopoiesis in cancer, and highlights a novel combination therapy for immune checkpoint blockade in humans.

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Bone marrow endothelial cells regulate myelopoiesis in diabetes

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