Acute myeloid leukaemia disrupts endogenous myelo-erythropoiesis by compromising the adipocyte bone marrow niche.

Acute myeloid leukaemia (AML) is distinguished by the generation of dysfunctional leukaemic blasts, and patients characteristically suffer from fatal infections and anaemia due to insufficient normal myelo-erythropoiesis. Direct physical crowding of bone marrow (BM) by accumulating leukaemic cells does not fully account for this haematopoietic failure. Here, analyses from AML patients were applied to both in vitro co-culture platforms and in vivo xenograft modelling, revealing that human AML disease specifically disrupts the adipocytic niche in BM. Leukaemic suppression of BM adipocytes led to imbalanced regulation of endogenous haematopoietic stem and progenitor cells, resulting in impaired myelo-erythroid maturation. In vivo administration of PPARγ agonists induced BM adipogenesis, which rescued healthy haematopoietic maturation while repressing leukaemic growth. Our study identifies a previously unappreciated axis between BM adipogenesis and normal myelo-erythroid maturation that is therapeutically accessible to improve symptoms of BM failure in AML via non-cell autonomous targeting of the niche.

Delayed but not Early Treatment with DNase Reduces Organ Damage and Improves Outcome in a Murine Model of Sepsis.

Sepsis is characterized by systemic activation of coagulation and inflammation in response to microbial infection. Although cell-free DNA (cfDNA) released from activated neutrophils has antimicrobial properties, it may also exert harmful effects by activating coagulation and inflammation. The authors aimed to determine whether deoxyribonuclease (DNase) administration reduces cfDNA levels, attenuates coagulation and inflammation, suppresses organ damage, and improves outcome in a cecal ligation and puncture (CLP) model of polymicrobial sepsis. Healthy C57Bl/6 mice were subjected to CLP, a surgical procedure involving two punctures of the ligated cecum, or sham surgery (no ligation/puncture). Mice were given DNase or saline by intraperitoneal injection 2, 4, or 6 h after surgery. Two hours after treatment, organs were harvested and plasma levels of cfDNA, interleukin-6 (IL-6), IL-10, thrombin-antithrombin complexes, lung myeloperoxidase, creatinine, alanine transaminase, and bacterial load were quantified. Survival studies were also performed. The CLP-operated mice had rapid time-dependent elevations in cfDNA that correlated with elevations in IL-6, IL-10, and thrombin-antithrombin complexes and had organ damage in the lungs and kidneys. Administration of DNase at 2 h after CLP resulted in increased IL-6 and IL-10 levels and organ damage in the lungs and kidneys. In contrast, DNase administration at 4 or 6 h after CLP resulted in reduced cfDNA and IL-6 levels, increased IL-10, and suppressed organ damage and bacterial dissemination. Deoxyribonuclease administration every 6 h after CLP also rescued mice from death. Our studies are the first to demonstrate that delayed but not early administration of DNase may be protective in experimental sepsis.