Background—Myocardial infarction (MI) is an ischemic wound that recruits millions of leukocytes. MI-associated blood leukocytosis correlates inversely with patient survival, yet the signals driving heightened leukocyte production after MI remain incompletely understood.
Methods and Results—With the use of parabiosis surgery, this study shows that soluble danger signals, among them interleukin-1β, increase bone marrow hematopoietic stem cell proliferation after MI. Data obtained in bone marrow reconstitution experiments reveal that interleukin-1β enhances hematopoietic stem cell proliferation by both direct actions on hematopoietic cells and through modulation of the bone marrow’s hematopoietic microenvironment. An antibody that neutralizes interleukin-1β suppresses these effects. Anti-interleukin-1β treatment dampens the post-MI increase in hematopoietic stem cell proliferation. Consequently, decreased leukocyte numbers in the blood and infarct reduce inflammation and diminish post-MI heart failure in ApoE–/– mice with atherosclerosis.
Conclusions—The presented insight into post-MI bone marrow activation identifies a mechanistic target for muting inflammation in the ischemically damaged heart
