Chronic treatment with clenbuterol modulates endothelial progenitor cells and circulating factors in a murine model of cardiomyopathy

The purpose of this study was to determine the effects of chronic treatment with the beta 2 adrenergic receptor agonist clenbuterol on endothelial progenitor cells (EPC) in a well-characterized model of heart failure, the muscle LIM protein knockout (MLP^-/-) mouse. MLP^-/- mice were treated daily with clenbuterol (2 mg/kg) or saline subcutaneously for 6 weeks. Clenbuterol led to a 30% increase in CD31⁺ cells in the bone marrow of MLP^-/- heart failure mice (p∈<∈0.004). Clenbuterol did not improve ejection fraction. Clenbuterol treatment in MLP ^-/- mice was associated with significant changes in the following circulating factors: tissue inhibitor of metalloproteinase-type 1, leukemia inhibitory factor 1, C-reactive protein, apolipoprotein A1, fibroblast growth factor 2, serum glutamic oxaloacetic transaminase, macrophage-derived chemokine, and monocyte chemoattractant protein-3. Clenbuterol treatment in the MLP ^-/- model of heart failure did not rescue heart function, yet did increase CD31⁺ cells in the bone marrow. This is the first evidence that a beta 2 agonist increases EPC proliferation in the bone marrow in a preclinical model of heart failure.