Background Ischemic cardiovascular disease is the leading cause of death worldwide. Current pharmacologic therapy has multiple limitations, and patients remain symptomatic despite maximal medical therapies. Deficiency or inhibition of thymidine phosphorylase (TYMP) in mice reduces thrombosis, suggesting that TYMP could be a novel therapeutic target for patients with acute myocardial infarction (AMI). Methods and Results A mouse AMI model was established by ligation of the left anterior descending coronary artery in C57BL/6J wild-type and TYMP-deficient (Tymp-/-) mice. Cardiac function was monitored by echocardiography or Langendorff assay. TYMP-deficient hearts had lower baseline contractility. However, cardiac function, systolic left ventricle anterior wall thickness, and diastolic wall strain were significantly greater 4 weeks after AMI compared with wild-type hearts. TYMP deficiency reduced microthrombus formation after AMI. TYMP deficiency did not affect angiogenesis in either normal or infarcted myocardium but increased arteriogenesis post-AMI. TYMP deficiency enhanced the mobilization of bone marrow stem cells and promoted mesenchymal stem cell (MSC) proliferation, migration, and resistance to inflammation and hypoxia. TYMP deficiency increased the number of larger MSCs and decreased matrix metalloproteinase-2 expression, resulting in a high homing capability. TYMP deficiency induced constitutive AKT phosphorylation in MSCs but reduced expression of genes associated with retinoid-interferon-induced mortality-19, a molecule that enhances cell death. Inhibition of TYMP with its selective inhibitor, tipiracil, phenocopied TYMP deficiency, improved post-AMI cardiac function and systolic left ventricle anterior wall thickness, attenuated diastolic stiffness, and reduced infarct size. Conclusions This study demonstrated that TYMP plays an adverse role after AMI. Targeting TYMP may be a novel therapy for patients with AMI.
Keywords: acute myocardial infarction; mesenchymal stem cells; stem cell therapy; thrombosis; thymidine phosphorylase.