Although most medicines have historically been small molecules, many newly 
approved drugs are derived from proteins. Protein therapies have been developed 
for treatment of diseases in almost every organ system, including the heart. 
Great excitement has now arisen in the field of regenerative medicine, 
particularly for cardiac regeneration after myocardial infarction. Every year, 
millions of people suffer from acute myocardial infarction, but the adult 
mammalian myocardium has limited regeneration potential. Regeneration of the 
heart after myocardium infarction is therefore an exciting target for protein 
therapeutics. In this review, we discuss different classes of proteins that have 
therapeutic potential to regenerate the heart after myocardial infarction. 
Protein candidates have been described that induce angiogenesis, including 
fibroblast growth factors and vascular endothelial growth factors, although thus 
far clinical development has been disappointing. Chemotactic factors that 
attract stem cells, e.g., hepatocyte growth factor and stromal cell-derived 
factor-1, may also be useful. Finally, neuregulins and periostin are proteins 
that induce cell-cycle reentry of cardiomyocytes, and growth factors like IGF-1 
can induce growth and differentiation of stem cells. As our knowledge of the 
biology of regenerative processes and the role of specific proteins in these 
processes increases, the use of proteins as regenerative drugs could develop as 
a cardiac therapy.