Researchers from Brigham and Women's Hospital and the University of Michigan Medical School used genetic engineering technology to replace alanine, one amino acid found in the adult form of troponin I, with a histidine from the fetal form of the same protein. The substitution improved cardiac function in mice and in damaged human heart cells, according to a study published online Jan. 22 in Nature Medicine.

When the calcium sensitivity of heart muscle cells, controlled by troponin I, is compromised, acidosis results, which can lead to cardiac failure. The adult form of troponin I is activated during times of stress or exercise. The fetal form of the protein, which is more resistant than the adult form to the harmful effects of acidosis, is turned off shortly after birth.

Researchers essentially created a genetic hybrid of troponin I to combine the advantages of the fetal and adult forms of the protein. The modified protein helps the heart respond to a harsh intracellular environment by boosting its performance during periods of stress, according to the study.