For the study, the scientists injected purified tropoelastin directly into heart walls of rats, four days after the rodents had experienced a heart attack. This task was accomplished via a new technique wherein a needle is precisely guided by ultrasound ?" it's reportedly much less invasive than conventional techniques. Twenty-eight days after the injections, the scars on the rats' hearts were found to have become smaller, softer and more elastic, to the point that the tissue exhibited "muscle function similar to before the heart attack." Additionally, in petri dish experiments, tropoelastin treatment was found to cause human cardiac fibroblasts ?" which are cells that maintain the structure of the heart ?" to produce elastin.