<p>According to the report in Science Advances suggested that the extracellular matrix gets into the way of the heart tissue restitution. It was observed that new born mice are able to repair injured heart tissue way better than injured animals few days later in their lives.</p><p>But in this the question arises that what accounts for this regenerative capacity and when and why it disappears, the investigators observed that the damage was less in mice who was injured on their first day of life but the damage appeared after that, even just a day later which led to the large fibrotic scars. “I thought this was an intriguing paper that was well done,” says stem cell and regeneration biologist Richard Lee of Harvard University who was not involved with the work. “It pinpoints the timeline [of neonatal heart regeneration] in a manner that&amp;rsquo;s more precise than what others have done.”</p><blockquote class="style-3"><p>Ditte Andersen, A clinical biochemist of the University of Southern Denmark, who experimented on new born mice by removing small portion of heart tissue from hundreds of new born mice but never observed any regeneration of the muscletissue.</p></blockquote><p>Whereas on the other side the other scientistis not getting easily convinces by this research and having doubt regarding it. Ditte Andersen, A clinical biochemist of the University of Southern Denmark, who experimented on new born mice by removing small portion of heart tissue from hundreds of new born mice but never observed any regeneration of the muscletissue. “There is a problem in this research field that we [rely on] this fibrosis hallmark because the [extent of] ventricle outgrowth is very hard to determine,” she says. “If fibrosis is absent, people are very eager to conclude, &amp;lsquo;OK, this is regeneration.&amp;rsquo; . . . But it is not evidence of myocardial regrowth.”</p><p>Many other scientists are also there working on it but despite the controversy, “we all want to see scarless healing in the adult heart,” says Lee, and with each paper “we&amp;rsquo;re learning more and more and inching along closer to potentially someday being able to do this.”</p>