After three weeks, the hydrogel worked even better than the control, the researchers say. This was a surprise, so the team worked out a supplementary study to determine why the hydrogel breaks down so readily and how the animals' bodies were able to use it to generate new dermal tissue. It turns out that the body's natural inflammatory response — involving neutrophils and macrophages — accumulated easily inside the hydrogel. Its physical structure enabled their easy entry, which promoted the breakdown of the hydrogel and enabling blood vessels to fill it in. Gerecht also believes the hydrogel might recruit bone marrow stem cells, which are naturally induced to differentiate into skin and blood vessel cells.