New collagen patch may speed repair of damaged heart

Researchers have developed a new patch composed of structurally modified collagen that can be grafted onto damaged heart tissue to speed its repair.
Muscle tissue in the adult human heart has a limited capacity to heal, which has spurred researchers to try to give the healing process a boost, researchers said.
Various methods of transplanting healthy cells into a damaged heart have been tried, but have yet to yield consistent success in promoting healing.
Researchers at the Stanford University School of Medicine and Lucile Packard Children's Hospital have developed a patch composed of structurally modified collagen that can be grafted onto damaged heart tissue.

Their studies in mice have demonstrated that the patch not only speeds generation of new cells and blood vessels in the damaged area, it also limits the degree of tissue damage resulting from the original trauma.
The key, according to Pilar Ruiz-Lozano, associate professor of pediatrics, is that the patch doesn't seek to replace the dead heart-muscle cells.

Instead, it replaces the epicardium, the outer layer of heart tissue, which is not muscle tissue, but which protects and supports the heart muscle, or myocardium.
"This synthetic tissue has the mechanical properties of the embryonic epicardium," said Ruiz-Lozano, senior author of a study published in the journal Biomaterials.

Embryonic epicardium is significantly more flexible than adult epicardium, but more rigid and structured than existing materials, making it more conducive to growth of new tissue.
"We paid tremendous attention to the physical properties of the materials and how their elasticity could modify the function of the heart," Ruiz-Lozano said.
The epicardium - or its artificial replacement - has to allow the cell migration and proliferation needed to rebuild damaged tissue, as well as be sufficiently permeable to allow nutrients and cellular waste to pass through the network of blood vessels that weaves through it.
Collagen is a fibrous protein found in connective tissue, including skin, bone, cartilage and tendons, as well as in the epicardium. Because the patch is made of acellular collagen, meaning it contains no cells, recipient animals do not need to be immunosuppressed to avoid rejection. With time, the collagen gets absorbed into the organ.

Compared with control mice that received no patch, mice that were given the patch promptly after experiencing a surgically induced heart attack showed significant improvement in overall cardiac function in echocardiograms two weeks later.
The patched hearts showed more migration of cells to the site of the injury four weeks after patch implantation. The new cells were present both in the patch and in the adjacent damaged heart tissue.
The patched hearts also had greater development of new blood vessels, which appeared to have improved delivery of oxygen and nutrients to the tissue, thus reducing the number of cells that perished compared to unpatched hearts.