*Hybrid ‘patch’ instead of heart transplants*

Because heart cells can’t multiply and cardiac muscles contain only a small number of stem cells, heart tissue is unable to repair itself after a heart attack.

By JUDY SIEGEL-ITZKOVICH
A magnified view of a CD34+ stem cell (photo credit: REUTERS)
A magnified view of a CD34+ stem cell
(photo credit: REUTERS)
Because heart cells can’t multiply and cardiac muscles contain only a small number of stem cells, heart tissue is unable to repair itself after a heart attack. Now Tel Aviv University researchers are literally setting a new gold standard in cardiac tissue engineering.
Dr. Tal Dvir and his graduate student Michal Shevach of the departments of biotechnology, materials science and engineering and the Center for Nanoscience and Nanotechnology have been developing sophisticated micro and nanotechnological tools ranging in size from one millionth to one billionth of a meter to develop functional substitutes for damaged heart tissues.
Searching for innovative methods to restore heart function, especially cardiac “patches” that could be transplanted into the body to replace damaged heart tissue, Dvir literally struck gold. He and his team discovered that gold particles are able to increase the conductivity of biomaterials. In a study published recently by Nano Letters, Dvir’s team presented their model for a superior hybrid cardiac patch that incorporates biomaterial harvested from patients, as well as gold nanoparticles.
“Cardiac tissue is engineered by allowing cells, taken from the patient or other sources, to grow on a three-dimensional scaffold, similar to the collagen grid that naturally supports the cells in the heart. Over time, the cells come together to form a tissue that generates its own electrical impulses and expands and contracts spontaneously. The tissue can then be surgically implanted as a patch to replace damaged tissue and improve heart function in patients.
Recent efforts in the scientific world focus on the use of scaffolds from pig hearts to supply the collagen grid, called the extracellular matrix, so they can be implanted in human patients. However, due to residual remnants of antigens such as sugar or other molecules, the human patients’ immune cells are likely to attack the animal matrix.
To address this immunogenic response, the team suggested a new approach. Fatty tissue from a patient’s own stomach could be easily and quickly harvested, its cells efficiently removed and the remaining matrix preserved.
This scaffold does not provoke an immune response.The second dilemma – to establish functional network signals – was complicated by the use of the human extracellular matrix.
“Engineered patches do not establish connections immediately,” said Dvir. “Biomaterial harvested for a matrix tends to be insulating and thus disruptive to network signals.”
Dvir explored in his lab the integration of gold nanoparticles into cardiac tissue to optimize electrical signaling between cells. Preliminary test results of the hybrid patch in animals have been positive. “We now have to prove that these autologous hybrid cardiac patches improve heart function after heart attacks with minimal immune response,” Dvir said. “Then we plan to move it to large animals and after that, to clinical trials.”