It is a sad truth that near all transplanted cells in near all cell therapies die quickly, and do not integrate with tissues to improve function. The benefits that do occur result from the signals secreted by the transplanted cells before they die. The research community has been undertaking a range of strategies to address this issue. One is to produce a scaffold material that mimics tissue sufficiently well to give cells the support they need to survive, populate it with suitable cells, and then transplant the resulting structure. This can produce 10% survival of transplanted cells, an enormous improvement over delivery of cells alone.

One manifestation of this approach is a heart patch, a thin structure that is placed onto the surface of an injured heart. Heart patches have performed fairly well to date in the lab, but like all tissue engineering work, that they use cells makes them logistically challenging and expensive to deploy. Researchers here report on how well a patch works if the cells are left out of the equation: just transplant the scaffold, a structure that can be mass manufactured and stored comparatively easily, and see whether it encourages native cells to greater regeneration.

Cardiac patches are being studied as a promising future option for delivering cell therapy directly to the site of heart attack injury. However, current cardiac patches are fragile, costly, time-consuming to prepare and, since they use live cellular material, increase risks of tumor formation and arrhythmia.

“We have developed an artificial cardiac patch that can potentially solve the problems associated with using live cells, yet still deliver effective cell therapy to the site of injury.” Researchers built the patch by first creating a scaffolding matrix from decellularized pig cardiac tissue. Synthetic cardiac stromal cells – made of a biodegradable polymer containing cardiac stromal cell-derived repair factors – were embedded in the matrix. The resulting patch contained all of the therapeutics secreted by the cells, without live cells that could trigger a patient’s immune response.

In a rat model of heart attack, treatment with the artificial cardiac patch resulted in ~50% improvement of cardiac function over a three-week period compared to non-treatment, as well as a ~30% reduction in scarring at the injury site. The researchers also conducted a seven-day pilot study of heart attack in a pig model, and saw ~30% reduction in scarring in some regions of the pig hearts, as well as stabilized heart function, compared to non-treatment. Additional experiments demonstrated that artificial patches that had been frozen were equally potent to freshly created patches.