Towards the generation of patient-specific patches for cardiac repair.

Cardiovascular diseases represent the main cause of morbidity and mortality worldwide. Millions of people are affected by such diseases in the industrialized countries, with hundreds of thousands new cases diagnosed every year. Among cardiac diseases, heart failure is the most common end-stage pathology, leading to impaired cardiac output and cardiac performance as a result of the irreversible loss of contractile cardiomyocytes. Tissue engineering holds the promise to provide personalized solutions to the problem of cardiac muscle repair. Indeed, the identification of little reservoirs of stem and progenitor cells within every body district opened new perspectives to the setup of patient-specific protocols for cardiac diseases. Nonetheless, the results of the first pre-clinical and clinical trials in which adult stem/progenitor cells were adopted pointed at the route of delivery to the injured organ as well as at the cell source as the main issues for cardiac tissue engineers. In fact, when adult stem cells were directly injected into the myocardium or delivered through bloodstream to the heart, no or few cells could be found engrafted within host tissue few days after the administration. Renewed enthusiasm was generated by the techniques set up to enrich cardiomyocytes obtained by embryonic stem cells and by the recent disclosure of the protocols to obtain reprogrammed pluripotent cells or reprogrammed cardiomyocytes out of patients' own somatic cells. In this context, additional efforts to setup efficient systems to deliver stem cells to the injured site are required. The application of forefront technologies to fabricate synthetic and hybrid scaffolds to be employed as cell delivery systems and the acknowledgement that surface physical, mechanical, chemical properties can exert specific effects on stem cells per se prompted new enthusiasm in the field. In this respect, a cardiac-specific scaffold should be able to comply with cardiac muscle architecture, be deformable as to indulge and possibly sustain cardiac contraction. As expected, such a scaffold should favor stem cell electromechanical coupling with host tissue, while promoting the vascularization of the newly-formed tissue.