Engineering human multilayer tissues: applications in vascular and orthopedic fields

This PhD thesis sets in tissue engineering (TE), a discipline which, starting from the principles of biology, medicine and engineering, it aims to restore, maintaining, or enhancing tissue and organ function. TE is performed following mainly three approaches: genetic engineering, cell therapy and scaffold/cells construct. The present work is focused on the latter approach, aiming to propose a change in its paradigm. In fact, TE by scaffold/cells construct develops in few consecutive steps, i.e. tissue harvesting, cell expansion in plastic, cell seeding onto a scaffold namely forming a so-called tissue engineering constructs (TECs), in vitro conditioning of TEC, and the final implantation into the donor site. However, targeting clinical translation, this strategy poses several constraints, especially in terms of economic burden, which still limits the definitive entrance of TE in clinics.To surmount this problem, hereby we propose a possible alternative way to repair or regenerate tissues presenting a multilayer architecture, with particular regard to blood vessels and articular cartilage. In particular, we propose a "onestep" approach, where the in vitro preconditioning of the constructs is not needed since the scaffold itself will provide the proper biochemical stimuli to the cells seeded therein. In our settings the differentiating factors are released from the scaffold, so driving the differentiation as well as the maturation of freshly-isolated constructs. Matching the neo extracellular matrix production time by seeded cells with polymer-based scaffold degradation time, it is possible to regenerate tissues directly in vivo, dramatically shortening times and costs, and also avoiding double-hospitalization. We hypothesize that this off-the-shelf devices could simplify logistical issues surrounding transfer of tissue-engineered constructs into the clinical arena, reduce the need for large and expensive GMP tissue engineering facilities and minimize operator handling, with the likely final result of reducing the cost of engineered grafts.