Engineered building bloks to print endogenous tissue and complex organs in vitro
Creators: name: Garziano, Alessandro
Publisher: name: Università degli Studi di Napoli Federico II
Year: 2015

description: The fabrication of in vitro tissue models necessitates of tools to create an initial architecture and to systematically manipulate their microenvironments in space and time [10]. In this scenario, the modular tissue engineering is emerging as new paradigm for the in vitro fabrication of 3D biological structures. The fabrication of engineered micromodules  able to control the synthesis and the assembly  of an endogenous ECM, represents a formidable task. In this direction, our group developed a new class of tissue micromodules, named micro tissue precursor (TP), which led to the formation of a completely endogenous 3D tissue [7, 13].  In the first chapter of this work we proposed tp as a new class of bio-ink for organ printing strategy and demonstrate that they evolve during culture time and strongly influence the morphology of the final printed tissue. We argue that the initial composition of the ECM present in the TP change with TP "age" and affects the maturation of the ECM in the final 3D tissue.  We focused our attention on crucial aspects such as fusion capability, degree of maturation and mechanical properties of its ECM, as well as the evolution of oxygen consumption kinetic parameters. Finally we demonstrated the capability of tp to be printed in unusual shapes meeting one of the need of organ printing strategy to overcome shape limitation and to obtain functional and complex tissues.
In the second chapter we proposed a model of TOC (tissue on chip) by inserted TP in a microfluidic platform, designed in order to induce flow perfusion of the TP. This micro-perfusion bioreactor, can be performed  in order to evaluate the effect of flow rate and biochemical factors on the tissue development. By using this system together with TP, it is possible in "short time" optimize the fluid dynamics parameters and bio-chemicals concentration inside the medium and evaluating  the effect of external factors on the collagen assembly, cells viability and metalloproteinase synthesis. These capabilities made it an important tool for studying cause-effect relation, in particular how each single factor influences the tissue characteristics. 
In the third chapter it is explored the possibility to realize TP by using bronchial fibroblast in order to obtain "lung-stroma" on which build up bronchial epithelium. We found  that TP not only synthesize their own ECM, but that they organize it leading to a final tissue having a morphology very similar to native lung stroma.  By seeding bronchial epithelial cells on this lung stroma, they differentiate and recreate the complete airway epithelium in air-liquid condition. Finally, by exploiting the knowledge of our group to recreate a human skin model, we evaluate its capability to maintains exogenous hair viability during the time, in terms of elongation capability and anagen phase of hair follicle maintenance. We realized a human skin model that, better than other competitors, is a good environment for the exogenous hair. This is a starting step in order to obtain a complete model that itself recapitulate all the hair follicle structures.