Printing Tissue Analogues using Decellularized Extracellular Matrix Bioinks:Its Application to Cardiac Repair

Doctor3D cell printing is an emerging strategy for creating an engineered tissue construct, and this technology enables to create the heterocellular tissue environment by localizing biological components (e.g. cells or biomolecules) at the desired site with a range of from micron to millimeter. For printing the cellular components, the cells are usually protected by the printable biomaterials, and it is called bioink. It should be biocompatible and meet several physicochemical properties for printing process. The tissue specific microenvironment should be implemented in the engineered structure to function similar to the actual tissue. The decellularized extracellular matrix has shown great promise for recapitulating the intact tissue microenvironment, and various applications of dECM biomaterial have been widely attempted for advanced tissue engineering. This thesis presents the development of printable decellularized extracellular matrix bioinks for the 3D cell printing application. In addition, printing of pre-vascularized tissue construct using vascular cell-laden dECM bioinks showed the rapid vascularization inside of the construct as well as enhanced tissue integration with the host tissue. Finally, the developed 3D cell printing method was applied for treating myocardial infarction. Details on the research are given below. A strategy to use decellularized extracellular matrix (dECM) as a printable bioink was proposed for engineering biological tissues, consisting of cells encapsulated in dECM with specific organization and matrix composition. The adapted printing technology of depositing cell laden dECM hydrogel that we used can comply with several important prerequisites of tissue engineered grafts, including tissue-specific matrix materials, engineered interconnected porosity, the introduction of living (progenitor) cells, and the possibility to investigate organizational aspects in tissue regeneration. Additionally, the developed two-step crosslinking process of dECM bioink was demonstrated by rheological, mechanical and biological analysis to generate the optimal bioink for the cardiac tissue engineering approach. With the use of tissue homologous bioink, the vascularized 3D printed tissue construct was developed. The results suggested that this method has benefit to induce rapid vascularization of 3D printed tissue construct with endothelial cells patterned. The direct fabrication method can be suggested as a simple way to print vascular network in 3D printed tissue construct. Moreover, the mixture of endothelial cells and mesenchymal stem cells showed the dramatically expedited vascular network formation. Efficiency of pre-vascularized 3D cardiac tissue construct on treating myocardial infarction was demonstrated by using physiological, histological and functional analysis. The pre-vascularized 3D cardiac tissue construct provided the higher cardiac tissue regeneration capacity by generating a cardiac stem cell niche-like microenvironment. Human cells encapsulated in the construct were actively migrated and differentiated into both cardiac muscle like cells and endothelium like cells. The approach attempted in this thesis will bring out the development of pre-vascularized and tissue specific microenvironment-embodied stem cell niche for applying into the fast metabolism tissue environment, including liver, pancreas and kidney tissues. Moreover, each developed technology can be applied into the various areas in tissue engineering and regenerative medicine