Effect Of Biomaterial Properties And Microenvironment On Cardiac Differentiation Of Mesenchymal Stem Cells

Cardiovascular disease is one of the leading cause of death worldwide. Achieving the next phase of potential treatment strategies and better prognostic tools requires a concerted effort from interdisciplinary fields. Biomaterial-based cardiac tissue models are revolutionizing the area of preclinical research and translational applications.The goal of in vitro cardiac tissue modeling is to create physiologically functional models of the human myocardium. Biomaterials and microsystems not only serve as scaffolds for tissue formation, but also provide a highly-controllable microenvironment that incorporates key niche elements to enable precise regulation of cell fate and function.Life cannot exist without cell, while cell cannot survive without the extracellular matrix. Through changing cell shape and the actin cytoskeleton, topography of the extracelluar matrix can affect a range of cellular processes, including cell migration, proliferation and differentiation. Microfabricated nanotopography can not only support cell culturing in vitro, but also influence their behavior, for instance, guiding stem cell differentiation, which is one of the important goals of stem cell research. In this paper, our goal is to promote a specific differentiation of mesenchymal stem cells (MSCs) into cardiomyocytes through the nanotopographical cues.MSCs are the most widely used stem cell because they can be easily harvested from bone marrow or from human umbilical cord besides their ability to differentiate into many cell lineages, such as osteoblasts, chondrocytes, adipocytes and neurocytes. We used MSCs isolated from human umbilical cord in this study.In this thesis, we choose gelatin as the main component for constructing scaffolds. Gelatin is collagen hydrolysate with good hydrophilicity. The gelatin gel is suitable for cell culture. The cross-linking of gelatin using biocompatible genipin can improve gelatin stability and provide a similar elastic modulus to human myocardial tissue. By soft lithgraphy technology, we fabricated microgrooved gelatin gels using microstructured silicon as template and transferring microstructures through PDMS. Aligned microgroove structures can guide cell growth in a highly ordered manner. The introduction of Graphene oxide nanosheets to gelatin gels renders a higher roughness and a better electrical conductivity, which could improve the electrical signal transmission between cells.In this thesis, we tried to induce human umbilical cord mesenchymal stem cells (hUCMSCs) to differentiate into cardiomyocytes by using 5-aza, or small molecules, or small molecules plus co-culturing with cardiomyocytes based on four different materials:glass, gelatin gel, GO-containing gelatin gel, and microgrooved GO-containing gelatin gel. The results show that the above three types gelatin scaffolds have good cellular compatibility and they can promote the cardiac differentiation of hUCMSCs into cardiomyocytes. Among these scaffolds, GO-containing gels show a better effect. Comparing three different inducing methods:using 5-aza, or small molecules, or small molecules plus co-culturing with cardiomyocytes, it is clear that small molecules show better effect on cardiac differentiation than 5-aza, while small molecules plus co-culturing with cardiomyocytes show most significant effect on cardiac differentiation of hUCMSCs.