California's Stem Cell Agency

In this project, we aim to develop a 3D bioprinting technology to create functional cardiac tissues via encapsulation of cardiomyocytes derived from hESCs. To further improve their viability and cardiac functionality, we are developing a new vascularization technique to enhance the cardiac tissue model through the incorporation of functional vasculature using 3D bioprinting. In Specific Aim 1, we have successfully developed and optimized a rapid 3D bioprinting technique to create biomimetic 3D micro-architectures using hyaluronic acid (HA)-based biomaterials and hESC-derived cardiomyocytes. A protocol for the synthesis of the photopolymeriable hydrogel biomaterial (hyaluronic acid-glycidyl methacrylate (HA-GM)) proposed for use with the 3D bioprinting platform has been created and refined. HA-GM chemical synthesis efficiency was evaluated. H7 human embryonic stem cells (hESC) were used. These hESC derived cardiomyoctes (hESC-CMs) were shown to be well differentiated based on examining surface markers (Nkx2.5 & cardiac troponin T) and mRNA expression (Nkx2.5, ISL1, MYL2, and MYL7). These cells have been encapsulated within a 3D vasculature pattern of photopolymerized HA-GM hydrogel biomaterial. Digital images derived from a 3D model of the heart have been printed and the direct printing of biomaterials and cell-laden materials has been successfully achieved. Fluorescent staining showed encapsulated cell survival of this structure after 2-weeks of incubation. We have successfully measured the physiological function of cells embedded within the hydrogel constructs. We assessed changes in the cell viability, alignment and function of cells within hydrogel constructs. We successfully characterized electrical function of cardiomyocytes by optical mapping of Spontaneous Beats in unpatterned and patterned tissue constructs. We further measured mechanical function in the tissue constructs by cantilever displacement. We have also measured calcium transients in our 3D printed tissue constructs by live confocal imaging at varying frequencies. In Specific Aim 2, we have created an advanced vascularization technique for 3D pre-vascularized cardiac tissues with precise control of spatial organization. Human umbilical vein endothelial cells (HUVECs) were encapsulated within a mesh of hexagonal channels and cardiomyocytes were encapsulated within islands between these channels to demonstrate the capability of spatially printing distinct cell populations into a simple prevascularized co-culture model. Cells in this bioprinted configuration showed proliferation and viability. To investigate the formation of the endothelial network, we performed immunofluorescence staining on the prevascularized tissues after 1-week culture in vitro. Human-specific CD31 staining (green) in confocal microscopy shows the conjunctive network formation of HUVECs at different patterned channel widths.