UC San Diego

To study human development and disease, and develop therapies for regenerative medicine, the ability to create scalable, physiologically relevant human tissues is critical. In this regard, engineering cells and tissues from pluripotent stem cells has led to significant advances in our understanding of human-specific biology and holds promise for therapies. However, several challenges remain, including the ability to differentiate diverse lineages and drive disease states, vascularization to build tissues at scale, and monitoring capabilities to assess function. In this dissertation, I present a multi-faceted approach to address these limitations in creating and assaying complex tissue. To rapidly discover methods to differentiate pluripotent stem cells, I developed a screening method leveraging single cell RNA-sequencing to study the effects of gene overexpression. Using this approach, I assayed both fitness and transcriptomic responses of transcription factors, mutant gene libraries and whole gene families on pluripotent stem cells in multiple culture conditions. From these responses I built gene regulatory networks and found ETV2 as a reprogramming factor toward endothelial cells. I further engineered the system in combination with teratoma formation to develop a multiplexed system to assay the potential of genes and variants to drive oncogenic transformation in a tissue-specific manner. I found that c-MYC alone or together with myristoylated AKT1 drives transformation of neural progenitor lineages, while MEK1 (S218D/S222D) drives proliferative advantage in mesenchymal lineages like fibroblasts. I then harnessed these reprogramming approaches to engineer densely vascularized human tissue. I combined reprogramming and chemically directed differentiation by overexpressing lineage-specifying transcription factors in differentiating vascular organoids to introduce neurons and skeletal muscle into the organoids, demonstrating maintenance of molecular and functional characteristics of the parenchymal and vascular lineages. Finally, I developed flexible, printed electrodes to enable the monitoring of electrophysiological signals and electrical perturbation of tissues. I enabled low noise, high spatial resolution measurement of clinically relevant signals using screen-printed, stretchable concentric ring electrodes. I then applied these screen-printed electrodes to study the effects of electrical stimulation on the wound healing response in vivo. Lastly, I demonstrated preliminary data on a novel fabrication method to print microelectrodes to map cellular electrical activity.