Engineering microcapsules for scalable differentiation of human pluripotent stem cells into hepatocytes

ABSTRACT Millions of people worldwide are affected by liver diseases. Some of these individuals progress to acute or acute- on-chronic liver failure where liver transplant becomes the only recourse. Given the shortage of transplantable organs, over >40% of patients on the waitlist do not receive a liver transplant in a timely manner. This motivates a strong interest in developing bioartificial liver (BAL) systems that may be used as a bridge-to-transplantation or a bridge-to-recovery for patients with liver failure. BAL systems are populated with liver cells (hepatocytes) that perform a wide array of liver functions (e.g. protein synthesis and glucose regulation) in addition to detoxifi- cation. Ideally, BAL systems should contain human hepatocytes, however, because such cells are typically derived from cadaveric organs, their availability is limited. Use of xenogenic (e.g. porcine) hepatocytes is com- mon but less than ideal because of the potential for zoonotic transmission of diseases. Human embryonic stem cells (hESCs) and induced pluripotent stem cells (iPSCs), generally known as human pluripotent stem cells (hPSCs), may be expanded indefinitely and differentiated into any desired cell type, including hepatocytes. hPSCs hold incredible promise as the source of cells for many therapeutic strategies, including BAL systems. There are, however, distinct challenges that remain to be addressed: 1) stem cell (SC)-hepatocytes need to be differentiated at scale to achieve sufficient liver mass (~ 200 gr) to treat a patient, and 2) functionality of SC- hepatocytes needs to be improved to approach that of adult hepatocytes. Our project will take a step toward addressing these challenges by developing bioactive heparin-containing microcapsules that will carry hPSCs, will be loaded with growth factors for local and sustained delivery, and will enable high-density suspension cul- tures. Broader Impact: This project will enable scalable differentiation of hPSCs through the use of microencapsula- tion. Microcapsules will be used to deliver inductive cues for stem cell differentiation and will protect cells from mechanical damage in a stirred bioreactor. The use of microcapsules will allow us to increase the rate of oxygen and nutrient delivery to the cells and will enable higher density cultures. While the present project focuses on using encapsulated SC-hepatocytes in a BAL system, immunoisolation and other survival advantages offered by microcapsules will also enable future applications for cell transplantation.