In situ expansion of engineered human liver tissue in a mouse model of chronic liver disease

Abstract

In spite of the vast collective experience in tissue engineering, control of both tissue architecture and scale are fundamental translational roadblocks. An experimental framework that enables investigation into how architecture and scaling may be coupled is needed. Here, we introduce an approach called ‘SEEDs’ (‘in Situ Expansion of Engineered Devices’), in which we fabricate a structurally organized engineered tissue unit that expands in response to regenerative cues after implantation. We find that tissues containing pre-patterned human primary hepatocytes, endothelial cells, and stromal cells in degradable hydrogel expand over 50-fold over the course of 11 weeks in animals with liver injury, with concomitant increased function as characterized by the production of multiple human liver proteins. Histologically, we observe the emergence of stereotypical microstructure via coordinated growth of hepatocytes in close juxtaposition with a perfused, chimeric vasculature. Importantly, we demonstrate the utility of this platform for probing the impact of multicellular geometric architecture on tissue expansion in response to regenerative cues. This approach represents a hybrid strategy that harnesses both biology and engineering to deploy a limited cell mass more efficiently than either approach could do in isolation, and thus offers a new convergent paradigm for tissue engineering.

Deciphering the relative roles of matrix metalloproteinase‐ and plasmin‐mediated matrix degradation during capillary morphogenesis using engineered hydrogels

“…First, we investigated whether stromal‐cell‐dependent differences in the mechanism of proteolysis in fibrin hydrogels observed in angiogenesis models extended to a model of vasculogenesis. This model mimics vascularization strategies often deployed for tissue engineering applications that involve injection of populations of cells or pre‐patterned cell aggregates that organize into microvasculature. The phenotype and angiogenic potential of microvascular ECs and stromal cells vary widely according to their origin.…”

Heterotopic vascularization and functionalization of implantable bio engineered hepatic tissue alleviates liver injury in rats

“…Artificially synthesized materials are among the most interesting topics in researchers. For instance, Stevens et al organized engineered tissue in degradable fibrin hydrogel that expanded 50‐fold in animals with liver injury . However, they did not evaluate the immunological incompatibility of the hydrogel in vivo since they used immunosuppressed mice to keep the implanted xenogenic cells alive.…”

Ectopic expansion of engineered human liver tissue seeds using mature cell populations

“…The major concern is the growing number of patients in need of liver transplantation coupled with a stagnant donor supply. In a recent article in Science Translational Medicine , Stevens et al have generated a multicellular human “liver seed,” which, upon implantation into a mouse model of liver injury, could perform many functions of the human liver, including the ability to grow and self‐organize in response to regenerative cues from the host. Their work adds to the growing body of literature over the past three decades that has already demonstrated efficacy of a tissue engineering approach for treating liver disease …”

“…Summary of the theoretical approach proposed by Stevens et al to overcome the current limitations for patients with cirrhotic liver disease caused by shortage of cadaveric donor organs and inability of transplanted hepatocytes to engraft and proliferate in a cirrhotic liver. In vitro generation of structurally organized “SEEDs” was accomplished by tissue engineering to combine primary human hepatocytes, normal human dermal fibroblasts, and human umbilical vein endothelial cells.…”

“…In the current work, Stevens et al have taken liver tissue engineering using adult human cells a step further by demonstrating expansion of in vitro assembled liver tissue in vivo. (1) The core concept of their work was controlled and guided construction of a liver "tissue seed" consisting of human hepatocytes, dermal fibroblasts, and umbilical vein endothelial cells patterned in a fibrin hydrogel. To begin, hepatocytes and fibroblasts were aggregated together in defined sizes using microwell technology.…”