Building hepatocytes a home: new frontiers in bioactive scaffolding techniques for liver tissue engineering

Abstract

Liver disease is one of the top five leading causes of premature death in the UK, with incidence rising sharply by 20% over the last decade, and mortality increasing over 400% since 1970. Liver disease incidence and mortality is rising in stark contrast to trends in the other top healthcare burdens, with stroke, cancer, heart disease and lung disease incidence and mortality rates plummeting and continuing to fall. Liver disease’s hallmark pathology of late diagnosis and rapid acute disease progression leads to an urgent need for donor organs; the only curative treatment for end stage liver disease. However, a chronic and ongoing shortage of suitable organs for transplant means many die before a donor liver can be found, and countless others live with severe, debilitating symptoms at a high cost to both the patient and the healthcare system. As part of the push for a solution to this problem, tissue engineers are focussing on creating niche microenvironments for hepatocytes which support their survival and function in as close to an in vivo like state as possible; addressing the need for an ideal in vitro model of the human liver and for lab created ‘organoids’ which could be used to treat patients. Such an environment would allow for the study of new pharmaceuticals, disease biology and hepatocyte behaviour in the laboratory and lead to more effective treatments for patients. While research to date is making inroads into this dilemma, we are yet to see a lab created environment which accurately recapitulates the complex, finely tuned and responsive extracellular matrix (ECM) of the liver. In an effort to address this, researchers have been incorporating bioactivity into scaffold environments for hepatocytes. This thesis presents three methods of incorporating bioactivity into scaffolds for liver tissue engineering; drug induced ECM biodecoration, synthetically derived ECM biodecoration and decellularized human liver ECM incorporation. Scaffolds were seeded with hepatocyte cells and their response to their microenvironment analysed. Mechanical characterisation and immunohistochemical analyses demonstrated the differences between the scaffold and the ECM biodecoration, as well as retention of ECM proteins through the manufacturing process. Each method altered the protein production and gene expression of hepatocytes, indicating that these methods provide a viable, translatable platform for creating a niche microenvironment for hepatocytes, supporting and manipulating phenotype and function. These scaffolds offer great potential for tissue engineering and regenerative medicine strategies for liver and a translatable method for other whole organ tissue engineering.