The liver has the ability to regenerate rapidly during acute liver injury by activating mature hepatocytes to divide and restore the damaged liver mass. In contrast, the liver relies on hepatic progenitor cells (HPCs) which have the ability to differentiate into both hepatocytes and biliary cells for regeneration during chronic liver injuries. Whole organ transplant is the most effective treatment for end stage liver diseases. However, there is a constant shortage of donor organs causing the death of many patients while waiting for suitable donor organs. HPC transplant is a potential alternative for whole organ transplant. However the isolation of HPC which is scarce in the liver and the expansion of these cells to a number that is suitable for transplant have been challenging. To investigate the plausibility of using HPCs as an alternative for liver transplant, I developed a protocol to isolate and expand HPC in vitro. Using this system, I investigated the complex hierarchy of HPCs in aid to select a defined population of HPC that is suitable for transplant. I found the EpCAM+ CD24+ population marks a naïve population of HPC that might be suitable for cell therapy. I further investigate the liver repopulating capacities of these cells by isolating EpCAM+CD24+ HPC population by Fluorescence Activated Cell Sorting (FACS) from a hepatocellular injury model. Surprisingly, a subpopulation of the EpCAM+ CD24+ HPCs which are also CD133+ possesses a higher colony forming capacities has been identified. Most importantly, this population can be expanded to a large scale in vitro and able to repopulate the injured liver after transplant. This defined population of HPCs can also be isolated from a mouse model of fatty liver disease and the isolated HPCs can be expanded in vitro. These cells are able to repopulate the liver after cell transplantation. The presence of HPCs that are capable of being isolated from the fatty liver proved the potential of using HPCs for transplant in a clinical setting by using cells isolated human fatty liver that are from rejected for transplant to overcome the shortage of donor organs.