ALDEHYDE DEHYDROGENASE (ALDH) ACTIVITY: A NEW STRATEGY TO PURIFY LIVER PROGENITOR CELLS

Background/aims: Several liver dysfunctions are life-threatening conditions for which the most effective treatments rely on orthotropic liver transplantation (OLT). However, drawbacks related to OLT reduce its application on a large-scale. Recently, the role of progenitor cells in liver repair and fibrosis has been described but strategies for their purification have been quite limited making their characterization and use in regenerative medicine difficult. To address this issue, we developed a liver progenitor cell isolation strategy based on ALDH activity, a main feature shared by many progenitor cells.
Methods: High levels of ALDH activity have been proposed to be a common feature of progenitor cells (hematopoietic, neural and mesenchymal stem cells). Using a substrate specific for ALDH1A1 activity, we sort out the liver progenitor cells using a Flow Cytometry Activated Cell Sorter (FACS).
Results: In normal liver, the enzyme is expressed in some fibroblasts, bile duct cells and canals of Hering, whereas under injured conditions, these cells overexpress ALDH1A1. By flow cytometry, an ALDH+ cell population can been isolated which co-expresses numerous of markers typically found in Liver Progenitor Cells (LPCs); for instance, EpCAM, Prominin-1, CK-19, and ABCG2, shown by immunofluorescence, flow cytometry and RT-qPCR analyses. In cell culture, these cells can give rise to hepatocyte-like cells.
Conclusions: The isolation of functional LPCs based on ALDH activity offers a new straightforward strategy for their isolation. Since these cells are located in the canals of Hering and are activated during hepatic injuries, we established a new role of ALDH1A1 in LPC activation.