The liver has an extensive regenerative capacity that can be leveraged in gene therapy to treat genetic liver metabolic disorders as well as diseases like hemophilia, which leads to defective coagulation. For example, Adeno Associated Viral (AAV) vectors are employed in commercially available therapies to deliver the functional copy of a coagulation factor gene in adults suffering from hemophilia. However, AAV vectors do not stably integrate into the recipient genome, thus the delivered gene copy does not persist in proliferative cells like hepatocytes, which keep dividing, to a certain extent, in homeostasis as well as upon hepatic damage.

Besides hepatocytes, cholangiocytes, also named biliary epithelial cells (BEC), can support liver regeneration. BEC are self-renewing, facultative stem cells that supply hepatocyte proliferation when this is impaired, but little is known about BEC heterogeneity and proliferative potential in the homeostatic liver, in the absence of tissue damage.

THE STUDY

The laboratory of Alessio Cantore, group leader in the Liver Gene Therapy unit at the San Raffaele Telethon Institute for Gene Therapy, has tested the efficiency and stability of lentiviral vectors (LV) for gene transfer to cholangiocytes of mice and in vitro models Differently than AAV vectors, LV gene cargo integrates into the recipient genome, thus providing a stable delivery of gene copies that are maintained across cell proliferation. This can be particularly advantageous in stably correcting inherited genetic diseases of the liver early in life, with a single administration, to prevent disease progression.

The results of the study, which has just been published in Cell Reports, show that LV-mediated gene transfer preferentially targets a subset of BEC that has a low clonogenic potential in vitro and shows a more hepatocyte-like gene expression profile in the homeostatic liver. The study provides the first evidence of BEC heterogeneity present in the liver of mice at steady state. LV-transduced BEC show less proliferation, and a more hepatocyte-committed (higher expression of Albumin and Hepatocyte Nuclear Factor 4α genes) phenotype as compared to untransduced BEC at steady state. Moreover, this BEC subset shows a transcriptional network orchestrated by the Hepatocyte Nuclear Factor 4α. Finally, identified LV-transduced cholangiocytes proliferate upon liver damage in mice, thus triggering a successful regenerative response also upon injury.

“I’m confident that this study will strengthen the concept that LV may correct inherited metabolic diseases of the liver, especially in the early phases of life, since they may deliver permanent genetic correction also upon liver injury and repair. In this context, the identification of a selective BEC subset which is highly permissive to LV-mediated gene transfer represents a promising strategy for permanent genetic correction”, comments Doctor Cantore.

In this context, he has also recently received the prestigious ERC Consolidator Grant to assess the efficacy, safety and stability of different genetic engineering strategies during early stages of life to treat genetic diseases of liver metabolism. Doctor Cantore is also a scientific co-founder of GeneSpire, an innovative Start-up company aimed to develop liver-directed gene therapy with engineered lentiviral vectors for inherited metabolic diseases.