Almost total conversion of pancreas to liver in the adult rat: a reliable model to study transdifferentiation.

Study of transdifferentiation provides an excellent opportunity to investigate various factors and mechanisms involved in repression of activated genes and derepression of inactivated genes. Here we describe a highly reproducible in vivo model, in which hepatocytes are induced in the pancreas of adult rats that were maintained on copper-deficient diet containing a relatively non-toxic copper-chelating agent, triethylenetetramine tetrahydrochloride (0.6% w/w) for 7-9 weeks and then returned to normal rat chow. This dietary manipulation resulted in almost complete loss of pancreatic acinar cells at the end of copper-depletion regimen, and in the development of multiple foci of hepatocytes during recovery phase. In some animals, liver cells occupied more than 60% of pancreatic volume within 6-8 weeks of recovery. Northern blot analysis of total RNA obtained from the pancreas of these rats revealed the expression of albumin mRNA. Albumin was demonstrated in these pancreatic hepatocytes by immunofluorescence. The advantages of this model over the previously described models are: a) low mortality (10%), b) depletion of acinar cells, and c) development of multiple foci of hepatocytes in 100% of rats.