Clonal and territorial development of the pancreas as revealed by eGFP-labelled mouse chimeras.

The clonal structure of the pancreas was analysed in neonatal and adult mouse chimeras in which one partner displayed cell patches expressing green fluorescent protein (eGFP). Coherent growth during pancreatic histogenesis was suggested by the presence of large eGFP-labelled acinar clusters rather than a scattered distribution of individual labelled acinar cells. The adult chimeric pancreas contained monophenotypic acini, whereas surprisingly 5% of acini in neonates were polyclonal. Monophenotypic acini presumably arose by coherent expansion leading to large 3D patches and may not be monoclonal. Islets of Langerhans were oligoclonal at both ages investigated. The proportion of eGFP positive cells within islets did not correlate with that of the surrounding acinar tissue indicating clonal independence of islets from their neighbourhood. The patterns observed argue against a secondary contribution of blood-borne progenitor/stem cells to the acinar compartment during tissue turnover. The different clonal origins of acini and islets are integrated into a model of pancreatic histogenesis.