Expression of growth factors in a pancreatic islet regeneration model.

In this model of pancreatic regeneration, the initial trophic effect of cellophane wrapping is upon the ductular-epithelium, as shown by autoradiographic analysis following a single pulse of 3H-TdR. The uptake of 3H-TdR by ductular cells is maximal approximately 4 weeks before the peak uptake of the label by islet cells. Six weeks after the pulse, most of the label is contained in differentiating islet cells, not ductular cells. This phenomenon suggests that wrapping of the pancreas induces "progenitor" cells to differentiate along the line of endocrine cells. The essentially negative observations on REG gene expression in the regenerating hamster pancreas indicate that the message for this gene is either not involved in the regeneration process or that it is sufficiently different from the rat gene (a rat control probe was used) that it precludes detection by our methodology. It might be necessary therefore, to generate a hamster REG specific probe in order to further study this issue. In conclusion, the established model of cellophane wrapping of the pancreas provides a useful tool whereby the induced growth of beta-cells can be observed. The sequence appears to be initial stimulation of ductal cells followed by islet differentiation. Of the candidate genes, it appears that reg does not participate in the process. We will however, examine other candidate genes to elucidate the mechanism whereby celophane wrapping induces growth of beta-cells.