Islet B cell neoproliferation in early low dose streptozocin induced diabetes in mice: a ducto-endocrine proliferation?

Several authors have documented cases of newly forming B cells from ductules of diabetic animals in their studies but few have enlarged on this phenomenon. We, therefore, diabetized 15 mice, with low dose injections of streptozocin (STZ) for 5 days, and observed their pancreatic islets 6 (group 1) and 14 (group 2) days after the last STZ injection in order to further the argument. We found that: i) mice without infiltration of their islets did not present any newly formed B cells; ii) mice belonging to group one, showing a mild or scarce lymphomonocytic infiltration, had a few (one or two) newly formed B cells; iii) mice belonging to group two, showing a massive islet infiltration, had two to three neoformed B cells; iv) we observed in one animal intact newly formed islets of Langerhans with a clearly observable ductule within each of them, as in a case of nesidioblastosis. All these neoformations occurred in animals with very low insulin levels. Morphometric evaluations did not show any significant modification in the number of D cells in group one animals when compared to control D cell numbers, but showed an increase in group two animals. We believe that the formation of these newly formed B cells, that might be named "ducto-endocrine proliferation", is an attempt to compensate for the loss of B cells at the onset of the diabetic syndrome.