Beta Cell Count Instead of Beta Cell Mass to Assess and Localize Growth in Beta Cell Population following Pancreatic Duct Ligation in Mice

BACKGROUND Pancreatic-tail duct ligation (PDL) in adult rodents has been reported to induce beta cell generation and increase beta cell mass but increases in beta cell number have not been demonstrated. This study examines whether PDL increases beta cell number and whether this is caused by neogenesis of small clusters and/or their growth to larger aggregates. METHODOLOGY Total beta cell number and its distribution over small (<50 µm), medium, large (>100 µm) clusters was determined in pancreatic tails of 10-week-old mice, 2 weeks after PDL or sham. PRINCIPAL FINDINGS PDL increased total beta cell mass but not total beta cell number. It induced neogenesis of small beta cell clusters (2.2-fold higher number) which contained a higher percent proliferating beta cells (1.9% Ki67+cells) than sham tails (<0.2%); their higher beta cell number represented <5% of total beta cell number and was associated with a similar increase in alpha cell number. It is unknown whether the regenerative process is causally related to the inflammatory infiltration in PDL-tails. Human pancreases with inflammatory infiltration also exhibited activation of proliferation in small beta cell clusters. CONCLUSIONS/SIGNIFICANCE The PDL model illustrates the advantage of direct beta cell counts over beta cell mass measurements when assessing and localizing beta cell regeneration in the pancreas. It demonstrates the ability of the adult mouse pancreas for neogenesis of small beta cell clusters with activated beta cell proliferation. Further studies should investigate conditions under which neoformed small beta cell clusters grow to larger aggregates and hence to higher total beta cell numbers.