Islet-cell regeneration in the diabetic hamster pancreas with restoration of normoglycaemia can be induced by a local growth factor(s)

Abstract

Partial pancreatic duct obstruction in the hamster leads to the induction of endocrine-cell differentiation and new islet formation. We prepared cytosolic extracts from the partially obstructed pancreas and identified one, which when administered i.p., produced significant increases in the incorporation of tritiated thymidine by ductular and islet cells, as well as a corresponding increase in islet mass. In this study, we evaluate the ability of this extract to reverse streptozotocin diabetes mellitus. Hamsters were treated i.p. twice daily for 7 weeks with either 0.9% NaCl (saline) (n = 10) or a cytosol extract (n = 10) prepared previously from partially obstructed hamster pancreata. All animals in the cytosol group survived vs only 60% of the saline group (p = 0.02). Random blood glucose levels were greater than 22.2 mmol/l in 90% of the saline group vs 40% in the cytosol group (p < 0.05). Pancreatic tissue from the surviving saline animals and from persistently hyperglycaemic cytosol-treated animals, showed intra-cytoplasmic vacuolation of islet cells, a characteristic lesion of sustained hyperglycaemic states. Vacuolation was not observed in normoglycaemic extract treated animals. Islets in hyperglycaemic animals demonstrated a profound decrease or absence of immunoreactive insulin, compared to an abundance of immunoreactive beta cells in cytosol-treated animals that reverted to normoglycaemia. In this group, single cells or nests of cells stained for insulin on glucagon cells were identified in ductal epithelium in association with cells budding from the duct. Morphometric analysis of pancreata in reverted cytosol-treated animals showed a new population of small islets compared with saline controls and an increased islet mass. In summary, streptozotocin diabetes can be reversed by new islet formation induced by local pancreatic growth factors, the exact nature of which remains to be determined.

The Role of Reg Proteins in Pancreatic Regeneration

“…Reg1-induced increase in β-cell proliferation was shown by an increase in [3H]-thymidine uptake in both rat islets grown in culture with Reg1 protein supplied in the culture medium and in islets isolated from transgenic mice overexpressing human REG1α protein specifically in the β-cells [33]. These data were supported by a paper reporting a reduced proliferation of pancreatic β-cells in Reg1 knockout mice [34]. Reg1-induced increase in β-cell mass have been demonstrated by a 2 month long intrapertioneal (IP) injection study of Reg1 in 90% pancreatectomized rats.…”

“…While β-cell replication is the best supported mechanism to account for islet regeneration in rodents, human β-cells only possess a limited capacity to replicate, and in both human and rodents the capacity declines with age [28]. This could suggest that neogenesis might be the most common mechanism to drive endogenous formation of β-cells in the human pancreas, and observations of single cells and small insulin positive clusters found near the ducts in human pancreas is suggestive for progenitor cells residing in 2 Alloxan treatment selectively destroys insulin-producing cells in the pancreas when administered to rodents and thereby induce pancreatic regeneration [29][30][31][32][33][34]. However, this is only speculation.…”

Differentiation of Affinity-Purified Human Pancreatic Duct Cells to β-Cells

“…A possible solution is to generate insulin-producing cells from adult stem/progenitor cells of the pancreas. In vivo new ␤-cells are generated through replication of preexisting ␤-cells and neogenesis, the latter from differentiation of non-hormone-expressing progenitor cells (1)(2)(3)(4)(5)(6)(7)(8). Putative adult stem/progenitor cells from mouse pancreas have been expanded clonally and after manipulation were found to express low levels of insulin and other pancreatic markers (9,10).…”

Recombinant human betacellulin promotes the neogenesis of beta-cells and ameliorates glucose intolerance in mice with diabetes induced by selective alloxan perfusion.

“…However, proliferation of preexisting ␤-cells and differentiation of ␤-cells from precursor cells, mainly residing in the pancreatic duct lining, have been demonstrated in some animal models (1)(2)(3)(4)(5). Recently, we developed a new mouse model of diabetes induced by selective perfusion of alloxan (100 µg/g body wt) during the clamping of the superior mesenteric artery (1).…”