Short-term Stimulation Studies on Neonatal Pig Pancreatic Duct-derived Cell Monolayers

Repeated gene transfection impairs the engraftment of transplanted porcine neonatal pancreatic cells

BACKGROUND

Previously, we reported that neonatal porcine pancreatic cells transfected with hepatocyte growth factor (HGF) gene in an Epstein-Barr virus (EBV)-based plasmid (pEBVHGF) showed improved proliferation and differentiation compared to those of the control. In this study, we examined if pancreatic cells transfected repeatedly with pEBVHGF can be successfully grafted to control blood glucose in a diabetes mouse model.

METHODS

Neonatal porcine pancreatic cells were cultured as a monolayer and were transfected with pEBVHGF every other day for a total of three transfections. The transfected pancreatic cells were re-aggregated and transplanted into kidney capsules of diabetic nude mice or normal nude mice. Blood glucose level and body weight were measured every other day after transplantation. The engraftment of the transplanted cells and differentiation into beta cells were assessed using immunohistochemistry.

RESULTS

Re-aggregation of the pancreatic cells before transplantation improved engraftment of the cells and facilitated neovascularization of the graft. Right before transplantation, pancreatic cells that were transfected with pEBVHGF and then re-aggregated showed ductal cell marker expression. However, ductal cells disappeared and the cells underwent fibrosis in a diabetes mouse model two to five weeks after transplantation; these mice also did not show controlled blood glucose levels. Furthermore, pancreatic cells transplanted into nude mice with normal blood glucose showed poor graft survival regardless of the type of transfected plasmid (pCEP4, pHGF, or pEBVHGF).

CONCLUSION

For clinical application of transfected neonatal porcine pancreatic cells, further studies are required to develop methods of overcoming the damage for the cells caused by repeated transfection and to re-aggregate them into islet-like structures.

Neonatal pig liver-derived progenitors for insulin-producing cells: an in vitro study

Beta (beta)-cell replacement represents an attractive approach for the possible cure of type 1 insulin-dependent diabetes mellitus (IDDM). In a search for potential sources of insulin-secreting cells for IDDM substitution therapy, we have focused on the neonatal pig liver, which is putatively enriched in multipotent stem cells. We then isolated cells measuring 10 to 15 microm in diameter, identified as small cells, characterized by a high proliferation rate and positive staining for immature liver and pancreatic endocrine cell markers (i.e., insulin and pancreatic duodenal homeobox). The ability of these cells to transdifferentiate into pancreatic beta-like cells under culture conditions with exendin-4 (Ex-4) or high glucose concentration was examined. We observed that insulin secretion was not physiological in basal conditions, although it became responsive to glucose after 5 days of exposure to Ex-4. This beta-cell-like phenotype remained physiologically stable, even after stimulus withdrawal. Based on these observations, we contend that the proposed cell and tissue model might offer several advantages as a candidate for substitution cell therapy in IDDM, because the neonatal pig liver seems enriched in cells, with a mixed pancreas-liver phenotype, that are easier to purify and grow in culture and are more functional than other beta-like cells upon in vitro single short-term stimulation challenge.

Is pancreatic diabetes (type 3c diabetes) underdiagnosed and misdiagnosed?

Exocrine pancreatic insufficiency is frequently associated with diabetes, with high prevalence in both insulin-dependent or insulin-independent patients. Exocrine pancreatic failure has often been perceived as a complication of diabetes. In contrast, recent clinical observations lead to the notion that nonendocrine pancreatic disease is a critical factor for development rather than a sequel to diabetes. The incidence of diabetes caused by exocrine pancreatic disease appears to be underestimated and may comprise 8% or more of the general diabetic patient population. Nonendocrine pancreas disease can cause diabetes by multiple mechanisms. Genetic defects have been characterized, resulting in a syndrome of both exocrine and endocrine failure. Regulation of beta-cell mass and physiological incretin secretion are directly dependent on normal exocrine function. Algorithms for diagnosis and therapy of diabetes should therefore address both endocrine and exocrine pancreatic function.

Stem cells therapy for type 1 diabetes

In this article, we have reviewed the developments of studies of stem cells therapy for type 1 diabetes since this century. Review of the literature was based on computer searches (PubMed) and our studies. Type 1 diabetes can now be ameliorated by islet transplantation, but this treatment is restricted by the scarcity of islet tissue. Hopes for a limitless supply of a substitute for primary islets of Langerhans and progress in stem cell biology have led to research into the feasibility of stem/progenitor cells to generate insulin-producing cells to use in replacement therapies for diabetes. An increasing body of evidence indicated that, in addition to embryonic stem cells, several potential adult stem/progenitor cells, derived from pancreas, liver, spleen, and bone marrow could differentiate into insulin-producing cells in vitro or in vivo. However, significant controversy currently exists in this field. Moreover, safe suppression of autoimmunity or specific tolerance to auto-antigens for patients with type 1 diabetes must be achieved before this promising new technology can lead to a great progress in clinical practice. To prevent type 1 diabetes through genetic engineering of hematopoietic stem cells represents another new strategy. Much basic research is still required.

Long-term cultured neonatal porcine islet cell monolayers: a potential tissue source for transplant in diabetes

BACKGROUND

The restricted availability of cadaveric human donor pancreases mandates validation of possibly inexhaustible, alternative sources of insulin secretory cells in order to expand islet transplant for the therapy of insulin dependent diabetes mellitus (T1DM).

METHODS

Neonatal pig pancreatic islets (NPI), isolated and purified by our method, were specially cultured until confluent cell monolayers were obtained. Expression of several beta-cell phenotype transcriptional factors, under glucose and other stimuli, were examined throughout 90 days of culture.

RESULTS

High glucose concentration and glucagon-like peptide 1 (GLP-1) were associated with maintenance either of insulin secretory patterns from the incubated cell monolayers, or expression of transcriptional markers associated with beta-cell like phenotypes.

CONCLUSION

Morphological and molecular expression of beta-cell markers and products from NPI cell monolayers seem to identify a novel and potentially powerful source of insulin producing cells that might fulfill transplant needs for insulin substitution therapy.