Enhanced rat islet function and survival in vitro using a biomimetic self-assembled nanomatrix gel.

Peptide amphiphile (PA) is a peptide-based biomaterial that can self-assemble into a nanostructured gel-like scaffold, mimicking the chemical and biological complexity of natural extracellular matrix. To evaluate the capacity of the PA scaffold to improve islet function and survival in vitro, rat islets were cultured in three different groups--(1) bare group: isolated rat islets cultured in a 12-well nontissue culture-treated plate; (2) insert group: isolated rat islets cultured in modified insert chambers; (3) nanomatrix group: isolated rat islets encapsulated within the PA nanomatrix gel and cultured in modified insert chambers. Over 14 days, both the bare and insert groups showed a marked decrease in insulin secretion, whereas the nanomatrix group maintained glucose-stimulated insulin secretion. Moreover, entire islets in the nanomatrix gel stained positive for dithizone up to 14 days, indicating better maintained glucose-stimulated insulin production. Fluorescein diacetate/propidium iodide staining results also verified necrosis in the bare and insert groups after 7 days, whereas the PA nanomatrix gel maintained islet viability after 14 days. Thus, these results demonstrate the potential of PAs as an intermediary scaffold for increasing the efficacy of pancreatic islet transplantation.

Adenovirus infection activates akt1 and induces cell proliferation in pancreatic islets1.

BACKGROUND: : Accumulated evidence has shown that insulin producing beta-cells in pancreatic islets have the limited potential to regenerate. Adenoviruses have been widely employed to deliver genes of interest into pancreatic islets. This study was aimed at investigating whether adenovirus infection has any impact on the potential of beta-cell proliferation. METHODS: : Human adenovirus type 5 (Ad5) encoding rat insulin promoter driven reporter genes were used to infect freshly isolated pancreatic islets. Western blotting assays were performed to evaluate the expression and activation of key molecules involved in cell survival and proliferation following Ad5 infection. Immunofluorescence staining was employed to identify proliferating cells after culturing the infected and control islets in the presence of BrdU, an analog of thymidine that can be incorporated into the genome of proliferating cells. RESULTS: : Ad5 infection of the islets resulted in expression and activation of Akt1, a key molecule in the PI3 kinase signaling pathway. Accordingly, a higher frequency of islet cell proliferation was detected in Ad5-infected islets than in control islets. DISCUSSION: : These data suggest adenovirus infection can activate beta-cell survival and proliferation machinery, in particular operating through the PI3K/Akt signaling pathway. This information has significant ramification for the use of adenovirus as a gene delivery vehicle for pancreatic islet cells.