Immunohistochemical characterization of pancreatic duodenal homeobox protein-1, neurogenin-3, and insulin protein expressions in islet-mesenchymal cell in vitro: a morphochronological evaluation.

Abstract

Objective(s): The use of a co-culture of islets with mesenchymal stromal cells (MSCs) is a promising therapy in islet transplantation to revert hyperglycaemia, but the resulting insulin-producing cells (IPCs) express low levels of pancreas endocrine developmental genes. This study aims to investigate the morphochronology of a co-culture of islets with MSCs from injured adult pancreata, and characterize pancreatic duodenal homeobox protein-1 (Pdx1), neurogenin-3 (Ngn3) and insulin protein expressions to establish the fate of their interaction. Materials and Methods: Islets and MSCs were isolated from sham operated control (SOC) and duct-ligated (PPDL) pancreata. Islets from SOC or PPDL tissues were cultured with or without MSCs in RPMI1640, supplemented by 1% Penicillin-Streptomycin, and maintained at 37 °C±1 °C at 95% relative humidity and 95% /5% air/CO2. Pdx1, Ngn3 and insulin expressions were determined by immunohistochemistry and islet morphochronological changes were assessed. Results: Pdx1 was expressed in all islet-cell cultures with or without MSCs. Pdx1+ islet cells were significantly increased in the presence of MSCs compared to the islet culture without MSCs. Similarly, Ngn3 was highly expressed in all cultures with MSCs from both SOC and PPDL tissues and the expression was prolonged in cultures using PPDL tissues before it was down-regulated, thereby, extending the period of Ngn3+ cell expansion and differentiation into mature functional islets. Conclusion: In vitro, MSCs maintain a pool of Ngn3+ that contributes to insulin production from mature beta cells but the activation of insulin production from non-beta cells may not be induced by direct signals from MSCs.