Using pancreas tissue slices for in situ studies of islet of Langerhans and acinar cell biology.

Studies on the cellular function of the pancreas are typically performed in vitro on its isolated functional units, the endocrine islets of Langerhans and the exocrine acini. However, these approaches are hampered by preparation-induced changes of cell physiology and the lack of an intact surrounding. We present here a detailed protocol for the preparation of pancreas tissue slices. This procedure is less damaging to the tissue and faster than alternative approaches, and it enables the in situ study of pancreatic endocrine and exocrine cell physiology in a conserved environment. Pancreas tissue slices facilitate the investigation of cellular mechanisms underlying the function, pathology and interaction of the endocrine and exocrine components of the pancreas. We provide examples for several experimental applications of pancreas tissue slices to study various aspects of pancreas cell biology. Furthermore, we describe the preparation of human and porcine pancreas tissue slices for the validation and translation of research findings obtained in the mouse model. Preparation of pancreas tissue slices according to the protocol described here takes less than 45 min from tissue preparation to receipt of the first slices.

Mouse pancreas tissue slice culture facilitates long-term studies of exocrine and endocrine cell physiology in situ.

Studies on pancreatic cell physiology rely on the investigation of exocrine and endocrine cells in vitro. Particularly, in the case of the exocrine tissue these studies have suffered from a reduced functional viability of acinar cells in culture. As a result not only investigations on dispersed acinar cells and isolated acini were limited in their potential, but also prolonged studies on pancreatic exocrine and endocrine cells in an intact pancreatic tissue environment were unfeasible. To overcome these limitations, we aimed to establish a pancreas tissue slice culture platform to allow long-term studies on exocrine and endocrine cells in the intact pancreatic environment. Mouse pancreas tissue slice morphology was assessed to determine optimal long-term culture settings for intact pancreatic tissue. Utilizing optimized culture conditions, cell specificity and function of exocrine acinar cells and endocrine beta cells were characterized over a culture period of 7 days. We found pancreas tissue slices cultured under optimized conditions to have intact tissue specific morphology for the entire culture period. Amylase positive intact acini were present at all time points of culture and acinar cells displayed a typical strong cell polarity. Amylase release from pancreas tissue slices decreased during culture, but maintained the characteristic bell-shaped dose-response curve to increasing caerulein concentrations and a ca. 4-fold maximal over basal release. Additionally, endocrine beta cell viability and function was well preserved until the end of the observation period. Our results show that the tissue slice culture platform provides unprecedented maintenance of pancreatic tissue specific morphology and function over a culture period for at least 4 days and in part even up to 1 week. This analytical advancement now allows mid -to long-term studies on the cell biology of pancreatic disorder pathogenesis and therapy in an intact surrounding in situ.

NADPH oxidase and eNOS control cardiomyogenesis in mouse embryonic stem cells on ascorbic acid treatment.

Ascorbic acid (AA) increases cardiomyogenesis of embryonic stem (ES) cells. Herein we show that treatment of mouse ES cells with AA enhanced cardiac differentiation accompanied by an upregulation of the NADPH oxidase isoforms NOX2 and NOX4, phosphorylation of endothelial nitric oxide synthase (eNOS), and cyclic GMP (cGMP) formation, indicating that reactive oxygen species (ROS) as well as nitric oxide (NO) may be involved in cardiomyogenesis. In whole mount embryoid bodies as well as isolated Flk-1-positive (Flk-1(+)) cardiovascular progenitor cells ROS elevation by AA was observed in early stages of differentiation (Days 4-7), and absent at Day 10. In contrast NO generation following incubation with AA was absent at Day 4 and increased at Days 7 and 10. AA-mediated cardiomyogenesis was blunted by the NADPH oxidase inhibitors diphenylen iodonium (DPI) and apocynin, the free radical scavengers N-(2-mercaptopropionyl)-glycine (NMPG) and ebselen, and the NOS inhibitor L-NAME. Downregulation of NOX4 by short hairpin RNA (shRNA) resulted in significant inhibition of cardiomyogenesis and abolished the stimulation of MHC-ß and MLC2v gene expression observed on AA treatment. Our data demonstrate that AA stimulates cardiomyocyte differentiation from ES cells by signaling pathways that involve ROS generated at early stages and NO at late stages of cardiomyogenesis.