329 Reduced Expression of Nerve Growth Factor in Aging Gastric Mucosal Endothelial Cells - A New Key Mechanism for Impaired Angiogenesis in Aging Gastric Mucosa?

croscopy (CLE) is a novel tool that enables in-vivo histologic imaging by detection of fluorescence. An ultrathin CLE catheter probe that inserts into a 19G FNA needle now allows for Needle-based confocal laser endomicroscopy (nCLE). This study was aimed to determine feasibility of in vivo visualization of the innervation of porcine pancreas using endoscopic ultrasound guided nCLE and a fluorescent neuronal marker; and to determine pancreatic nerve cell expression of: nerve growth factor (NGF neurotrophic factor that promotes survival of neuronal cells), its high affinity receptor Trk A and melatonin receptor 1 (MR1). Methods. Studies were performed in anesthetized pigs. NeuroTrace (fluorescent neuronal marker) was injected into pancreas tail and body using endoscopic ultrasound guided 19G FNA needle, followed by nCLE in vivo imaging (Cellvizio AQ-Flex-19, Mauna Kea Technologies, Paris, France). Pigs were then euthanized and pancreatic specimens obtained for histology, ex-vivo immunostaining and molecular imaging. Studies: 1) nCLE image analysis, 2) quantitative histology and visualization of neuronal labeling under fluorescence, 3) immunostaining and quantification for NGF, its TrkA receptor and MR1 using specific antibodies. Results: nCLE imaging visualized an extensive network of intrapancreatic ganglia and nerves labeled with NeuroTrace. There was a higher density of neural elements in the body than the tail. On histologic sections examined under fluorescence microscope, in-vivo injected NeuroTrace was localized to the neural structures and nerves in pancreatic stromal tissue with features similar to those seen on nCLE. NGF was strongly expressed in intrapancreatic neuronal cells and nerves and was also expressed in epithelial cells of pancreatic acini and endothelial cells of blood vessels. TrkA was expressed in some neuronal cells and nerves distributed throughout the acini. MR1 was expressed in about 60% of ganglion cells and nerves and also in pancreatic acini. Quantitatively its expression was 2.5fold lower (p,0.01) compared to NGF. Conclusions: 1)This study showed feasibility of in vivo visualization of neuronal network in porcine pancreas nCLE. 2)The pancreatic neural network is extensive; numerous neuronal cells express NGF, Trk A and MTR1. 3)NGF and MR1 expression in epithelial acinar cells and endothelium of blood vessels, in addition to neural structures, indicates local interactions between neural, epithelial and vascular components of pancreas.