Euthanasia treatment having been provided for a few individuals. All experiments followed the Mulberroside A tenets and regulations of the Declaration of Helsinki, Cartagena protocol, and the pet experimental guidelines of Sapporo Medical University, and were performed with approvals from the Animal Treatment and the Institutional Ethics Committees of Sapporo Medical University. == Partial pancreatectomy == Partial pancreatectomy on SD rat was performed under systemic anesthesia, using a Gemini Cautery kit and a swab as described earlier by Lehv et al [1], paying particular attention to avoid any damage to communicating vessels. == Pancreatic stellate Mulberroside A cells == Isolation of pancreatic stellate cells (PSCs) was performed, essentially based on the method by Apte et al. duodenal areas with normal pancreatic features. After PX, BrdU uptake of acinar cells and islet cells significantly increased, but was suppressed by treatment with VA-lip siRNA HSP47. BrdU uptake by acinar cells was augmented by co-culturing with aPSCs and the augmentation was nullified by siRNA HSP47. BrdU uptake by progenitor cells in foci area was slightly enhanced by the same treatment. New area which exhibited intermediate features between those of duodenal and area of foci, emerged after the treatment. == Conclusion == aPSCs play a crucial role in regeneration of remnant pancreas, proliferation of acinar and islet cells after PX through the activity of secreted collagen. Characterization of new area emerged by siRNA HSP47 treatment as to its origin is a future task. == Introduction == Evidence offers accumulated indicating that the adult adult pancreas is capable of undergoing regeneration, similar to the liver, although to a lesser [1, 2] extent. In animals, mechanisms underlying this pancreatic regeneration imply; 1)neogenesis, which includes differentiation of progenitor cells to adult cellular components [311], or trans-differentiation of adult cells into other adult cell types; conversion Mulberroside A of acinar cells to cells orcell to cell, and 2) self-replication of pre-existing exocrine [12] and /or endocrine [13, 14] cells. Such diversity in proposed mechanisms may be due to differences in experimental models or methodologies employed. In a model such as one that total acinar and cell loss was induced by diphtheria toxin[6, 11], proof of self- replication of these cells was practically limited, and neogenesis could be the predominant mechanism. In much less harsh models such as partial pancreatectomy [3, 8, 12, 13] or pancreatic duct ligation [4, 5, 10, 14], not only neogenesis from stem cell foci which are characterized by a number of tubule-like cells within massively deposited extracellular matrix (ECM) [3, 8] but also self-replication of remnant mature cells could readily take place. Further, in most of these animal experiments implications from the results with regard to the mechanism of regeneration could vary depending upon the markers chosen and timing of forced gene expression because lineage tracing methods utilizing cell type specific markers [5, 12, 14] were generally applied in these experiments to follow the conversion of cells. Regardless of these discrepancies in mechanisms, numerous experiments conducted so far in animals, with no exception, assured plasticity and regeneration of both exocrine and endocrine cells in pancreas. In humans, however , evidence intended for regeneration of endocrine components has been vague, albeit a small body of circumstantial evidence based on the observation of surgically Mouse monoclonal to LSD1/AOF2 resected pancreas suggested self replication of -cells [15, 16] or new -cell formation [17]. In contrast, histological and functional recovery of exocrine components were definitively confirmed by long term observation of two consecutive pancreatectomy cases [16] and by histological analysis of double biopsied specimens, before and after the steroid therapy intended for autoimmune pancreatitis[18]. Nonetheless, in both animals and humans, investigations were mainly focused on the sources of cells which underwent regeneration, and little continues to be studied on the molecular mechanisms by which regeneration is triggered by extracellular stimuli although intracellular genetic events, expression of transcription factors which facilitate neogenesis, have been explored [19, 20]. With regard to humoral factor(s) which may regulate regeneration of pancreas, most of the efforts were made to identify cell proliferating substances [21] with no direct evidence of their activity during the recovery phase from tissue damage in vivo, and the molecular mechanisms of exocrine cell proliferation has been inadequately investigated. Further inter-cellular networks which may regulate mature cell proliferation or neogenesis have not been adressed extensively. Stellate cells were first identified as vitamin A storing star-shaped cells in the liver and subsequently were found to be distributed essentially to all organs, including pancreas [22]. When activated by inflammation with tissue damage, they proliferate and secrete collagen [22]. We have previously.