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StellaTUM: current consensus and discussion on pancreatic stellate cell research

The field of pancreatic stellate cell (PSC) biology is very young, as the essential in-vitro tools to study these cells (ie, methods to isolate and culture PSC) were only developed as recently as in 1998. Nonetheless, there has been an exponential increase in research output in this field over the past decade, with numerous research groups around the world focusing their energies into elucidating the biology and function of these cells. It is now well established that PSC are responsible for producing the stromal reaction (fibrosis) of two major diseases of the pancreas—chronic pancreatitis and pancreatic cancer. Despite exponentially increasing data, the methods for studying PSC remain variable. Although within individual laboratories methods are consistent, different methodologies used by various research groups make it difficult to compare results and conclusions. This article is not a review article on the functions of PSC. Instead, members of the Pancreatic Star Alliance (http://www.pancreaticstaralliance.com) discuss here and consolidate current knowledge, to outline and delineate areas of consensus or otherwise (eg, with regard to methodological approaches) and, more importantly, to identify essential directions for future research. Hepatic stellate cells (HSC) were first described by Karl von Kupffer in 1876; however, similar cells in the pancreas were first observed in the 1980s.1–3 In 1998, Apte et al 4 and Bachem et al 5 isolated and cultured PSC.4 5 In the normal pancreas, PSC are located in close proximity to the basal aspect of pancreatic acinar cells. In sections immunostained for the marker desmin (a cytoskeletal protein), quiescent PSC can be seen as cells with a central cell body and long cytoplasmic projections extending along the base of adjacent acinar cells similar to that of pericytes in the mammary gland. …

Fibrosis of the pancreas: the initial tissue damage and the resulting pattern.

Fibrosis in the pancreas is caused by such processes as necrosis/apoptosis, inflammation or duct obstruction. The initial event that induces fibrogenesis in the pancreas is an injury that may involve the interstitial mesenchymal cells, the duct cells and/or the acinar cells. Damage to any one of these tissue compartments of the pancreas is associated with cytokine-triggered transformation of resident fibroblasts/pancreatic stellate cells into myofibroblasts and the subsequent production and deposition of extracellular matrix. Depending on the site of injury in the pancreas and the involved tissue compartment, predominantly inter(peri)lobular fibrosis (as in alcoholic chronic pancreatitis), periductal fibrosis (as in hereditary pancreatitis), periductal and interlobular fibrosis (as in autoimmune pancreatitis) or diffuse inter- and intralobular fibrosis (as in obstructive chronic pancreatitis) develops.

Pancreatic fibrosis associated with age and ductal papillary hyperplasia

Little is known about the frequency, type and pathogenesis of fibrotic changes that may occur in the pancreas of persons without any clinically apparent or macroscopically visible pancreatic disease. We screened pancreas specimens for the presence and pattern of fibrosis, determined the relationship between fibrosis, age, and duct lesions, and studied the fibrogenic mechanisms. In 89 postmortem specimens from persons without any known pancreatic disease (age range 20–86 years), fibrosis was recorded and graded and the patients were divided into two age classes (younger or older than 60 years). In addition, we analyzed the association between ductal papillary hyperplasia [i.e., pancreatic intraepithelial neoplasia type 1B (PanIN-1B)] and fibrotic foci in the pancreatic tissue to determine the potential impact of obliterating duct lesions on pancreatic fibrosis. Finally, we studied the occurrence in the pancreas of myofibroblasts, identified on the basis of their α-SMA and desmin positivity, and determined their relationship to the fibrotic foci. Thirty-eight (44%) of 89 pancreata showed scattered foci of lobular fibrosis affecting peripheral lobuli. Fibrotic changes were significantly more common in individuals older than 60 years. Fibrotic foci were commonly associated (p<0.05) with ductal papillary hyperplasia in ducts draining fibrotic lobuli. Myofibroblasts were detected in the fibrotic foci. The “normal” pancreas develops a specific type of focally accentuated fibrosis that is highly age related. This patchy lobular fibrosis in the elderly (PLFE) was closely associated with PanIN-1B lesions in the ducts, suggesting that the narrowing of a duct due to papillary hyperplasia of the epithelium may hamper secretion and cause fibrosis of the drained lobule. The presence of myofibroblasts in association with the fibrotic foci indicates an ongoing fibrogenic process.

Pain in chronic pancreatitis: the role of neuropathic pain mechanisms

Pain mechanisms in patients with chronic pancreatitis are incompletely understood and probably multifactorial. Recently, evidence from experimental human pain research has indicated that in many of these patients pain processing in the central nervous system is abnormal and mimics that seen in neuropathic pain disorders. The current review focuses on several lines of evidence supporting this hypothesis. Hence, the spontaneous and postprandial pain in chronic pancreatitis may reflect the characteristic pain features seen in patients with neuropathic pain. Biochemical and histopathological findings in tissues from patients with chronic pancreatitis are similar to those observed in patients with other nerve fibre lesions. Experimental studies have shown that patients with chronic pancreatitis show signs of spinal hyper-excitability counter-balanced by segmental and descending inhibition. Changes in the brain with cortical reorganisation to gut stimulation and increased activity in specific electroencephalographic features characteristic for neuropathic pain are also seen in patients with chronic pancreatitis. Finally, principles involved in the treatment of pancreatic pain have many similarities with those recommended in neuropathic pain disorders. In conclusion, a mechanism-based understanding of pain in chronic pancreatitis may have important implications for the treatment.

Diagnosis of autoimmune pancreatitis by core needle biopsy: application of six microscopic criteria

Autoimmune pancreatitis (AIP) has been established as a special entity of chronic pancreatitis (CP). However, its clinical distinction from pancreatic cancer and other types of CP is still difficult. The aim of this study was to evaluate the efficacy of pancreatic core needle biopsy for the diagnosis of AIP. In 44 core needle biopsy specimens, we assessed the following microscopic features: granulocytic epithelial lesions (GELs), more than ten IgG4-positive plasma cells/HPF, more than ten eosinophilic granulocytes/HPF, cellular fibrosis with inflammation, lymphoplasmacytic infiltration, and venulitis. All biopsies that showed four or more of the six features (22 of 44) were obtained from 21 of 26 patients whose clinical diagnosis and follow-up were consistent with AIP. All non-AIP CP patients (n = 14) showed three or less than three of the features in their biopsies. GELs were only observed in biopsy specimens from AIP patients. In conclusion, our data indicate that the six criteria we applied were able to recognize AIP in 76% of biopsy specimens using a cut-off level of four. When the specimens that revealed only three features but showed GELs were added, the sensitivity rose to 86%. Pancreatic core needle biopsy can therefore make a significant contribution to the diagnosis of AIP.

Autoimmune pancreatitis: the clinicopathological characteristics of the subtype with granulocytic epithelial lesions

Autoimmune pancreatitis (AIP) has been established as a distinct form of chronic pancreatitis that is distinguishable from other types such as alcoholic, hereditary or obstructive chronic pancreatitis. AIP seems to be a global disease, since it has been reported in many different countries, especially from Japan, USA and Europe (Germany, Italy, United Kingdom). Typical histopathological findings in the pancreas in AIP include a periductal lymphoplasmacytic infiltration with fibrosis, causing narrowing of the involved ducts. The typical clinical features include presentation with obstructive jaundice/pancreatic mass and a dramatic response to steroids. However, while the reports from Japan describe uniform changes called lymphoplasmacytic sclerosing pancreatitis (LPSP) in the pancreas from AIP patients, the reports from Europe and USA distinguish two histopathologic patterns in AIP patients: one with the characteristics of LPSP and another with slightly different histological features, called idiopathic duct centric pancreatitis (IDCP) or AIP with granulocytic epithelial lesions (GELs). This article reviews the evidence that GEL-positive AIP or IDCP is a second type of AIP, distinct from LPSP, in regard to pancreatic pathology, immunology and epidemiology.

Autoimmune pancreatitis: expression and cellular source of profibrotic cytokines and their receptors.

Chronic pancreatitis is a fibrogenic disease. In autoimmune pancreatitis (AIP), a lymphoplasmacytic infiltration is followed by fibrosis. In vitro it has been shown that pancreatic stellate cells are transformed into proliferating myofibroblasts mainly by transforming growth factor β (TGF-β) and platelet-derived growth factor (PDGF). We studied the expression of these profibrotic cytokines, their receptors, and their cellular sources in AIP. Pancreatic tissues from 21 patients with AIP of different grades of severity were selected from a series of 52 AIP cases. Myofibroblasts (ie, activated pancreatic stellate cells), macrophages, lymphocytes, plasma cells, and the cytokines latency-associated peptide, a TGF-β1 propeptide, TGF-β receptor II (TGF-β-RII), PDGF-B, and the α and β isoforms of the PDGF receptor (PDGF-Rα and PDGF-Rβ) were identified immunohistochemically. Their expression and cellular distribution were related to the severity of AIP. In grade 1 and 2 AIP, macrophages and myofibroblasts expressing profibrotic cytokines and their receptors were found in periductal areas showing lymphoplasmacytic inflammation. In grade 3 AIP, there were numerous macrophages, myofibroblasts, and epithelial cells which were positive for latency-associated peptide, PDGF-B, TGF-β-RII, PDGF-Rα, and PDGF-Rβ not only in periductal, but also in interlobular and intralobular areas. In grade 4 AIP, which is characterized by advanced fibrosis, cellularity and expression of cytokines and their receptors were greatly reduced. Our data indicate that in AIP the occurrence of myofibroblasts is intimately related to the presence of macrophages and lymphoplasmacytic cells. These cells and adjacent epithelial cells express profibrotic cytokines and their receptors, which are probably responsible for the initiation and maintenance of the fibrogenic process.

Key players in pancreatic cancer-stroma interaction: Cancer-associated fibroblasts, endothelial and inflammatory cells

Pancreatic cancer (PC) is the most aggressive type of common cancers, and in 2014, nearly 40000 patients died from the disease in the United States. Pancreatic ductal adenocarcinoma, which accounts for the majority of PC cases, is characterized by an intense stromal desmoplastic reaction surrounding the cancer cells. Cancer-associated fibroblasts (CAFs) are the main effector cells in the desmoplastic reaction, and pancreatic stellate cells are the most important source of CAFs. However, other important components of the PC stroma are inflammatory cells and endothelial cells. The aim of this review is to describe the complex interplay between PC cells and the cellular and non-cellular components of the tumour stroma. Published data have indicated that the desmoplastic stroma protects PC cells against chemotherapy and radiation therapy and that it might promote the proliferation and migration of PC cells. However, in animal studies, experimental depletion of the desmoplastic stroma and CAFs has led to more aggressive cancers. Hence, the precise role of the tumour stroma in PC remains to be elucidated. However, it is likely that a context-dependent therapeutic modification, rather than pure depletion, of the PC stroma holds potential for the development of new treatment strategies for PC patients.

Fibrogenesis in alcoholic chronic pancreatitis: the role of tissue necrosis, macrophages, myofibroblasts and cytokines

Myofibroblasts and cytokines such as transforming growth factor-β1 (TGF-β1) and platelet-derived growth factor (PDGF)-B have been found to play an important role in pancreatitis-associated fibrogenesis. It is still unclear, however, where in the inflamed pancreas and when these fibrogenic cells and cytokines can be detected. In this study we examined pancreatic tissue from patients with alcoholic chronic pancreatitis to determine the localization and distribution of myofibroblasts and the expression of cytokines in relation to the tissue damage and the activity of the inflammatory process. In tissue from pancreatic specimens from 59 patients with alcoholic chronic pancreatitis the inflammatory process was histologically staged. Myofibroblasts and the cytokines latency-associated peptide, a TGF-β propeptide, TGF-β receptor II, PDGF-B and the α-isoform of the PDGF receptor were immunohistochemically identified in 10 selected cases representing the four defined stages of alcoholic chronic pancreatitis. In stage I, the stage with overt tissue injury, myofibroblasts were numerous and especially associated with macrophages around areas of necrosis. In stage II, the stage with cellular fibrosis, myofibroblasts were the main component of the interlobular tissue. In stage III, the stage with dense fibrosis, myofibroblasts were rare, and in stage IV, when calculi were present, myofibroblasts were only detected adjacent to duct ulcerations caused by calculi. Latency-associated peptide and TGF-β receptor II as well as PDGF-B and PDGF receptor-α were mainly expressed by macrophages, myofibroblasts and epithelial cells in stages I and II. The results suggest that the fibrogenic process in alcoholic chronic pancreatitis is initiated by a cytokine-based interplay of macrophages and myofibroblasts that follows tissue injury.

Clinical features and relapse rates after surgery in type 1 autoimmune pancreatitis differ from type 2: A study of 114 surgically treated European patients

BACKGROUND At the recent consensus conference on autoimmune pancreatitis (AIP) in Honolulu, we presented preliminary data from our study of surgically treated AIP patients. Our data strongly supported the separation of AIP into type 1 and type 2. Our study is based on a total of 114 surgically treated European AIP patients. Our aims were to elucidate serum IgG4 elevation, other organ involvement, relapse of disease, steroid treatment and diabetes after surgery in 114 surgically treated European AIP patients. METHODS 88 pancreaticoduodenectomies, 22 left-sided resections and 4 total pancreatectomies were examined. All cases were graded for granulocytic epithelial lesions, IgG4-positive cells, storiform fibrosis, phlebitis and eosinophilic granulocytes. Follow-up data were obtained from 102/114 patients, mean follow-up was 5.3 years. RESULTS Histologically, 63 (55.3%) of the 114 patients fulfilled the criteria of type 1 AIP, while 51 (44.7%) patients fulfilled the criteria of type 2 AIP. Type 1 AIP patients were older and more often males than type 2 AIP patients. Elevation of serum IgG4, involvement of extrapancreatic organs, disease relapse, systemic steroid treatment and diabetes after surgery were noted more often in type 1 AIP, while inflammatory bowel disease (IBD) was observed mainly in type 2 AIP. CONCLUSIONS Histological typing of AIP is clinically important because type 1 AIP is part of the IgG4-related disease and type 2 AIP is associated with IBD. Our data also show that relapse of disease and steroid treatment after surgery occur more frequently in type 1 than in type 2 AIP.