Effects of octreotide on activated pancreatic stellate cell-induced pancreas graft fibrosis in rats. J Surg Res. 2012;176:248-259. [PMID: 21816420 DOI: 10.1016/j.jss.2011.06.009]

The pancreatic clock is a key determinant of pancreatic fibrosis progression and exocrine dysfunction

Chronic pancreatitis (CP) is characterized by progressive fibrosis and exocrine dysregulation, which have long been considered irreversible. As a peripheral oscillator, the pancreas harbors autonomous and self-sustained timekeeping systems in both its endocrine and exocrine compartments, although the role of the latter remains poorly understood. By using different models of CP established in mice with dysfunctional pancreatic clocks, we found that the local clock played an important role in CP pathology, and genetic or external disruption of the pancreatic clock exacerbated fibrogenesis and exocrine insufficiency. Mechanistically, an impaired retinoic acid receptor-related orphan receptor A (Rora)/nuclear receptor subfamily 1, group D, member 1 (Nr1d1)/aryl hydrocarbon receptor nuclear translocator-like (Arntl or Bmal1) loop, called the circadian stabilizing loop, resulted in the deficiency of pancreatic Bmal1, which was responsible for controlling the fibrogenic properties of pancreatic stellate cells (PSCs) and for rewiring the function of acinar cells in a clock-TGF signaling-IL-11/IL-11RA axis-dependent manner. During PSC activation, the antagonistic interaction between Nr1d1 and Rora was unbalanced in response to the loss of cytoplasmic retinoid-containing lipid droplets. Patients with CP also exhibited reduced production of endogenous melatonin. Enhancing the clock through pharmacological restoration of the circadian stabilizing loop using a combination of melatonin and the Rora agonist SR1078 attenuated intrapancreatic pathological changes in mouse models of CP. Collectively, this study identified a protective role of the pancreatic clock against pancreatic fibrosis and exocrine dysfunction. Pancreatic clock-targeted therapy may represent a potential strategy to treat CP.

Pancreatic Stellate Cells: The Key Orchestrator of The Pancreatic Tumor Microenvironment

Pancreatic cancer is one of the most challenging adenocarcinomas due to its hostile molecular behavior and complex tumor microenvironment. It has been recently postulated that pancreatic stellate cells (PSCs), the resident lipid-storing cells of the pancreas, are important components of the tumor microenvironment as they can transdifferentiate into highly proliferative myofibroblasts in the context of tissue injury. Targeting tumor-stromal crosstalk in the tumor microenvironment has emerged as a promising therapeutic strategy against pancreatic cancer progression and metastasis. This chapter brings a broad view on the biological and pathological role of PSCs in the pancreas, activated stellate cells in the onset of tissue fibrosis, and tumor progression with particular emphasis on the bidirectional interactions between tumor cells and PSCs. Further, potential therapeutic regimens targeting activated PSCs in the pre-clinical and clinical trials are discussed.

Pancreatic stellate cell: Pandora's box for pancreatic disease biology

Pancreatic stellate cells (PSCs) were identified in the early 1980s, but received much attention after 1998 when the methods to isolate and culture them from murine and human sources were developed. PSCs contribute to a small proportion of all pancreatic cells under physiological condition, but are essential for maintaining the normal pancreatic architecture. Quiescent PSCs are characterized by the presence of vitamin A laden lipid droplets. Upon PSC activation, these perinuclear lipid droplets disappear from the cytosol, attain a myofibroblast like phenotype and expresses the activation marker, alpha smooth muscle actin. PSCs maintain their activated phenotype via an autocrine loop involving different cytokines and contribute to progressive fibrosis in chronic pancreatitis (CP) and pancreatic ductal adenocarcinoma (PDAC). Several pathways (e.g., JAK-STAT, Smad, Wnt signaling, Hedgehog etc.), transcription factors and miRNAs have been implicated in the inflammatory and profibrogenic function of PSCs. The role of PSCs goes much beyond fibrosis/desmoplasia in PDAC. It is now shown that PSCs are involved in significant crosstalk between the pancreatic cancer cells and the cancer stroma. These interactions result in tumour progression, metastasis, tumour hypoxia, immune evasion and drug resistance. This is the rationale for therapeutic preclinical and clinical trials that have targeted PSCs and the cancer stroma.

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.

Somatostatin expression in the pancreatic cells of smoking and non-smoking chronic pancreatitis patients with or without diabetes

OBJECTIVES

The aim of the analysis is to determine the location and degree of the hormone immunoreactivity in tissues of patients with chronic pancreatitis and diabetes.

METHODS

The study was performed on 11 non-smoking and 12 smoking patients with chronic pancreatitis (CP) with/without diabetes. The hormone was located in the pancreatic tissues by means of the immunohistochemical method using somatostatin antibodies. The histopathological evaluation of the hormone expression intensity in tissue sections was carried out using the semi-quantitative method and was calculated by means of a digital image analysis.

RESULTS

The hormone's strong immunohistochemical reaction and the modified D-cell location may be a result of the pancreatic tissue fibrosis process prevention in patients with CP. Changes in the intensity of SS immunoreactivity and the D-cell distribution in the pancreas of patients with CP and diabetes may possibly result from the additional hormone compensatory effect in the excessive glucagon secretion inhibition. Smoking patients with diabetes showed significantly higher hormone immunostaining in the pancreas compared to non-smoking patients without diabetes and healthy persons.

CONCLUSIONS

The severity of histopathological changes in smoking CP patients indicates that the cigarette smoke components may further exacerbate the inflammatory reactions. Patients with CP were found to have a strong immunohistochemical reaction to SS and changes in the distribution of D cells when compared to healthy patients. The strongest immunohistochemical SS reaction has been identified in the pancreatic tissue from smoking patients with diabetes.

Effect of oxymatrine on expression of molecules of Smad signal pathway in pancreatic stellate cells stimulated with TGF-β1

AIM: To investigate the effect of oxymatrine (OM) on the expression of molecules of the Smad signal pathway in pancreatic stellate cell line (LTC-14 cells) stimulated with transforming growth factor-β1 (TGF-β1).

METHODS: LTC-14 cells were divided into a normal control group, a TGF-β1 stimulated group and a TGF-β1 + OM (1 mg/mL) group. The mRNA and protein were extracted from LTC-14 cells 12 h after treatment. The mRNA and protein expression of Smad2/3/4/7 was detected by real-time PCR and Western blot, respectively.

RESULTS: Compared with the TGF-β1 stimulated group, the mRNA and protein expression of Smad2/3/4 was dramatically reduced in the OM treated group (P < 0.05). Compared with the TGF-β1 stimulated group, the mRNA expression of Smad7 was significantly decreased in the OM treated group (P < 0.05), whereas the Smad7 protein expression was increased.

CONCLUSION: OM might exert a therapeutic effect against pancreatic fibrosis in pancreatic stellate cells stimulated with TGF-β1 by interfering with the mRNA and protein expression of molecules of the TGF-β1/Smad pathway.

Activated pancreatic stellate cells can impair pancreatic islet function in mice

BACKGROUND

Pancreatic or islet fibrosis is often associated with activated pancreatic stellate cells (PSCs). PSCs are considered not only to promote fibrosis, but also to be associated with glucose intolerance in some diseases. We therefore evaluated morphological and functional relationships between islets and PSCs in the normal mouse pancreas and transplanted islets.

METHODS

Immunohistochemistry was used to map the presence of PSCs in the normal mouse pancreas and islets implanted under the renal capsule. We isolated and cultured mouse PSCs and characterized them morphologically by immunofluorescence staining. Furthermore, we measured their cytokine production and determined their effects on insulin release from simultaneously cultured islets.

RESULTS

PSCs were scattered throughout the pancreas, with occasional cells within the islets, particularly in the islet capsule. In islet transplants they were found mainly in the graft periphery. Cultured PSCs became functionally activated and produced several cytokines. Throughout the culture period they linearly increased their production of interleukin-6 and mammalian keratinocyte-derived chemokine. PSC cytokine production was not affected by acute hyperglycemia. Syngeneic islets co-cultured with PSCs for 24-48 h increased their insulin release and lowered their insulin content. However, short-term insulin release in batch-type incubations was unaffected after 48 h of co-culture. Increased islet cell caspase-3 activation and a decreased islet cell replication were consistently observed after co-culture for 2 or 7 days.

CONCLUSION

Activated PSCs may contribute to impaired islet endocrine function seen in exocrine pancreatitis and in islet fibrosis associated with some cases of type 2 diabetes.

Astragaloside IV ameliorates renal fibrosis via the inhibition of mitogen-activated protein kinases and antiapoptosis in vivo and in vitro

Apoptosis of renal tubular cells plays a crucial role in renal fibrosis. Astragaloside IV (AS-IV), a compound extracted from Radix Astragali, has been shown to inhibit renal tubular cell apoptosis induced by high glucose, but its role in preventing chronic renal fibrosis as well as the underlying molecular mechanisms involved still remain obscure. In this study, human kidney tubular epithelial cells induced by transforming growth factor-β1 (TGF-β1) were used to investigate the protective role of AS-IV in antifibrosis. As an in vivo model, mice subjected to unilateral ureteral obstruction (UUO) were administered AS-IV (20 mg/kg) by intraperitoneal injection for 7 days. AS-IV significantly alleviated renal mass loss and reduced the expression of α-smooth muscle actin, fibronectin, and collagen IV both in vitro and in vivo, suggesting that this compound functions in the inhibition of renal tubulointerstitial fibrosis. Furthermore, transferase-mediated dUTP nick-end labeling assay results both in vivo and in vitro showed that AS-IV significantly attenuated both UUO and TGF-β1-induced cell apoptosis and prevented renal tubular epithelial cell injury in a dose-dependent manner. Western blotting results also revealed that the antiapoptotic effect of AS-IV was reflected in the inhibition of caspase-3 activation, which might be mediated primarily by the downregulation of mitogen-activated protein kinase effectors phospho-p38 and phospho-c-Jun N-terminal kinase. These data infer that AS-IV effectively attenuates the progression of renal fibrosis after UUO injury and may have a promising clinical role as a potential antifibrosis treatment in patients with chronic kidney disease.

The naïve effector cells of collagen type I during acute experimental pancreatitis are acinar cells and not pancreatic stellate cells

OBJECTIVE

The purpose of this study was to investigate the expression of collagen type I and the mRNA level of its regulatory factor, TGF-β1, in tissue samples of acute pancreatitis and to determine the significance of collagen type I in predisposition to pancreatic fibrosis during acute pancreatitis.

METHODS

Sprague-Dawley rats were divided into an experimental group (30 rats) and a control group (12 rats). The rats in the experimental group were intraperitoneally injected with cerulein to induce acute pancreatitis. The distribution and expression of collagen type I in the pancreatic tissues were examined by immunohistochemical staining. The mRNA level of TGF-β1 was determined by real-time polymerase chain reaction (PCR).

RESULTS

(1) Collagen type I was localized in the cytoplasm of pancreatic acinar cells. With pancreatitis progressed, strong positive staining for collagen type I covered whole pancreatic lobules, whereas, the islet tissue, interlobular area, and pancreatic necrotic area were negative for collagen type I. (2) The level of TGF-β1 mRNA in rats from the experimental group increased gradually the establishment of acute pancreatitis, and was significantly higher than that in the control group at every time point.

CONCLUSIONS

(1) During acute pancreatitis, pancreatic acinar cells, not pancreatic stellate cells as traditionally believed, were the naïve effector cells of collagen type I. (2) TGF-β1 played a key role in regulating collagen I expression during acute pancreatitis.