In vivo characterization of developing chronic pancreatitis in rats

Recent advances in the understanding and management of chronic pancreatitis pain

Abdominal pain is the most common symptom of chronic pancreatitis (CP) and is often debilitating for patients and very difficult to treat. To date, there exists no cure for the disease. Treatment strategies focus on symptom management and on mitigation of disease progression by reducing toxin exposure and avoiding recurrent inflammatory events. Traditional treatment protocols start with medical management followed by consideration of procedural or surgical intervention on selected patients with severe and persistent pain. The incorporation of adjuvant therapies to treat comorbidities including psychiatric disorders, exocrine pancreatic insufficiency, mineral bone disease, frailty, and malnutrition, are in its early stages. Recent clinical studies and animal models have been designed to improve investigation into the pathophysiology of CP pain, as well as to improve pain management. Despite the array of tools available, many therapeutic options for the management of CP pain provide incomplete relief. There still remains much to discover about the neural regulation of pancreas-related pain. In this review, we will discuss research from the last 5 years that has provided new insights into novel methods of pain phenotyping and the pathophysiology of CP pain. These discoveries have led to improvements in patient selection for optimization of outcomes for both medical and procedural management, and identification of potential future therapies.

Dynamic Contrast-Enhanced MRI Assessing Antifibrotic Therapeutic Effects of Pancreatic Fibrosis with Curcumin - An Experimental Study at 11.7 T

RATIONALE AND OBJECTIVES

Pancreatic fibrosis is the hallmark of chronic pancreatitis (CP), which is associated with microcirculatory disturbance. Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) can assess the perfusion and permeability of the pancreas by providing information about microcirculation. We hypothesize that DCE-MRI parameters can be utilized to assess pancreatic fibrosis and may furthermore provide an opportunity to evaluate response to antifibrotic treatment with curcumin. Our study was to evaluate the feasibility of quantitative DCE-MRI in assessing pancreatic fibrosis and the antifibrotic effect of curcumin in a rat model of CP.

MATERIALS AND METHODS

Pancreatic fibrosis was induced by injecting dibutyltin dichloride (DBTC). Seventy rats were randomized to five groups: the control group (n = 10); DBTC for 2 weeks (n = 15); DBTC for 4 weeks (n = 15); DBTC + curcumin for 2 weeks (n = 15); DBTC + curcumin for 4 weeks (n = 15). DCE-MRI was performed at an 11.7 T MR scanner. DCE-MRI quantitative parameters (Ktrans, Ve, and Vp) were derived from an extended Tofts model. Fibrosis content and DCE-MRI parameters were compared among the above groups (one-way analysis of variance). The correlations between DCE-MRI parameters and pancreatic fibrosis content as well as the expression of α-SMA were computed by Spearman correlation coefficients.

RESULTS

Fifty-three rats survived and underwent MR imaging. Ktrans in rats 4 weeks after DBTC injection was significantly lower than DBTC 2 weeks rats and control rats (0.30 ± 0.06 min vs 0.49 ± 0.09 vs 0.62 ± 0.09, respectively). Vp in DBTC 4 weeks rats was also significantly lower than control rats (0.048 ± 0.010 min-1 vs 0.065 ± 0.011 min-1, respectively). Ktrans and Vp significantly correlated with fibrosis content of pancreas (r = -0.619 and -0.450, all P < 0.001), and the expression of α-SMA (r = -0.688 and -0.402, all P < 0.01). Ktrans and Vp in rats with daily curcumin treatment for 4 weeks were significantly higher than DBTC 4 weeks rats (Ktrans, 0.51 ± 0.09 vs 0.30 ± 0.06; Vp, 0.064 ± 0.015 vs 0.048 ± 0.010).

CONCLUSION

DCE-MRI parameters (Ktrans and Vp) have the potential to noninvasively assess pancreatic fibrosis and the antifibrotic treatment response of curcumin.

Saikosaponin D Attenuates Pancreatic Injury Through Suppressing the Apoptosis of Acinar Cell via Modulation of the MAPK Signaling Pathway

Chronic pancreatitis (CP) is a progressive fibro-inflammatory syndrome. The damage of acinar cells is the main cause of inflammation and the activation of pancreatic stellate cells (PSCs), which can thereby possibly further aggravate the apoptosis of more acinar cells. Saikosaponind (SSd), a major active ingredient derived from Chinese medicinal herb bupleurum falcatum, which exerted multiple pharmacological effects. However, it is not clear whether SSd protects pancreatic injury of CP via regulating the apoptosis of pancreatic acinar cells. This study systematically investigated the effect of SSd on pancreatic injury of CP in vivo and in vitro. The results revealed that SSd attenuate pancreatic damage, decrease the apoptosis and suppress the phosphorylation level of MAPK family proteins (JNK1/2, ERK1/2, and p38 MAPK) significantly in the pancreas of CP rats. In addition, SSd markedly reduced the apoptosis and inflammation of pancreatic acinar AR42J cells induced by cerulein, a drug induced CP, or Conditioned Medium from PSCs (PSCs-CM) or the combination of PSCs-CM and cerulein. Moreover, SSd significantly inhibited the activated phosphorylation of JNK1/2, ERK1/2, and p38 MAPK induced by cerulein or the combination of PSCs-CM and cerulein in AR42J cells. Furthermore, SSd treatment markedly decreased the protein levels of p-JNK and p-p38 MAPK caused by PSCs-CM alone. In conclusion, SSd ameliorated pancreatic injury, suppressed AR42J inflammation and apoptosis induced by cerulein, interrupted the effect of PSCs-CM on AR42J cells inflammation and apoptosis, possibly through MAPK pathway.

Animal Models: Challenges and Opportunities to Determine Optimal Experimental Models of Pancreatitis and Pancreatic Cancer

At the 2018 PancreasFest meeting, experts participating in basic research met to discuss the plethora of available animal models for studying exocrine pancreatic disease. In particular, the discussion focused on the challenges currently facing the field and potential solutions. That meeting culminated in this review, which describes the advantages and limitations of both common and infrequently used models of exocrine pancreatic disease, namely, pancreatitis and exocrine pancreatic cancer. The objective is to provide a comprehensive description of the available models but also to provide investigators with guidance in the application of these models to investigate both environmental and genetic contributions to exocrine pancreatic disease. The content covers both nongenic and genetically engineered models across multiple species (large and small). Recommendations for choosing the appropriate model as well as how to conduct and present results are provided.

Identifying miRNA-mRNA regulation network of chronic pancreatitis based on the significant functional expression

BACKGROUND

The aim of this study was to explore the underlying molecular mechanism and potential molecular biomarkers of chronic pancreatitis (CP) and construct a miRNA-mRNA regulation network.

METHODS

To explore the involvement of miRNAs in CP, we downloaded the miRNA and mRNA expression profiles of CP patients and healthy controls and identified the differentially expressed miRNAs and genes. Functional analysis was conducted and significant pathways were utilized. Finally, the miRNA-mRNA regulation network of CP was constructed.

RESULTS

A total of 44 miRNA risk gene pathway relationships were identified, and a complex regulation network was constructed with 3 genes (ABL1, MYC, and ANAPC13) having the highest degree in affecting the network of CP. Importantly, 4 risk genes (NOTCH3, COX5A, THBS1, and KARS) and 1 risk miRNA (hsa-miR-324-5p) were identified with high prediction accuracy.

CONCLUSIONS

In conclusion, we analyzed miRNAs and mRNAs expression profiles in CP, 1 risk miRNA, and 4 risk genes were identified with high prediction accuracy as biomarkers of CP. Although further evaluation in clinical study is needed, our findings provide new insights into the pathogenesis of CP and may improve the diagnosis and therapy by identifying novel targets.

Determination of dorsal root ganglion segments projecting to the pancreas in a rat model of chronic pancreatitis pain

AIM: To establish a rat model of chronic pancreatitis and determine dorsal root ganglion (DRG) segments projecting to the pancreas, in order to lay a foundation for further study of the pathogenesis of chronic visceral pain

METHODS: Adult male Sprague Dawley rats were randomly divided into an experimental group and a control group. The experimental group was intravenously given 8 mg/kg body weight dibutyltin dichloride to induce chronic pancreatitis, and the control group was injected with ethanol solution. Mechanical withdraw threshold at different time points was detected. Rats of the two groups were sacrificed after 8 wk. HE staining was used to detect the histological changes of pancreatic tissue, and RT-PCR was used to measure c-fos mRNA expression in DRG.

RESULTS: Compared with the control group, the rats in the experimental group showed chronic inflammation in pancreatic tissue at 8 wk and had significantly decreased mechanical withdraw threshold. 1,1'-dioctadecyl-3,3,3',3'-tetramethindo-carbocyanine perchlorate (Dil) retrograde tracing confirmed that the dorsal root ganglion (DRG) segments projecting to the pancreas were T8-12, and c-fos expression in DRG significantly increased (P < 0.05).

CONCLUSION: The dorsal root ganglion (DRG) segments projecting to the pancreas are T8-12. c-fos expression in chronic DRG significantly increases in rats with chronic pancreatitis pain.

Assessment of Chronic Pancreatitis: Use of Whole Pancreas Perfusion With 256-Slice Computed Tomography

OBJECTIVE: We aimed to compare perfusion computed tomography (CTP) characteristics of the normal pancreas with those of chronic pancreatitis (CP) and to examine the possibility of evaluating pancreatic exocrine function with CTP. METHODS: Thirty-two patients (control group, n = 18; CP group, n = 14) who completed the whole pancreas CT perfusion examination with 256-slice CT were studied. Four parameters, including perfusion (PF), peak enhancement intensity (PEI), time-to-peak (TTP), and blood volume (BV), were measured and compared between the control and CP groups, and between patients with and without exocrine pancreatic insufficiency (EPI) in the CP group. Pancreatic exocrine function was determined via serum trypsinogen. RESULTS: There was no significant difference between the distribution of PF, PEI, and BV in different pancreas regions, namely, the head, body, and tail (P > 0.05). PF, PEI, and BV of the CP group were significantly decreased, and TTP was significantly increased compared with the control group (P < 0.05). A significant decrease of PF, PEI, and BV and increase of TTP were observed in patients with EPI than in patients without EPI (P < 0.05). CONCLUSIONS: Perfusion CT is an appropriate imaging technique to diagnose CP and may be useful as a screening test to rule out early EPI.

DCE-MRI in experimental chronic pancreatitis

To assess pancreatic perfusion in experimental chronic pancreatitis (CP) by dynamic contrast-enhanced (DCE) magnetic resonance imaging (MRI). DCE MRI on a 1.5 T MR scanner was performed on 21 piglets with the ligation of pancreatic duct. They were divided into four groups based on pathology, including seven normal pigs and seven, three and four piglets with grade I, II and III CP, respectively. The signal intensity measured in the pancreatic body on DCE MRI was plotted against time to create a signal intensity-time (SI-T) curve for each piglet. The steepest slope (SS), time-to-peak (TTP) and peak enhancement ratio (PER) of the SI-T curve were noted. In the four groups, on the SI-T curve derived from DCE MRI, the SS was, respectively, 10.88 +/- 1.20, 10.59 +/- 1.02, 6.67 +/- 1.31 and 5.48 +/- 1.97%/s (F = 20.509, p = 0.000) from normal piglets to piglets with grade III CP. The TTP was 13.82 +/- 3.09, 12.31 +/- 5.52, 20.55 +/- 3.79 and 37.26 +/- 14.56 s (F = 10.681, p = 0.000) and the PER was 62.95 +/- 20.20, 60.44 +/- 20.00, 46.33 +/- 22.70 and 67.65 +/- 32.66% (F = 0.529, p = 0.668), respectively. The SS (r = -0.719, p = 0.000) and TTP (r = 0.538, p = 0.012) of the SI-T curve was correlated to the severity of CP, respectively. DCE MRI has a potential to diagnose moderate to advanced CP. The SS and TTP of the SI-T curve were correlated to the severity of CP.

Role of oxidative stress in pancreatic inflammation

Reactive oxygen and reactive nitrogen species (ROS/RNS) have been implicated in the pathogenesis of acute and chronic pancreatitis. Clinical and basic science studies have indicated that ROS/RNS formation processes are intimately linked to the development of the inflammatory disorders. The detrimental effects of highly reactive ROS/RNS are mediated by their direct actions on biomolecules (lipids, proteins, and nucleic acids) and activation of proinflammatory signal cascades, which subsequently lead to activation of immune responses. The present article summarizes the possible sources of ROS/RNS formation and the detailed signaling cascades implicated in the pathogenesis of pancreatic inflammation, as observed in acute and chronic pancreatitis. A therapeutic ROS/RNS-scavenging strategy has been advocated for decades; however, clinical studies examining such approaches have been inconsistent in their results. Emerging evidence indicates that pancreatitis-inducing ROS/RNS generation may be attenuated by targeting ROS/RNS-generating enzymes and upstream mediators.

Early rise in inflammation and microcirculatory disorder determine the development of autoimmune pancreatitis in the MRL/Mp-mouse

Autoimmune pancreatitis (AIP) is a rare cause of chronic pancreatitis and mimics pancreatic cancer. Although there is strong interest in research, etiology and pathophysiology of AIP are still unknown. Therefore, we analyzed a total of 92 MRL/Mp-mice of either sex, which are prone to develop AIP, in four different age groups (8-12, 16-20, 24-28, and 32-40 wk). Using intravital fluorescence microscopy, histology, laboratory analysis, and Western blot, onset, severity, and pathophysiological mechanisms of AIP were evaluated. Female animals showed in vivo an age-dependent increase of intrapancreatic leukocyte accumulation, as well as a loss in functional capillary perfusion. In contrast, intrapancreatic inflammation in male mice was less pronounced and not age dependent. Furthermore, pancreatic tissue specimen of female animals exhibited major organ destruction with significantly higher values of mean pathological scores (1.5 +/- 0.3 vs. < or =0.2; P < 0.05), as well as significantly increased CD4-, CD8-, CD11b-, and CD138-positive cells compared with male animals of the same age. Interestingly, there was a significant positive correlation between intravascular leukocyte adherence and the histopathological score of the pancreas, indicating a determining role of the innate immune system for the late onset of AIP. The present study shows that the onset of AIP is characterized by an inflammatory response and microcirculatory failure, most probably constituting initiators and propagators of this autoimmune disease.

Nutritive perfusion of pancreatic endocrine tissue during hemorrhagic hypotension: how differ islets in situ from islet isografts?

Although the exocrine gland frequently has I/R-associated complications such as posttransplant pancreatitis, hypoxia-induced dysfunction of pancreatic endocrine tissue is rarely observed. However, sympathetic hypersensitivity is accused of impaired endocrine function observed in human pancreatic grafts. These tissue-confined differences in susceptibility might be attributed to a distinct islet-specific regulatory control of blood flow (BF). To investigate this hypothesis, intravital microscopy was used for visualization of islets in situ and revascularized islet isografts in Syrian golden hamsters. Blood withdrawal was performed to induce sympathetic stimulation and to evoke an appropriate stress response of the tissue under investigation. Hypotension resulted in a perfusion pressure-dependent reduction of perfusion in both islets in situ and islet isografts. This was associated with comparable microhemodynamics of the tissues in direct vicinity, that is, pancreatic exocrine and host muscle tissue. There was a progressive decrease in functional capillary density of islets in situ and islet isografts that significantly correlated with the stepwise reduction of arterial blood pressure and did not differ in the hypotension-induced perfusion pattern in the neighboring exocrine and host skeletal muscle tissue. Concomitantly, capillary BF in islets in situ and islet isografts and in pancreatic exocrine and host muscle tissue was found to be reduced due to hypotension-associated decreases in capillary diameters and BF velocity. Microvascular perfusion of pancreatic islets and islet isografts is not preserved but strongly parallels perfusion pattern of the neighboring tissue under hemorrhagic stress. This disproves the existence of an individual islet-specific regulatory control of blood flow.

Allopurinol in rat chronic pancreatitis: effects on pancreatic stellate cell activation

OBJECTIVES

Activation of pancreatic stellate cells (PSCs) is a key event in pancreatic fibrosis. Xanthine oxidase-derived free radicals are involved in the mechanism of chronic pancreatitis (CP). We here searched the in vivo effects of allopurinol on PSC activation and its relation to tissue oxidative stress and histological findings in rat CP.

METHODS

Rat CP was induced with intraductal trinitrobenzene sulfonic acid in groups 1 (n = 16) and 2 (n = 10). Group 3 (n = 10) received intraductal saline. Four weeks after induction, group 1 received allopurinol (200 mg/kg, s.c.), and groups 2 and 3 received saline. After 4 weeks, oxidative stress parameters, histological evaluation, and immunostaining for alpha-smooth muscle actin (+) PSCs were performed in the pancreata.

RESULTS

Oxidative stress parameters improved significantly in group 1 compared with groups 2 and 3. Collagen deposition and lobular/sublobular atrophy were significantly lower in group 1 than in group 2. Alpha-smooth muscle actin (+) PSCs counts in group 1 were significantly lower than in group 2, and were in correlation with the degree of fibrosis and atrophy.

CONCLUSIONS

Allopurinol inhibits PSC activation in vivo. Pancreatic fibrosis can be prevented, at least in part, by antioxidant treatment through xanthine oxidase metabolism. Long-term use of allopurinol and its analogs may be considered in clinical trials with CP.

Granulocyte-colony stimulating factor enhances muscle proliferation and strength following skeletal muscle injury in rats

Insufficiency of skeletal muscle regeneration often impedes the healing process with functional deficiencies and scar formation. We tested the hematopoietic growth factor granulocyte-colony stimulating factor (G-CSF) with respect to its efficacy to improve functional muscle regeneration following skeletal muscle injury in Wistar rats. After crush injury to the left soleus muscle, animals received daily G-CSF (20 μg/kg ip) or vehicle solution ( n = 30 per group each). Sham-operated animals without muscle injury served as controls ( n = 15). After in vivo assessment of the fast-twitch and tetanic contraction capacity of the soleus muscles at days 4, 7, and 14 post-injury, sampling of muscle tissue served for analysis of satellite cell proliferation [bromodeoxyuridine (BrdU)/laminin and BrdU/desmin double immunohistochemistry] and cell apoptosis (transferase nick-end labeling analysis). Muscle strength analysis revealed recovery of contraction forces to 26 ± 2, 35 ± 3, and 53 ± 3% (twitch force) and to 20 ± 3, 24 ± 2, and 37 ± 2% (tetanic force) within the 14-day observation period in vehicle-treated animals. In contrast, G-CSF increased contractile forces with markedly higher values at day 7 (twitch force: 42 ± 2%; tetanic force: 34 ± 2%) and day 14 (twitch force: 62 ± 3%; tetanic force: 43 ± 3%). This enhancement of muscle function was preceded by a significant increase of satellite cell proliferation (BrdU-positive cells/mm2: 27 ± 6 vs. vehicle: 12 ± 3) and a moderate decrease of cell apoptosis (transferase nick-end labeling-positive cells/mm2: 11 ± 2 vs. vehicle: 16 ± 3) at day 4. In conclusion, G-CSF histologically promoted viability and proliferation of muscle cells and functionally enhanced recovery of muscle strength. Thus G-CSF might represent a therapeutic option to optimize the posttraumatic course of muscle tissue healing.