Growth-associated protein-43 and protein gene-product 9.5 innervation in human pancreas: changes in chronic pancreatitis

Effect of Neurostimulation on Chronic Pancreatic Pain: A Systematic Review

BACKGROUND

Chronic pancreatic pain is one of the most severe causes of visceral pain, and treatment response is often limited. Neurostimulation techniques have been investigated for chronic pain syndromes once there are pathophysiological reasons to believe that these methods activate descending pain inhibitory systems. Considering this, we designed this systematic literature review to investigate the evidence on neuromodulation techniques as a treatment for chronic pancreatic pain.

MATERIALS AND METHODS

We performed a literature search using the databases MEDLINE, Cochrane Central Register of Controlled Trials (CENTRAL), and Embase until April 2024. The included studies used neurostimulation techniques in participants with chronic pancreatic pain and reported pain-related outcomes, with a focus on pain scales and opioid intake. Two reviewers screened and extracted data, and a third reviewer resolved discrepancies. We assessed the risk of bias using the Jadad scale. The authors then grouped the findings by the target of the neurostimulation, cortex, spinal cord, or peripheral nerves; described the findings qualitatively in the results section, including qualitative data reported by the articles; and calculated effect sizes of pain-related outcomes.

RESULTS

A total of 22 studies were included (7 randomized clinical trials [RCTs], 14 case series, and 1 survey), including a total of 257 clinical trial participants. The two outcomes most commonly reported were pain, measured by the visual analogue scale (VAS), numeric rating scale (NRS), and pressure pain threshold scores, and opioid intake. Two RCTs investigated repetitive transcranial magnetic stimulation (rTMS), showing a reduction of 36% (±16) (d = 2.25; 95% CI, 0.66-3.83) and 27.2% (±24.5%) (d = 2.594; 95% CI, 1.303-3.885) in VAS pain scale. In another clinical trial, transcranial direct-current stimulation (tDCS) and transcranial pulsed current stimulation were not observed to effect a significant reduction in VAS pain (χ2 = 5.87; p = 0.12). However, a complete remission was reported in one tDCS case. Spinal cord stimulation (SCS) and dorsal root ganglion stimulation were performed in a survey and 11 case series, showing major pain decrease and diminished opioid use in 90% of participants after successful implantation; most studies had follow-up periods of months to years. Two noninvasive vagal nerve stimulation (VNS) RCTs showed no significant pain reduction in pain thresholds or VAS (d = 0.916; 95% CI, -0.005 to 1.838; and d = 0.17; -0.86 to 1.20; p = 0.72; respectively). Splanchnic nerve stimulation in one case report showed complete pain reduction accompanied by discontinuation of oral morphine and fentanyl lozenges and a 95% decrease in fentanyl patch use. Two RCTs investigated transcutaneous electrical nerve stimulation (TENS). One found a significant pain reduction effect with the NRS (d = 1.481; 95% CI, 1.82-1.143), and decreased opioid use, while the other RCT did not show significant benefit. Additionally, one case report with TENS showed pain improvement that was not quantitatively measured.

DISCUSSION

The neuromodulation techniques of rTMS and SCS showed the most consistent potential as a treatment method for chronic pancreatic pain. However, the studies have notable limitations, and SCS has had no clinical trials. For VNS, we have two RCTs that showed a non-statistically significant improvement; we believe that both studies had a lack of power issue and suggest a gap in the literature for new RCTs exploring this modality. Additionally, tDCS and TENS showed mixed results. Another important insight was that opioid intake decrease is a common trend among most studies included and that adverse effects were rarely reported. To further elucidate the potential of these neurostimulation techniques, we suggest the development of new clinical trials with larger samples and adequate sham controls.

Neurogenic Appendicitis: A Reappraisal of the Clinicopathological Features and Pathogenesis

In 1921; Masson and Maresch first coined the term “neurogenic appendicitis (NA)” to describe “neuroma-like” lesions in the appendix. To date, our knowledge about NA is limited; therefore, we conducted a comprehensive analysis of the literature (1921 to 2020) to examine the clinicopathological features of NA. We also addressed the pathophysiology of acute abdominal pain and fibrosis in this entity. We performed a meta-analysis study by searching the PubMed database, using several keywords, such as: “appendix,” “neurogenic,” “obliterative,” “neuroma,” “fibrous obliteration,” “appendicopathy,” and “appendicitis.” Our study revealed that patients with NA usually present clinically with features of acute appendicitis, bud2t they have grossly unremarkable appendices. Histologically, the central appendiceal neuroma was the most common histological variant of NA, followed by the submucosal and intramucosal variants. To conclude, NA represents a form of neuroinflammation. The possibility of NA should be considered in patients with clinical features of acute appendicitis who intraoperatively show a grossly unremarkable appendix. Neuroinflammation and neuropeptides play roles in the development of pain and fibrosis in NA.

Prenatal development of sympathetic innervation of the human pancreas

BACKGROUND

The sympathetic nervous system plays an important role in the regulation of pancreatic exocrine and endocrine secretion. The results of experimental studies also demonstrate the involvement of the sympathetic nervous system in the regulation of endocrine cell differentiation and islet formation during the development of the pancreas. However, the prenatal development of sympathetic innervation of the human pancreas has not yet been studied.

MATERIAL AND METHODS

Pancreatic autopsy samples from 24 human fetuses were examined using immunohistochemistry with antibodies to tyrosine hydroxylase (TH). The density, concentration, and size (width, length, perimeter and area) of the TH-positive sympathetic nerves were compared in four developmental periods: pre-fetal (8-11 weeks post conception (w.p.c.), n = 6), early fetal (13-20 gestational weeks (g.w.), n = 7), middle fetal (21-28 g.w., n = 6) and late fetal (29-40 g.w., n = 5) using morphometric methods and statistical analysis (Multiple Comparisons p values). Double immunofluorescence with antibodies to TH and either insulin or glucagon and confocal microscopy were applied to analyze the interaction between the sympathetic nerves and endocrine cells, and the co-localization of TH with hormones.

RESULTS

TH-positive sympathetic nerves were detected in the fetal pancreas starting from the early stages (8 w.p.c.). The developmental dynamics of sympathetic nerves was follows: from the pre-fetal period, the amount of TH-positive nerves gradually increased and their branching occurred reaching the highest density and concentration in the middle fetal period, followed by a decrease in these parameters in the late fetal period. From the 14th g.w. onwards, thin TH-positive nerve fibers were mainly distributed in the vicinity of blood vessels and around the neurons of intrapancreatic ganglia, which is similar in adults. There were only rare TH-positive nerve fibers adjacent to acini or located at the periphery of some islets. The close interactions between the TH-positive nerve fibers and endocrine cells were observed in the neuro-insular complexes. Additionally, non-neuronal TH-containing cells were found in the pancreas of fetuses from the pre-fetal and early fetal periods. Some of these cells simultaneously contained glucagon.

CONCLUSIONS

The results demonstrate that sympathetic innervation of the human pancreas, including the formation of perivascular and intraganglionic nerve plexuses, extensively develops during prenatal period, while some processes, such as the formation of sympathetic innervation of islet capillaries, may occur postnatally. Non-neuronal TH-containing cells, as well as the interactions between the sympathetic terminals and endocrine cells observed in the fetal pancreas may be necessary for endocrine pancreas development in humans.

Risk factors for pain after Frey's procedure in chronic pancreatitis

Pancreatic pain is the most frequent symptom of chronic pancreatitis (CP) and is difficult to treat. This retrospective study aimed to determine the risk factors for pain in CP.From January 2009 and March 2014, 75 consecutive patients with CP who underwent Frey's procedure were reviewed for this study. According to Izbicki pain scores, these patients were divided into 2 groups: (1) pain (Izbicki pain score of >10 after a decrease of >50%) and (2) pain-free (Izbicki pain score of ≤10). Demographic data, medical history, postoperative variables, and follow-up evaluations of the patients were documented.The postoperative pain score (11.8) was significantly lower than the preoperative score (51.8) after a median follow-up of 4.2 years. Alcoholism (odds ratio [OR] 7.767, P = .002) and preoperative analgesic medication use (OR 4.113, P = .030) were independent risk factors for pain.Frey's procedure is an effective operation for pain relief in patients with CP. Alcoholism and preoperative analgesic medication use were 2 factors for failure to achieve complete pain relief.

Noradrenergic and Cholinergic Reinnervation of Islet Grafts in Diabetic Rats

Grafted islets become denervated due to the islet transplantation procedure. The aim of the present study was 1) to examine whether islet grafts in the liver, the spleen, and under the kidney capsule in rats become reinnervated following the transplantation and experimental procedures used in our laboratory, 2) whether there is any difference in reinnervation at these different sites, and 3) how these results relate to previous physiological experiments. Isogeneic isolated islets were transplanted into diabetic Albino Oxford rats, resulting in normoglycaemia. After at least 5 wk, graft-receiving organs were removed and several antibodies were employed to detect insulin, neuron-specific proteins, and cholinergic and noradrenergic nerve fibers. Islets in all three receiving organs contained viable insulin-positive B-cells. Neuron-specific enolase (NSE) as well as the growth-associated protein B-50 was observed at all sites. The cholinergic marker choline acetyltransferase (ChAT) was localized in islets grafts at all sites, but with the lowest density in the spleen. Staining for the noradrenergic markers tyrosine hydroxylase (TH) and dopamine-β-hydroxylase (DBH) was observed in islet grafts at all sites with the lowest density in grafts under the kidney capsule. All these neurochemical substances were most frequently observed in fibers associated with blood vessels, which may be the route along which nerves grow into the graft. It can be concluded that 1) islet grafts in the liver, in the spleen and under the kidney capsule become reinnervated; 2) the innervation pattern of the islet grafts differs only slightly from that in the control pancreatic islets; and 3) in combination with our previously physiological data, we can conclude that these nerve fibers are, at least partly, functionally active.

Structure of neuro-endocrine and neuro-epithelial interactions in human foetal pancreas

In the pancreas of many mammals including humans, endocrine islet cells can be integrated with the nervous system components into neuro-insular complexes. The mechanism of the formation of such complexes is not clearly understood. The present study evaluated the interactions between the nervous system components, epithelial cells and endocrine cells in the human pancreas. Foetal pancreas, gestational age 19-23 weeks (13 cases) and 30-34 weeks (7 cases), were studied using double immunohistochemical labeling with neural markers (S100 protein and beta III tubulin), epithelial marker (cytokeratin 19 (CK19)) and antibodies to insulin and glucagon. We first analyse the structure of neuro-insular complexes using confocal microscopy and provide immunohistochemical evidences of the presence of endocrine cells within the ganglia or inside the nerve bundles. We showed that the nervous system components contact with the epithelial cells located in ducts or in clusters outside the ductal epithelium and form complexes with separate epithelial cells. We observed CK19-positive cells inside the ganglia and nerve bundles which were located separately or were integrated with the islets. Therefore, we conclude that neuro-insular complexes may forms as a result of integration between epithelial cells and nervous system components at the initial stages of islets formation.

Ontogeny of neuro-insular complexes and islets innervation in the human pancreas

The ontogeny of the neuro-insular complexes (NIC) and the islets innervation in human pancreas has not been studied in detail. Our aim was to describe the developmental dynamics and distribution of the nervous system structures in the endocrine part of human pancreas. We used double-staining with antibodies specific to pan-neural markers [neuron-specific enolase (NSE) and S100 protein] and to hormones of pancreatic endocrine cells. NSE and S100-positive nerves and ganglia were identified in the human fetal pancreas from gestation week (gw) 10 onward. Later the density of S100 and NSE-positive fibers increased. In adults, this network was sparse. The islets innervation started to form from gw 14. NSE-containing endocrine cells were identified from gw 12 onward. Additionally, S100-positive cells were detected both in the periphery and within some of the islets starting at gw 14. The analysis of islets innervation has shown that the fetal pancreas contained NIC and the number of these complexes was reduced in adults. The highest density of NIC is detected during middle and late fetal periods, when the mosaic islets, typical for adults, form. The close integration between the developing pancreatic islets and the nervous system structures may play an important role not only in the hormone secretion, but also in the islets morphogenesis.

Substance P and neprilysin in chronic pancreatitis

BACKGROUND/AIMS

We aimed to analyze substance P (SP) and neprilysin (NEP), the membrane metallopeptidase that degrades SP, in chronic pancreatitis (CP).

METHODS

SP and NEP mRNA levels were analyzed by qRT-PCR in tissue samples from 30 patients with CP and 8 organ donors. In addition, SP serum levels were determined before and after surgery in the same patients, by means of a competitive ELISA assay. Genetic and epigenetic analyses of the NEP gene were also performed.

RESULTS

SP mRNA expression levels were higher in CP tissues compared to controls (p = 0.0152), while NEP mRNA showed no significant differences between CP and healthy subjects (p = 0.2102). In CP patients, SP serum levels correlated with those in tissue, and after surgical resection SP serum levels were reduced compared to the preoperative values. Failure of NEP to overexpress in CP tissues was associated with significant miR-128a overexpression (p = 0.02), rather than with mutations in the NEP coding region or the presence of hypermethylation sites in the NEP promoter region.

CONCLUSION

Tissue and serum levels of SP were increased in CP, while NEP levels remained unaltered. In an SP/NEP-mediated pathway, it would appear that NEP fails to provide adequate surveillance of SP levels. Failure of NEP to overexpress could be associated with miRNA regulation.

Pain mechanisms in chronic pancreatitis: of a master and his fire

BACKGROUND

Unraveling the mechanisms of pain in chronic pancreatitis (CP) remains a true challenge. The rapid development of pancreatic surgery in the twentieth century, usage of advanced molecular biological techniques, and emergence of clinician-scientists have enabled the elucidation of several mechanisms that lead to the chronic, complicated neuropathic pain syndrome in CP. However, the proper analysis of pain in CP should include three main arms of mechanisms: "peripheral nociception," "peripheral/pancreatic neuropathy and neuroplasticity," and "central neuropathy and neuroplasticity."

DISCUSSION

According to our current knowledge, pain in CP involves sustained sensitization of pancreatic peripheral nociceptors by neurotransmitters and neurotrophic factors following neural damage. This peripheral pancreatic neuropathy leads to intrapancreatic neuroplastic alterations that involve a profound switch in the autonomic innervation of the human pancreas via "neural remodeling." Furthermore, this neuropathy entails a hyperexcitability of spinal sensory second-order neurons, which are subject to modulation from the brainstem via descending facilitation. Finally, viscerosensory cortical areas react to this central sensitization via spatial reorganization and thus a central neuroplasticity. The present review summarizes the current findings in these arms of mechanisms and introduces a novel concept to consistently describe pain in CP as a "predominantly neuropathic," "mixed-type" pain.

Fate of nerves in chronic pancreatitis: Neural remodeling and pancreatic neuropathy

There is probably no other gastrointestinal disorder which is as much characterized by concomitant local, intra-organ and central neuropathic and neuroplastic alterations as chronic pancreatitis (CP). While some key features of this neuropathy have recently been elucidated, there is still no satisfying pathophysiological explanation for the generation of neuropathic pain in CP. It is becoming increasingly clear that an effective pain treatment in CP can probably not be achieved without consideration of the exact fate of intrapancreatic nerves and central neuroplastic alterations. This review is intended to illustrate the temporal and spatial alterations of intrapancreatic nerves in the course of CP. At the same time, it depicts the reciprocal relationship between these plastic changes and thus underlines the notion of a 'common fate' for all these alterations. Moreover, it points out numerous aspects of this fate that are yet to be unveiled and should therefore be subject to future investigation.

Nerve growth factor and artemin are paracrine mediators of pancreatic neuropathy in pancreatic adenocarcinoma

OBJECTIVE

To further characterize the neurotrophic attributes of pancreatic cancer (PCa).

SUMMARY BACKGROUND DATA

PCa is characterized by neuropathic alterations which are resulting in pancreatic pain. To further characterize pancreatic neuropathy, we aimed: to analyze whether neuropathic alterations in PCa are only limited to the tumor-core or whether they are similarly encountered in neural structures in the noncancerous pancreas, to demonstrate whether PCa features neurotrophic attributes and finally to identify responsible neurotrophic molecules.

METHODS

Nerve density and area were quantified in normal pancreas (NP, n=45), histologically "normal" pancreas next to pancreatic cancer (NNPCa, n=61) and PCa (n=97). Growth-associated protein-43, nerve growth factor (NGF), and Artemin expressions were assessed by Immunohistochemistry, Western-Blot, and quantitative real time polymerase chain reaction-analyses. Isolated myenteric plexus of newborn rats were exposed to NP, NNPCa, and PCa tissue extracts and supernatants of Panc1 and T3M4 cancer cells with or without Artemin and NGF depletion, followed by neurite density analysis.

RESULTS

Dense neural networks and enlarged nerves were not only detected in PCa but were also present in NNPCa. Growth-associated protein-43, NGF, and Artemin expressions were absent/weak in NP, but increased in both NNPCa and PCa and were closely associated with intrapancreatic neuropathy. PCa and NNPCa tissue extracts and Panc1/T3M4 supernatants noticeably increased neurite density in myenteric plexus-cultures, which were attenuated by depletion of NGF and Artemin.

CONCLUSIONS

The neurotrophic effects of PCa extend into the peritumoral "normal" pancreatic areas without neuro-cancer interactions. The neurotrophic characteristics of PCa can be mimicked by in vitro analyses and reveal NGF and Artemin as potential key players in the generation of pancreatic neuropathy in PCa.

Review article: pain and chronic pancreatitis

BACKGROUND

Pain in chronic pancreatitis chronic pancreatitis is a frustrating and challenging symptom for both the patient and clinician. It is the most frequent and most significant symptom. Many patients fail the currently available conservative options and require opiates or endoscopic/surgical therapy. Aim To highlight the pathophysiology and management of chronic pancreatitis pain, with an emphasis on recent developments and future directions.

METHODS

Expert review, utilizing in addition a comprehensive search of PubMed utilizing the search terms chronic pancreatitis and pain, treatment or management and a manual search of recent conference abstracts for articles describing pain and chronic pancreatitis.

RESULTS

Pancreatic pain is heterogenous in its manifestations and pathophysiology. First-line medical options include abstinence from alcohol and tobacco, pancreatic enzymes, adjunctive agents, antioxidants, and non-opiate or low potency opiate analgesics. Failure of these options is not unusual. More potent opiates, neurolysis and endoscopic and surgical options can be considered in selected patients, but this requires appropriate expertise. New and better options are needed. Future options could include new types of pancreatic enzymes, novel antinociceptive agents nerve growth factors, mast cell-directed therapy, treatments to limit fibrinogenesis and therapies directed at the central component of pain.

CONCLUSIONS

Chronic pancreatitis pain remains difficult to treat. An approach utilizing conservative medical therapies is appropriate, with more invasive therapies reserved for failure of this conservative approach. Treatment options will continue to improve with new and novel therapies on the horizon.

Pain and chronic pancreatitis: is it the plumbing or the wiring?

Our progress in understanding the biology of chronic pancreatitis has been slow, particularly with respect to the pathogenesis of pain, the cardinal symptom. Although traditional theories have focused on anatomic changes, with interstitial and ductal hypertension as the main inciting factors for pain generation, subsequent studies have not confirmed a correlation between ductal pressure and the severity of pain or its relief after ductal decompression. Empirical approaches directed at anatomic causes are at best of marginal value. Although these phenomena are clearly associated with the disease, they are not likely the root cause of the pain. Instead, they probably are inciting factors on a background of neuronal sensitization induced by damage to the perineurium and subsequent exposure of the nerves to mediators and products of inflammation. In this review, we discuss the inherent limitations in our current therapies and try to identify new targets and approaches for the future, such as TRPV1, nerve growth factor-TrkA signaling, and perhaps protease activator receptor-2.

Pancreatic pain

Abdominal pain is an important clinical symptom in pancreatic diseases. There is increasing evidence that pain in chronic pancreatitis and pancreatic cancer is triggered by pancreatic neuropathy. Damage to intrapancreatic nerves seems to support the maintenance and exacerbation of neuropathic pain. In chronic pancreatitis, intrapancreatic nerves are invaded by immune cells. This observation led to the hypothesis that neuro-immune interactions play a role in the pathogenesis of chronic pancreatitis and the accompanying abdominal pain syndrome. Similarly, pancreatic cancer cells infiltrate the perineurium of local nerves, which may in part explain the severe pain experienced by the patients. Furthermore, perineural invasion extending into extrapancreatic nerves may preclude curative resection and thus often leads to local recurrence. In recent years, the involvement of a variety of neurotrophins and neuropeptides in the pathogenesis of pancreatic pain was discovered. This review summarises recent data on the mechanisms of neuropathy and pain generation in pancreatic disorders.

Effects of sensory denervation by neonatal capsaicin administration on experimental pancreatitis induced by dibutyltin dichloride

Increase in the number of intrapancreatic sensory nerve fibers has been implicated in the generation of pain in chronic pancreatitis. Because some sensory neurotransmitters (e.g., substance P) are known to have proinflammatory effects, we hypothesized that denervation of intrapancreatic nerves might influence not only pain generation but also inflammation. Neonatal Lewis rats were injected with capsaicin (50 mg/kg or 0 mg/kg), a neurotoxin, to induce denervation of primary sensory neurons. When rats reached 170-190 g body weight, experimental pancreatitis was induced by a single administration of dibutyltin dichloride (7 mg/mg). The severity of pancreatitis was evaluated in both groups in the acute phase (at 3 and 7 days) and chronic phase (at 28 days). At day 7, the sensory denervation induced by neonatal capsaicin administration inhibited pancreatic inflammation on both histological (determination of interstitial edema, expansion of interlobular septa and intercellular spaces, and inflammatory cell infiltration) and biochemical (intrapancreatic myeloperoxidase activity) evaluation. Furthermore, at day 28, glandular atrophy, pseudotubular complexes, and rate of fibrosis were each significantly lower in the capsaicin-pretreated group than in the vehicle-pretreated group. Our findings provide in vivo evidence that primary sensory neurons play important roles in both acute pancreatitis and chronic pancreatic inflammation with fibrosis.

Intrapancreatic axonal hyperbranching of dorsal root ganglia neurons in chronic pancreatitis model rats and its relation to pancreatic pain

OBJECTIVES

Increase in number of intrapancreatic nerve bundles has been implicated in the generation of persistent pain in chronic pancreatitis. To examine the origin of these nerve fibers and the mechanisms linking neural morphological change to pain generation, we used neuronal tracing techniques in combination with immunohistochemistry in spontaneous chronic pancreatitis in the Wistar Bonn/Kobori (WBN/Kob) rats.

METHODS

For retrograde tracing, horseradish peroxidase was injected into the pancreas, and labeled neurons in the sensory ganglia were counted. For anterograde tracing, biotinylated dextran amine was injected into the dorsal root ganglia (DRGs), and labeled intrapancreatic sensory fibers were histochemically assessed. For assessment of pain generation, we evaluated c-Fos-positive neurons in the spinal dorsal horn and behavioral changes of the animals.

RESULTS

In WBN/Kob rats, the numbers of horseradish peroxidase-labeled neurons were decreased in the DRGs, and the numbers of biotinylated dextran amine-labeled intrapancreatic nerve fibers and terminals were increased. Biotinylated dextran amine-labeled nerve fibers contained growth-associated protein 43. The number of c-Fos-positive neurons in the dorsal horn was also increased and was correlated with intrapancreatic growth-associated protein 43 immunoreactivity. Grooming behavior was reduced in WBN/Kob rats, and this reduction was facilitated by exocrine stimulation.

CONCLUSIONS

Axonal branching in DRG neurons innervating the pancreas increases in WBN/Kob rats, and these morphological changes are likely involved in pain generation in chronic pancreatitis.

Increased galanin expression in the celiac ganglion of BB diabetic rats

BB rats lose >50% of their islet sympathetic nerve terminals soon after diabetes onset, markedly impairing the glucagon response to activation of these nerves. In this study, we sought evidence that this degree of disease-induced nerve terminal damage affected their neuronal cell bodies. Increased galanin expression was used as a marker of the change of phenotype that occurs in neuronal cell bodies when their axons are severely damaged. The celiac ganglion (CG) was analyzed because it is a major source of the sympathetic nerves that project to the pancreatic islets. But we first needed to determine if damaging nerve terminals could increase galanin expression in this ganglion and, if so, when that expression was maximal. Severe, global nerve terminal damage produced a dramatic increase of CG galanin expression which was maximal 5 days later. We next determined if a global, but partial, nerve terminal loss would also increase galanin expression and found a significant increase of galanin mRNA and its peptide in the CG. Finally, we determined if the disease-induced, partial and islet-selective loss of nerve terminals seen in BB diabetic rats was sufficient to increase galanin: we, again, found a significant increase of galanin mRNA and its peptide in their CG. These increases did not occur in their superior cervical ganglia. We conclude that the selective damage to islet sympathetic nerve terminals seen in BB diabetic rats, rather than the systemic factors of diabetic hyperglycemia or insulin deficiency, causes the increased galanin expression observed in the CG of this animal model of type 1 diabetes.

Remodeling of the innervation of pancreatic islets accompanies insulitis preceding onset of diabetes in the NOD mouse

The innervation of the islets of Langerhans may constitute a first target for the autoimmunity that develops in type 1 diabetes. Here, we report the occurrence of a decrease in general innervation within the islets in the nonobese diabetic (NOD) mouse, and the establishment of strands of Schwann cells, as detected via p75 and S-100 immunoreactivity (IR), and varicose nerve fibers expressing tyrosine kinase A (TrkA) in association with the immune cells. The findings suggest that there are marked attempts for neurotrophins to promote nerve ingrowth and survival for islet tissue and that remodeling of innervation occurs in the continuation of the insulitis process preceding the onset of type 1 diabetes.

Autonomic nerve changes in the mouse pancreas after pancreatic duct ligation

INTRODUCTION

The mouse pancreas exhibits distinct atrophy of the exocrine tissue following pancreatic duct ligation.

AIM

To investigate changes of innervation in the whole pancreas after pancreatic duct ligation.

METHODOLOGY

The mouse pancreatic duct was ligated at 6 weeks of age. Pancreatic tissues were removed 7 days and 14 days after the ligation, fixed by perfusion and immersion with Zamboni solution, and embedded in gelatin. The whole organ was serially sectioned at a thickness of 100 microm, histochemically stained for cholinesterase, and observed by light microscopy. The number and volume of intrapancreatic ganglia, number of ganglion cells, and volume of each ganglion cell in the whole pancreas were quantitated. Some sections were analyzed using transmission electron microscopy after histochemically staining for cholinesterase.

RESULTS

In the normal pancreas, ganglia were often situated on the outer surface of the islets of Langerhans. Thick nerve bundles ran along the arteries and emanated thin nerve fibers that surrounded the arterioles. In the atrophied pancreas following pancreatic duct ligation, ganglia remained on the islets of Langerhans as in normal mice, while the nerve fibers appeared dense, bending and curling in a more complex manner. The thin nerves also crossed each other in a complex network. Using morphometry in the pancreas following pancreatic duct ligation, the total ganglion cell number was found to decrease from normal levels. The mean ganglion cell volume in the ligated pancreas was significantly smaller than that in normal mice. As observed by transmission electron microscopy, some ganglion cells in the ligated pancreas were negative for cholinesterase activity but were surrounded by positive staining around the surface.

CONCLUSIONS

These results suggest that the function of pancreatic ganglion cells changes with organ atrophy after pancreatic duct ligation.

Surgery and chronic pancreatitis

It is hoped that, in this millennium, chronic pancreatitis will be diagnosed earlier in the course of the disease process. Improved axial imaging of the pancreatic duct and pancreatic parenchyma will diminish the need for other invasive tests. Surgical procedures are directed at pancreatic duct decompression or resection of the pancreas (head, body or tail) or, infrequently, total pancreatectomy. Pain relief in 75% to 90% is the general rule, with diabetes developing subsequently in as many as 33% of patients. Surgery for chronic pancreatitis is effective in correcting sequelae of pancreatic fibrosis. Endoscopic stenting of the pancreatic and bile duct is used more frequently today. Until their place is ascertained, careful performance of surgery will continue to be a mainstay of treatment.

Quantitative comparison of growth-associated protein GAP-43, neuron-specific enolase, and protein gene product 9.5 as neuronal markers in mature human intestine

This study was performed to compare GAP-43, PGP 9.5, synaptophysin, and NSE as neuronal markers in the human intestine. GAP-43-immunoreactive nerve fibers were abundant in all layers of the ileum and colon. GAP-43 partially co-localized partially with every neuropeptide (VIP, substance P, galanin, enkephalin) studied. All neuropeptide-immunoreactive fibers also showed GAP-43 reactivity. By blind visual estimation, the numbers of GAP-43-immunoreactive fibers in the lamina propria were greater than those of PGP 9.5, synaptophysin, or NSE. In the muscle layer, visual estimation indicated that the density of GAP-43-immunoreactive fiber profiles was slightly greater than that of the others. The number and intensity of GAP-43-, PGP 9.5-, and NSE-immunoreactive fibers were estimated in sections of normal human colon and ileum using computerized morphometry. In the colon, the numbers of GAP-43-immunoreactive nerve profiles per unit area and their size and intensity were significantly greater than the values for PGP and NSE. A similar trend was observed in the ileum. Neuronal somata lacked or showed only weak GAP-43 immunoreactivity, variable PGP 9.5 immunoreactivity, no synaptophysin immunoreactivity, and moderate to strong NSE immunoreactivity. We conclude that GAP-43 is the superior marker of nerve fibers in the human intestine, whereas NSE is the marker of choice for neuronal somata. (J Histochem Cytochem 47:1405-1415, 1999)

Neuroimmune appendicitis

BACKGROUND

15-25% of appendices removed from patients with suspected appendicitis appear normal on histological examination. The cause of pain in such patients is unknown. Since the content of neuropeptides seems to be altered in chronic inflammation, we investigated possible changes in peptidergic innervation for substance P (SP), vasoactive intestinal peptide (VIP), and growth-associated protein-43 (GAP-43).

METHODS

Appendices classified as showing acute appendicitis, non-acute appendicitis (clinical signs of acute appendicitis, but histologically not inflamed), or normal were processed for SP, VIP, and GAP-43 immunocytochemistry. The density of SP immunostaining was assessed by digitised morphometry.

FINDINGS

31 appendix specimens were studied (16 acute, 15 non-acute). 16 specimens were used as controls. Expression of GAP-43 was increased in the non-acute appendices. We observed larger amounts of SP-immunoreactive and VIP-immunoreactive nerves in the mucosal layer of the appendix in patients with non-acute appendicitis than in controls and patients with acute appendicitis (mean % area SP-immunoreactive 0.0496 [SD 0.0113] non-acute, 0.0221 [0.0049] acute, 0.0229 [0.0068] controls). In addition, a close spatial relation between SP-immunoreactive and VIP-immunoreactive nerve fibres and lymphoid cells was detected in the outer zone of lymph follicles.

INTERPRETATION

Neuroproliferation in the appendix, in association with an increase in neurotransmitters SP and VIP, may be involved in the pathophysiology of acute right abdominal pain in the absence of an acute inflammation of the appendix. Our data, together with increasing knowledge about the way in which the nervous system and immune cells interact, suggest that neuroimmune appendicitis is a distinct pathological entity.

Expression of tyrosine hydroxylase, calcitonin gene-related peptide, substance P and protein gene product 9.5 in mouse islets transplanted under the kidney capsule

Pancreatic islets transplanted to the kidney of syngeneic mice were stained for calcitonin gene-related peptide (CGRP), substance P (SP), tyrosine hydroxylase (TH), acetylcholinesterase and the pan-neuronal marker, protein gene product 9.5 (PGP). Nerve fibers expressing TH-like immunoreactivity (TH-LI) and CGRP-LI were rare for 4 days but increased 2 (CGRP) or 6 (TH) weeks after transplantation. In 1-year-old grafts the CGRP-LI innervation resembled that in situ, while TH-LI and PGP-LI innervations were increased. SP-LI fibers remained rare throughout. Perikarya intrinsic to the islets did not show CGRP-LI or SP-LI. The results indicate a progressive ingrowth of sensory fibers into the grafts and that the TH-LI innervation becomes even more pronounced than in the pancreas. The post-transplantation reaction of islet intrinsic neurons does not involve CGRP and SP, contrasting with previous observations for vasoactive intestinal polypeptide.

B-50, the growth associated protein-43: modulation of cell morphology and communication in the nervous system

The growth-associated protein B-50 (GAP-43) is a presynaptic protein. Its expression is largely restricted to the nervous system. B-50 is frequently used as a marker for sprouting, because it is located in growth cones, maximally expressed during nervous system development and re-induced in injured and regenerating neural tissues. The B-50 gene is highly conserved during evolution. The B-50 gene contains two promoters and three exons which specify functional domains of the protein. The first exon encoding the 1-10 sequence, harbors the palmitoylation site for attachment to the axolemma and the minimal domain for interaction with G0 protein. The second exon contains the "GAP module", including the calmodulin binding and the protein kinase C phosphorylation domain which is shared by the family of IQ proteins. Downstream sequences of the second and non-coding sequences in the third exon encode species variability. The third exon also contains a conserved domain for phosphorylation by casein kinase II. Functional interference experiments using antisense oligonucleotides or antibodies, have shown inhibition of neurite outgrowth and neurotransmitter release. Overexpression of B-50 in cells or transgenic mice results in excessive sprouting. The various interactions, specified by the structural domains, are thought to underlie the role of B-50 in synaptic plasticity, participating in membrane extension during neuritogenesis, in neurotransmitter release and long-term potentiation. Apparently, B-50 null-mutant mice do not display gross phenotypic changes of the nervous system, although the B-50 deletion affects neuronal pathfinding and reduces postnatal survival. The experimental evidence suggests that neuronal morphology and communication are critically modulated by, but not absolutely dependent on, (enhanced) B-50 presence.

Increase of B-50/GAP-43 immunoreactivity in uninjured muscle nerves of MDX mice

Lack of dystrophin in mdx mice leads to muscle fibre degeneration followed by the formation of new myofibres. This degeneration-regeneration event occurs in clusters. It is accompanied by inflammation and remodelling of the intramuscular terminal nerve fibres. Since the growth-associated protein B-50/GAP-43 has been shown to be involved in axonal outgrowth and synaptic remodelling following neuronal injury, we have investigated the presence of B-50 in gastrocnemius and quadriceps muscles of mdx mice. Using immunocytochemistry we demonstrate increased presence of B-50 in terminal nerve branches at motor endplates of mdx mice, particularly in the clusters of de- and regenerating myofibres. In comparison, the control mice displayed no B-50 immunoreactivity in nerve fibres contacting motor endplates. Our findings indicate that during axonal remodelling and collateral sprouting the B-50 level in the terminal axon arbours is increased although there is no direct injury to the motoneurons. We suggest that the degenerating target and/or the inflammatory reaction induces the increased B-50 level in the motoaxons. The increased B-50 may be important for sprouting of the nerve fibres and re-establishment of synaptic contacts, and in addition, for maturation and survival of the newly formed myofibres.

Noradrenergic and cholinergic reinnervation of islet grafts in diabetic rats

Grafted islets become denervated due to the islet transplantation procedure. The aim of the present study was 1) to examine whether islet grafts in the liver, the spleen, and under the kidney capsule in rats become reinnervated following the transplantation and experimental procedures used in our laboratory, 2) whether there is any difference in reinnervation at these different sites, and 3) how these results relate to previous physiological experiments. Isogeneic isolated islets were transplanted into diabetic Albino Oxford rats, resulting in normoglycaemia. After at least 5 wk, graft-receiving organs were removed and several antibodies were employed to detect insulin, neuron-specific proteins, and cholinergic and noradrenergic nerve fibers. Islets in all three receiving organs contained viable insulin-positive B-cells. Neuron-specific enolase (NSE) as well as the growth-associated protein B-50 was observed at all sites. The cholinergic marker choline acetyltransferase (ChAT) was localized in islets grafts at all sites, but with the lowest density in the spleen. Staining for the noradrenergic markers tyrosine hydroxylase (TH) and dopamine-beta-hydroxylase (DBH) was observed in islet grafts at all sites with the lowest density in grafts under the kidney capsule. All these neurochemical substances were most frequently observed in fibers associated with blood vessels, which may be the route along which nerves grow into the graft. It can be concluded that 1) islet grafts in the liver, in the spleen and under the kidney capsule become reinnervated; 2) the innervation pattern of the islet grafts differs only slightly from that in the control pancreatic islets; and 3) in combination with our previously physiological data, we can conclude that these nerve fibers are, at least partly, functionally active.