Morphological and physiological evidence for interstitial cell of Cajal-like cells in the guinea pig gallbladder

Presence and significance of telocytes in cholelithiasis and biliary dilatation in benign biliary disorders

Telocytes are closely associated with the regulation of tissue smooth muscle dynamics in digestive system disorders. They are widely distributed in the biliary system and exert their influence on biliary motility through mechanisms such as the regulation of CCK and their electrophysiological effects on smooth muscle cells. To investigate the relationship between telocytes and benign biliary diseases,such as gallbladder stone disease and biliary dilation syndrome, we conducted histopathological analysis on tissues affected by these conditions. Additionally, we performed immunohistochemistry and immunofluorescence double staining experiments for telocytes. The results indicate that the quantity of telocytes in the gallbladder and bile duct is significantly lower in pathological conditions compared to the control group. This reveals a close association between the decrease in telocyte quantity and impaired gallbladder motility and biliary fibrosis. Furthermore, further investigations have shown a correlation between telocytes in cholesterol gallstones and cholecystokinin-A receptor (CCK-AR), suggesting that elevated cholesterol levels may impair telocytes, leading to a reduction in the quantity of CCK-AR and ultimately resulting in impaired gallbladder motility.Therefore, we hypothesize that telocytes may play a crucial role in maintaining biliary homeostasis, and their deficiency may be associated with the development of benign biliary diseases, including gallstone disease and biliary dilation.

Pacemaking in the lymphatic system

Lymphatic collecting vessels exhibit spontaneous phasic contractions that are critical for lymph propulsion and tissue fluid homeostasis. This rhythmic activity is driven by action potentials conducted across the lymphatic muscle cell (LMC) layer to produce entrained contractions. The contraction frequency of a lymphatic collecting vessel displays exquisite mechanosensitivity, with a dynamic range from <1 to >20 contractions per minute. A myogenic pacemaker mechanism intrinsic to the LMCs was initially postulated to account for pressure-dependent chronotropy. Further interrogation into the cellular constituents of the lymphatic vessel wall identified non-muscle cell populations that shared some characteristics with interstitial cells of Cajal, which have pacemaker functions in the gastrointestinal and lower urinary tracts, thus raising the possibility of a non-muscle cell pacemaker. However, recent genetic knockout studies in mice support LMCs and a myogenic origin of the pacemaker activity. LMCs exhibit stochastic, but pressure-sensitive, sarcoplasmic reticulum calcium release (puffs and waves) from IP3R1 receptors, which couple to the calcium-activated chloride channel Anoctamin 1, causing depolarisation. The resulting electrical activity integrates across the highly coupled lymphatic muscle electrical syncytia through connexin 45 to modulate diastolic depolarisation. However, multiple other cation channels may also contribute to the ionic pacemaking cycle. Upon reaching threshold, a voltage-gated calcium channel-dependent action potential fires, resulting in a nearly synchronous calcium global calcium flash within the LMC layer to drive an entrained contraction. This review summarizes the key ion channels potentially responsible for the pressure-dependent chronotropy of lymphatic collecting vessels and various mechanisms of IP3R1 regulation that could contribute to frequency tuning.

Expression and functional study of cholecystokinin-A receptors on the interstitial Cajal-like cells of the guinea pig common bile duct

BACKGROUND

Many studies have shown that interstitial Cajal-like cell (ICLC) abnormalities are closely related to a variety of dynamic gastrointestinal disorders. ICLCs are pacemaker cells for gastrointestinal movement and are involved in the transmission of nerve impulses.

AIM

To elucidate the expression profile and significance of cholecystokinin-A (CCK-A) receptors in ICLCs in the common bile duct (CBD), as well as the role of CCK in regulating CBD motility through CCK-A receptors on CBD ICLCs.

METHODS

The levels of tyrosine kinase receptor (c-kit) and CCK-A receptors in CBD tissues and isolated CBD cells were quantified using the double immunofluorescence labeling technique. The CCK-mediated enhancement of the movement of CBD muscle strips through CBD ICLCs was observed by a muscle strip contraction test.

RESULTS

Immunofluorescence showed co-expression of c-kit and CCK-A receptors in the CBD muscularis layer. Observations of isolated CBD cells showed that c-kit was expressed on the surface of ICLCs, the cell body and synapse were colored and polygonal, and some cells presented protrusions and formed networks adjacent to the CBD while others formed filaments at the synaptic terminals of local cells. CCK-A receptors were also expressed on CBD ICLCs. At concentrations ranging from 10-6 mol/L to 10-10 mol/L, CCK promoted CBD smooth muscle contractility in a dose-dependent manner. In contrast, after ICLC removal, the contractility mediated by CCK in CBD smooth muscle decreased.

CONCLUSION

CCK-A receptors are highly expressed on CBD ICLCs, and CCK may regulate CBD motility through the CCK-A receptors on ICLCs.

Impact of interstitial cells of Cajal on slow wave and gallbladder contractility in a guinea pig model of acute cholecystitis

BACKGROUND

Impaired interstitial cells of Cajal (ICCs) are central to the pathophysiology of acute cholecystitis (AC). Common bile duct ligation is a common model of AC, producing acute inflammatory changes and decrease in gallbladder contractility.

AIM

To investigate the origin of slow wave (SW) in the gallbladder and the effect of ICCs on gallbladder contractions during the process of AC.

METHODS

Methylene blue (MB) with light was used to establish selective impaired ICCs gallbladder tissue. Gallbladder motility was assessed using the frequency of SW and gallbladder muscle contractility in vitro in normal control (NC), AC12h, AC24h, and AC48h groups of guinea pigs. Hematoxylin and eosin and Masson-stained gallbladder tissues were scored for inflammatory changes. ICCs pathological changes alterations were estimated using immunohistochemistry and transmission electron microscopy. The alterations of c-Kit, α-SMA, cholecystokinin A receptor (CCKAR), and connexin 43 (CX43) were assessed using Western blot.

RESULTS

Impaired ICCs muscle strips resulted in the decrease in gallbladder SW frequency and contractility. The frequency of SW and gallbladder contractility were significantly lower in the AC12h group. Compared with the NC group, the density and ultrastructure of ICCs were remarkably impaired in the AC groups, especially in the AC12h group. The protein expression levels of c-Kit were significantly decreased in the AC12h group, while CCKAR and CX43 protein expression levels were significantly decreased in the AC48h group.

CONCLUSION

Loss ICCs could lead to a decrease in gallbladder SW frequency and contractility. The density and ultrastructure of ICCs were clearly impaired in the early stage of AC, while CCKAR and CX43 were significantly reduced at end stage.

Distribution of interstitial cells of Cajal in the Esophagus and change in distribution after thoracic trauma

Interstitial cells of Cajal (ICCs) function as pacemaker cells in the gastrointestinal tract. Acute thoracic trauma is a common and lethal cause of death due to physical trauma caused by traffic accidents. This study aimed to explore the distribution of esophageal ICCs and distribution changes observed after acute thoracic trauma. Thirty rabbits were randomly divided into a control group and two study groups. The control group animals underwent an esophagectomy. All animals in the study groups underwent right chest puncture using the Hopkinson bar technique. The study groups were subjected to esophagectomy 24 and 72 h after chest puncture. Distribution, morphology, and density of esophageal ICCs were detected using transmission electron microscopy, toluidine blue staining, and immunohistochemistry. Apoptosis of esophageal ICCs was evaluated using the terminal deoxynucleotidyl transferase (TdT) dUTP Nick-End Labeling assay. Western blotting and reverse transcription polymerase chain reaction were used to detect changes in the SCF/c-kit signaling pathway. Esophageal ICCs distribution and SCF/c-kit signal pathway decreased from the upper part to the lower part in both physiological state and after thoracic trauma. In contrast, death of ICCs increased from the upper part to the lower part, both in physiological and injured state (P < 0.05). After thoracic trauma, increased ICCs and decreased death of ICCs in all parts of the esophagus (P < 0.05) were observed. The observed distribution and changes in esophageal ICCs would have an impact on motility and motility disorders of the esophagus.

Neutrophil depletion reduces interstitial cajal-like cell injury and alleviates inflammation-induced motor dysfunction in guinea-pig gallbladder during acute cholecystitis

Objectives

Gallbladder interstitial Cajal-like cells (ICLCs) are known as some of the players in the complex motility mechanisms affecting gallbladder motility. This study aims to explore the mechanism of guinea-pig gallbladder motility disorders during Acute Cholecystitis (AC), focusing on the relationships between neutrophil alterations, gallbladder ICLCs, and smooth muscle contractility.

Materials and Methods

Forty-eight guinea pigs were randomly divided into four groups: normal, sham, common bile duct ligation (CBDL), and anti-PMN (anti-polymorphonuclear antibody treated +CBDL). Hematoxylin and eosin-stained slides from each gallbladder sample were examined for inflammation, and myeloperoxidase (MPO) activity was evaluated. The contractile response of gallbladder muscle to Ach, CCK-8, and KCl was registered by a tension transducer, and ultrastructure features of ICLCs were observed.

Results

Pretreatment with anti-PMN significantly reduced the circulating neutrophils by 80% and also considerably decreased the gallbladder MPO activity by 52.9% compared with the CBDL group (P<0.05). After adding Ach, CCK-8, and KCl, the contraction ability in CBDL and anti-PMN groups was lower than those of normal and sham groups (P<0.05), and they were increased substantially in the anti-PMN group compared with the CBDL group (P<0.05). Transmission electron microscopy confirmed that the cytoplasm of the neutrophils was full of granules, and neutrophils contacted closely with ICLCs. The ultrastructure of ICLCs in the anti-PMN group was less inflamed and the endoplasmic reticulum was mildly dilated, and cell processes also increased.

Conclusion

Anti-PMN could relieve the ultrastructure injury of ICLCs and alleviate gallbladder dysmotility during AC. Neutrophils may damage gallbladder ICLCs at first followed by dysmotility.

Cholesterol gallstones: Focusing on the role of interstitial Cajal-like cells

Cholesterol gallstone (CG) is a common, frequent biliary system disease in China, with a complex and multifactorial etiology. Declined gallbladder motility reportedly contributes to CG pathogenesis. Furthermore, interstitial Cajal-like cells (ICLCs) are reportedly present in human and guinea pig gallbladder tissue. ICLCs potentially contribute to the regulation of gallbladder motility, and aberrant conditions involving the loss of ICLCs and/or a reduction in its pacing potential and reactivity to cholecystokinin may promote CG pathogenesis. This review discusses the association between ICLCs and CG pathogenesis and provides a basis for further studies on the functions of ICLCs and the etiologies of CG.

Developments in research on interstitial Cajal-like cells in the biliary tract

INTRODUCTION

Interstitial cells of Cajal (ICCs) are a special type of interstitial cells located in the gastrointestinal tract muscles. They are closely related to smooth muscle cells and neurons, participate in gastrointestinal motility and nerve signal transmission, and are pacemaker cells for gastrointestinal electrical activity. Research interest in ICCs has continuously grown since they were first discovered in 1893. Later, researchers discovered that they are also present in other organs, including the biliary tract, urethra, bladder, etc.; these cells were named interstitial Cajal-like cells (ICLCs), and attempts have been made to explain their relationships with certain diseases.

AREAS COVERED

This review paper summarizes the morphology, identification, classification, function, and distribution of ICLCs in the biliary tract and their relationship to biliary tract diseases.

EXPERT OPINION

Based on the function and distribution of ICLCs in the biliary tract system, ICLCs will provide a more reliable theoretical basis for the mechanisms of pathogenesis of and treatments for biliary tract diseases.

Effect of cholesterol on in vitro cultured interstitial Cajal-like cells isolated from guinea pig gallbladders

BACKGROUND

Loss and/or dysfunction of interstitial Cajal-like cells (ICLCs) in the gallbladder may promote cholesterol gallstone formation by decreasing gallbladder motility.

AIM

To study the effect of cholesterol on the proliferation and apoptosis of ICLCs from guinea pig gallbladders.

METHODS

Guinea pig gallbladder ICLCs were isolated and cultured in vitro. The cells were exposed to cholesterol solutions at different concentrations (0, 25, 50, and 100 mg/L) for 24 h. Then, cell proliferation was detected by the CCK-8 method and the apoptosis rate was detected by flow cytometry. Further, the expression of the c-Kit protein was detected by Western blot and the expression level of c-Kit mRNA in the cells was detected by real-time quantitative PCR.

RESULTS

After ICLCs were cultured with cholesterol at concentrations of 25, 50, and 100 mg/L, the proliferation rates decreased significantly (P < 0.05), whereas the apoptosis rates increased significantly (P < 0.05). Moreover, the expression of c-Kit protein and mRNA decreased significantly (P < 0.05).

CONCLUSION

High cholesterol concentrations can inhibit the proliferation of ICLCs and promote apoptosis. This decrease in the ICLC proliferation rate might be caused by the inhibition of the stem cell factor/c-Kit signaling pathway.

The impact of acute stress disorder on gallbladder interstitial cells of Cajal

Physical and psychological stress exerts a substantial effect on gastrointestinal motility disorders, where trauma enhances symptoms of digestive dysfunction. Interstitial cells of Cajal (ICCs) act as pacemakers for gastrointestinal motility regulation and are likely important in stress-associated gastrointestinal motility disorders. This study explored the mechanisms underlying gallbladder ICCs function under acute stress conditions using a rabbit chest puncture and cholecystectomy model. The stem cell factor (SCF)/c-kit pathway is essential for the development of ICCs, and gene expression was investigated to identify stress-induced transcriptional alterations. Immunohistochemistry, terminal deoxynucleotidyl transferase dUTP nick end labeling assays were used to determine ICCs apoptosis, whereas western blot analysis and reverse-transcription polymerase chain reaction were used to detect changes in the SCF/c-kit signaling pathway. These methods revealed a reduction in ICCs via apoptosis following stress, and ICCs increased over time after stressor removal. Therefore, this study demonstrates the impact of stress on ICCs development and survival and further confirms the link between stress and gastrointestinal motility.

Ursodeoxycholic acid protects interstitial Cajal-like cells in the gallbladder from undergoing apoptosis by inhibiting TNF-α expression

Hypomotility is a common symptom of gallstone disease, which is accompanied by a loss of interstitial Cajal-like cells (ICLCs) in the gallbladder. Ursodeoxycholic acid (UDCA) is widely used in treating gallstone disease, and has shown anti-apoptotic and anti-inflammatory effects apart from its ability to dissolve gallstones. In this study, we investigated the anti-apoptotic and anti-inflammatory effects of UDCA on ICLCs in guinea pigs with gallstones. Guinea pigs were fed a high-cholesterol diet for 8 weeks to induce the formation of gallstones. A group of animals was administered UDCA (50 mg·kg^-1·d^-1, ig) simultaneously. At the end of 8 weeks, the animals were euthanized with anesthesia, cholecystectomy was performed immediately and gallbladder was collected for further analysis. We showed that in the model group the contractility of gallbladder muscle strips in response to both acetylcholine (ACh) and CCK-8 was severely impaired, which was significantly improved by UDCA administration. Furthermore, UDCA administration significantly reduced the apoptotic ratio of ICLCs, based on the observation of co-localization imaging of apoptotic cells and c-kit-positive cells. Western blotting analysis and real-time PCR results revealed that the TNF-α/Caspase8/Caspase3 pathway was suppressed in the UDCA-treated animals, confirming the anti-apoptotic effect of UDCA in the gallbladder. The H&E staining showed that UDCA administration significantly attenuated inflammatory cell infiltration in the gallbladder wall. In conclusion, UDCA can protect ICLCs in the gallbladder from undergoing apoptosis by inhibiting the TNF-α/Caspase8/caspase3 pathway.

Neutrophils injure gallbladder interstitial Cajal-like cells in a guinea pig model of acute cholecystitis

Acute cholecystitis is a common disease with gallbladder dysmotility. Disease pathogenesis involves immune cell infiltration as well as changes in gallbladder interstitial Cajal-like cells (ICLCs). However, it remains unclear if or how the immune cells affect ICLC morphology, density, distribution, and function in gallbladder tissue during acute cholecystitis. In this study, we explored the acute cholecystitis-related alterations in gallbladder ICLCs in a guinea pig model, focusing on the effects of neighboring neutrophils. Adult guinea pigs were randomly divided into four groups (control, 24 hr common bile duct ligation [CBDL], 48-hr CBDL, and antipolymorphonuclear neutrophil [PMN] treated) and analyzed using methylene blue staining and immunofluorescence. Gallbladder contractility was also monitored. To culture gallbladder ICLCs, collagenase digestion was performed on tissue from 10- to 15-day-old guinea pigs. Neutrophils isolated from the peripheral blood of experimental animals 48-hr postsurgery were also cocultured with the gallbladder ICLCs. Intracellular calcium was detected with Fluo-4 AM dye. Our results showed that gallbladder ICLC density significantly declined during acute cholecystitis and was accompanied by shortening of the cellular processes and damage to their network-like structure. However, pretreatment with anti-PMN partially prevented these changes. Gallbladder contraction was also significantly decreased during acute cholecystitis, and this appeared to be mediated by the neutrophils. Moreover, ICLCs cocultured with neutrophils also had shortened and reduced processes and impaired network-like structure formation. Intracellular calcium transient was less sensitive to contraction agonists and inhibitors when cocultured with neutrophils. Taken together, neutrophils greatly affect gallbladder ICLCs and dysmotility during acute cholecystitis.

Telocytes and interstitial cells of Cajal in the biliary system

A novel type of interstitial tissue cells in the biliary tree termed telocytes (TCs), formerly known as interstitial Cajal‐like cells (ICLCs), exhibits very particular features which unequivocally distinguish these cells from interstitial cells of Cajal (ICCs) and other interstitial cell types. Current research substantiates the existence of TCs and ICCs in the biliary system (gallbladder, extrahepatic bile duct, cystic duct, common bile duct and sphincter of Oddi). Here, we review the distribution, morphology and ultrastructure of TCs and ICCs in the biliary tree, with emphasis on their presumptive roles in physiological and pathophysiological processes.

Distribution changes of interstitial cells of Cajal during cholesterol gallstone formation in guinea pigs fed a high cholesterol diet

BACKGROUND

Cholesterol gallstone is commonly observed in patients with gallbladder disorders. Interstitial cells of Cajal (ICCs) in the gallbladder are important for regulating gallbladder motility and have a close relationship with cholelithiasis.

AIM

The aim of this study was to explore changes in the distribution of gallbladder ICCs during cholesterol gallstone formation.

MATERIALS AND METHODS

Thirty guinea pigs were randomly divided into three groups: the control group and study groups. Animals in study groups were fed on high cholesterol diet for 4 weeks or 8 weeks. Animals in the control groups were fed on a standard diet for 8 weeks. Immunohistochemistry was performed to observe the shape, size, morphology, and numbers of ICCs from the neck of the gallbladder to the fundus of the gallbladder, and terminal deoxynucleotidyl transferase dUTP nick-end labeling was performed to detect apoptosis in ICCs from the upper part of the gallbladder to the lower part of the gallbladder.

RESULTS

There were no differences in the shape, size, and morphology of the gallbladder ICCs in all groups. Cholesterol gallstones formed in guinea pigs fed on high cholesterol diet. The numbers of gallbladder ICCs were significantly decreased from the neck of the gallbladder to the fundus of the gallbladder, and gallbladder ICC apoptosis was significantly increased from the upper part of the gallbladder to the lower part of the gallbladder in both guinea pigs fed on high cholesterol diet (all P<0.05).

CONCLUSION

Cholesterol gallstone formation reduced the density of gallbladder ICCs and increased the frequency of apoptotic gallbladder ICCs from the neck of the gallbladder to the fundus of the gallbladder, and these alterations may affect gallbladder ICC function.

Telocytes: New Players in Gallstone Disease

Cholesterol gallstone disease is highly prevalent in Western countries, particularly in women and some specific ethnic groups. The mechanisms behind the formation of gallstones are not clearly understood, but gallbladder dysmotility seems to be a key factor that triggers the precipitation of cholesterol microcrystals from supersaturated lithogenic bile.Given that newly described interstitial cells, telocytes, are present in the gallbladder and they are located in close vicinity of smooth muscle cell and neural fibers possibly interfering with gallbladder motility or contractility, authors are trying to summarize the current knowledge on the role of telocytes with respect to disturbed gallbladder function in gallstone disease.

Biliary Polyunsaturated Fatty Acids and Telocytes in Gallstone Disease

It has been reported that intake of ω-3 polyunsaturated fatty acids (PUFAs) reduces the risk of coronary heart disease. It also influences bile composition, decreasing biliary cholesterol saturation in the bile of patients with gallstones. In addition to bile composition disturbances, gallbladder hypomotility must be a cofactor in the pathogenesis of cholelithiasis, as it leads to the prolonged nucleation phase. Our current knowledge about gallbladder motility has been enhanced by the study of a population of newly described interstitial (stromal) cells-telocytes (TCs). The purpose of this study was to determine whether TC loss, reported by our team recently, might be related to bile lithogenicity, expressed as cholesterol saturation index or the difference in biliary PUFA profiles in patients who suffer from cholecystolithiasis and those not affected by this disease. We determined biliary lipid composition including the fatty acid composition of the phospholipid species in bile. Thus, we investigated whether differences in biliary fatty acid profiles (ω-3 PUFA and ω-6 PUFA) in gallbladder bile may influence its lithogenicity and the quantity of TCs within the gallbladder wall. We conclude that the altered PUFA concentrations in the gallbladder bile, with elevation of ω-6 PUFA, constitute important factors influencing TC density in the gallbladder wall, being one of the possible pathophysiological components for the gallstone disease development. This study established that altered bile composition in patients with cholelithiasis may influence TC quantity within the gallbladder muscle, and we concluded that reduction in TC number may be a consequence of the supersaturated bile toxicity, while some other bile components (ω-3 PUFA, glycocholic, and taurocholic acids) may exert protective effects on TC and thus possibly influence the mechanisms regulating gallbladder and extrahepatic bile duct motility. Thus, ω-3 PUFA may represent a possible option to prevent formation of cholesterol gallstones.

C-Kit expression in the gallbladder of guinea pig with chronic calculous cholecystitis and the effect of Artemisia capillaris Thunb on interstitial cells of Cajal

OBJECTIVES

To study the c-Kit expression in the gallbladder of cholesterol lithogenic guinea pig model and the effect of Artemisia capillaris Thunb on interstitial cells of Cajal (ICCs).

MATERIALS AND METHODS

A total of 45 guinea pigs were randomly assigned into three groups: the control group (guinea pigs fed a standard diet, normal group); the model group (guinea pigs fed a cholesterol gallstone-inducing diet); and the Chinese medicine group (guinea pigs fed the cholesterol gallstone-inducing diet and treated with A. capillaris through intragastric administration, therapy group). Each group had 15 guinea pigs. The gallbladders of the guinea pigs were harvested after 8 weeks. C-Kit expression was detected using an immunohistochemistry staining, real-time PCR, and Western blot analyses. The effect of A. capillaris on ICCs was evaluated by muscle strip contraction experiments.

RESULTS

C-Kit expression significantly decreased in the gallbladder of model group, but increased in the Chinese medicine group. The Contractility of guinea pig gallbladder muscle strip significantly improved in the Chinese medicine group.

CONCLUSION

Our results indicated that A. capillaris improves gallbladder impairment by up-regulating c-Kit expression, and it also can improve the contractile response of in vitro guinea pig gallbladder muscle strips.

Functions of the Gallbladder

The gallbladder stores and concentrates bile between meals. Gallbladder motor function is regulated by bile acids via the membrane bile acid receptor, TGR5, and by neurohormonal signals linked to digestion, for example, cholecystokinin and FGF15/19 intestinal hormones, which trigger gallbladder emptying and refilling, respectively. The cycle of gallbladder filling and emptying controls the flow of bile into the intestine and thereby the enterohepatic circulation of bile acids. The gallbladder also largely contributes to the regulation of bile composition by unique absorptive and secretory capacities. The gallbladder epithelium secretes bicarbonate and mucins, which both provide cytoprotection against bile acids. The reversal of fluid transport from absorption to secretion occurs together with bicarbonate secretion after feeding, predominantly in response to an adenosine 3',5'-cyclic monophosphate (cAMP)-dependent pathway triggered by neurohormonal factors, such as vasoactive intestinal peptide. Mucin secretion in the gallbladder is stimulated predominantly by calcium-dependent pathways that are activated by ATP present in bile, and bile acids. The gallbladder epithelium has the capacity to absorb cholesterol and provides a cholecystohepatic shunt pathway for bile acids. Changes in gallbladder motor function not only can contribute to gallstone disease, but also subserve protective functions in multiple pathological settings through the sequestration of bile acids and changes in the bile acid composition. Cholecystectomy increases the enterohepatic recirculation rates of bile acids leading to metabolic effects and an increased risk of nonalcoholic fatty liver disease, cirrhosis, and small-intestine carcinoid, independently of cholelithiasis. Among subjects with gallstones, cholecystectomy remains a priority in those at risk of gallbladder cancer, while others could benefit from gallbladder-preserving strategies. © 2016 American Physiological Society. Compr Physiol 6:1549-1577, 2016.

The Density of Interstitial Cells of Cajal Is Diminished in Choledochal Cysts

BACKGROUND AND AIMS

Interstitial cells of Cajal (ICC) have been shown to be present in the extrahepatic biliary tract of animals and humans. However, ICC distribution in choledochal cysts (CC) has not been investigated. A study was conducted to investigate the distribution of ICC in the extrahepatic biliary tract, including CC, in pediatric human specimens.

METHOD

The specimens were divided into two main groups as gallbladders and common bile ducts. Gallbladders were obtained from the cholelithiasis, CC operations and autopsies. Common bile ducts were obtained from autopsies. Tissues were stained using c-kit immunohistochemical staining. ICC were assessed semi-quantitatively by applying morphological criteria and were counted as the number of cells/0.24 mm(2) in each area under light microscopy.

RESULTS

A total of 35 gallbladders and 14 CC were obtained from operations. Ten gallbladders plus common bile ducts were obtained from autopsies. The mean numbers of ICC in the gallbladders of cholelithiasis and the gallbladders of CC were 12.2 ± 4.9 and 5.3 ± 1.2, respectively (p = 0.003). The mean numbers of ICC in the common bile ducts and CC were 9.8 ± 2.9 and 3.4 ± 1.4, respectively (p = 0.001).

CONCLUSION

The scarcity of ICC in the extrahepatic biliary tract may be responsible for the etiopathogenesis of the CC.

Decreased expression of stem cell factor mRNA and protein in the gallbladders of guinea pigs fed on high cholesterol diet

OBJECTIVE

Sufficient evidence suggests that the c-kit protooncogene receptor and its ligand stem cell factor (scf) signal pathway play a crucial role in interstitial cells of Cajal (ICCs) development and maintenance of their phenotype. We aimed to determine the expressions of scf mRNA and scf protein in the gallbladders in guinea pigs fed on high cholesterol diet (HCD).

METHODS

The gallbladder and serum samples from 20 guinea pigs of HCD and from 20 guinea pigs of standard diet (StD) were used for this study. Serum lipid analysis was performed using standard laboratory procedure. Expression of scf mRNA was detected by reverse transcription polymerase chain reaction (RT-PCR), and expression of scf protein was detected by Western blot analysis.

RESULTS

Laboratory results showed serum total cholesterol (TC), low density lipoprotein (LDL) cholesterol , high density lipoprotein (HDL) cholesterol and triglyceride (TG) concentrations were significantly higher in the HCD group than in the StD group of guinea pigs (P < 0.001, respectively). Decreased expression of scf mRNA and protein were demonstrated in the HCD group compared with the StD group (P < 0.05 respectively).

CONCLUSION

The data indicates that the expression of scf mRNA and c-kit protein is significantly decreased in the gallbladders in guinea pigs of HCD.

The role of interstitial Cajal-like cells in the formation of cholesterol stones in guinea pig gallbladder

OBJECTIVES

To investigate the effect of interstitial Cajal-like cells (ICLCs) on contraction of gallbladder muscle strips; and to analyze the changes of ICLCs during cholesterol gallstone formation in guinea pig.

METHODS

The cholesterol gallstone animal model was made by feeding guinea pig with high cholesterol diet (HCD). In vitro isolated gallbladder muscle strips were prepared. Gallbladder motility was assessed by the contraction frequency and amplitude of slow wave in response to CCK-8. The alteration in ICLC density was estimated by using immunohistochemistry. The expression of c-kit and stem cell factor (SCF) were determined.

RESULTS AND CONCLUSIONS

The amplitude and frequency of slow wave was significantly lower in gallbladder muscle strips with the impaired ICLCs. And it is correlated with the decreased contractile response to CCK-8. In HCD guinea pig, the ICLC density and bile flow in response to CCK-8 were remarkably decreased. The results indicated that gallbladder ICLCs can create slow wave potential, and also get involved in the regulation of CCK-8 induced gallbladder smooth muscle motility. In the process of cholesterol gallstone formation, ICLC density clearly decreased. This further impaired gallbladder motility. The decrease in ICLC density may result from decreased expression of c-kit and SCF during cholesterol gallstone formation.

Impaired cholecystokinin-induced gallbladder emptying incriminated in spontaneous "black" pigment gallstone formation in germfree Swiss Webster mice

"Black" pigment gallstones form in sterile gallbladder bile in the presence of excess bilirubin conjugates ("hyperbilirubinbilia") from ineffective erythropoiesis, hemolysis, or induced enterohepatic cycling (EHC) of unconjugated bilirubin. Impaired gallbladder motility is a less well-studied risk factor. We evaluated the spontaneous occurrence of gallstones in adult germfree (GF) and conventionally housed specific pathogen-free (SPF) Swiss Webster (SW) mice. GF SW mice were more likely to have gallstones than SPF SW mice, with 75% and 23% prevalence, respectively. In GF SW mice, gallstones were observed predominately in heavier, older females. Gallbladders of GF SW mice were markedly enlarged, contained sterile black gallstones composed of calcium bilirubinate and <1% cholesterol, and had low-grade inflammation, edema, and epithelial hyperplasia. Hemograms were normal, but serum cholesterol was elevated in GF compared with SPF SW mice, and serum glucose levels were positively related to increasing age. Aged GF and SPF SW mice had deficits in gallbladder smooth muscle activity. In response to cholecystokinin (CCK), gallbladders of fasted GF SW mice showed impaired emptying (females: 29%; males: 1% emptying), whereas SPF SW females and males emptied 89% and 53% of volume, respectively. Bilirubin secretion rates of GF SW mice were not greater than SPF SW mice, repudiating an induced EHC. Gallstones likely developed in GF SW mice because of gallbladder hypomotility, enabled by features of GF physiology, including decreased intestinal CCK concentration and delayed intestinal transit, as well as an apparent genetic predisposition of the SW stock. GF SW mice may provide a valuable model to study gallbladder stasis as a cause of black pigment gallstones.

Decreased SCF/c-kit signaling pathway contributes to loss of interstitial cells of Cajal in gallstone disease

Cholecystolithiasis is a common disease, and gallbladder dysmotility is considered as a pivotal pathogenesis. Interstitial cells of Cajal (ICCs) serve as pacemakers and mediators of neuromuscular transmission for gastrointestinal motility. Reduction of ICCs has been reported in gallstone diseases. However, there are no reasonable mechanisms for the cholecystolithiasis-associated loss of ICCs in humans. Stem cell factor (SCF) and its ligand c-kit are essential for normal development and survival of ICCs. To date, little is known about the SCF/c-kit signaling pathway in gallstone diseases. The purpose of this study was to investigate the role of the SCF/c-kit signaling pathway in the loss of ICCs in cholecystolithiasis. Data from 18 patients with gallstones and 14 individuals without gallstones were compared. The gallbladder contractility was assessed by measuring the gallbladder ejection fraction (GEF) ultrasonographically. Tissues samples were obtained during surgery, changes of ICC quantities were analyzed by immunohistochemistry, and the mRNA and protein expression of SCF and c-kit were detected by Real-Time PCR and Western-blot analysis. Compared with the controls, the GEF was significantly reduced in the gallstone group, and decreased number of ICCs was present obviously in the gallstone group. Furthermore, the mRNA and protein expression of SCF and c-kit were significantly attenuated in the gallstone group. These data indicate that gallbladder motility may be affected by reduction of ICCs in gallstone disease. Additionally, the decreased of SCF/c-kit signaling pathway play an important role in the loss of ICCs.

Spatial organization and coordination of slow waves in the mouse anorectum

The internal anal sphincter (IAS) develops tone and is important for maintaining a high anal pressure while tone in the rectum is less. The mechanisms responsible for tone generation in the IAS are still uncertain. The present study addressed this question by comparing the electrical properties and morphology of the mouse IAS and distal rectum. The amplitude of tone and the frequency of phasic contractions was greater in the IAS than in rectum while membrane potential (Em) was less negative in the IAS than in rectum. Slow waves (SWs) were of greatest amplitude and frequency at the distal end of the IAS, declining in the oral direction. Dual microelectrode recordings revealed that SWs were coordinated over a much greater distance in the circumferential direction than in the oral direction. The circular muscle layer of the IAS was divided into five to eight 'minibundles' separated by connective tissue septa whereas few septa were present in the rectum. The limited coordination of SWs in the oral direction suggests that the activity in adjacent minibundles is not coordinated. Intramuscular interstitial cells of Cajal and platelet-derived growth factor receptor alpha-positive cells were present in each minibundle suggesting a role for one or both of these cells in SW generation. In summary, three important properties distinguish the IAS from the distal rectum: (1) a more depolarized Em; (2) larger and higher frequency SWs; and (3) the multiunit configuration of the muscle. All of these characteristics may contribute to greater tone generation in the IAS than in the distal rectum.

Effects of imatinib mesylate on the spontaneous activity generated by the guinea-pig prostate

What's known on the subject? and what does the study add?: Several studies have examined the functional role of tyrosine kinase receptors in the generation of spontaneous activity in various segments of the gastrointestinal and urogenital tracts through the application of its inhibitor, imatinib mesylate (Glivec®), but results are fairly inconsistent. This is the first study detailing the effects of imatinib mesylate on the spontaneous activity in the young and ageing prostate gland. As spontaneous electrical activity underlies the spontaneous rhythmic prostatic contractions that occur at rest, elucidating the mechanisms involved in the regulation of the spontaneous electrical activity and the resultant phasic contractions could conceivably lead to the identification of better targets and the development of more specific therapeutic agents to treat prostate conditions.

OBJECTIVE

To investigate the effect of imatinib mesylate, a tyrosine kinase receptor inhibitor, in the generation of spontaneous electrical and contractile activity in the young and ageing guinea-pig prostate.

MATERIALS AND METHODS

Standard tension and intracellular recording were used to measure spontaneous contractions and slow waves, respectively from the guinea-pig prostate at varying concentrations of imatinib mesylate (1-50 μm).

RESULTS

Imatinib mesylate (1-10 μm), did not significantly affect slow waves recorded in the prostate of both age groups but at 50 μm, the amplitude of slow waves from the ageing guinea-pig prostate was significantly reduced (P < 0.05, n = 5). In contrast, the amplitude of contractions across all concentrations in the young guinea-pig prostate was reduced to between 35% and 41% of control, while the frequency was reduced to 15.7% at 1 μm (n = 7), 49.8% at 5 μm (n = 10), 46.2% at 10 μm (n = 7) and 53.1% at 50 μm (n = 5). Similarly, imatinib mesylate attenuated the amplitude and slowed the frequency of contractions in ageing guinea-pigs to 5.15% and 3.3% at 1 μm (n = 6); 21.1% and 20.8% at 5 μm (n = 8); 58.4% and 8.8% at 10 μm (n = 11); 72.7% and 60% at 50 μm (n = 5).

CONCLUSIONS

A significant reduction in contractions but persistence of slow waves suggests imatinib mesylate may affect the smooth muscle contractile mechanism. Imatinib mesylate also significantly reduced contractions in the prostates of younger guinea pigs more than older ones, which is consistent with the notion that the younger guinea-pig prostate is more reliant on the tyrosine-dependent pacemaker ability of interstitial cells of Cajal-like prostatic interstitial cells.

Telocytes: new insight into the pathogenesis of gallstone disease

The major mechanisms of gallstone formation include biliary cholesterol hypersecretion, supersaturation and crystallization, mucus hypersecretion, gel formation and bile stasis. Gallbladder hypomotility seems to be a key event that triggers the precipitation of cholesterol microcrystals from supersaturated lithogenic bile. Telocytes, a new type of interstitial cells, have been recently identified in many organs, including gallbladder. Considering telocyte functions, it is presumed that these cells might be involved in the signalling processes. The purpose of this study was to correlate the quantity of telocytes in the gallbladder with the lithogenicity of bile. Gallbladder specimens were collected from 24 patients who underwent elective laparoscopic cholecystectomy for symptomatic gallstone disease. The control group consisted of 25 consecutive patients who received elective treatment for pancreatic head tumours. Telocytes were visualized in paraffin sections of gallbladders with double immunofluorescence using primary antibodies against c-Kit (anti-CD117) and anti-mast cell tryptase. Cholesterol, phospholipid and bile acid levels were measured in gallbladder bile. The number of telocytes in the gallbladder wall was significantly lower in the study group than that in the control group (3.03 ± 1.43 versus 6.34 ± 1.66 cell/field of view in the muscularis propria, P < 0.001) and correlated with a significant increase in the cholesterol saturation index. The glycocholic and taurocholic acid levels were significantly elevated in the control subjects compared with the study group. The results suggest that bile composition may play an important role in the reduction in telocytes density in the gallbladder.

Loss of gallbladder interstitial Cajal-like cells in patients with cholelithiasis

BACKGROUND

Interstitial cells of Cajal (ICCs) play an important role in the regulation of gut motility. There is growing evidence that interstitial Cajal-like cells (ICLCs) are present in the gallbladder wall. We hypothesize that changes in the density of ICLCs in the gallbladder wall may lead to the development of cholelithiasis due to the impairment of the gallbladder motility. The purpose of this study was to identify ICLCs in the gallbladders of patients with gallstones and to assess their densities.

METHODS

Data from 30 patients with gallstones and 25 individuals without gallstones were compared. Tissue samples were obtained during surgery, embedded in paraffin, and cut into sections. Following staining for CD117 and mast cell tryptase, the number of ICLCs and mast cells was determined using image analysis.

KEY RESULTS

Cells positive for the c-Kit receptor (CD117) were detected in the gallbladder wall in all cases examined. Interstitial Cajal-like cells were most frequently observed in the muscularis propria. The density of ICLCs in the muscularis propria was significantly lower in the patients with gallstones than the density observed in the controls (26.24 ± 10.89 vs 56.29 ± 13.35 cells/mm(2)). In contrast, the number of mast cells in the gallbladder was increased in the patients with gallstones when compared with the controls (143 ± 24 vs 112 ± 19 cells/mm(2)).

CONCLUSIONS & INFERENCES

The histopathological differences observed in this study may help elucidate the pathophysiology of gallstones. Gallbladder motility may be affected by the decreased number of ICLCs in patients with cholelithiasis.

Role of calcium in activation of hyperpolarization-activated cyclic nucleotide-gated channels caused by cholecystokinin octapeptide in interstitial cells of cajal

BACKGROUND

Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels regulate pacemaker activity in some cardiac cells and neurons. Little is known about the effects of cholecystokinin octapeptide (CCK-8) on HCN channels and excitability of murine interstitial cells of Cajal (ICCs).

METHODS

In the present study, the effects and mechanisms of CCK-8 on HCN channels were investigated by measuring mechanical contraction of smooth muscle strips and ionic channels of ICCs in murine gastric antrum.

RESULTS

Sulfated CCK-8 (CCK-8S) was used, and we found that CCK-8S increased the contraction of smooth muscle strips in the gastric antrum, which could be suppressed by specific HCN channel blockers CsCl and ZD7288. Extracellular calcium could also intensify the contraction. Under the same conditions, when antral strips were exposed to calcium ion (Ca²⁺)-free solution, no significant changes could be recorded with CCK-8S or ZD7288. Isolated ICCs from the murine gastric antrum identified by specific c-Kit antibody primers were chosen for electrophysiological recordings. HCN current (I(h)) of cultured ICCs was studied by whole-cell patch clamp techniques. A spontaneous transient inward current was recorded in ICCs, which could be inhibited by addition of CsCl and ZD7288; the current proved to be I(h). CCK-8S-facilitated I(h) in cultured ICCs could be inhibited by CsCl and ZD7288. When cultured ICCs were exposed to Ca²⁺-free solution, no significant changes could be recorded by application of CCK-8S on I(h), which proved extracellular calcium might have an excitatory effect on HCN channels.

CONCLUSION

We demonstrate that HCN channels are present in ICCs in the murine gastric antrum; they might be an important regulator of ICC excitability and pacemaker activity and are strongly affected by CCK-8S. Extracellular calcium might be a trigger in the activation of HCN channels caused by CCK-8S in cultured ICCs.

Identification of interstitial Cajal-like cells in the human thoracic duct

Interstitial Cajal-like cells (ICLCs) are speculated to be pacemakers in smooth muscle tissues. While the human thoracic duct (TD) is spontaneously active, the origin of this activity is unknown. We hypothesized that ICLCs could be present in the TD and using histological techniques, immunohistochemistry and immunofluorescence we have investigated the presence of ICLCs, protein markers for ICLCs and the cellular morphology of the human TD. Transmission electron microscopy was employed to investigate ultrastructure. Methylene blue staining, calcium-dependent fluorophores and confocal microscopy were used to identify ICLCs in live tissue. Methylene blue stained cells with morphology suggestive of ICLCs in the TD. Immunoreactivity localized the ICLC protein markers c-kit, CD34 and vimentin to many cells and processes associated with smooth muscle cells (SMCs): coexpression of c-kit with vimentin or CD34 was observed in some cells. Electron microscopy analysis confirmed ICLCs as a major cell type of the human TD. Lymphatic ICLCs possess caveolae, dense bands, a patchy basal lamina, intermediate filaments and specific junctions to SMCs. ICLCs were ultrastructurally differentiable from other interstitial cells observed: fibroblasts, mast cells, macrophages and pericytes. Lymphatic ICLCs were localized to the subendothelial region of the wall as well as in intimate association with smooth muscle bundles throughout the media. ICLCs were morphologically distinct with multiple processes and also spindle shapes. Confocal imaging with calcium-dependent fluorophores corroborated cell morphology and localization observed in fixed tissues. Lymphatic ICLCs thus constitute a significant cell type of the human TD and physically interact with lymphatic SMCs.

Telocytes in the interstitium of human exocrine pancreas: ultrastructural evidence

OBJECTIVES

Pancreatic interstitial cells are located among acini, ducts, nerves, and blood vessels. They are essential for pancreas development, physiology, and for oncogenic microenvironment. We identified cells with characteristic ultrastructural features of telocytes in pancreatic interstitium. Telocytes were initially described as interstitial Cajal-like cells, but it gradually became clear that they were a distinct novel cell type not directly related to canonical interstitial Cajal cells.

METHODS

Serial ultrathin sections of human pancreatic tissue were studied by transmission electron microscopy. Computer analysis software was used to obtain 2-dimensional compositions from serial micrographs and to perform morphometry.

RESULTS

Pancreatic telocytes appear as small-body cells with prolongations called telopodes. The ultrastructural features of telopodes are the following: (a) number: 1 to 3; (b) length: tens of micrometers; (c) moniliform aspect: with podoms (thicker portions) and podomers (thin segments, with a mean width of 60 nm, undetectable by light microscopy); (d) dichotomous branching forming a network; (e) establish homocellular and heterocellular junctions; (f) release of microvesicles/multivesicular bodies. Telopodes pass close to blood vessels, nerves, and pancreatic acinar cells and ducts.

CONCLUSIONS

Telocytes are present as distinct interstitial cells in the exocrine pancreatic stroma. They act as important players in intercellular signaling via stromal synapses and shed vesicle transfer.

Progress in research of interstitial cells of Cajal

Interstitial cells of Cajal (ICCs) are a kind of cells mainly found in the gastrointestinal tract as pacemaker and signal transduction cells. They have a close connection with muscular cells and terminal neurons and can stimulate and promote gastrointestinal motility. With the help of electron microscopes, we can clearly recognize their distribution and inner structure. C-kit protein is expressed by ICCs. Besides, many disorders of gastrointestinal motility are related to ICCs. In recent years, many scholars have found the trace of ICCs in different organs such as the gastrointestinal tract, biliary tract, bladder, and uterus, and they have tried to state the relationship between abnormal ICCs and some diseases. This article will review the progress in research of ICCs in terms of their origin, morphology, receptors, function, and related diseases.

Serotonin augments gut pacemaker activity via 5-HT3 receptors

Serotonin (5-hydroxytryptamine: 5-HT) affects numerous functions in the gut, such as secretion, muscle contraction, and enteric nervous activity, and therefore to clarify details of 5-HT's actions leads to good therapeutic strategies for gut functional disorders. The role of interstitial cells of Cajal (ICC), as pacemaker cells, has been recognised relatively recently. We thus investigated 5-HT actions on ICC pacemaker activity. Muscle preparations with myenteric plexus were isolated from the murine ileum. Spatio-temporal measurements of intracellular Ca(2+) and electric activities in ICC were performed by employing fluorescent Ca(2+) imaging and microelectrode array (MEA) systems, respectively. Dihydropyridine (DHP) Ca(2+) antagonists and tetrodotoxin (TTX) were applied to suppress smooth muscle and nerve activities, respectively. 5-HT significantly enhanced spontaneous Ca(2+) oscillations that are considered to underlie electric pacemaker activity in ICC. LY-278584, a 5-HT(3) receptor antagonist suppressed spontaneous Ca(2+) activity in ICC, while 2-methylserotonin (2-Me-5-HT), a 5-HT(3) receptor agonist, restored it. GR113808, a selective antagonist for 5-HT(4), and O-methyl-5-HT (O-Me-5-HT), a non-selective 5-HT receptor agonist lacking affinity for 5-HT(3) receptors, had little effect on ICC Ca(2+) activity. In MEA measurements of ICC electric activity, 5-HT and 2-Me-5-HT caused excitatory effects. RT-PCR and immunostaining confirmed expression of 5-HT(3) receptors in ICC. The results indicate that 5-HT augments ICC pacemaker activity via 5-HT(3) receptors. ICC appear to be a promising target for treatment of functional motility disorders of the gut, for example, irritable bowel syndrome.

Extrahepatic and intrahepatic human portal interstitial Cajal cells

Portal interstitial cells of Cajal (PICCs), acting as vascular pacemakers, were previously only identified in nonhumans. Moreover, there is no evidence available about the presence of such cells within the liver. The objective of the study is to evaluate whether or not PICCs are identifiable in humans and, if they are, whether or not they are following the scaffold of portal vein (PV) branches within the liver. We obtained extrahepatic PVs and liver samples from six adult human cadavers, negative for liver disease, in accordance with ethical rules. They were stained with hematoxylin-eosin (HE) and Giemsa, and then we performed immunohistochemistry on formalin-fixed paraffin-embedded specimens for CD117/c-kit, a marker of the Cajal's cells. Immune labeling was also performed for S-100 protein, desmin, glial fibrillary acidic protein (GFAP), neurofilaments, α-smooth muscle actin (α-SMA), and CD34. c-kit-Positive PICCs were identified within the extrahepatic PV, in portal spaces, and septa. On adjacent sections, these PICCs were negative for all the other antibodies used. In conclusion, our study confirms the presence of extrahepatic PICCs on humans, which may act as a possible intrinsic pacemaker in the human PV. However, the intrahepatic PICCs, which were evidenced here for the first time, are in need for further experimental studies to evaluate their functional role. A promising further direction of the study is the PICCs role in the idiopathic portal hypertension.

Telocytes accompanying cardiomyocyte in primary culture: two- and three-dimensional culture environment

Recently, the presence of telocytes was demonstrated in human and mammalian tissues and organs (digestive and extra-digestive organs, genitourinary organs, heart, placenta, lungs, pleura, striated muscle). Noteworthy, telocytes seem to play a significant role in the normal function and regeneration of myocardium. By cultures of telocytes in two- and three-dimensional environment we aimed to study the typical morphological features as well as functionality of telocytes, which will provide important support to understand their in vivo roles. Neonatal rat cardiomyocytes were isolated and cultured as seeding cells in vitro in two-dimensional environment. Furthermore, engineered myocardium tissue was constructed from isolated cells in three-dimensional collagen/Matrigel scaffolds. The identification of telocytes was performed by using histological and immunohistochemical methods. The results showed that typical telocytes are distributed among cardiomyocytes, connecting them by long telopodes. Telocytes have a typical fusiform cell body with two or three long moniliform telopodes, as main characteristics. The vital methylene blue staining showed the existence of telocytes in primary culture. Immunohistochemistry demonstrated that some c-kit or CD34 immuno-positive cells in engineered heart tissue had the morphology of telocytes, with a typical fusiform cell body and long moniliform telopodes. Also, a significant number of vimentin⁺ telocytes were present within engineered heart tissue. We suggest that the model of three-dimensional engineered heart tissue could be useful for the ongoing research on the functional relationships of telocytes with cardiomyocytes. Because the heart has the necessary potential of changing the muscle and non-muscle cells during the lifetime, telocytes might play an active role in the heart regeneration process. Moreover, telocytes might be a useful tool for cardiac tissue engineering.

Role of connexin 43 in the maintenance of spontaneous activity in the guinea pig prostate gland

BACKGROUND AND PURPOSE

To investigate the role of connexin 43 in the maintenance of spontaneous activity in prostate tissue from young and old guinea pigs.

EXPERIMENTAL APPROACH

Conventional intracellular microelectrode and tension recording techniques, coupled with Western blot analysis and immunohistochemistry for connexin 43 (CX43) were used. The effects of three gap junction uncouplers, 18β glycyrrhetinic acid (10 µM, 40 µM), carbenoxolone (10 µM, 50 µM) and octanol (0.5 mM, 1 mM), were studied in cells displaying slow wave activity and on spontaneously contracting tissue from prostate glands of young (2-5 months) and old (9-16 months) guinea pigs.

KEY RESULTS

18β Glycyrrhetinic acid (40 µM), carbenoxolone (50 µM) or octanol (0.5 mM) abolished slow wave activity in prostate tissue from young and old guinea pigs and depolarized membrane potential by approximately 5 mV. These treatments also abolished all contractions in both sets of prostate tissue. These effects were reversed upon washout. Western blot analysis and CX43 immunohistochemistry showed that there was no age-related difference in the expression and distribution of CX43 in prostate tissues.

CONCLUSION AND IMPLICATIONS

When gap junctional communication via CX43 was disrupted, spontaneous activity was abolished at a cellular and whole tissue level; CX43 is therefore essential for the maintenance of spontaneous slow wave activity and subsequent contractile activity in the guinea pig prostate gland.

Relationship between interstitial cells of Cajal, fibroblast-like cells and inhibitory motor nerves in the internal anal sphincter

Interstitial cells of Cajal (ICC) have been shown to participate in nitrergic neurotransmission in various regions of the gastrointestinal (GI) tract. Recently, fibroblast-like cells, which are positive for platelet-derived growth factor receptor α (PDGFRα(+)), have been suggested to participate additionally in inhibitory neurotransmission in the GI tract. The distribution of ICC and PDGFRα(+) cell populations and their relationship to inhibitory nerves within the mouse internal anal sphincter (IAS) are unknown. Immunohistochemical techniques and confocal microscopy were therefore used to examine the density and arrangement of ICC, PDGFRα(+) cells and neuronal nitric-oxide-synthase-positive (nNOS(+)) nerve fibers in the IAS of wild-type (WT) and W/W ( v ) mice. Of the total tissue volume within the IAS circular muscle layer, 18% consisted in highly branched PDGFRα(+) cells (PDGFRα(+)-IM). Other populations of PDGFRα(+) cells were observed within the submucosa and along the serosal and myenteric surfaces. Spindle-shaped intramuscular ICC (ICC-IM) were present in the WT mouse IAS but were largely absent from the W/W ( v ) IAS. The ICC-IM volume (5% of tissue volume) in the WT mouse IAS was significantly smaller than that of PDGFRα(+)-IM. Stellate-shaped submucosal ICC (ICC-SM) were observed in the WT and W/W ( v ) IAS. Minimum surface distance analysis revealed that nNOS(+) nerve fibers were closely aligned with both ICC-IM and PDGFRα(+)-IM. An even closer association was seen between ICC-IM and PDGFRα(+)-IM. Thus, a close morphological arrangement exists between inhibitory motor neurons, ICC-IM and PDGFRα(+)-IM suggesting that some functional interaction occurs between them contributing to inhibitory neurotransmission in the IAS.

Ultrastructural properties of interstitial cells of Cajal in the Guinea pig bladder

PURPOSE

We investigated the ultrastructural characteristics of interstitial cells of Cajal in the guinea pig bladder.

MATERIALS AND METHODS

Bladders were removed from guinea pigs and processed for transmission electron microscopy. Some sections were labeled with c-Kit antibodies and colloidal gold particles for positive identification of interstitial cells of Cajal.

RESULTS

Kit positive cells, identified with 10 nm gold particles, were located on the periphery of detrusor smooth muscle bundles and in the interbundle spaces. Interstitial cells of Cajal in these regions contained mitochondria, rough and smooth endoplasmic reticulum, thin and intermediate filaments, caveolae, Golgi apparatus, free ribosomes, cytoplasmic vesicles and had a discontinuous basal lamina. They were distinct from smooth muscle cells by an absence of dense bodies, membrane attachment bands and thick filaments. The ultrastructure of interstitial cells of Cajal in all regions of the bladder wall examined were similar and the myofibroblast characteristic, fibronexus, was not evident in any of the cells examined. Interstitial cells of Cajal had lateral branches which extended toward other interstitial cells of Cajal, neighboring smooth muscle cells or nerves. Cells with the ultrastructural profile of interstitial cells of Cajal were associated with bladder microvessels and their branched processes were in close proximity to vascular smooth muscle cells.

CONCLUSIONS

Bladder interstitial cells of Cajal have typical ultrastructural characteristics of interstitial cells of Cajal from other tissues and were immunopositive for the interstitial cell of Cajal marker Kit. They were closely associated with detrusor smooth muscle and often networked with other interstitial cells of Cajal. The observation of perivascular cells with interstitial cells of Cajal characteristics indicates that there may be more subtypes of these cells in the bladder than previously considered.

Effects of imatinib mesylate in interstitial cells of Cajal from murine small intestine

The interstitial cells of Cajal (ICCs) are pacemakers in the gastrointestinal tract. The possibility of whether imatinib mesylate, a Kit receptor tyrosine kinase inhibitor, modulates pacemaker activities in the ICC was examined using the whole cell patch clamp technique. Imatinib decreased the amplitude of pacemaker potentials in a dose-dependent manner in current-clamp mode. Because the effects of imatinib on pacemaker potentials were the same as those of pinacidil, we examined the effect of glibenclamide on ICC exposed to imatinib. The effects of imatinib on pacemaker potentials were blocked by glibenclamide. To see whether the production of prostaglandins (PGs) is involved in the inhibitory effect of imatinib on pacemaker potentials, we tested the effects of naproxen (a non-selective cyclooxygenase inhibitor) and AH6809 (a prostaglandin EP1 and EP2 receptor antagonist). Naproxen and AH6809 blocked the inhibitory effects of imatinib on ICC. Butaprost (an EP2 receptor agonist) showed the actions on pacemaker potentials in the same manner as imatinib. However, SC 19220 (an EP1 receptor antagonist) has no effects. To investigate the involvement of cAMP and protein kinase A (PKA) in the effects of imatinib on ICC, SQ 22536 (an inhibitor of adenylate cyclase) and mPKAI (an inhibitor of myristoylated PKA) were used. Both SQ-22536 and mPKAI blocked the imatinib-mediated inhibition of pacemaker potentials. However, the protein kinase C (PKC) inhibitors did not block the imatinib-mediated inhibition of pacemaker potentials. These results indicate that imatinib inhibits the pacemaker potentials of ICC by activating ATP-sensitive K(+) channels and PKA-dependent, PKC-independent manner.

Interstitial cells of Cajal in the urinary tract

The study of novel interstitial cells in the tissues of the urinary tract has defined advances in the field in the last decade. These intriguing cells belong to the same family as the better known interstitial cells of Cajal (ICC) of the gastrointestinal tract, and their discovery has been interpreted to suggest that pacemaker cells may be present in the urinary tract, driving the spontaneous or myogenic activity of the neighboring smooth muscle. This scenario may be true for the urethra where ICC have been described as "loose pacemakers" providing multiple, random inputs to modulate urethral smooth muscle activity. However, there is a paucity of direct evidence available to support this hypothesis in the bladder (where the smooth muscle cells are spontaneously active) or the renal pelvis (where atypical smooth muscle cells are the pacemakers), and it now seems more likely that urinary tract ICC act as modulators of smooth muscle activity.Interestingly, the literature suggests that the role of urinary tract ICC may be more apparent in pathophysiological conditions such as the overactive bladder. Several reports have indicated that the numbers of ICC present in overactive bladder tissues are greater than those from normal tissues; moreover, the contractility of tissues from overactive bladders in vitro appears to be more sensitive to the Kit antagonist, glivec, than those from normal bladder. Future research on urinary tract ICC in the short to medium term is likely to be dynamic and exciting and will lead to increasing our understanding of the roles of these cells in both normal and dysfunctional bladder.

Hydrophobic bile salts inhibit gallbladder smooth muscle function via stimulation of GPBAR1 receptors and activation of KATP channels

Hydrophobic bile salts are thought to contribute to the disruption of gallbladder smooth muscle (GBSM) function that occurs in gallstone disease, but their mechanism of action is unknown. The current study was undertaken to determine how hydrophobic bile salts interact with GBSM, and how they reduce GBSM activity. The effect of hydrophobic bile salts on the activity of GBSM was measured by intracellular recording and calcium imaging using wholemount preparations from guinea pig and mouse gallbladder. RT-PCR and immunohistochemistry were used to evaluate expression of the G protein-coupled bile acid receptor, GPBAR1. Application of tauro-chenodeoxycholate (CDC, 50-100 microm) to in situ GBSM rapidly reduced spontaneous Ca(2+) flashes and action potentials, and caused a membrane hyperpolarization. Immunoreactivity and transcript for GPBAR1 were detected in gallbladder muscularis. The GPBAR1 agonist, tauro-lithocholic acid (LCA, 10 microm) mimicked the effect of CDC on GBSM. The actions of LCA were blocked by the protein kinase A (PKA) inhibitor, KT5720 (0.5-1.0 microm) and the K(ATP) channel blocker, glibenclamide (10 microm). Furthermore, LCA failed to disrupt GBSM activity in Gpbar1(/) mice. The findings of this study indicate that hydrophobic bile salts activate GPBAR1 on GBSM, and this leads to activation of the cyclic AMP-PKA pathway, and ultimately the opening of K(ATP) channels, thus hyperpolarizing the membrane and decreasing GBSM activity. This inhibitory effect of hydrophobic bile salt activation of GPBAR1 could be a contributing factor in the manifestation of gallstone disease.

Morphological expression of KIT positive interstitial cells of Cajal in human bladder

PURPOSE

We investigated the 3-dimensional morphological arrangement of KIT positive interstitial cells of Cajal in the human bladder and explored their structural interactions with neighboring cells.

MATERIALS AND METHODS

Human bladder biopsy samples were prepared for immunohistochemistry/confocal or transmission electron microscopy.

RESULTS

Whole mount, flat sheet preparations labeled with anti-KIT (Merck, Darmstadt, Germany) contained several immunopositive interstitial cell of Cajal populations. A network of stellate interstitial cells of Cajal in the lamina propria made structural connections with a cholinergic nerve plexus. Vimentin positive cells of several morphologies were present in the lamina propria, presumably including fibroblasts, interstitial cells of Cajal and other cells of mesenchymal origin. Microvessels were abundant in this region and branched, elongated KIT positive interstitial cells of Cajal were found discretely along the vessel axis with each perivascular interstitial cell of Cajal associated with at least 6 vascular smooth muscle cells. Detrusor interstitial cells of Cajal were spindle-shaped, branched cells tracking the smooth muscle bundles, closely associated with smooth muscle cells and vesicular acetylcholine transferase nerves. Rounded, nonbranched KIT positive cells were more numerous in the lamina propria than in the detrusor and were immunopositive for anti-mast cell tryptase. Transmission electron microscopy revealed cells with the ultrastructural characteristics of interstitial cells of Cajal throughout the human bladder wall.

CONCLUSIONS

The human bladder contains a network of KIT positive interstitial cells of Cajal in the lamina propria, which make frequent connections with a cholinergic nerve plexus. Novel perivascular interstitial cells of Cajal were discovered close to vascular smooth muscle cells, suggesting interstitial cells of Cajal-vascular coupling in the bladder. KIT positive detrusor interstitial cells of Cajal tracked smooth muscle bundles and were associated with nerves, perhaps showing a functional tri-unit controlling bladder contractility.

Interstitial cells of Cajal are present in human extrahepatic bile ducts

BACKGROUND AND AIMS

Interstitial cells of Cajal (ICC) are distributed with smooth muscle throughout the gastrointestinal tract and are involved in regulating motility. ICC were recently discovered in the wall of the human gallbladder. This study sought to determine whether ICC are present in human bile ducts.

METHODS

Biliary tract samples were obtained from several sources: surgical specimens (n = 16, 11 women, mean age 61 years); archival post-mortem specimen (n = 1, 86 years, man); and cadavers (n = 2, 68 and 80 years, men). Paraffin-embedded sections (3 microm) from the gallbladder (fundus, body and neck) and both extrahepatic and intrahepatic bile ducts were investigated. A double immunofluorescence protocol using polyclonal and monoclonal c-kit antibodies and mast cell tryptase was used to distinguish c-kit-positive cells with typical ICC morphology from c-kit-positive mast cells. Small bowel samples were used as positive controls. ICC in the gallbladder were confirmed by ultrastructural study.

RESULTS

c-kit-positive cells with characteristic ICC morphology were identified in the subepithelial and muscular layers of the gallbladder and extrahepatic bile ducts. They were most prominent within the muscle layer of the extrahepatic bile ducts where they were organized into loosely arranged laminae running parallel to circular smooth muscle fibers. ICC were not found in intrahepatic bile ducts.

CONCLUSION

This study demonstrates for the first time that ICC are present in human extrahepatic bile ducts where they are more densely aggregated than in the gallbladder. This cellular network is likely to be involved in biliary tract motility and its related disorders.

Myometrial interstitial cells and the coordination of myometrial contractility

A strict regulation of contractility in the uterus and fallopian tube is essential for various reproductive functions. The uterus contributes, through either increased contractility or periods of relative quiescence, to: (i) expulsion of menstrual debris, (ii) sperm transport, (iii) adequate embryo placement during implantation, (iv) enlarging its capacity during pregnancy and (v) parturition. The dominant cell population of the uterine wall consists of smooth muscle cells that contain the contractile apparatus responsible for the generation of contractile force. Recent interest has focused on a new population of cells located throughout the myometrium on the borders of smooth muscle bundles. These cells are similar to interstitial cells of Cajal (ICC) in the gut that are responsible for the generation of electrical slow waves that control peristalsis. A precise role for myometrial Cajal-like interstitial cells (m-ICLC) has not been identified. m-ICLC express the c-kit receptor, involved in creating and maintaining the ICC phenotype in the gastrointestinal tract. However, both acute and prolonged inhibition of this receptor with the c-kit antagonist imatinib mesylate does not appear to affect the spontaneous contractility of myometrium. Calcium imaging of live tissue slices suggests that contractile signalling starts on the borders of smooth muscle bundles where m-ICLC are located and recently the possible role of extracellular ATP signalling from m-ICLC has been studied. This manuscript reviews the evidence regarding tissue-level signalling in the myometrium with a particular emphasis on the anatomical and possible functional aspects of m-ICLC as new elements of the contractile mechanisms in the uterus.

Expression of C-kit messenger ribonucleic acid and C-kit protein in the gallbladders in guinea pigs of high cholesterol diet

The c-kit protooncogene receptor and its ligand-stem cell factor regulating the proliferation and survival of interstitial cells of Cajal (ICCs) have been described. The aim of this study was to determine the expression of c-kit mRNA and c-kit protein in the gallbladders in guinea pigs of high cholesterol diet (HCD). The gallbladder samples from 16 guinea pigs of HCD and from 16 guinea pigs of standard diet (StD) were used for this study. Expression of c-kit mRNA was detected by reverse transcription polymerase chain reaction (RT-PCR), and expression of c-kit protein was detected by Western blot analysis. Serum total cholesterol (TC) (39 +/- 6 vs. 109 +/- 20 mg/dl), low density lipoprotein (LDL) cholesterol (24 +/- 4 vs. 71 +/- 10 mg/dl), high density lipoprotein (HDL) cholesterol (2.4 +/- 0.4 vs. 7.0 +/- 1.6 mg/dl), and triglyceride (TG) (58 +/- 8 vs. 118 +/- 23 mg/dl) concentrations were significantly higher in the HCD group than in the StD group of guinea pigs (P < 0.001, respectively). Decreased expression of c-kit mRNA was demonstrated in the HCD group compared with the StD group. The ratio of c-kit mRNA and GAPDH was 0.56 +/- 0.09 in controls and 0.50 +/- 0.07 in the HCD group (P = 0.033). C-kit protein expression significantly declined in the HCD group. The mean value of optical density was 129 +/- 25 in the StD group and 103 +/- 19 in the HCD group (P = 0.0009). The data indicate that the expression of c-kit mRNA and c-kit protein significantly decreased in the gallbladders in guinea pigs of HCD.

A distinct type of cell in myocardium: interstitial Cajal-like cells (ICLCs)

The existence of a novel type of interstitial cells in the heart, interstitial Cajal-like cells (ICLCs), had been described for the first time in 2005. Their identification was mainly based on ultrastructural criteria: very long (tens up to hundreds of micrometres) and moniliform prolongations, which are extremely thin (less than 0.2 μm), below the resolving power of light microscopy. Myocardial ICLCs were also identified by methylene-blue vital staining, silver impregnation, and immunoreactivity for CD 34, vimentin, CD117/c-kit, etc. Although a series of studies provided evidence for the existence of ICLCs in human atria and rat ventricles, further investigations in other laboratories, using additional techniques, are required to substantiate the consistency of these findings. Here we provide further evidence for the existence of ICLCs in human and mammalian hearts (by transmission and scanning electron microscopy, as well as confocal laser scanning microscopy). Noteworthy, we confirm that ICLCs communicate with neighbouring cells via shedding (micro)vesicles. Although these so-called ICLCs represent a distinct type of cells, different from classical interstitial cells of Cajal, or fibroblasts, their role(s) in myocardium remain(s) to be established. Several hypotheses are proposed: (i) adult stromal (mesenchymal) stem cells, which might participate in cardiac repair/remodelling; (ii) intercellular signalling (e.g. via shedding microvesicles); (iii) chemo-mechanical transducers and (iv) players in pacemaking and/or arrhytmogenesis, and so on.

Distribution of the interstitial Cajal-like cells in the gallbladder and extrahepatic biliary duct of the guinea-pig

It has been suggested that interstitial Cajal-like cells (ICLC) may be involved in the spontaneous rhythmic electrical activities of the extrahepatic bile duct system. The present study investigated the distribution and characteristics of ICLC, which are immunopositive for CD117/ Kit receptor tyrosine kinase, using immunohistochemistry employing a monoclonal antibody raised against CD117/Kit on whole-mount preparations. The Kit-positive ICLC were examined using confocal laser scanning microscopy or fluorescence microscopy. ICLC, immunoreactive for Kit, were pleiomorphic and/or spindle-shaped cells with a few bipolar processes and distributed in the smooth muscle layers of the gallbladder and bile duct system. They were scattered in the hepatic duct, cystic duct and gallbladder as well as in the upper part of the common bile duct. The ICLC gradually increased in number and formed a completed cellular network in the lower part of the common bile duct and ampulla. The numbers of ICLC in the ampulla were similar to that of the duodenum and significantly much greater in number than in the gallbladder and bile ducts. The density of the ICLC in the common bile duct was significantly higher than that of other bile ducts. Our results suggested that the ICLC might contribute to the regulation of the spontaneous rhythmic contraction and development of motility disorders of the bile duct system.

Effects of cholecystokinin on gallbladder muscle stripes of guinea pigs with cholesterol gallstone in vitro

AIM: To establish an animal model of cholesterol stone and to explore the effects of cholecystokinin (CCK) on gallbladder muscle stripes of guinea pigs with cholesterol stone in vitro as well as to investigate the role of biliary kinetics in cholesterol stone formation.

METHODS: The animal model of cholesterol stone was established by feeding guinea pig with stone-leading forage. The guinea pigs were assigned to four groups: group A (the normal guinea pigs), group B (stone-leading forage for 4 wk), group C (stone-leading forage for 8 wk), and group D (the normal guinea pigs with injury of interstitial cell of cajal (ICC). Effects of 10^-9, 10^-8 and 10^-7 mol/L cholecystokinin (CCK) on gallbladder muscle stripes of guinea pigs in vitro among the four groups were recorded and analyzed.

RESULTS: No cholesterol stone was observed in group A, and a total of 13 cases of cholesterol stone were observed in group B and C. The amplitude of contraction showed a dose-independent relationship with CCK-8 in groups A, B and C. Compared with group A, there was statistically significant diffference in group B and group C (P < 0.05). The contraction of smooth muscle was nearly abolished when interstitial cells of Cajal were destroyed using methylene blue incubation and intensive illumination. Although CCK was administered, there was no significant difference in the amplitude of the contraction of smooth muscle strip in group D (10^-9 mol/L: 0.461 ± 0.071 vs 1.461 ± 0.252; 10^-8 mol/L: 0.608 ± 0.118 vs 2.484 ± 0.283; 10^-7 mol/L: 0.641 ± 0.129 vs 3.312 ± 0.311, all P < 0.01).

CONCLUSION: Muscular tension is significantly inhibited following injury of interstitial cells of Cajal. The damage of interstitial cells of Cajal may be an important factor related to cholelithiasis.

ATP induces guinea pig gallbladder smooth muscle excitability via the P2Y4 receptor and COX-1 activity

The purpose of this study was to elucidate the mechanisms by which ATP increases guinea pig gallbladder smooth muscle (GBSM) excitability. We evaluated changes in membrane potential and action potential (AP) frequency in GBSM by use of intracellular recording. Application of ATP (100 microM) caused membrane depolarization and a significant increase in AP frequency that were not sensitive to block by tetrodotoxin (0.5 microM). The nonselective P2 antagonist, suramin (100 microM), blocked the excitatory response, resulting in decreased AP frequency in the presence of ATP. The excitatory response to ATP was not altered by pyridoxal-phosphate-6-azophenyl-2,4-disulfonic acid (30 microM), a nonselective P2X antagonist. UTP also caused membrane depolarization and increased AP frequency, with a similar dose-response relationship as ATP. RT-PCR demonstrated that the P2Y(4), but not P2Y(2), receptor subtype is expressed in guinea pig gallbladder muscularis. ATP induced excitation was blocked by indomethacin (10 microM) and the cyclooxygenase (COX)-1 inhibitor SC-560 (300 nM), but not the COX-2 inhibitor nimesulide (500 nM). These data suggest that ATP stimulates P2Y(4) receptors within the gallbladder muscularis and, in turn, stimulate prostanoid production via COX-1 leading to increased excitability of GBSM.

Uterine contractions depend on KIT-positive interstitial cells in the mouse: genetic and pharmacological evidence

In the gastrointestinal tract, interstitial cells of Cajal (ICCs) generate a pacemaker activity. They produce electric slow waves that trigger and coordinate gut smooth muscle contractions. Interstitial cells of Cajal's slender shape is revealed by KIT immunostaining. Based on several features, including KIT expression and KIT dependence, ICC-like cells were identified in nongastrointestinal tissues. Here, we investigated in the mouse whether uterine contractions depend on ICC-like cells' activity. By labeling KIT-expressing cells, we found putative ICC-like cells in the uterus, observed as KIT-positive interstitial, long spindle-shaped cells with fine branched cytoplasm processes, distributed in muscular layers and in subepithelial connective tissue. We then checked the potential KIT dependence of ex vivo contractile activity of the uterus by combining genetic and pharmacological approaches, using the Kit W-v hypomorphic mutation, and imatinib as a KIT noncompetitive inhibitor. We found a significant reduction in frequency of longitudinal uterine contractions in Kit W-v/Kit W-v compared with Kit+/+ mice, whereas amplitude was unaffected. There was no difference in frequency or amplitude of circular uterine contractions between Kit W-v/Kit W-v and Kit+/+ mice. Ex vivo treatment of Kit+/+ uterine horns with imatinib resulted in a dose-dependent reduction of the frequency and amplitude of longitudinal myometrial contractions. Amplitude and frequency of circular contractions were unaffected in presence of imatinib. These concurrent results suggest that longitudinal contractions of the uterus depend on a KIT signaling pathway of ICC-like cells. The existence of ICC-like cells in the myometrium may enhance our understanding of uterine spontaneous contractile activity and suggest new approaches for treatment of uterine contractility disorders.