The identification of specialized pacemaking cells in the anal sphincters

Resveratrol improves urinary dysfunction in rats with chronic prostatitis and suppresses the activity of the stem cell factor/c-Kit signaling pathway

Chronic prostatitis (CP) is a common urological disorder, with bladder voiding dysfunction being the primary clinical manifestation. Resveratrol is polyphenolic compound isolated from numerous plants, with widely‑reported anti-inflammatory properties. The present study aimed to investigate whether resveratrol may improve overactive bladder in rats with CP and to investigate the underlying molecular mechanisms. Furthermore, the potential pharmacological synergy between resveratrol and solifenacin was also investigated as a potential treatment for CP. Following the successful establishment of a rat model of CP by subcutaneously injecting DPT vaccine, rats were treated with resveratrol or a combination of resveratrol + solifenacin. Bladder pressure and volume tests were performed to investigate the effect of resveratrol and solifenacin on urinary dysfunction in rats with chronic prostatitis. Western blot analysis and immunohistochemical staining were used to examine the expression of c‑Kit receptor, stem cell factor (SCF), AKT and phosphorylated‑AKT (p‑AKT) in the bladder tissue. The results of the bladder pressure and volume test indicated that the maximum capacity of the bladder, residual urine volume and maximum voiding pressure in the control group were 0.57 ml, 0.17 ml and 29.62 cm H2O, respectively. These values were increased by 71, 27 and 206% in rats in the CP group compared with the control group. Following treatment with resveratrol, the results in the resveratrol group were reduced by 25.77, 44.23 and 13.32% compared with the CP group. The results of western blot analysis, immunohistochemical staining and immunofluorescence labeling demonstrate that the protein expression of SCF, c‑Kit and p‑AKT in the bladder of rats in the CP group was 4.32, 6.13 and 6.31 times higher compared with the control group, respectively. Following treatment with resveratrol, protein expression was significantly reduced. However, no significant differences were observed between the protein expression of the SCF, c‑Kit and p‑AKT in the bladder between the resveratrol and combination groups. In conclusion, resveratrol may improve overactive bladder by downregulating the protein expression of SCF, c‑Kit and p‑AKT in the bladder of rats with CP. Furthermore, a combination of resveratrol and solifenacin may have potential pharmacological synergy as a treatment for patients with CP.

Three Gaseous Neurotransmitters, Nitric oxide, Carbon Monoxide, and Hydrogen Sulfide, Are Involved in the Neurogenic Relaxation Responses of the Porcine Internal Anal Sphincter

Background/Aims

The internal anal sphincter (IAS) plays an important role in maintaining continence and a number of neurotransmitters are known to regulate IAS tone. The aim of this study was to determine the relative importance of the neurotransmitters involved in the relaxant and contractile responses of the porcine IAS.

Methods

Responses of isolated strips of IAS to electrical field stimulation (EFS) were obtained in the absence and presence of inhibitors of neurotransmitter systems.

Results

Contractile responses of the sphincter to EFS were unaffected by the muscarinic receptor antagonist, atropine (1 μM), but were almost completely abolished by the adrenergic neuron blocker guanethidine (10 μM). Contractile responses were also reduced (by 45% at 5 Hz, P < 0.01) following desensitisation of purinergic receptors with α,β-methylene-ATP (10 μM). In the presence of guanethidine, atropine, and α,β-methylene-ATP, the remaining relaxatory responses to EFS were examined. These responses were not altered by the cyclooxygenase inhibitor, indomethacin (5 μM), the vasoactive intestinal polypeptide receptor antagonist, [_d-p-Cl-Phe6,Leu17]-vasoactive intestinal peptide (PheLeu-VIP; 100 nM), or the purinoceptor antagonists, 8-phenyltheophyline (P1 receptors) or suramin (P2 receptors). However, relaxation responses were reduced by Nω-nitro-L-arginine (L-NNA; 100 μM), an inhibitor of nitric oxide synthesis (40–50% reduction), zinc protoprophyrin IX (10 μM), an inhibitor of carbon monoxide synthesis (20–40% reduction), and also propargylglycine (30 μM) and aminooxyacetic acid (30 μM), inhibitors of hydrogen sulphide synthesis (15–20% reduction).

Conclusions

Stimulation of IAS efferent nerves releases excitatory and inhibitory neurotransmitters: noradrenaline is the predominant contractile transmitter with a smaller component from ATP, whilst 3 gases mediate relaxation responses to EFS, with the combined contributions being nitric oxide > carbon monoxide > hydrogen sulfide.

Defining the histopathological changes induced by nonablative radiofrequency treatment of faecal incontinence--a blinded assessment in an animal model

AIM

Nonablative radiofrequency (RF) sphincter remodelling has been used to treat gastro-oesophageal reflux disease (GERD) and faecal incontinence (FI). Its mechanism of action is unclear. We aimed to investigate the histomorphological and pathophysiological changes to the internal and external anal sphincter (IAS and EAS) following RF remodelling.

METHOD

An experimental FI model was created in 12 female pigs: eight underwent RF 6 weeks following induction of FI (FI+RF) and four were untreated (UFI). Four animals served as controls (CG). Two blinded pathologists examined all haematoxylin and eosin and trichrome stained slides.

RESULTS

Compared with the UFI group, histological examination of the IAS in the FI+RF group demonstrated an increased smooth muscle (SM)/connective tissue ratio (77.2 vs 68.1%, P < 0.05) and increased collagen I compared with collagen III content (67.2 vs 54.9%, P < 0.001). The RF+FI group exhibited greater SM bundle thickness compared with the UFI group (SM width 486.93 vs 338.59 μm, P < 0.01; height 4384.4 vs 3321.0 μm, P < 0.05). The EAS of the FI+RF animals showed a significantly higher type I/II fibre ratio (33.5 vs 25.2%, P = 0.023) and fibre type I diameter (67.2 vs 59.7 μm, P < 0.001) compared with the UFI group. Post-RF manometry showed higher basal (18.8 vs 0 mmHg, P < 0.001) and squeeze (76.8 vs 12.4 mmHg, P < 0.05) anal pressures. After RF treatment, the number of interstitial cells of Cajal was significantly reduced compared with the UFI and CG groups [0.9 (FI+RF) vs 6.7 (UFI) vs 0.7 (CG) per mm(2) , P < 0.001].

CONCLUSION

In an animal model nonablative RF appeared to induce morphological changes in the IAS and EAS leading to an anatomical state reminiscent of normal sphincter structure.

Interstitial cells of Cajal modulate the tone of the human internal anal sphincter in vitro

BACKGROUND

Interstitial cells of Cajal, expressing the proto-oncogene c-kit, have been shown to regulate the spontaneous activity of the gastrointestinal tract. They have been described in the human internal anal sphincter; however, their function is still unclear.

OBJECTIVE

We examined the effects of the c-kit tyrosine kinase inhibitor imatinib mesylate on sphincter strips to investigate the function of the interstitial cells.

DESIGN

This was a case series study.

SETTIGS

This was a single-center study conducted at the University of Oxford.

PATIENTS

Internal anal sphincter strips were collected from 10 patients undergoing abdominoperineal resection or proctectomy and mounted in organ bath. Responses to electrical field stimulation and chemical agents were monitored in the absence of drugs and after the administration of increasing doses of imatinib mesylate. Immunohistochemistry was performed to identify interstitial cells.

MAIN OUTCOME MEASURES

The role of the interstitial cells in the internal anal sphincter was assessed.

RESULTS

Imatinib mesylate significantly reduced the tone and the spontaneous activity of the strips. In the absence of drugs, the tone generated was 147.7 ± 33.0 mg/mg of tissue. Administration of ≥5 μM of imatinib mesylate caused a dose-dependent reduction in the tone. Strips exhibited spontaneous activity characterized by intermittent low-amplitude contractions superimposed on basal tone (135.6 ± 4.6 contractions in 10 minutes). Imatinib mesylate significantly reduced the number of contractions at concentration >5 μM. No differences were observed in the responses to electrical field stimulation, carbachol, or phenylephrine. Immunohistochemistry showed c-kit-positive cells.

LIMITATIONS

This study was limited by the relatively small number of patients enrolled and thus the difficulty of finding human tissue for laboratory studies.

CONCLUSIONS

Our results suggest that the interstitial cells modulate the tone and the spontaneous activity of the internal anal sphincter. This provides a foundation for new approaches to preclinical and clinical research. Moreover, these cells may represent a target for drugs inhibiting the c-kit receptor and provide a new approach for treating anorectal diseases.

Differentiation of interstitial cells of Cajal in the human distal colon

At the end of the embryonic period of human development, interstitial cells of Cajal (ICC) are present in the esophagus, stomach, and proximal duodenum, around the inception of the myenteric plexus (MP) ganglia. In the small and large bowel, ICC appear later. The object of the present study was to determine the timing of appearance and pattern of distribution of ICC in the human embryonic and fetal distal colon. Human distal colon specimens were obtained from 8 embryos and 14 fetuses without gastrointestinal disorders. The specimens were 7-16 weeks of gestational age. The specimens were exposed to anti-c-kit antibodies to investigate ICC differentiation. Enteric plexuses were immunohistochemically examined using anti-neuron-specific enolase, and the differentiation of smooth muscle cells was studied with anti-desmin antibodies. In the distal colon, ICC emerged at weeks 10-11 of the fetal period in the form of two parallel belts of densely packed cells extending at the submucous plexus (SMP) and the MP level. These cells correspond to ICC of the SMP (ICC-SMP) and ICC of the MP (ICC-MP). The simultaneous appearance of ICC at the SMP and MP level in the distal colon can be explained by the fact that there are differences in the migration of neural crest cells in particular portions of the digestive tube. In conclusion, in humans, there was a difference in the patterns of development of ICC in the distal colon compared to the rest of the gut.

Short-term effects of neoadjuvant chemoradiotherapy on internal anal sphincter function: a human in vitro study

BACKGROUND

Neoadjuvant chemoradiotherapy is recommended in the treatment of locally advanced rectal cancer. Studies have suggested that chemoradiotherapy adversely affects anorectal function. However, the functional implication and the underlying neuromyogenic changes involved in radiation-induced damage are poorly understood.

OBJECTIVE

This study evaluated the functional changes following chemoradiotherapy on the internal anal sphincter.

DESIGN AND PATIENTS

This article describes an in vitro study on the internal anal sphincter collected from patients undergoing abdominoperineal resection or proctectomy. Five patients were treated by surgery alone (control group), and 6 received preoperative chemoradiotherapy (treatment group). Sphincter strips were mounted in organ bath, and the responses to electrical field stimulation and drugs were monitored.

SETTINGS

The study was performed at the University of Oxford.

MAIN OUTCOME MEASURES

The end points of this study were to investigate whether chemoradiotherapy has any significant effects on internal anal sphincter function and, subsequently, to establish the type of injury induced.

RESULTS

Chemoradiotherapy strips developed similar tone, but significantly lower spontaneous activity (p = 0.001) than controls. Electrical field stimulation induced relaxation, followed by contraction. At 50 Hz, electrical field stimulation produced 25.6 ± 4.9% (mean ± SE) of maximum relaxation followed by a contraction of 5.5 ± 0.9% of basal tone in chemoradiotherapy strips i9n comparison with 47.0 ± 6.2% (p = 0.009) and 17.7 ± 4.0% (p = 0.007) in controls. Relaxation was significantly attenuated by N-nitro-L-arginine. Significant differences were found in responses to carbachol (p = 0.018) and phenylephrine (p = 0.022), but not to sodium nitroprusside.

LIMITATIONS

This work was limited by the relatively small number of patients enrolled, because of the difficulty of finding human tissue for laboratory studies, and the lack of long-term results.

CONCLUSIONS

Chemoradiotherapy significantly impairs internal anal sphincter function and intrinsic nerves seem more susceptible than smooth muscle. The exclusion of anal canal from the radiation field is recommended, when oncologically safe.