Interstitial cells of Cajal in the human normal urinary bladder and in the bladder of patients with megacystis-microcolon intestinal hypoperistalsis syndrome

Defining the molecular fingerprint of bladder and kidney fibroblasts

Fibroblasts are integral to the organization and function of all organs and play critical roles in pathologies such as fibrosis; however, we have limited understanding of the fibroblasts that populate the bladder and kidney. In this review, I describe how transcriptomics is leading to a revolution in our understanding of fibroblast biology by defining the molecular fingerprint (i.e., transcriptome) of universal and specialized fibroblast types, revealing gene signatures that allows one to resolve fibroblasts from other mesenchymal cell types, and providing a new comprehension of the fibroblast lineage. In the kidney, transcriptomics is giving us new insights into the molecular fingerprint of kidney fibroblasts, including those for cortical fibroblasts, medullary fibroblasts, and erythropoietin (EPO)-producing Norn fibroblasts, as well as new information about the gene signatures of kidney myofibroblasts and the transition of kidney fibroblasts into myofibroblasts. Transcriptomics has also revealed that the major cell type in the bladder interstitium is the fibroblast, and that multiple fibroblast types, each with their own molecular fingerprint, are found in the bladder wall. Interleaved throughout is a discussion of how transcriptomics can drive our future understanding of fibroblast identification, diversity, function, and their roles in bladder and kidney biology and physiology in health and in disease states.

Neurogenic Lower Urinary Tract Dysfunction in Spinal Dysraphism: Morphological and Molecular Evidence in Children

Spinal dysraphism, most commonly myelomeningocele, is the typical cause of a neurogenic lower urinary tract dysfunction (NLUTD) in childhood. The structural changes in the bladder wall in spinal dysraphism already occur in the fetal period and affect all bladder wall compartments. The progressive decrease in smooth muscle and the gradual increase in fibrosis in the detrusor, the impairment of the barrier function of the urothelium, and the global decrease in nerve density, lead to severe functional impairment characterized by reduced compliance and increased elastic modulus. Children present a particular challenge, as their diseases and capabilities evolve with age. An increased understanding of the signaling pathways involved in lower urinary tract development and function could also fill an important knowledge gap at the interface between basic science and clinical implications, leading to new opportunities for prenatal screening, diagnosis, and therapy. In this review, we aim to summarize the evidence on structural, functional, and molecular changes in the NLUTD bladder in children with spinal dysraphism and discuss possible strategies for improved management and for the development of new therapeutic approaches for affected children.

Studies of ultrastructure, gene expression, and marker analysis reveal that mouse bladder PDGFRA+ interstitial cells are fibroblasts

Fibroblasts are crucial to normal and abnormal organ and tissue biology, yet we lack basic insights into the fibroblasts that populate the bladder wall. Candidates may include bladder interstitial cells (also referred to as myofibroblasts, telocytes, and interstitial cells of Cajal-like cells), which express the fibroblast-associated marker PDGFRA along with VIM and CD34 but whose form and function remain enigmatic. By applying the latest insights in fibroblast transcriptomics, coupled with studies of gene expression, ultrastructure, and marker analysis, we observe the following: 1) that mouse bladder PDGFRA+ cells exhibit all of the ultrastructural hallmarks of fibroblasts including spindle shape, lack of basement membrane, abundant endoplasmic reticulum and Golgi, and formation of homotypic cell-cell contacts (but not heterotypic ones); 2) that they express multiple canonical fibroblast markers (including Col1a2, CD34, LY6A, and PDGFRA) along with the universal fibroblast genes Col15a1 and Pi16 but they do not express Kit; and 3) that PDGFRA+ fibroblasts include suburothelial ones (which express ACTA2, CAR3, LY6A, MYH10, TNC, VIM, Col1a2, and Col15a1), outer lamina propria ones (which express CD34, LY6A, PI16, VIM, Col1a2, Col15a1, and Pi16), intermuscular ones (which express CD34, VIM, Col1a2, Col15a1, and Pi16), and serosal ones (which express CD34, PI16, VIM, Col1a2, Col15a1, and Pi16). Collectively, our study revealed that the ultrastructure of PDFRA+ interstitial cells combined with their expression of multiple canonical and universal fibroblast-associated gene products indicates that they are fibroblasts. We further propose that there are four regionally distinct populations of fibroblasts in the bladder wall, which likely contribute to bladder function and dysfunction.NEW & NOTEWORTHY We currently lack basic insights into the fibroblasts that populate the bladder wall. By exploring the ultrastructure of mouse bladder connective tissue cells, combined with analyses of their gene and protein expression, our study revealed that PDGRA+ interstitial cells (also referred to as myofibroblasts, telocytes, and interstitial cells of Cajal-like cells) are fibroblasts and that the bladder wall contains multiple, regionally distinct populations of these cells.

Differentiation of human urine-derived stem cells into interstitial cells of Cajal-like cells by exogenous gene modification: A preliminary study

Human urine-derived stem cells (hUSCs) show multipotential differentiation ability and can differentiate into mesodermal cell lineages. Interstitial cells of Cajal-like cells (ICC-LCs) are crucial for the pace-making function of spontaneous contraction in the bladder. However, the mechanisms by which hUSCs generate ICC-LCs have not been elucidated. In this study, we developed a strategy for directional differentiation of hUSCs into ICC-LCs. hUSCs were transfected with lentiviral vectors encoding c-Kit, stem cell factor (SCF), hyperpolarization activated cyclic nucleotide gated potassium channel 4 (HCN4), and 5-azacytidine induced 2 (AZI2) genes, and the cells were cultured for an additional 7 days in specific medium. The expression of the surface marker c-Kit on ICC-LCs was determined at 7 days after transfection. hUSCs were successfully expanded and transfected with the four lentiviral vectors. hUSCs transfected with lentiviral-c-Kit, lentiviral-HCN4, and lentiviral-AZI2 showed higher expression of c-Kit 7 days after transfection, but only the lentiviral-HCN4-transfected cells showed morphological alterations in ICC-LCs. These cells also displayed visible HCN current amplitude and density. This approach may provide a new strategy for the treatment of underactive bladder.

Combination of Luteolin and Solifenacin Improves Urinary Dysfunction Induced by Diabetic Cystopathy in Rats

Background

The purpose of the present study was to assess the effect of luteolin and solifenacin on diabetic cystopathy (DCP) and to investigate the mechanism of action. A novel link between the overexpression of c-Kit in the bladder and voiding dysfunction was identified in rats with DCP.

Material/Methods

A rat model of DCP was successfully established by intraperitoneal injection of streptozotocin and a diet high in glucose and lipids, and animals were treated with luteolin and solifenacin. The effect of luteolin and solifenacin on urinary dysfunction in DCP rats was investigated by assessing bladder pressure and performing a volume test. The protein levels of c-Kit, stem cell factor (SCF), p110, and phosphorylated p110 in the bladder were detected by Western blot analysis and immunohistochemical staining.

Results

In DCP rats, the protein levels of c-Kit, SCF and phosphorylated p110 in the bladder were significantly increased. However, oral treatment of DCP rats with luteolin combined with solifenacin resulted in effective improvement of overactive bladder and reduced the protein expression of c-Kit, SCF, and phosphorylated p110. Moreover, the effect of luteolin combined with solifenacin on maximum voiding pressure and residual urine volume was improved compared to that of luteolin alone.

Conclusions

Luteolin improved overactive bladder in DCP rats, which may be due to SCF/c-kit inhibition, as well as the downregulation of the phosphoinositide-3 kinase signaling pathway. Moreover, solifenacin enhanced the potential pharmacological effect of luteolin in the treatment of DCP.

The Mystery of the Interstitial Cells in the Urinary Bladder

Intrinsic mechanisms to restrain smooth muscle excitability are present in the bladder, and premature contractions during filling indicate a pathological phenotype. Some investigators have proposed that c-Kit⁺ interstitial cells (ICs) are pacemakers and intermediaries in efferent and afferent neural activity, but recent findings suggest these cells have been misidentified and their functions have been misinterpreted. Cells reported to be c-Kit⁺ cells colabel with vimentin antibodies, but vimentin is not a specific marker for c-Kit⁺ cells. A recent report shows that c-Kit⁺ cells in several species coexpress mast cell tryptase, suggesting that they are likely to be mast cells. In fact, most bladder ICs labeled with vimentin antibodies coexpress platelet-derived growth factor receptor α (PDGFRα). Rather than an excitatory phenotype, PDGFRα⁺ cells convey inhibitory regulation in the detrusor, and inhibitory mechanisms are activated by purines and stretch. PDGFRα⁺ cells restrain premature development of contractions during bladder filling, and overactive behavior develops when the inhibitory pathways in these cells are blocked. PDGFRα⁺ cells are also a prominent cell type in the submucosa and lamina propria, but little is known about their function in these locations. Effective pharmacological manipulation of bladder ICs depends on proper identification and further study of the pathways in these cells that affect bladder functions.

Distribution of interstitial cells of Cajal in the bladders of fetal rats with retinoic acid induced myelomeningocele

OBJECTIVE

Myelomeningocele (MMC) is one of the most common reason of neurogenic bladder dysfunction in children. Although neurogenic bladder dysfunction occurrence is related with bladder innervation, also there are some changes seen in the smooth muscle and neural cells of the bladder. Interstitial cells of Cajal (ICC) are the pacemaker cells found in organs with peristaltic activity. Although it has been shown that ICC are diminished in the rat urinary bladder with traumatic spinal cord injury, there is no data about ICC in fetal rat bladders with MMC. This study has been conducted to investigate the ICC in the bladders of fetal rats with retinoic acid induced MMC.

MATERIALS AND METHODS

Time dated pregnant Wistar albino rats were divided into 3 groups. In MMC group, dams were fed with gavage solution containing 60 mg/kg all-trans retinoic acid dissolved in olive oil on 10. embryologic day. Sham group animals were fed only olive oil. Control group dams were fed with standard rat chow. Fetuses were delivered by cesarean section and harvested on 22. embryologic day. MMC was identified by observing MMC sacs at the back of the fetuses. Distribution of ICCs were evaluated using immunohistochemical staining.

RESULTS

ICCs were found in all groups, which have the same morphological features that had been described earlier in the gastrointestinal tract and the bladder. The density of the ICC in the MMC group was found to be significantly decreased when compared with the control and the sham groups (p<0.05).

CONCLUSION

The density of the ICC in the urinary bladder decreased in the neurogenic bladder developed in MMC.

Megacystis microcolon intestinal hypoperistalsis syndrome: Case series and updated review of the literature with an emphasis on urologic management

INTRODUCTION

Megacystis microcolon intestinal hypoperistalsis (MMIHS) is a rare disorder characterized by distended nonobstructed bladder, microcolon, and decreased intestinal peristalsis. MMIHS has a particularly poor prognosis; however, when appropriately managed, survival can be prolonged.

STUDY DESIGN

A systematic review (1996-2016) was performed with the key words "megacystis microcolon intestinal hypoperistalsis syndrome." In addition, a case series of four patients is presented as well as algorithms for the diagnosis and treatment of MMIHS.

RESULTS

135 patients with MMIHS were identified in the literature. 73% (88/121) of the patients were female, 65% underwent diagnostic biopsy (64/99), and 63% (66/106) were identified with prenatal imaging. The majority of patients were treated with TPN as well as gastrostomy or ileostomy and CIC, however 15% (18/116) received multivisceral or intestinal transplant, and 30% (22/73) had a vesicostomy. The survival rate was 57% (68/121).

CONCLUSION

Appropriate management of MMIHS patients is crucial. An enlarged, acontractile bladder in a child with bowel motility problems should be considered diagnostic. Bladder distension can be managed with CIC or vesicostomy in addition to prophylactic antibiotics if frequent urinary tract infections are present. These patients often require gastrostomy or ileostomy as well as total parenteral nutrition. This management has led to significant improvement in survival rates.

ACTG2 variants impair actin polymerization in sporadic Megacystis Microcolon Intestinal Hypoperistalsis Syndrome

Megacystis Microcolon Intestinal Hypoperistalsis Syndrome (MMIHS) is a rare congenital disorder, in which heterozygous missense variants in the Enteric Smooth Muscle actin γ-2 (ACTG2) gene have been recently identified. To investigate the mechanism by which ACTG2 variants lead to MMIHS, we screened a cohort of eleven MMIHS patients, eight sporadic and three familial cases, and performed immunohistochemistry, molecular modeling and molecular dynamics (MD) simulations, and in vitro assays. In all sporadic cases, a heterozygous missense variant in ACTG2 was identified. ACTG2 expression was detected in all intestinal layers where smooth muscle cells are present in different stages of human development. No histopathological abnormalities were found in the patients. Using molecular modeling and MD simulations, we predicted that ACTG2 variants lead to significant changes to the protein function. This was confirmed by in vitro studies, which showed that the identified variants not only impair ACTG2 polymerization, but also contribute to reduced cell contractility. Taken together, our results confirm the involvement of ACTG2 in sporadic MMIHS, and bring new insights to MMIHS pathogenesis.

Interstitial cells: regulators of smooth muscle function

Smooth muscles are complex tissues containing a variety of cells in addition to muscle cells. Interstitial cells of mesenchymal origin interact with and form electrical connectivity with smooth muscle cells in many organs, and these cells provide important regulatory functions. For example, in the gastrointestinal tract, interstitial cells of Cajal (ICC) and PDGFRα(+) cells have been described, in detail, and represent distinct classes of cells with unique ultrastructure, molecular phenotypes, and functions. Smooth muscle cells are electrically coupled to ICC and PDGFRα(+) cells, forming an integrated unit called the SIP syncytium. SIP cells express a variety of receptors and ion channels, and conductance changes in any type of SIP cell affect the excitability and responses of the syncytium. SIP cells are known to provide pacemaker activity, propagation pathways for slow waves, transduction of inputs from motor neurons, and mechanosensitivity. Loss of interstitial cells has been associated with motor disorders of the gut. Interstitial cells are also found in a variety of other smooth muscles; however, in most cases, the physiological and pathophysiological roles for these cells have not been clearly defined. This review describes structural, functional, and molecular features of interstitial cells and discusses their contributions in determining the behaviors of smooth muscle tissues.

Telocytes subtypes in human urinary bladder

Urinary bladder voiding is a complex mechanism depending upon interplay among detrusor, urothelium, sensory and motor neurons and connective tissue cells. The identity of some of the latter cells is still controversial. We presently attempted to clarify their phenotype(s) in the human urinary bladder by transmission electron microscopy (TEM) and immunohistochemistry. At this latter aim, we used CD34, PDGFRα, αSMA, c-Kit and calreticulin antibodies. Both, TEM and immunohistochemistry, showed cells that, sharing several telocyte (TC) characteristics, we identified as TC; these cells, however, differed from each other in some ultrastructural features and immunolabelling according to their location. PDGFRα/calret-positive, CD34/c-Kit-negative TC were located in the sub-urothelium and distinct in two subtypes whether, similarly to myofibroblasts, they were αSMA-positive and had attachment plaques. The sub-urothelial TC formed a mixed network with myofibroblasts and were close to numerous nerve endings, many of which nNOS-positive. A third TC subtype, PDGFRα/αSMA/c-Kit-negative, CD34/calret-positive, ultrastructurally typical, was located in the submucosa and detrusor. Briefly, in the human bladder, we found three TC subtypes. Each subtype likely forms a network building a 3-D scaffold able to follow the bladder wall distension and relaxation and avoiding anomalous wall deformation. The TC located in the sub-urothelium, a region considered a sort of sensory system for the micturition reflex, as forming a network with myofibroblasts, possessing specialized junctions with extracellular matrix and being close to nerve endings, might have a role in bladder reflexes. In conclusions, the urinary bladder contains peculiar TC able to adapt their morphology to the organ activity.

Distribution of interstitial cells of Cajal in the neurogenic urinary bladder of children with myelomeningocele

PURPOSE

C-kit positive interstitial cells of Cajal (ICCs) play an important role in the regulation of the smooth muscle motility, acting as pacemakers to provide the slow wave activity in various organs. Recent studies have shown that c-kit positive ICCs are widely distributed in the urinary tract of animals and humans. The aim of our study was to examine the distribution of ICCs in the children's neurogenic bladder.

METHODS

An immunohistochemical study of specimens obtained from neurogenic urinary bladder (from the trigonum and the corpus) of children with meningomyelocele and during autopsy was performed using antibody against c-kit (CD 117). Histological morphometry of immunoexpression of c-kit positive ICCs was performed by means of an image analyzing system.

RESULTS

Our investigation demonstrated ICCs located in the vesical muscle layers. The distribution of those cells is different in the trigonum and the corpus of the urinary bladder. No remarkable differences were observed in c-kit immunoexpression between the neurogenic and the control group.

CONCLUSION

There was no difference in the distribution of ICCs in the urinary bladder of healthy children as compared to children with myelomeningocele. Biopsy revealed different distribution of ICCs in particular parts of the bladder (trigonum/ corpus) in both groups of children.

Control of urinary drainage and voiding

Urine differs greatly in ion and solute composition from plasma and contains harmful and noxious substances that must be stored for hours and then eliminated when it is socially convenient to do so. The urinary tract that handles this output is composed of a series of pressurizable muscular compartments separated by sphincteric structures. With neural input, these structures coordinate the delivery, collection, and, ultimately, expulsion of urine. Despite large osmotic and chemical gradients in this waste fluid, the bladder maintains a highly impermeable surface in the face of a physically demanding biomechanical environment, which mandates recurring cycles of surface area expansion and increased wall tension during filling, followed by rapid wall compression during voiding. Afferent neuronal inflow from mucosa and submucosa communicates sensory information about bladder fullness, and voiding is initiated consciously through coordinated central and spinal efferent outflow to the detrusor, trigonal internal sphincter, and external urethral sphincter after periods of relative quiescence. Provocative new findings suggest that in some cases, lower urinary tract symptoms, such as incontinence, urgency, frequency, overactivity, and pain may be viewed as a consequence of urothelial defects (either urothelial barrier breakdown or inappropriate signaling from urothelial cells to underlying sensory afferents and potentially interstitial cells). This review describes the physiologic and anatomic mechanisms by which urine is moved from the kidney to the bladder, stored, and then released. Relevant clinical examples of urinary tract dysfunction are also discussed.

Alterations of the myovesical plexus of the human overactive detrusor

Objectives. The human bladder shows spontaneous autonomous activity. Detrusor overactivity could be seen as a consequence of exaggerated autonomous activity. Interstitial cells (ICs) play a potential role in coordination of autonomous activity. As it is suggested that changes in ICs coexist with detrusor overactivity (DO), we investigated possible alterations to human bladder ICs. Methods. Biopsies were obtained from 23 patients and were categorized into four groups: genuine stress incontinence (without DO) (n = 5), neurogenic disease with DO (n = 6), bladder outlet obstruction with DO (n = 6), or idiopathic DO (n = 6). Specimens were processed to investigate expression of N-cadherin and PGP9.5. N-cadherin expression was semiquantitatively analyzed and correlated to PG9.5 expression and bladder wall morphology. Results. The population of cells expressing N-cadherin is altered in the overactive detrusor, making no difference between the sources of DO. Punctate distribution of morphological changes was found and downregulation of PGP9.5 expression seemed to coexist with upregulation of N-cadherin expression in the detrusor layer. Conclusions. The population of N-cadherin+ cells of the interstitial compartment of the human bladder has the ability to proliferate. As this proliferation seems to coexist with denervation, it could be possible that a highly developed network of interstitial cells replaces the loss of innervation in overactive detrusor.

Heterozygous de novo and inherited mutations in the smooth muscle actin (ACTG2) gene underlie megacystis-microcolon-intestinal hypoperistalsis syndrome

Megacystis-microcolon-intestinal hypoperistalsis syndrome (MMIHS) is a rare disorder of enteric smooth muscle function affecting the intestine and bladder. Patients with this severe phenotype are dependent on total parenteral nutrition and urinary catheterization. The cause of this syndrome has remained a mystery since Berdon's initial description in 1976. No genes have been clearly linked to MMIHS. We used whole-exome sequencing for gene discovery followed by targeted Sanger sequencing in a cohort of patients with MMIHS and intestinal pseudo-obstruction. We identified heterozygous ACTG2 missense variants in 15 unrelated subjects, ten being apparent de novo mutations. Ten unique variants were detected, of which six affected CpG dinucleotides and resulted in missense mutations at arginine residues, perhaps related to biased usage of CpG containing codons within actin genes. We also found some of the same heterozygous mutations that we observed as apparent de novo mutations in MMIHS segregating in families with intestinal pseudo-obstruction, suggesting that ACTG2 is responsible for a spectrum of smooth muscle disease. ACTG2 encodes γ2 enteric actin and is the first gene to be clearly associated with MMIHS, suggesting an important role for contractile proteins in enteric smooth muscle disease.

Classification and diagnostic criteria of variants of Hirschsprung's disease

"Variants of Hirschsprung's disease" are conditions that clinically resemble Hirschsprung's disease (HD), despite the presence of ganglion cells in rectal suction biopsies. The diagnosis and management of these patients can be challenging. Specific histological, immunohistochemical and electron microscopic investigations are required to characterize this heterogeneous group of functional bowel disorders. Variants of HD include intestinal neuronal dysplasia, intestinal ganglioneuromatosis, isolated hypoganglionosis, immature ganglia, absence of the argyrophil plexus, internal anal sphincter achalasia and congenital smooth muscle cell disorders such as megacystis microcolon intestinal hypoperistalsis syndrome. This review article systematically classifies variants of HD based on current diagnostic criteria with an additional focus on pathogenesis, epidemiology, clinical presentation, management and outcome.

Bladder interstitial cells: an updated review of current knowledge

The field of bladder research has been energized by the study of novel interstitial cells (IC) over the last decade. Several subgroups of IC are located within the bladder wall and make structural interactions with nerves and smooth muscle, indicating integration with intercellular communication and key physiological functions. Significant progress has been made in the study of bladder ICs' cellular markers, ion channels and receptor expression, electrical and calcium signalling, yet their specific functions in normal bladder filling and emptying remain elusive. There is increasing evidence that the distribution of IC is altered in bladder pathophysiologies suggesting that changes in IC may be linked with the development of bladder dysfunction. This article summarizes the current state of the art of our knowledge of IC in normal bladder and reviews the literature on IC in dysfunctional bladder.

Altered distribution of interstitial cells and innervation in the rat urinary bladder following spinal cord injury

Changes in the distribution of interstitial cells (IC) are reportedly associated with dysfunctional bladder. This study investigated whether spinal cord injury (SCI) resulted in changes to IC subpopulations (vimentin-positive with the ultrastructural profile of IC), smooth muscle and nerves within the bladder wall and correlated cellular remodelling with functional properties. Bladders from SCI (T8/9 transection) and sham-operated rats 5 weeks post-injury were used for ex vivo pressure–volume experiments or processed for morphological analysis with transmission electron microscopy (TEM) and light/confocal microscopy. Pressure-volume relationships revealed low-pressure, hypercompliance in SCI bladders indicative of decompensation. Extensive networks of vimentin-positive IC were typical in sham lamina propria and detrusor but were markedly reduced post-SCI; semi-quantitative analysis showed significant reduction. Nerves labelled with anti-neurofilament and anti-vAChT were notably decreased post-SCI. TEM revealed lamina propria IC and detrusor IC which formed close synaptic-like contacts with vesicle-containing nerve varicosities in shams. Lamina propria and detrusor IC were ultrastructurally damaged post-SCI with retracted/lost cell processes and were adjacent to areas of cellular debris and neuronal degradation. Smooth muscle hypertrophy was common to SCI tissues. In conclusion, IC populations in bladder wall were decreased 5 weeks post-SCI, accompanied with reduced innervation, smooth muscle hypertrophy and increased compliance. These novel findings indicate that bladder wall remodelling post-SCI affects the integrity of interactions between smooth muscle, nerves and IC, with compromised IC populations. Correlation between IC reduction and a hypercompliant phenotype suggests that disruption to bladder IC contribute to pathophysiological processes underpinning the dysfunctional SCI bladder.

Cellular expression profile for interstitial cells of cajal in bladder - a cell often misidentified as myocyte or myofibroblast

BACKGROUND

Interstitial cells of Cajal (ICC) have been identified in urinary bladder of several species, but their presence in mice remains uncertain. Meanwhile, dozens of reports indicate that dysregulation of connexin 43 plays an important role in bladder overactivity, but its localization has not been clearly defined, with reports of expression in either the smooth muscle or in myofibroblasts. We recently identified a population of ectonucleoside triphosphate diphosphohydrolase 2 (NTPDase2) positive cells that resemble ICC and are distinct from smooth muscle, fibroblasts, myofibroblasts and neurons. Thus we sought to define more clearly the molecular signature of ICC and in doing so resolve some of these uncertainties.

PRINCIPLE FINDINGS

Immunofluorescent localization revealed that NTPDase2-positive cells lie closely adjacent to smooth muscle but are separate from them. NTPDase2 positive cells exhibited co-localization with the widely accepted ICC marker - c-kit. They were further shown to co-localize with other ICC markers CD34 and Ano1, but not with mast cell marker tryptase. Significantly, they show convincing co-localization with connexin 43, which was not present in smooth muscle. The identity of these cells as ICC was further confirmed by the presence of three mesenchymal markers - vimentin, desmin, and PDGFβ receptor, which indicates their mesenchymal origin. Finally, we observed for the first time, the presence of merlin/neurofibromin 2 in ICC. Normally considered a neuronal protein, the presence of merlin suggests ICC in bladder may have a role in neurotransmission.

CONCLUSIONS

NTPDase2 positive cells in mice bladder are ICC, which can be defined by the presence of c-Kit, CD34, Ano1, NTPDase2, connexin 43, vimentin, desmin, PDGFβ receptor and merlin/NF2. These data establish a definitive molecular expression profile, which can be used to assist in explorations of their functional roles, and the presence of NTPDase2 suggests that purinergic signaling plays a role in regulation of ICC function.

An intrapelvic extraintestinal gastrointestinal stromal tumor of undetermined origin: diagnosis by prostate needle biopsy

We herein report a case of intrapelvic gastrointestinal stromal tumor (GIST) of undetermined origin in a 48-year-old male who presented with dysuria. An enlarged tumor was detected on digital rectal examination. Imaging studies showed a solid and lobular homogenous tumor of 7.0 cm in diameter. The tumor was attached to the right dorsal aspect of the prostate with compression of the seminal vesicles and rectum. It was considered that the tumor had arisen from the prostate, although the patient's serum prostate-specific antigen level was low (0.436 ng/mL). The histological diagnosis by prostate needle biopsy was a spindle cell tumor. At cystoprostatectomy, the tumor was confirmed to be separated from the prostate by a fibrous band, and showed spindle cells with a fascicular growth pattern, but without necrotic areas. Mitotic figures were noted in 12 of 50 high-power fields. The tumor cells were immunoreactive for the KIT protein (CD117), CD34, Discovered on GIST-1 (DOG-1), and vimentin. In contrast, they were negative for desmin, α-smooth muscle actin, pancytokeratin (AE1/AE3), and S100 protein. The Ki-67 labeling index was 5%. The genetic analyses targeting the c-kit gene revealed a point mutation at codon 559 (GTT→GAT). The diagnosis of GIST was confirmed on the basis of the morphological features, immunoprofile, and results of the molecular analyses. Since extraintestinal GIST can resemble a prostatic tumor clinically, KIT (CD117) and DOG-1 should be considered for inclusion in the immunohistochemical panel for spindle cell tumors obtained by prostate needle biopsy.

Identification of PDGFRα positive populations of interstitial cells in human and guinea pig bladders

PURPOSE

The bladder wall comprises a complex array of cells, including urothelium, smooth muscle, nerves and interstitial cells. Interstitial cells have several subtypes based on site, morphology and differential expression of markers such as anti-vimentin and anti-KIT. We examined whether a subpopulation of interstitial cells immunopositive for PDGFRα exists in human and guinea pig bladders.

MATERIALS AND METHODS

Human and guinea pig bladder tissues were processed for immunohistochemistry and examined by bright field or confocal microscopy. Whole mount tissues and paraffin sections were labeled with antibodies to PDGFRα, vimentin, KIT and PGP9.5. Protein expression was assessed by Western blot.

RESULTS

PDGFRα(+) cells were present in human and guinea pig bladders. In the guinea pig PDGFRα(+) cells had a branched stellate morphology and formed networks in the lamina propria. In human and guinea pig detrusors PDGFRα(+) cells were elongated on the boundary of smooth muscle bundles or were seen as groups of stellate cells in the interbundle spaces. PDGFRα(+) cells were located close to nerves labeled by PGP9.5. Double labeling revealed that PDGFRα(+) cells were a subgroup of the vimentin(+) population. A significant proportion of PDGFRα(+) cells were also KIT(+). Bands corresponding to PDGFRα, KIT and vimentin proteins were detected on Western blot.

CONCLUSIONS

To our knowledge this study is the first to identify PDGFRα(+)/KIT(+) cells in the bladder lamina propria and detrusor layers. These cells are a subgroup of the vimentin(+) population, showing the complexity of bladder interstitial cells. PDGFRα(+) cells are apparently structurally associated with intramural nerves, indicating integration with bladder control mechanisms.

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.

Pseudosarcomatous proliferation of cx43- and kit-expressing interstitial cell in the urinary bladder

The authors report a case showing proliferation of KIT- and connexin 43-expressing mesenchymal cells of the urinary bladder. A 75-year-old woman had an ulcerated endophytic mass (size, approximately 2 × 2 cm) in the left posterolateral wall. She underwent transurethral resection and subsequent partial cystectomy. The suburothelial mass extended to the muscularis propria. The histopathological analysis revealed spindle-shaped mesenchymal cells that were loosely arranged with myxoid stroma and showed a focal compact fascicular arrangement. In the immunohistochemical analysis, these spindle cells were stained with specific antibodies to KIT and connexin 43. The patient is currently free of disease at 5 years after operation. The proliferating spindle cells in the present case might represent a phenotype of interstitial cells of the lamina propria.

Interstitial cells of Cajal, the Maestro in health and disease

Interstitial cells of Cajal (ICC) are important players in the symphony of gut motility. They have a very significant physiological role orchestrating the normal peristaltic activity of the digestive system. They are the pacemaker cells in gastrointestinal (GI) muscles. Absence, reduction in number or altered integrity of the ICC network may have a dramatic effect on GI system motility. More understanding of ICC physiology will foster advances in physiology of gut motility which will help in a future breakthrough in the pharmacological interventions to restore normal motor function of GI tract. This mini review describes what is known about the physiologic function and role of ICCs in GI system motility and in a variety of GI system motility disorders.

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.

Ultrastructure of Cajal-like interstitial cells in the human detrusor

The aim of this ultrastructural study was to examine the human detrusor for interstitial cells of Cajal (ICC)-like cells (ICC-L) by conventional transmission electron microscopy (TEM) and immuno-transmission electron microscopy (I-TEM) with antibodies directed towards CD117 and CD34. Two main types of interstitial cells were identified by TEM: ICC-L and fibroblast-like cells (FLC). ICC-L were bipolar with slender (0.04 microm) flattened dendritic-like processes, frequently forming a branching labyrinth network. Caveolae and short membrane-associated dense bands were present. Mitochondria, rough endoplasmic reticulum and Golgi apparatus were observed in the cell somata and cytoplasmic processes. Intermediate filaments were abundant but no thick filaments were found. ICC-L were interconnected by close appositions, gap junctions and peg-and-socket junctions (PSJ) but no specialised contacts to smooth muscle or nerves were apparent. FLC were characterised by abundant rough endoplasmic reticulum but no caveolae or membrane-associated dense bands were observed; gap junctions and PSJ were absent and intermediate filaments were rare. By I-TEM, CD34 gold immunolabelling was present in long cytoplasmic processes corresponding to ICC-L between muscle fascicles but CD117 gold immunolabelling was negative. Thus, ICC-like cells are present in the human detrusor. They are CD34-immunoreactive and have a myoid ultrastructure clearly distinguishable from fibroblast-like cells. ICC-L may be analogous to interstitial cells of Cajal in the gut.

CD34-positive interstitial cells of the human detrusor

Interstitial cells of Cajal (ICC) are well described in the bowel wall. They are c-kit positive and play a role as pacemaker cells. Similar c-kit-positive cells have recently been described in the human bladder. The aim of this study was to characterize interstitial cells of the bladder detrusor using a panel of antibodies directed against CD117/c-kit, CD34, CD31, S100, tryptase, neurofilament, NSE, Factor-VIII and GFAP. A striking finding was an interstitial type of cell which is CD34 immunoreactive (CD34-ir) but CD117/c-kit negative. The cells have a tentacular morphology, enveloping and intermingling with individual muscle fasicles. Morphologically and immunohistochemically, they show no neurogenic, endothelial or mast cell differentiation. Transmission electron microscopy (TEM) showed the presence of interstitial cells with a round-to-oval nucleus, sparse perinuclear cytoplasm and long flattened processes, ramifying primarily in a bipolar fashion. Using immunoelectron microscopy (I-TEM) it was possible to view CD34 gold labelling of cells corresponding to interstitial cells. Although similar CD34-positive cells have been demonstrated in the bowel wall, they have never been described in the detrusor. The ontogeny and function of CD34-ir, a kit-negative cell, is unknown, but it may be involved in smooth muscle contraction.

Interstitial Cells of Cajal and their Role in Veterinary Gastrointestinal Pathologies

This study highlights the importance of interstitial cells of Cajal (ICs) in gastrointestinal disease. Human research is already considering IC pathologies but in veterinary research IC pathologies are rarely studied. Nevertheless, recent studies of ICs show a growing interest in the pathophysiology of gastrointestinal diseases and emphasize the consideration of this cell type in the pathophysiology of veterinary gastrointestinal malfunctions.

Interstitial Cajal-like cells in human uterus and fallopian tube

Recently, parallels have been drawn between enteric interstitial cells of Cajal (ICC) and similar cells outside the gut-interstitial Cajal-like cells (ICLC). This article reviews our laboratory findings on ICLC in the female reproductive tract. Since the morphology and function of ICLC are still a subject of debate, our purpose was to investigate whether ICLC are present in the fallopian tube and/or uterus, and if they share ultrastructural and immunohistochemical (IHC) features and/or functional roles. We studied ICLC presence in the human fallopian tube and myometrium primarily by light microscopy, and then by transmission electron microscopy (TEM), in tissue samples and at a single cell level. Taking advantage of our ICLC studies of several organs (pancreas, mammary gland, myocardium), we assembled a set of criteria, derived from ultrastructural features of ICLC, called "platinum standard." Besides the putative pacemaker function, ICLC might have other physiological roles, depending on tissue type (e.g., intercellular signaling, immune surveillance, steroid sensors). Consequently, there is a great urge for a conceptual framework that could allow a better understanding, from a functional point of view, and more so, as the ICLC processes are the longest cellular prolongations (except neurons).

Kit-positive interstitial cells in the rabbit urethra: structural relationships with nerves and smooth muscle

OBJECTIVE

To identify interstitial cells (ICs) in the wall of the rabbit urethra using antibodies to the Kit receptor, and to examine their location, morphology and relationship with nerves and smooth muscle cells (SMCs), as studies of enzymatically isolated cells from the rabbit urethra have established that there are specialized cells that show spontaneous electrical activity and have morphological properties of ICs.

MATERIALS AND METHODS

Urethral tissues from rabbits were fixed, labelled with antibodies and examined with confocal microscopy. Some specimens were embedded in paraffin wax and processed for histology. Histological sections from the most proximal third and mid-third region of rabbit urethra were stained with Masson's Trichrome to show their cellular arrangement.

RESULTS

Sections from both regions had outer longitudinal and inner circular layers of SM, and a lamina propria containing connective tissue and blood vessels; the lumen was lined with urothelial cells. The mid-third region had a more developed circular SM layer than the most-proximal samples, and had extensive inner longitudinal SM bundles in the lamina propria. Labelling with anti-Kit revealed immunopositive cells within the wall of the rabbit urethra, in the circular and longitudinal layers of the muscularis. Double-labelling with an antibody to SM myosin showed Kit-positive cells on the boundary of the SM bundles, orientated parallel to the axis of the bundles. Others were in spaces between the bundles and often made contact with each other. Kit-positive cells were either elongated, with several lateral branches, or stellate with branches coming from a central soma. Similar cells could be labelled with vimentin antibodies. Their relationship with intramural nerves was examined by double immunostaining with an anti-neurofilament antibody. There were frequent points of contact between Kit-positive cells and nerves, with similar findings in specimens double-immunostained with anti-neuronal nitric oxide synthase (nNOS).

CONCLUSION

Kit-positive ICs were found within the SM layers of the rabbit urethra, in association with nerves, on the edge of SM bundles and in the interbundle spaces. The contact with nNOS-containing neurones might imply participation in the nitrergic inhibitory neurotransmission of the urethra.

Gastrointestinal stromal tumors (GISTs) on prostate needle biopsy: A clinicopathologic study of 8 cases

Gastrointestinal stromal tumors (GISTs) are typically not included in the differential diagnosis of spindle cell tumors seen on prostate needle biopsy. However, their recognition is critical due to their unique clinical management. We report the rare phenomenon of 8 cases of GISTs diagnosed on prostate needle biopsy. The mean patient age at diagnosis was 53.6 years (range: 42 to 65 years). Tumors variably presented with rectal fullness, urinary obstructive symptoms, and abnormal digital rectal examination. Four tumors were resected. One of these cases was shown to be primary in the rectum without prostatic involvement. The second case extensively involved the prostate but its epicenter was in the rectal muscularis propria. The third case was an encapsulated mass separated by a thin fibrous capsule from the prostate. The fourth case was a perirectal mass that underwent local excision. Four lesions have not been resected. On the basis of imaging studies, one seemed to be a prostatic mass, however, additional imaging investigations showed the mass to be separate from the prostate. Three cases have not yet been studied radiographically. Tumors measured 1.0, 1.7, 5.4, 7.0, 7.4, and 8.5 cm. The sizes of 2 recently diagnosed tumors remain undetermined. Histologically, all 8 GISTs showed spindled cells with a fascicular growth pattern. Additional histologic findings included focal epithelioid features (n = 3), necrosis (n = 3), mitotic rates of >5 per 50 high-power field (n = 2), and cytologically malignant features (n = 3). CD117/c-kit was diffusely positive in all 8 cases and CD34 in 7/8 cases. In all cases studied, stains for S100, desmin, and smooth muscle actin were negative. Two patients were treated with imatinib mesylate. One underwent radical prostatectomy after reduction in tumor size after imatinib administration. Another patient was treated with imatinib for several months with complete tumor response and no residual tumor seen in a subsequent local excision. Rectal or extraintestinal GIST can result in a clinical impression of a prostatic lesion. One should consider CD117/c-kit in the immunohistochemical panel to exclude GIST before diagnosing a solitary fibrous tumor, leiomyosarcoma, or specialized prostatic stromal tumor on prostate needle biopsy.

[Complexity of pathological interpretation in megacystis-microcolon-intestinal hypoperistalsis syndrome]

Megacystis-microcolon-intestinal hypoperistalsis syndrome is very rare, and is the most severe of the chronic intestinal pseudoobstructions. Diagnosis is usually made in the neonatal period, is clinical and radiological, and is confirmed by manometric studies. Microscopic abnormalities are variable, inconstant and nonspecific. They involve the smooth muscle more often than the intrinsic innervation of the gut and the bladder. A girl, currently seven years old, presented with megacystis observed on prenatal ultrasound at 21 weeks of gestation. At first, amniotic fluid volume was appropriate for gestational age, and then hydramnios appeared at 30 weeks of gestation. Microcolon was discovered at birth, with microileum, dilatation of the duodenum and proximal jejunum, intestinal malposition, and severe hypoperistalsis of the entire gastrointestinal tract, which indicated enterostomy and total parenteral nutrition from birth. At pathological examination, rectal biopsy and enteric nervous plexuses were normal. There was hypoplasia of the external longitudinal layer of the muscularis propria in the colon and ileum. Cajal cells could not be demonstrated immunohistochemically in the colon. This case highlights the complexity and difficulties of pathological interpretation in this syndrome, and the necessity of a large study of controls at different ages and different levels of the digestive tract and the bladder.

Interstitial cells of Cajal at the clinical and scientific interface

Considerable work over the past two decades has determined that interstitial cells of Cajal (ICC) serve as pacemaker cells, conduits for active transmission of electrical slow waves, sites of innervation by peripheral motor neurons, and mechanotransducers. While most of the physiology of ICC has been learned from studies of the cells within the gastrointestinal tract, ICC are found in a variety of smooth muscle tissues and may have analogous or novel physiological functions in those organs. Clinical investigations of muscles from patients with a variety of gastrointestinal motility disorders have raised the exciting possibility that loss of ICC may be responsible for the development of motor dysfunction. This review discusses the development of ICC, the kinds of human disorders in which ICC loss may be important, what factors regulate the ICC phenotype, and what therapeutic approaches might be utilized to restore or regenerate ICC. This field is primed for translational discoveries. ICC are responsible for critical physiological functions in smooth muscle tissues, they are lost in pathophysiological conditions, and it will be important now to decipher the conditions that are responsible for ICC loss and develop new therapies to relieve patients of this problem. Success in this endeavour might improve the quality of life for millions of patients.

Location of interstitial cells and neurotransmitters in the mouse bladder

INTRODUCTION

To investigate whether interstitial cells (ICs) are present in the adult mouse bladder, and what transmitters characterize adjacent nerve fibres, as ICs in human and guinea-pig bladder lie close to nerve fibres but transmitters present in these nerves have not yet been reported.

MATERIALS AND METHODS

Sections of the bladder wall from 12 adult male mice (six each, aged 3-4 or 18-24 months) were incubated in carboxygenated Krebs' solution containing isobutyl-methyl-xanthene (1 mm), followed by the nitric oxide (NO) donor diethylamino-NONOate; control tissues remained in Krebs' solution. Samples were fixed in 4% paraformaldehyde and processed for immunofluorescence histochemistry for cGMP, neuronal NO synthase (nNOS), vesicular acetylcholine transferase (VAChT), calcitonin gene-related polypeptide (CGRP) and protein gene product (PGP) 9.5. ICs were identified as non-neuronal cells of appropriate morphology manifesting an increase in cGMP after exposure to the NO donor.

RESULTS

ICs were apparent in the outer muscle, but not the inner muscle or suburothelial region. nNOS- and CGRP-immunoreactive fibres were close to and alongside IC processes. In contrast, nerve fibres containing VAChT were only occasionally found close to ICs and rarely running alongside them. ICs showed no immunoreactivity to c-kit. There was no overt difference in IC cell distribution between young and aged adult specimens. Older mice showed patchy denervation of the detrusor, but ICs were not specifically affected.

CONCLUSIONS

ICs are confined to the outer part of the bladder wall in the mouse and may receive peptidergic and nitrergic innervation, which might serve to modulate their putative functional role. Alterations in the overall IC population do not appear to underlie ageing-related changes in lower urinary tract function.

Mechanisms of Disease: specialized interstitial cells of the urinary tract--an assessment of current knowledge

Scientists interested in the smooth muscles of the urinary tract, and their control, have recently been studying cells in the interstitium of tissues that express the c-kit antigen (Kit(+) cells). These cells have morphologic features that are reminiscent of the well-described pacemaker cells in the gut, the interstitial cells of Cajal (ICC). The spontaneous contractile behavior of muscles in the urinary tract varies widely, and it is clear that urinary tract Kit(+) interstitial cells cannot be playing an identical role to that played by the ICC in the gut. Nevertheless, there is increasing evidence that they do play a role in modulating the contractile behavior of adjacent smooth muscle, and might also be involved in mediating neural control. This review outlines the properties of ICC in the gut, and gives an account of the discovery of cells in the interstitium of the main components of the urinary tract. The physiologic properties of such cells and the functional implications of their presence are discussed, with particular reference to the bladder. In this organ, Kit(+) cells are found under the lamina propria, where they might interact with the urothelium and with sensory nerves, and also between and within the smooth-muscle bundles. Confocal microscopy and calcium imaging are being used to assess the physiology of ICC and their interactions with smooth muscles. Differences in the numbers of ICC are seen in smooth muscle specimens obtained from patients with various pathologies; in particular, bladder overactivity is associated with increased numbers of these cells.

The functional effects of a c-kit tyrosine inhibitor on guinea-pig and human detrusor

OBJECTIVE

To describe the effect of a specific c-kit receptor inhibitor (imatinib mesylate) on human detrusor strips in vitro and guinea-pig cystometry in vivo, and to show histological data suggesting differences in the distribution of interstitial cells of Cajal (ICC)-like cells in 'normal' and overactive human detrusor, as these cells have been identified as possible mediators of spontaneous activity and excitability in bladder smooth muscle.

MATERIALS AND METHODS

Specimens of human detrusor were stained immunohistochemically with a c-kit antibody. Human detrusor strips were mounted in a superfused organ-bath apparatus, and smooth muscle contraction was evoked with carbachol and electrical field stimulation in the presence and absence of imatinib mesylate. Also, guinea-pig urodynamic studies were conducted before and after i.v. administration of imatinib mesylate, and changes in bladder variables and spontaneous activity were recorded.

RESULTS

Imatinib mesylate (10(-6)M) inhibited evoked smooth muscle contraction and spontaneous activity in overactive human detrusor, with less effect on normal human tissue. Imatinib mesylate (10(-5)M) improved bladder capacity, compliance, voided volumes, urinary frequency, and reduced contraction thresholds and spontaneous activity during guinea-pig cystometry. c-kit labelling showed significantly more ICC-like cells in overactive human detrusor than in normal specimens.

CONCLUSION

c-kit receptor blockers have inhibitory effects on guinea-pig and overactive human detrusor, possibly via c-kit receptors on bladder ICC-like cells. This and the possibility that there are more ICC-like cells in overactive bladder suggest that the c-kit receptor may provide a novel target for treating detrusor overactivity.

Contractile properties of the proximal urethra and bladder in female pig: morphology and function

AIMS

To compare the contractile properties of proximal urethral and bladder muscle of the female pig.

MATERIALS AND METHODS

In two proximal segments (I and II) of the urethra, small muscle bundles were excised to measure the force-length (maximum force) and the force-velocity (unloaded shortening velocity) relation using the stop-test. The rate of force development was calculated using phase plots. Contractile properties of urethral and bladder segments were statistically compared using the Mann-Whitney U-test. Immunohistochemical staining of whole circumference urethral cross sections was used to identify the location of smooth and striated muscle fibres.

RESULTS

On isometric force development, the urethral muscle bundles revealed a fast ( approximately 0.5 sec) and a slow ( approximately 2.1 sec) time constant, whereas in bladder only a slow ( approximately 2.3 sec) component was measured. On average, isometric force was highest in bladder. The length range over which force was produced was smallest in urethral segment II, followed by urethral segment I and finally bladder. The unloaded shortening velocity was 0.15, 0.25 and 0.35 1/sec, respectively. Histological preparations showed that smooth as well as striated muscle was present in proximal urethra. In urethral muscle bundles, spontaneous contractions were measured with a frequency of 0.4 Hz.

CONCLUSIONS

Differences in contractility found between urethra and bladder may be ascribed to the presence of striated muscle in the proximal urethra. The regulation of tone and spontaneous contractions may be part of the continence mechanism in the female pig urinary tract.

Novel type of interstitial cell (Cajal-like) in human fallopian tube

We describe here--presumably for the first time--a Cajal-like type of tubal interstitial cells (t-ICC), resembling the archetypal enteric ICC. t-ICC were demonstrated in situ and in vitro on fresh preparations (tissue cryosections and primary cell cultures) using methylene-blue, crystal-violet, Janus-Green B or MitoTracker-Green FM Probe vital stainings. Also, t-ICC were identified in fixed specimens by light microscopy (methylene-blue, Giemsa, trichrome stainings, Gomori silver-impregnation) or transmission electron microscopy (TEM). The positive diagnosis of t-ICC was strengthened by immunohistochemistry (IHC; CD117/c-kit+ and other 14 antigens) and immunofluorescence (IF; CD117/c-kit+ and other 7 antigens). The spatial density of t-ICC (ampullar-segment cryosections) was 100-150 cells/mm2. Non-conventional light microscopy (NCLM) of Epon semithin-sections revealed a network-like distribution of t-ICC in lamina propria and smooth muscle meshwork. t-ICC appeared located beneath of epithelium, in a 10-15 microm thick 'belt', where 18+/-2% of cells were t-ICC. In the whole lamina propria, t-ICC were about 9%, and in muscularis approximately 7%. In toto, t-ICC represent ~8% of subepithelial cells, as counted by NCLM. In vitro, t-ICC were 9.9+/-0.9% of total cell population. TEM showed that the diagnostic 'gold standard' (Huizinga et al., 1997) is fulfilled by 'our' t-ICC. However, we suggest a 'platinum standard', adding a new defining criterion- characteristic cytoplasmic processes (number: 1-5; length: tens of microm; thickness: < or =0.5 microm; aspect: moniliform; branching: dichotomous; organization: network, labyrinthic-system). Quantitatively, the ultrastructural architecture of t-ICC is: nucleus, 23.6+/-3.2% of cell volume, with heterochromatin 49.1+/-3.8%; mitochondria, 4.8+/-1.7%; rough and smooth endoplasmic-reticulum (1.1+/-0.6%, 1.0+/-0.2%, respectively); caveolae, 3.4+/-0.5%. We found more caveolae on the surface of cell processes versus cell body, as confirmed by IF for caveolins. Occasionally, the so-called 'Ca2+-release units' (subplasmalemmal close associations of caveolae+endoplasmic reticulum+mitochondria) were detected in the dilations of cell processes. Electrophysiological single unit recordings of t-ICC in primary cultures indicated sustained spontaneous electrical activity (amplitude of membrane potentials: 57.26+/-6.56 mV). Besides the CD117/c-kit marker, t-ICC expressed variously CD34, caveolins 1&2, alpha-SMA, S-100, vimentin, nestin, desmin, NK-1. t-ICC were negative for: CD68, CD1a, CD62P, NSE, GFAP, chromogranin-A, PGP9.5, but IHC showed the possible existence of (neuro)endocrine cells in tubal interstitium. We call them 'JF cells'. In conclusion, the identification of t-ICC might open the door for understanding some tubal functions, e.g. pace-making/peristaltism, secretion (auto-, juxta- and/or paracrine), regulation of neurotransmission (nitrergic/purinergic) and intercellular signaling, via the very long processes. Furthermore, t-ICC might even be uncommitted bipotential progenitor cells.

Megacystis microcolon intestinal hypoperistalsis syndrome

Megacystis microcolon intestinal hypoperistalsis syndrome (MMIHS) is a rare and the most severe form of functional intestinal obstruction in the newborn. The major features of this congenital and usually lethal anomaly are abdominal distension, bile-stained vomiting, and absent or decreased bowel peristalsis. Abdominal distension is a consequence of the distended, unobstructed urinary bladder with or without upper urinary tract dilation. Most patients with MMIHS are not able to void spontaneously. This article reviews the pathogenesis of MMIHS as well as the clinical, radiological, surgical and histological findings in all reported cases of this syndrome.