Cajal-like cells in the human upper urinary tract

Interstitial Cells of Cajal and P2X3 Receptors at Ureteropelvic Junction Obstruction and Their Relationship with Pain Response

Introduction: Etiopathogenesis and the symptomatology of ureteropelvic junction obstruction (UPJO) in the pediatric population has not yet been definitely clarified, suggesting a multifactorial nature of the condition. The aim was to analyze the association between the number of Interstitial Cells of Cajal (ICCs), as well as P2X3 receptors in ureteropelvic junction (UPJ) and the pain response in pediatric patients with hydronephrosis. Methods: 50 patients with congenital hydronephrosis underwent open or laparoscopic pyeloplasty at one of two departments of pediatric surgery and urology in Poland. Patients were divided into two groups according to the pain symptoms before surgery. A total of 50 samples of UPJ were obtained intraoperatively and underwent histopathological and immunohistochemical (IHC) analysis. Quantitative assessment of ICCs was based on the number of CD117(+) cells of adequate morphology in the subepithelial layer and the muscularis propria. Expression of P2X3 receptors was evaluated as the intensity of IHC staining. Results: Patients with hydronephrosis and accompanying pain were on average 60 months older (77 vs. 17 months) than children with asymptomatic hydronephrosis (p = 0.017). Symptomatic children revealed higher numbers of ICCs in both the subepithelial layer and in the lamina muscularis propria. In particular, symptomatic patients aged 2 years or more exhibited significantly higher numbers of ICCs in the subepithelial layer. Significant differences in the distribution of ICCs between the subepithelial layer and the lamina muscularis propria were observed in both groups. Expression of P2X3 receptors was limited to the urothelium and the muscle layer and correlated between these structures. There was no relationship between pain response and the expression of P2X3 receptors. Conclusions: ICCs and P2X3 receptors may participate in the pathogenesis of UPJO and in the modulation of pain response to a dilatation of the pyelocaliceal system. Explanation of the role of ICCs and P2X3 receptors in propagation of ureteral peristaltic wave and the modulation of pain stimuli requires further studies.

The influence of interstitial cells of Cajal density in the outcomes of pyeloplasty in adults: A prospective analysis

Purpose:

To evaluate if the density of interstitial cells of Cajal (ICC) in the ureteropelvic junction (UPJ) influences the outcomes of pyeloplasty in adults.

Methods:

Twenty-three patients with the diagnosis of ureteropelvic junction obstruction (UPJO) that underwent laparoscopic dismembered pyeloplasty were included. ICC density was measured using immunohistochemistry reaction for c-KIT expression in the resected UPJ segment. Pyeloplasty outcome was evaluated by patient self-report pain, urinary outflow using DTPA renogram and hydronephrosis assessment using ultrasound (US) at 12 months of follow-up. A logistic regression analysis was performed to assess the association of pyeloplasty outcomes and ICC density.

Results:

Low, moderate, and high ICC density were present in 17.4%, 30.4%, and 52.2% of the patients, respectively. Complete pain resolution was observed in 100%, 85.7%, and 75% of patients with low, moderate and high ICC density, respectively ( p = 0.791). DTPA renogram improved in 75%, 85.7%, and 91.7% of patients with low, moderate and high ICC density, respectively ( p = 0.739). Hydronephrosis improved in 25%, 85.7%, and 91.7% of patients with low, moderate and high ICC density, respectively ( p = 0.032).

Conclusions:

Patients with high ICC density have a significant amelioration of hydronephrosis after pyeloplasty. However, ICC density is not associated with functional outcomes.

Variations in the Density and Distribution of Cajal Like Cells Associated With the Pathogenesis of Ureteropelvic Junction Obstruction: A Systematic Review and Meta-Analysis

Introduction: Cajal like cells (CLCs) in the upper urinary tract have an ability to generate coordinated spontaneous action potentials and are hypothesized to help propel urine from renal pelvis into the ureter. The objective of this review was to describe the variations in the density and distribution of CLCs associated with ureteropelvic junction obstruction (UPJO). Materials and Methods: Studies comparing the density and distribution of CLCs in the human upper urinary tract in patients with UPJO and healthy controls were included in this systematic review. We searched online electronic databases; Ovid MEDLINE, Scopus, PubMed and Cochrane reviews for the studies published before October 31, 2020. A meta-analysis was conducted to compare the density of CLCs at the ureteropelvic junction (UPJ) in patients with UPJO and matched controls. Results: We included 20 and seven studies in the qualitative and quantitative synthesis, respectively. In majority (55%) CLCs were located between the muscle layers of the upper urinary tract. The CLC density in the UPJ gradually increased with aging in both healthy subjects and patients with UPJO. The pooled analysis revealed that the density of CLCs at the UPJ was significantly low in patients with UPJO compared to the controls (SMD = -3.00, 95% CI = -3.89 to -2.11, p < 0.01). Conclusions: The reduction in CLC density at the UPJ in patients with UPJO suggests a contribution from CLCs in the pathogenesis of UPJO. Since age positively correlates with CLC density, it is imperative to carefully match age when conducting case control studies comparing the CLC density and distribution. Protocol Registration Number: CRD42020219882.

Pacemaker Mechanisms Driving Pyeloureteric Peristalsis: Modulatory Role of Interstitial Cells

The peristaltic pressure waves in the renal pelvis that propel urine expressed by the kidney into the ureter towards the bladder have long been considered to be 'myogenic', being little affected by blockers of nerve conduction or autonomic neurotransmission, but sustained by the intrinsic release of prostaglandins and sensory neurotransmitters. In uni-papilla mammals, the funnel-shaped renal pelvis consists of a lumen-forming urothelium and a stromal layer enveloped by a plexus of 'typical' smooth muscle cells (TSMCs), in multi-papillae kidneys a number of minor and major calyces fuse into a large renal pelvis. Electron microscopic, electrophysiological and Ca²⁺ imaging studies have established that the pacemaker cells driving pyeloureteric peristalsis are likely to be morphologically distinct 'atypical' smooth muscle cells (ASMCs) that fire Ca²⁺ transients and spontaneous transient depolarizations (STDs) which trigger propagating nifedipine-sensitive action potentials and Ca²⁺ waves in the TSMC layer. In uni-calyceal kidneys, ASMCs predominately locate on the serosal surface of the proximal renal pelvis while in multi-papillae kidneys they locate within the sub-urothelial space. 'Fibroblast-like' interstitial cells (ICs) located in the sub-urothelial space or adventitia are a mixed population of cells, having regional and species-dependent expression of various Cl^-, K⁺, Ca²⁺ and cationic channels. ICs display asynchronous Ca²⁺ transients that periodically synchronize into bursts that accelerate ASMC Ca²⁺ transient firing. This review presents current knowledge of the architecture of the proximal renal pelvis, the role Ca²⁺ plays in renal pelvis peristalsis and the mechanisms by which ICs may sustain/accelerate ASMC pacemaking.

Is there a difference in the number of interstitial cells, neurons, presence of fibrosis and inflammation in ureteropelvic junction tissues of patients with ureteropelvic junction obstruction with and without crossing vessels?

OBJECTIVE

We compared the number of interstitial cells (ICs), nerves, presence of fibrosis and inflammation at the level of full-thickness human ureteropelvic junction (UPJ) tissues obtained from normal subjects, and patients with UPJ obstruction with and without crossing vessels.

MATERIAL AND METHODS

Normal UPJ tissues (n=12) histopathologically confirmed to be without tumor involvement were obtained from subjects who underwent radical nephrectomy for kidney mass. Additional UPJ tissues were obtained from patients who underwent pyeloplasty due to UPJ obstruction. Crossing vessel was identified in 17 patients. In 57 patients, no crossing-vessel was noted. ICs were stained immunohistochemically with anti-human CD117 (c-kit) antibody. Neural tissue was stained with S-100. The numbers of ICs and neurons were compared between the groups: controls with normal UPJ (Group I), Ureteropelvic junction obtruction (UPJO) with crossing vessel (Group II) and UPJ obstruction without crossing vessel (Group III). Groups were also compared in terms of the presence of fibrosis and inflammation.

RESULTS

The mean age of total population included in the study was 30.5±18.5 years. No significant differences were detected between the three groups regarding mean and median numbers of ICs at the level of UPJ (lamina propria and muscle layer) and mean and median numbers of neurons at the level of lamina propria (p>0.05). Likewise, no significant differences were detected between the three groups regarding the presence of fibrosis and inflammation (p>0.05).

CONCLUSION

Number of ICs, neurons, presence of fibrosis and inflammation seem to be similar in the intact UPJ and UPJ with obstruction with and without crossing vessel. Cellular function rather than the number ICs might play a role that warrants further research.

Molecular phenotypes of the human kidney: Myoid stromal cells/telocytes and myoepithelial cells

The connective stromal and epithelial compartments of the kidney have regenerative potential and phenotypic flexibility. A few studies have shown that cells appertaining to both compartments can exhibit myoid phenotypes. The purpose of our study was to investigate the myoid pattern of kidney and its association with the kidney niches containing stromal cells/telocytes (SC/TCs). We performed an immunohistochemical study using a panel of endothelial, myoid, mesenchymal and stem/progenitor markers, namely CD31, CD34, CD105 (endoglin), CD117/c-kit, nestin, desmin, α-smooth muscle actin (α-SMA) and the heavy chain of smooth muscle myosin (SMM). We used histologically normal kidney samples, obtained after nephrectomy, from nine adult patients. The capsular SC/TCs had a strong CD34 and partial nestin and CD105 immunopositivity. Subcapsular and interstitial SC/TCs expressed c-kit, nestin, CD105, but also α-SMA and SMM, therefore having a myoid phenotype. The endothelial SC/TCs phenotype was CD31+/CD34+/CD105+/nestin±/SMM±/α-SMA±. All three myoid markers were expressed in periendothelial SC/TCs. We also found a scarce expression of nestin in parietal epithelial cells of Bowman's capsule, and in podocytes. In epithelial cells, we found a positive expression for CD31, CD117/c-kit, desmin, CD34, SMM, and CD105. In epithelial tubular cells, we found a predominant basal expression of the myoid markers (SMM and desmin). In conclusion, myoepithelial tubular cells, myoid endothelial cells and myoid SC/TCs are normal constituents of the kidney.

The role of HCN channels in peristaltic dysfunction in human ureteral tuberculosis

Objective

To explore the role of HCN channels in ureteral peristaltic dysfunction by comparing the changes in HCN channel levels between normal and tuberculous ureters.

Methods

A total of 32 specimens of human upper ureters were collected by nephrectomy from patients with renal tumor (control group, n = 16) or from patients with renal tuberculosis (experimental group, n = 16); the two groups did not receive radiotherapy, chemotherapy, immunotherapy, or any other special treatment before the surgical procedure. An experimental study on smooth muscle strips of human upper ureters showed variation in contraction amplitude and frequency after adding ZD7288, a specific blocker of HCN channels. The expression of HCN channels in the ureter was confirmed by Western blot (WB) and by confocal analysis of double immunostaining for c-kit and HCN channel proteins.

Results

Before the addition of ZD7288, the experimental and control groups showed significant differences in the frequency and amplitude of the spontaneous contraction of isolated ureteral smooth muscle strips. After ZD7288 was added, the frequency and amplitude of the contractions of the ureteral smooth muscle strips were significantly lower in both groups. The differences observed before and after ZD7288 treatment in each group were significant (P < 0.001), and the difference in contraction amplitude observed between the two groups before ZD7288 was also significantly different (P < 0.001). By using WB technology, we showed that the expression of HCN channels was present in normal human ureters, with the expression of HCN4 and HCN1 being the highest; the expression of HCN4 and HCN1 in the control and experimental groups were both statistically significant (P < 0.001). HCN4 and HCN1 were expressed in the mucosal and smooth muscle layers of human control ureters and tuberculous ureters, as revealed by a confocal analysis of double immunostaining for c-kit and HCNs proteins; there were significant differences between the two groups (P < 0.001).

Conclusion

Four HCN channels are expressed in the ureter, mainly HCN4 and HCN1, suggesting that HCN channels are involved in the peristaltic contraction of ureteral ICCs, which may be an important reason for peristaltic dysfunction in ureteric tuberculosis.

Neuronal defects an etiological factor in congenital pelviureteric junction obstruction?

INTRODUCTION

Congenital pelviureteric junction obstruction (PUJO) is one of the most frequent causes of neonatal hydronephrosis. Obstruction at the PUJ has potential severe adverse outcomes, such as renal damage. While pyeloplasty has been established as the definitive treatment, the exact pathophysiology of congenital PUJO remains unknown. Recent research has proposed neuronal innervation defects as an etiological factor in congenital PUJO. We aim to study the expression of various neuronal markers in PUJO specimens compared with controls, and evaluate whether severity of renal disease or dysfunction pre-operatively is related to expression of neuronal markers in resected PUJO specimens.

MATERIALS AND METHODS

All consecutive patients who underwent dismembered pyeloplasty at KK Women's and Children's Hospital, Singapore, for intrinsic PUJO from 2008 to 2012 were included. Patients with other co-occurring renal pathologies were excluded. Controls were obtained from nephrectomy patients with Wilm's tumor or other benign renal conditions during the same period. Specimens were stained immunohistochemically with neuronal markers protein gene product 9.5 (PGP9.5), synaptophysin, and S-100, and with CD-117, a marker for interstitial cells of Cajal (Table). Levels of expression of the markers were assessed semiquantitatively (decreased, increased or no change) in comparison with controls by two independent observers. Pre-operative data of patients' renal anatomical (ultrasonography measurements of renal pelvis size) and functional parameters (differential renal function measured using MAG-3 renal scans) were obtained.

DISCUSSION

Thirty-eight PUJO specimens (38 renal units) and 20 controls were studied. Mean patient age at pyeloplasty was 25.3 months (2.9-167.6 months). Median pre-operative pelvic size was 25.0 mm (17.0-50.0 mm). Both PUJO specimens and controls showed great heterogeneity in distribution of innervation. All four immunohistochemical markers were not predictive of significant pre-operative renal pelvis dilation or pre-operative diminished renal function of the operated kidney.

CONCLUSIONS

There exists marked variability in expression of neuronal markers synaptophysin, PGP9.5, and S-100, and CD-117 in PUJO specimens compared with controls. Our results show no clinical significance of the expression of neuronal markers in predicting degree of pre-operative renal pelvis dilation or differential renal function. The heterogeneity of expression of neuronal markers in PUJO specimens and controls in our population is at variance with prior studies. The etiology of PUJO is likely to be complex and multifactorial.

Risks of flexible ureterorenoscopy: pathophysiology and prevention

Currently, indications for flexible ureterorenoscopy (fURS) are expanding, mainly due to technological advancements. Although data from clinical series definitely presents fURS as a safe procedure, serious complications including sepsis and ureteral lesions do occur. These complications seem to be a result of the unique elements of fURS, ureteral access and irrigation, pushing normal upper urinary tract physiology into pathophysiological processes, including intrarenal/pyelo-veneous backflow and ureteral contractions, potentially resulting in septic, haemorrhagic and ureteral lesional complications. Knowledge on normal upper urinary tract physiology are crucial for understanding how these harmful effects of fURS may be avoided or minimized. The pathophysiology of intrarenal pressure increases and ureteral access will be discussed as a basis for understanding preventive measures. Role of antibiotics, ureteral access sheaths, safty guidewires, pain medication, prestenting and pharmacologic modulation of pyeloureteral dynamics are reviewed from a pathophysiological perspective.

Interstitial cell modulation of pyeloureteric peristalsis in the mouse renal pelvis examined using FIBSEM tomography and calcium indicators

Typical and atypical smooth muscle cells (TSMCs and ASMCs, respectively) and interstitial cells (ICs) within the pacemaker region of the mouse renal pelvis were examined using focused ion beam scanning electron (FIB SEM) tomography, immunohistochemistry and Ca²⁺ imaging. Individual cells within 500-900 electron micrograph stacks were volume rendered and associations with their neighbours established. 'Ribbon-shaped', Ano1 Cl^- channel immuno-reactive ICs were present in the adventitia and the sub-urothelial space adjacent to the TSMC layer. ICs in the proximal renal pelvis were immuno-reactive to antibodies for Ca_V3.1 and hyperpolarization-activated cation nucleotide-gated isoform 3 (HCN3) channel sub-units, while basal-epithelial cells (BECs) were intensely immuno-reactive to Kv7.5 channel antibodies. Adventitial to the TSMC layer, ASMCs formed close appositions with TSMCs and ICs. The T-type Ca²⁺channel blocker, Ni²⁺ (10-200 μM), reduced the frequency while the L-type Ca²⁺ channel blocker (1 μM nifedipine) reduced the amplitude of propagating Ca²⁺ waves and contractions in the TSMC layer. Upon complete suppression of Ca²⁺ entry through TSMC Ca²⁺ channels, ASMCs displayed high-frequency (6 min^-1) Ca²⁺ transients, and ICs distributed into two populations of cells firing at 1 and 3 min^-1, respectively. IC Ca²⁺ transients periodically (every 3-5 min^-1) summed into bursts which doubled the frequency of ASMC Ca²⁺ transient firing. Synchronized IC bursting and the acceleration of ASMC firing were inhibited upon blockade of HCN channels with ZD7288 or cell-to-cell coupling with carbenoxolone. While ASMCs appear to be the primary pacemaker driving pyeloureteric peristalsis, it was concluded that sub-urothelial HCN3(+), Ca_V3.1(+) ICs can accelerate ASMC Ca²⁺ signalling.

Immunohistochemistry in Ureteropelvic Junction Obstruction and Its Correlation to Postoperative Outcome

Aim:

To investigate the correlation between the status of interstitial cells of Cajal (ICC) in ureteropelvic junction (UPJ) and the resected ureteric margin and the postoperative outcome of Anderson-Hynes pyeloplasty in UPJ obstruction (UPJO) and to compare the ICC in the UPJ and the resected margin of the normal ureter.

Materials and Methods:

An observational study was conducted over a period of 2 years at the Department of Pediatric Surgery at Niloufer Institute of Women and Child Health. Children with intrinsic UPJO who underwent Anderson-Hynes dismembered pyeloplasty were included in the study. Six months postoperatively, the patients were divided into two groups based on diuretic isotopic renogram using technetium-99m-labeled diethylene triaminepentaacetic acid. Group 1 comprised patients with good surgical outcome. Group 2 comprised patients with a poor outcome. The histologic specimens were evaluated for ICC, and the immunohistochemical findings were correlated with the outcome.

Results:

Twenty-five patients were included in this study (19 male and 6 female). Seventy-six percent of patients were under the age of 1 year. Group 1 had 23 cases and Group 2 had 2 cases. Out of the two patients with a poor outcome, one had negative grading at the UPJ and one had positive grading. Both these patients had a negative grading at the lower resected margins. More number of patients (24%) had +++ grading at the lower resected margin when compared to the UPJ (8%).

Conclusion:

This is the first study which correlates the status of ICC in UPJ with the outcome of pyeloplasty in pediatric patients. Both the cases with bad outcome had no ICC at the lower margin of the resected specimen and one case had no ICC at the UPJ. There is a statistically significant difference (P = 0.001) in the number of ICC at the UPJ and the resected margin.

Physiopathology of vesico-ureteral reflux

Vescico-Ureteral Reflux (VUR) is a common condition in childhood, caused by a congenital anomaly at the Vescico-Ureteral Junction (VUJ) level. It seems that the main cause could be an abnormal embryological development occurred during the early stage of fetal life.

Refluxing ureteral endings show structural and functional anomalies: previous studies have shown a significant decrease in alfa actin, miosin and desmin contents as well as an high rate of atrophy and muscular degeneration with disorganized muscular fibres. The roles played by Cajal cells and Connexin 43 in generating peristaltic waves appears to be fundamental for the physiological VUJ function and activity. Attention was focused also on the congenital muscular deficiency of the RUs, on regard to general morphology, smooth muscle cells architecture, inflammatory markers and the distribution of collagen composition.

This review will discuss and investigate the importance of the modified configuration of Sarcoglycan (SG) sub complex (particularly the deficiency of the ε-SG and the increased expression of the α-SG), the role played by Cajal Cells, the intravescical tunnel length to ureteral diameter ratio as possible causes of the functional alterations in the refluxing ureteral ends leading towards the VUJ incompetence.

Changes in Cajal cell density in ureteropelvic junction obstruction in children

INTRODUCTION

Congenital ureteropelvic junction obstruction is one the most common causes of neonatal hydronephrosis. The etiology of the ureteropelvic junction (UPJ) obstruction has not been clearly established. The presence of a hypoplastic, adynamic ureteral segment is thought to be the major cause of an UPJ obstruction.

OBJECTIVE

We evaluated the distribution of Cajal cells using immunohistologic methods coupled with light microscopy of the UPJ tissues in obstructed and normal UPJs.

STUDY DESIGN

The study group consisted of 19 patients who underwent pyeloplasty for UPJ obstruction. Twelve patients who had been operated on for oncological indications constituted the control group. The sections were stained immunohistochemically using CD117 (c-kit) antibody; the numbers of CD117 (+) interstitial cells of Cajal were counted in 10 consecutive high-power fields under the light microscope and the cell density was determined for each case.

RESULTS

The mean age of the cases who underwent dismembered pyeloplasty and the control group were 116 ± 116 months (14 male, 5 female; 6-420 months) and 279 ± 312 months (9 male, 3 female; 24-948 months) (p = 0.1), respectively. The mean interstitial Cajal cell number in the UPJ obstruction and the control groups were 2.37 ± 2.19 and 24.5 ± 9.73, respectively (p < 0.0001). Thirteen (68.4%) patients had very few, five (26.3%) patients had few, and one (5.3%) patient had many Cajal cells in the UPJ obstruction group. In the control group, all patients had more than seven cells per high-power field.

DISCUSSION

We found that in cases of UPJ, obstruction the numbers of interstitial Cajal cells were decreased, being either absent or significantly reduced. Although data about the motility are currently not sufficient, the decrease in the number of Cajal cells in patients with UPJ highlights that they might be responsible for the initiation, coordination, and conduction of peristaltic activity along the pelvicalyceal system. Improvement and enhancement of contraction waves arising from the upper urinary system depend on interstitial cells of Cajal, which are the pacemaker cells in smooth muscles. We think that a decreased number of interstitial cells of Cajal have a close relationship with changing ureteral motility when we compare our UPJ obstruction cases with the limited data in the literature.

CONCLUSION

Further investigations on these cells will probably give detailed information about the neurophysiology of the urinary system and the diseases that cause congenital hydronephrosis.

Electrical propagation in the renal pelvis, ureter and bladder

Under normal conditions, following the passage of urine from the collecting duct, the urine is stored briefly in the renal pelvis before being transported through the ureter to the bladder where the urine is stored for a longer time (hours) before being voided through the urethra. The transport of urine from the renal pelvis to the bladder occurs spontaneously due to contractions of the muscles in the wall of the pelvis and ureter. Spontaneous contractions also occur in the detrusor muscle and are responsible for maintaining the bladder shape during the filling phase. These muscle contractions occur as result of electrical impulses, which are generated and propagated through different parts of the urinary tract. The renal pelvis and the ureter differ from the bladder in relation to the origin, characteristics and propagation of these electrical impulses. In the ureter, the electrical impulses originate mainly at the proximal region of the renal pelvis and are transmitted antegradely down the length of the ureter. The electrical impulses in the bladder, on the other hand, originate at any location in the bladder wall and can be transmitted in different directions with the axial direction being the prominent one. In this manuscript, an overview of the current state of research on the origin and propagation characteristics of these electrical impulses in the normal and pathological conditions is provided.

Urinary tract pacemaker cells: current knowledge and insights from nonrenal pacemaker cells provide a basis for future discovery

Coordinated ureteric peristalsis propels urine from the kidney to the bladder. Cells in the renal pelvis and ureter spontaneously generate and propagate electrical activity to control this process. Recently, c-kit tyrosine kinase and hyperpolarization-activated cyclic nucleotide-gated channel 3 (HCN3) were identified in the upper urinary tract. Both of these proteins are required for coordinated proximal to distal contractions in the ureter. Alterations in pacemaker cell expression are present in multiple congenital kidney diseases, suggesting a functional contribution by these cells to pathologic states. In contrast to gut and heart pacemaker cells, the developmental biology of ureteric pacemaker cells, including cell lineage and signaling mechanisms, is undefined. Here, we review pacemaker cell identify and function in the urinary pelvis and ureter and the control of pacemaker function by Hedgehog-GLI signaling. Next, we highlight current knowledge of gut and heart pacemaker cells that is likely to provide insight into developmental mechanisms that could control urinary pacemaker cells.

Altered expression of interstitial cells of Cajal in primary obstructive megaureter

OBJECTIVE

A marked decrease in the density of interstitial cells of Cajal (ICC) has been shown in patients with ureteropelvic junction obstruction. ICC may also play a role in primary obstructive megaureter (POM). An immunohistochemical study was conducted to investigate the density of ICC in ureterovesical junction (UVJ) segments resected from patients with POM and from control autopsy specimens.

MATERIALS AND METHODS

Resected UVJ segments from 11 patients operated for POM comprised the study group. Control UVJs were obtained from autopsy specimens of 7 children who died from causes other than urogenital pathology. The UVJs including the narrowest parts were studied using immunohistochemical staining for C-kit positive cells.

RESULTS

The number of ICC was significantly lower in the UVJs of the POM compared to the control group. The UVJs of the POM group had 1.75 ± 1.14 ICC (mean ± 1SD), whereas the control group had 5.76 ± 2.99 ICC (mean ± 1SD).

CONCLUSION

The number of ICC was decreased in the UVJs of the patients with POM compared to the normal control group. As dilation of the ureter during fetal life is a common condition and ureteral dilation is often self limiting, we hypothesize that ureteral peristalsis is a maturational event including the maturational development of ICC.

Immunohistochemical and morphometric evaluation of neuronal dysfunction in pelviureteral junction obstruction

PURPOSE

The pathophysiology of pelviureteral junction obstruction remains unclear. In this study, we attempted to evaluate the neuronal dysfunction using immunohistochemical and morphometric parameters.

MATERIALS AND METHODS

Using specific antibodies, we studied the neuronal markers and morphometry of specimens from 10 cases of pelviureteral junction obstruction and 10 normal pelviureteral junctions by immunohistochemistry using synaptophysin (synaptic vesicle membrane protein), S-100 (nerve cell fiber marker), protein gene product 9.5 (neuron specific protein) and CD-117 (transmembrane receptor with tyrosine kinase activity).

RESULTS

In pelviureteral junction obstruction, smooth muscle thickness was significantly higher than in normal specimens. Cytoplasmic cells stained by synaptophysin were found in the pelviureteral junction obstruction specimens but were absent in normal pelviureteral junction specimens. In addition, significantly more intense staining for S-100 was found in the pelviureteral junction obstruction specimens compared with the normal specimens. Immunohistochemical staining for protein gene product 9.5 showed no differences between the normal and pelviureteral junction obstruction specimens. Neither the normal specimens nor pelviureteral junction obstruction groups were stained by CD-117.

CONCLUSION

We propose that the cause of neuronal dysfunction in pelviureteral junction obstruction depends on the increase in number and structure of neuronal cells and smooth muscle thickness. These factors could play an important role in the pathophysiology of pelviureteral junction obstruction by affecting motility and peristalsis.

Immunohistochemical and electron microscopic examination of Cajal cells in ureteropelvic junction obstruction

OBJECTIVE

We examine the ultrastructural configurations of Cajal cells by electron microscopy, as well as the quantitative changes occurring in Cajal cells by light microscopy.

METHODS

In total, 35 patients with ureteropelvic junction (UPJ) obstruction and 7 patients without obstruction were compared immunohistochemically with c-kit (CD117) to quantify the number of cells. On electron microscopic examination, 7 patients with UPJ obstruction and 3 patients without obstruction were compared to evaluate the changes which occurred in the ultrastructural configuration of the Cajal cells.

RESULTS

On light microscopic examination, it was determined that the Cajal cells, which demonstrate c-kit (CD117) immunoreactive character, were located near the circular muscle layer and parallel to the muscle cells. The number of Cajal cells in the control group was significantly increased compared to the number of cells in patients with UPJ obstruction (p < 0.001). On electron microscopic examination, the number of interstitial cells was also higher in the control group. A decrease in the number of the caveolae in these cells was seen in the group with UPJ obstruction compared to the control group.

CONCLUSION

In UPJ obstruction, a decrease in the number of Cajal cells, as well as the changes in the morphologic structure of the Cajal cells, indicates that these cells have a role in the pacemaker system and are associated with ureteral peristalsis.

Lower urinary tract development and disease

Congenital anomalies of the lower urinary tract (CALUT) are a family of birth defects of the ureter, the bladder, and the urethra. CALUT includes ureteral anomaliesc such as congenital abnormalities of the ureteropelvic junction (UPJ) and ureterovesical junction (UVJ), and birth defects of the bladder and the urethra such as bladder-exstrophy-epispadias complex (BEEC), prune belly syndrome (PBS), and posterior urethral valves (PUVs). CALUT is one of the most common birth defects and is often associated with antenatal hydronephrosis, vesicoureteral reflux (VUR), urinary tract obstruction, urinary tract infections (UTI), chronic kidney disease, and renal failure in children. Here, we discuss the current genetic and molecular knowledge about lower urinary tract development and genetic basis of CALUT in both human and mouse models. We provide an overview of the developmental processes leading to the formation of the ureter, the bladder, and the urethra, and different genes and signaling pathways controlling these developmental processes. Human genetic disorders that affect the ureter, the bladder and the urethra and associated gene mutations are also presented. As we are entering the postgenomic era of personalized medicine, information in this article may provide useful interpretation for the genetic and genomic test results collected from patients with lower urinary tract birth defects. With evidence-based interpretations, clinicians may provide more effective personalized therapies to patients and genetic counseling for their families.

The distribution of interstitial cells of Cajal in congenital ureteropelvic junction obstruction

Purpose

The authors analysed the distribution of c-kit-positive interstitial cells of Cajal (ICCs) in obstructed ureteropelvic junction (UPJ) and its age-related changes.

Methods

Twenty specimens were obtained from children with intrinsic ureteropelvic junction obstruction (UPJO), at the average age of 8.1 years (8 months–16.8 years), fixed in formalin and embedded in paraffin. Five control samples were taken from children at the average age of 2.3 years (2.4 months–7.4 years). All specimens were analysed by the immunohistochemistry test with light microscopy with respect to c-kit expression. The distribution of c-kit-positive ICCs in the two groups was compared and the correlation between the distribution of c-kit-positive ICCs and the patients’ age in UPJO cases was analysed. The results were examined by Yates’ χ² test, Mann–Whitney U test, and t test for Pearson’s correlation coefficient. A P value < 0.05 was considered as statistically significant.

Results

No statistically significant differences were found in the distribution of c-kit-positive ICCs between UPJO and the control group. No correlation was established between the age of patients with UPJO and the distribution of c-kit-positive ICCs.

Conclusion

No distributional difference found in obstructed and unobstructed UPJ seems to indicate that UPJO is not associated with anomalous distribution of c-kit-positive ICCs. Age-related changes in the expression of c-kit-positive ICCs are equally distributed in obstructed UPJ.

Is the pelviureteric junction an anatomical entity?

OBJECTIVE

The concept of the pelviureteric junction has existed for more than a century and yet there is no clear anatomical definition of this junction. This systematic review addresses the question of whether the human pelviureteric junction is a discrete anatomical entity.

METHODS

A systematic literature review was undertaken to investigate the normal gross and microscopic anatomy of the pelviureteric junction using the electronic databases MEDLINE, PubMed, Cochrane Library and Google Scholar.

RESULTS

In most individuals there is a gradual transition between the renal pelvis and ureter with no external features indicating the presence of a discrete pelviureteric 'junction'. Internally, however, luminal mucosal folds are prominent in this region. There is no consensus on the arrangement of muscle fibers at the pelviureteric junction (which may be age-dependent) although some studies suggest a focal thickening in the muscle wall consistent with physiological observations suggesting a high pressure zone capable of regulating urine flow. Studies of innervation have shown no evidence of specialization at this site.

CONCLUSIONS

There is some evidence that a pelviureteric region can be delineated anatomically and physiologically. However, although it may be a useful clinical concept, there is no sound anatomical basis for an actual pelviureteric junction.

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.

Potassium and ANO1/ TMEM16A chloride channel profiles distinguish atypical and typical smooth muscle cells from interstitial cells in the mouse renal pelvis

BACKGROUND AND PURPOSE

Although atypical smooth muscle cells (SMCs) in the proximal renal pelvis are thought to generate the pacemaker signals that drive pyeloureteric peristalsis, their location and electrical properties remain obscure.

EXPERIMENTAL APPROACH

Standard patch clamp, intracellular microelectrode and immunohistochemistry techniques were used. To unequivocally identify SMCs, transgenic mice with enhanced yellow fluorescent protein (eYFP) expressed in cells containing α-smooth muscle actin (α-SMA) were sometimes used.

KEY RESULTS

Atypical SMCs were distinguished from typical SMCs by the absence of both a transient 4-aminopyridine-sensitive K(+) current (I(KA) ) and spontaneous transient outward currents (STOCs) upon the opening of large-conductance Ca(2+) -activated K(+) (BK) channels. Many typical SMCs displayed a slowly activating, slowly decaying Cl(-) current blocked by niflumic acid (NFA). Immunostaining for K(V) 4.3 and ANO1/ TMEM16A Cl(-) channel subunits co-localized with α-SMA immunoreactive product predominately in the distal renal pelvis. Atypical SMCs fired spontaneous inward currents that were either selective for Cl(-) and blocked by NFA, or cation-selective and blocked by La(3+) . α-SMA(-) interstitial cells (ICs) were distinguished by the presence of a Xe991-sensitive K(V) 7 current, BK channel STOCs and Cl(-) selective, NFA-sensitive spontaneous transient inward currents (STICs). Intense ANO1/ TMEM16A and K(V) 7.5 immunostaining was present in Kit(-) α-SMA(-) ICs in the suburothelial and adventitial regions of the renal pelvis.

CONCLUSIONS AND IMPLICATIONS

We conclude that K(V) 4.3(+) α-SMA(+) SMCs are typical SMCs that facilitate muscle wall contraction, that ANO1/ TMEM16A and K(V) 7.5 immunoreactivity may be selective markers of Kit(-) ICs and that atypical SMCs which discharge spontaneous inward currents are the pelviureteric pacemakers.

Changes in interstitial cell of Cajal-like cells density in congenital ureteropelvic junction obstruction

PURPOSE

The authors examined the number of interstitial cells of Cajal-like cells (ICC-LCs) in obstructed ureteropelvic junction (UPJ) in comparison with normal UPJ specimens and age-related changes.

MATERIALS AND METHODS

A total of 20 human formalin fixed, paraffin-embedded specimens of intrinsic UPJO from children at the mean age of 8.1 years (age range: 8 months-16.8 years) and 5 control samples from children at the mean age of 2.3 years (range 2.4 months-7.4 years) were investigated immunohistochemically for the expression of c-kit proto-oncogene by light microscopy with computerized image analysis. The results were examined by Fisher's exact test, Yates' chi-square test, and t test for Pearson's correlation coefficient. A P value less than 0.05 was considered statistically significant.

RESULTS

The number of ICC-LCs-dense fields was significantly higher in UPJO specimens in comparison with the normal group (P = 0.0004). The number of ICC-LCs-sparse fields was significantly lowered in UPJO specimens in comparison with the normal group (P = 0.0122). There was no significant difference in the number of ICC-LCs-medium fields in obstructed and normal UPJ specimens. The number of ICC-LCs was decreasing significantly with increasing age of the patients with UPJO (P = 0.0038).

CONCLUSIONS

The higher density of c-kit-positive ICC-LCs in UPJ may manifest the compensation of altered peristalsis in UPJO. The number of ICC-LCs-dense fields decreasing with age may show the failure of compensation and regression of the compensatory changes.

Spontaneous contractions augmented by cholinergic and adrenergic systems in the human ureter

Interstitial cells of Cajal (ICC) evoke pacemaker activities in many tissues. The purpose of this study was to investigate the relationship between interstitial cell and pacemaker activity in the human ureter through the recording of spontaneous contractions. Spontaneous contractions of eight circular and longitudinal smooth muscle strips of the human ureter to acetylcholine (ACh) and/or norepinephrine (NE) were observed. Human ureteral strips were divided into proximal and distal groups, and each group was subdivided into circular and longitudinal groups. The proximal group showed spontaneous activities of 3~4 times within 5 minutes in the longitudinal group. ACh (10(-4) M) augmented the frequency of the spontaneous contractions. The cumulative application of NE also augmented the frequency in a dose-dependent manner. The effects of NE application were inhibited by concomitant application of 10(-5) M glibenclamide. Receptor tyrosine kinase (c-kit) staining revealed abundant ICCs only in proximal tissues. Therefore, spontaneous contractions of the human ureter might be modulated by ICC in the proximal region, and the actions might be related with the activation of cholinergic and/or adrenergic system mediated by a glibenclamide-sensitive pathway.

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.

The roles of extracellular matrix proteins, apoptosis and c-kit positive cells in the pathogenesis of ureteropelvic junction obstruction

AIM

To investigate histopathological changes in ureteropelvic junction obstruction (UPJO) from an etiological perspective.

PATIENTS AND METHODS

Medical records of patients with UPJO were reviewed and pathological specimens collected. Nephrectomy materials from forensic autopsies were taken as controls. Specimens were assessed with light microscopy. Fibronectin, type 4 collagen, laminin, Bax and Bcl-2 expression for apoptosis, together with interstitial cells of Cajal determination with c-kit were determined immunohistochemically. Staining scores were evaluated semiquantitatively. Results were evaluated using Mann-Whitney U-test.

RESULTS

Control group comprised 14 children (median age, 3.5 years; 6 months-17 years). Study group comprised 22 children with UPJO (median age, 9 months; 1 month-10 years). Light microscopy revealed non-specific inflammation, epithelial proliferation and atrophy with fibrosis in the smooth muscle of the UPJ in all patients. Fibronectin, type 4 collagen and laminin were found to be significantly increased in UPJO at the intrafascicular space of smooth muscle and the matrix of stroma. Bcl-2 expression was increased in UPJO. c-Kit was unable to stain interstitial cells of Cajal, but staining for mast cells was significant.

CONCLUSIONS

High expression of fibronectin, laminin and type 4 collagen may indicate a relation to the pathogenesis of UPJO. Defective kidney morphogenesis, during branching and tubulogenesis of ureteric bud, may be responsible for this congenital pathology.

Functions of ICC-like cells in the urinary tract and male genital organs

Interstitial cells of Cajal (ICC)-like cells (ICC-LCs) have been identified in many regions of the urinary tract and male genital organs by immunohistochemical studies and electron microscopy. ICC-LCs are characterized by their spontaneous electrical and Ca²⁺ signalling and the cellular mechanisms of their generation have been extensively investigated. Spontaneous activity in ICC-LCs rises from the release of internally stored Ca²⁺ and the opening of Ca²⁺-activated Cl⁻ channels to generate spontaneous transient depolarizations (STDs) in a manner not fundamentally dependent on Ca²⁺ influx through L-type voltage-dependent Ca²⁺ channels. Since urogenital ICC-LCs have been identified by their immunoreactivity to Kit (CD117) antibodies, the often-used specific marker for ICC in the gastrointestinal tract, their functions have been thought likely to be similar. Thus ICC-LCs in the urogenital tract might be expected to act as either electrical pacemaker cells to drive the smooth muscle wall or as intermediaries in neuromuscular transmission. However, present knowledge of the functions of ICC-LCs suggests that their functions are not so predetermined, that their functions may be very region specific, particularly under pathological conditions. In this review, we summarize recent advances in our understanding of the location and function of ICC-LCs in various organs of the urogenital system. We also discuss several unsolved issues regarding the identification, properties and functions of ICC-LCs in various urogenital regions in health and disease.

Altered expression of c-kit-positive cells in the ureterovesical junction after surgically created vesicoureteral reflux

PURPOSE

Peristaltic contractions propel urine unidirectionally from the renal pelvis trough the ureter and into the bladder. A morphologically and functionally competent ureterovesical junction prevents vesicoureteral reflux (VUR). According to current knowledge, pyeloureteral peristalsis is driven by atypical muscle cells within the upper urinary tract. Another likely relevant cell population, which is c-kit-positive, has been shown to be present within the whole urinary tract. Morphological changes of c-kit-positive cells have been described in VUR and pyeloureteral junction (PUJ) obstruction. Nevertheless, the functional importance of c-kit-positive interstitial cells has not yet been elucidated fully. Therefore, we investigated the influence of experimentally created VUR on the expression of c-kit-positive cells.

MATERIALS AND METHODS

We created left-sided unilateral VUR in eight Vietnamese pigs using an open surgical technique. The VUR was shown to be grade II-III by voiding cystourethrogram (VCUG), 1 and 6 months after the procedure. The animals were killed after 6 months. The vesicoureteral junction and the distal ureters were excised and fixed in 4% PFA. Paraffin sections were stained using c-kit immunohistochemistry. A quantitative evaluation was performed by two independent investigators. The unaffected, contralateral, nonrefluxing ureters served as controls.

RESULTS

We identified two types of c-kit-immunoreactive cells within the ureterovesical junction and distal ureter. The first group was comprised of round-shaped cells with substantial intracellular granulas, which resembled mast cells. Mast cells were found in the subepithelial region as well as between the muscle bundles. The number of mast cells was slightly increased in the VUR group. The second group consisted of spindle-shaped, bipolar ICC-like cells, which were seen mainly in the submucosal and muscular layers. The number of spindle-shaped c-kit-immunoreactive cells was markedly decreased in the refluxing ureter compared to the controls.

CONCLUSIONS

Surgically created VUR leads to altered expression of c-kit-positive cells. The altered distribution of c-kit-positive ICC-like cells might further contribute to the impairment of coordinated pyeloureteral peristalsis.

Spontaneous electrical and Ca2+ signals in the mouse renal pelvis that drive pyeloureteric peristalsis

1. Peristalsis in the smooth muscle cell (SMC) wall of the pyeloureteric system is unique in physiology in that the primary pacemaker resides in a population of atypical SMCs situated near the border of the renal papilla. 2. Atypical SMCs display high-frequency Ca(2+) transients upon the spontaneous release of Ca(2+) from inositol 1,4,5-trisphosphate (IP(3))-dependent stores that trigger cation-selective spontaneous transient depolarizations (STDs). In the presence of nifedipine, these Ca(2+) transients and STDs seldom propagate > 100 mum. Synchronization of STDs in neighbouring atypical SMCs into an electrical signal that can trigger action potential discharge and contraction in the typical SMC layer involves a coupled oscillator mechanism dependent on Ca(2+) entry through L-type voltage-operated Ca(2+) channels. 3. A population of spindle- or stellate-shaped cells, immunopositive for the tyrosine receptor kinase kit, is sparsely distributed throughout the pyeloureteric system. In addition, Ca(2+) transients and action potentials of long duration occurring at low frequencies have been recorded in a population of fusiform cells, which we have termed interstitial cells of Cajal (ICC)-like cells. 4. The electrical and Ca(2+) signals in ICC-like cells are abolished upon blockade of Ca(2+) release from either IP(3)- or ryanodine-dependent Ca(2+) stores. However, the spontaneous Ca(2+) signals in atypical SMCs or ICC-like cells are little affected in W/W(-v) transgenic mice, which have extensive lesions of their intestinal ICC networks. 5. In summary, we have developed a model of pyeloureteric pacemaking in which atypical SMCs are indeed the primary pacemakers, but the function of ICC-like cells has yet to be determined.

Vesicoureteral reflux

Vesicoureteral reflux (VUR), the retrograde flow of urine from the bladder toward the kidney, is common in young children. About 30% of children with urinary tract infections will be diagnosed with VUR after a voiding cystourethrogram. For most, VUR will resolve spontaneously; 20% to 30% will have further infections, but few will experience long-term renal sequelae. Developmentally, VUR arises from disruption of complex signaling pathways and cellular differentiation. These mechanisms are probably genetically programmed but may be influenced by environmental exposures. Phenotypic expression of VUR is variable, ranging from asymptomatic forms to severe renal parenchymal disease and end-stage disease. VUR is often familial but is genetically heterogeneous with variability in mode of inheritance and in which gene, or the number of genes, that are involved. Numerous genetic studies that explore associations with VUR are available. The relative utility of these for understanding the genetics of VUR is often limited because of small sample size, poor methodology, and a diverse spectrum of patients. Much, if not all, of the renal parenchymal damage associated with end-stage disease is likely to be congenital, which limits the opportunity for intervention to familial cases where risk prediction may be available. Management of children with VUR remains controversial because there is no strong supportive evidence that prophylactic antibiotics or surgical intervention improve outcomes. Furthermore, well-designed genetic epidemiological studies focusing on the severe end of the VUR phenotype may help define the causal pathway and identify modifiable or disease predictive factors.

C-kit receptor in the human vas deferens: distinction of mast cells, interstitial cells and interepithelial cells

The molecular mechanisms underlying the regulation of vas deferens (VD) motility and semen emission are still poorly understood. Interstitial cells of Cajal (ICC), which harbour the c-kit receptor (CD117), provide the basis of coordinated gut motility. We investigated whether c-kit receptor-positive cells also exist in the normal human VD. Enzyme and fluorescence immunohistochemical techniques were applied on serial sections of human proximal, middle, and distal VD segments (n=49) employing 13 different monoclonal and polyclonal antibodies recognizing the c-kit receptor. The c-kit receptor was detected in either round- or spindle-shaped cells. On account of their antigenic profile, the round- and oval-shaped c-kit receptor-positive cells were identified as mast cells (MC) occurring in all layers of the VD except the epithelium. In contrast, two distinct populations of exclusively c-kit receptor-positive spindle-shaped cells were found within the lamina propria and, rarely, in the inner and outer smooth muscle layers, as well as within the epithelium. Different shaped c-kit receptor-positive MC and IC were present in all layers of the human VD. Our findings demonstrate the presence of different c-kit receptor-positive cells also in the human VD. Their rather ubiquitous distribution within the lamina propria and muscle layers suggests that IC and MC may modulate the neuromuscular transmission and the propagation of electrical signals in multiple systems involved in the draining of fluids. The importance of the c-kit receptor-positive interepithelial cells remains unclear.

C-Kit receptor (CD117) in the porcine urinary tract

C-Kit positive interstitial cells of Cajal (ICC) play an important role in the regulation of the smooth muscle motility, acting as internal pacemakers to provide the slow wave activity within various luminal organs. Recently c-Kit-(CD117)-positive interstitial cells (IC) have been shown in the genitourinary tract, but systematic studies on the distribution and density of IC within the urinary tract are still lacking. Therefore the aim of the present study was to analyze systematically the localization and distribution of the c-Kit receptor in the urinary tract of the pig using immunohistochemical and molecular methods. Tissue samples were harvested from the porcine urinary tract including renal calices and pelvis, ureteropelvic junction, proximal, middle and distal ureter, ureteral orifice, fundus, and corpus of the bladder and the internal urethral orifice. Small and large intestine specimen served as controls. Immunohistochemistry (APAAP, IF) was applied on serial frozen sections using four monoclonal and polyclonal antibodies recognizing CD117. Whole mounts of the porcine upper urinary tract were prepared and investigated using conventional and confocal fluorescence microscopy followed by three-dimensional reconstruction. UV-laser microdissection and RT-PCR were applied to confirm the immunohistochemical results. CD117-immunoreactivity labeled bipolar IC and round-shaped mast cells (MC) throughout the adventitia, tunica muscularis and submucosa within the whole porcine urinary tract. While MC were found continuously in all investigated segments, a gradient of bipolar IC was evident. The whole mount preparations gave a detailed cytomorphology of IC within the various layers of the porcine urinary tract. Whole mount preparations revealed closed apposition of bi- and tripolar c-Kit positive IC parallel to the smooth muscle bundles and to veins of the tunica muscularis and adventitia. In the urothelium single CD117-positive interepithelial cells were found. The highest density of CD117-positive cells was found at the ureteropelvic junction, however the differences in between the segments were minimal. Microdissection and RT-PCR confirmed the results uncovered by immunohistochemistry. The ubiquitous distribution of IC and their close relationship to smooth muscle provides strong evidence that IC could contribute to the intrinsic pacemaker activity within the porcine (upper and lower) urinary tract. The role of the interepithelial CD117-positive cells as mechanosensors or as a precursor cell in the regeneration of the urothelium, is conceivable.

Role of Ca2+ entry and Ca2+ stores in atypical smooth muscle cell autorhythmicity in the mouse renal pelvis

BACKGROUND AND PURPOSE

Electrically active atypical smooth muscle cells (ASMCs) within the renal pelvis have long been considered to act as pacemaker cells driving pelviureteric peristalsis. We have investigated the role of Ca2+ entry and uptake into and release from internal stores in the generation of Ca2+ transients and spontaneous transient depolarizations (STDs) in ASMCs.

EXPERIMENTAL APPROACH

The electrical activity and separately visualized changes in intracellular Ca2+ concentration in typical smooth muscle cells (TSMCs), ASMCs and interstitial cells of Cajal-like cells (ICC-LCs) were recorded using intracellular microelectrodes and a fluorescent Ca2+ indicator, fluo-4.

RESULTS

In 1 microM nifedipine, high frequency (10-30 min(-1)) Ca2+ transients and STDs were recorded in ASMCs, while ICC-LCs displayed low frequency (1-3 min(-1)) Ca2+ transients. All spontaneous electrical activity and Ca2+ transients were blocked upon removal of Ca2+ from the bathing solution, blockade of Ca2+ store uptake with cyclopiazonic acid (CPA) and with 2-aminoethoxy-diphenylborate (2-APB). STD amplitudes were reduced upon removal of the extracellular Na+ or blockade of IP3 dependent Ca2+ store release with neomycin or U73122. Blockade of ryanodine-sensitive Ca2+ release blocked ICC-LC Ca2+ transients but only reduced Ca2+ transient discharge in ASMCs. STDs in ASMCS were also little affected by DIDS, La3+, Gd3+ or by the replacement of extracellular Cl(-) with isethionate.

CONCLUSIONS

ASMCs generated Ca2+ transients and cation-selective STDs via mechanisms involving Ca2+ release from IP3-dependent Ca2+ stores, STD stimulation of TSMCs was supported by Ca2+ entry through L type Ca2+ channels and Ca2+ release from ryanodine-sensitive stores.

Spontaneous electrical and Ca2+ signals in typical and atypical smooth muscle cells and interstitial cell of Cajal-like cells of mouse renal pelvis

Electrical rhythmicity in the renal pelvis provides the fundamental drive for the peristaltic contractions that propel urine from the kidney to bladder for storage until micturition. Although atypical smooth muscles (ASMCs) within the most proximal regions of the renal pelvis have long been implicated as the pacemaker cells, the presence of a sparsely distributed population of rhythmically active Kit-positive interstitial cells of Cajal-like cells (ICC-LCs) have confounded our understanding of pelviureteric peristalsis. We have recorded the electrical activity and separately visualized changes in intracellular Ca(2+) concentration in typical smooth muscle cells (TSMCs), ASMCs and ICC-LCs using intracellular microelectrodes and a fluorescent Ca(2+) indicator, fluo-4. Nifedipine (1-10 microm)-sensitive driven action potentials and Ca(2+) waves (frequency 6-15 min(-1)) propagated through the TSMC layer at a velocity of 1-2 mm s(-1). High frequency (10-40 min(-1)) Ca(2+) transients and spontaneous transient depolarizations (STDs) were recorded in ASMCs in the absence or presence of 1 microm nifedipine. ICC-LCs displayed low frequency (1-3 min(-1)) Ca(2+) transients which we speculated arose from cells that displayed action potentials with long plateaus (2-5 s). Neither electrical activity propagated over distances > 50 microm. In 1 microm nifedipine, ASMCs or ICC-LCs separated by < 30 microm displayed some synchronicity in their Ca(2+) transient discharge suggesting that they may well be acting as 'point sources' of excitation to the TSMC layer. We speculate that ASMCs act as the primary pacemaker in the renal pelvis while ICC-LCs play a supportive role, but can take over pacemaking in the absence of the proximal pacemaker drive.

Altered 'active' antireflux mechanism in primary vesico-ureteric reflux: a morphological and manometric study

OBJECTIVE

To immunolocate c-kit-positive interstitial cells of Cajal (ICCs, known to be responsible for pacemaker activity in human ureters, coordinating ureteric motility) in the intramural ureter of patients with different grades of vesico-ureteric reflux (VUR), to assess the ureteric histology and correlate these findings with manometric patterns.

PATIENTS AND METHODS

The VU junction (VUJ) represents the boundary between the low-pressure of the upper and high pressure of the lower urinary tract, protecting the upper tract from VUR using active and passive antireflux mechanisms. The contraction of the longitudinal muscle coat of the VUJ possibly functions as an 'active' antireflux system, but previous manometric findings on refluxing ureteric units (RUs) have shown altered patterns. In all, 32 RU ends were stained using both picro-Mallory and Sirius Red techniques; in a parallel immunohistochemical procedure, using mast cell tryptase and CD117 antibodies (to identify ICCs), they were compared with eight control ureteric ends. Ureteric manometry of the VUJ was also done during ureteric reimplantation.

RESULTS

The histochemical and immunohistochemical results in the RUs showed a replacement of the altered smooth muscle fascicles by collagenous stroma and significant loss of ICCs in RU ends, both correlated with the grade of VUR. Ureteric manometry showed significant impairment of basal and maximum pressure in RUs, correlated, respectively, with histological lesions and loss of ICCs.

CONCLUSION

Deficiency of the longitudinal muscle coat probably leads to dysfunction and insufficiency of the ostial valve mechanism, with subsequent impairment of the active valve mechanism. Histological, histochemical and immunohistochemical changes support the alterations of ureteric peristalsis in RUs.

Electrical characterization of interstitial cells of Cajal-like cells and smooth muscle cells isolated from the mouse ureteropelvic junction

PURPOSE

We characterized membrane currents in smooth muscle cells and interstitial cells freshly isolated from the mouse ureteropelvic junction.

MATERIALS AND METHODS

Interstitial cells of Cajal-like cells were identified using c-Kit antibodies and fresh whole mount preparations of ureteropelvic junction. Whole cell and ion channel currents were recorded in collagenase dispersed single cells using standard patch clamp techniques.

RESULTS

Membrane depolarization of single smooth muscle cells evoked a complex K(+) selective outward current consisting of a rapidly activating 4-aminopyridine sensitive transient outward current, followed by a more slowly developing outward current that was decreased by blockers of large conductance Ca(2+) activated K(+) channels. In contrast, membrane depolarization of stellate interstitial cells evoked a slowly developing outward current that did not arise from the opening of transient outward current or large conductance Ca(2+) activated K(+) channels. Under current clamp interstitial cells showed random fluctuations of membrane potential and occasional large, long lasting depolarizations. Under voltage clamp interstitial cells showed high frequency spontaneous transient inward currents that often occurred in bursts to sum and produce long lasting large inward currents. Large inward currents had reversal potentials of almost -10 mV if the Nernst potential for Cl(-) was set at -4 or -78 mV. They were little affected by the Cl(-) channel blockers DIDS (4,4'-diisothiocyanostilbene-2,2'-disulphonic acid) and niflumic acid.

CONCLUSIONS

We speculate that single stellate interstitial cells are c-Kit positive interstitial cells of Cajal-like cells viewed in intact tissue, which generate cationic selective spontaneous transient inward currents that sum to form large inward currents. In the absence of a proximal pacemaker drive these interstitial cells of Cajal-like cells could well trigger contraction in neighboring smooth muscle cell bundles in the ureteropelvic junction.

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.

Pyeloureteric peristalsis: role of atypical smooth muscle cells and interstitial cells of Cajal-like cells as pacemakers

Pyeloureteric peristalsis has long been considered to be triggered by pacemaker atypical smooth muscle cells (SMC) located in the proximal regions of the renal pelvis. However, interstitial cells with many of the morphological features and c-Kit immuno-reactivity of interstitial cells of Cajal (ICC), the established pacemaker cells in the intestine, have been demonstrated to be present in small numbers within the ureteropelvic junction (UPJ) of many mammals. Freshly isolated ICC-like cells (ICC-LC) of the mouse UPJ also display autorhyhmicity. This review discusses the notion that ureteric peristalsis depends on the presence of both atypical SMC and ICC-LC which form separate but interconnected networks that drive electrically quiescent typical SMC. In contrast to the intestine or prostate, all regenerative potential discharge in the mouse UPJ is abolished by the L-type Ca(2+) channel blocker nifedipine revealing a fundamental pacemaker signal. Whether these pacemaker transients arise from atypical SMC or ICC-LC or both has yet to be established. We speculate that the presence of spontaneously active ICC-LC in the distal regions of the UPJ maintains rudimentary peristaltic waves and movement of urine towards the bladder after pyeloureteral obstruction or pyeloplasty and disconnection from the proximal pacemaker drive.

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.

Pacemaker activity in the upper urinary tract

Ureteral peristaltic activity begins with the origin of electrical activity at pacemaker sites. These sites are located in the proximal portion of the urinary collecting system. The 'atypical' smooth muscle cells at these sites fire 'pacemaker' potentials at a frequency higher than the 'driven' action potentials recorded from typical smooth muscle cells. In contrast to typical smooth muscle cells, these atypical pacemaker cells have less than 40% of their cellular area occupied by contractile filaments and demonstrate a sparse immunoreactivity for alpha-smooth muscle actin. Expression of c-Kit, a tyrosine kinase receptor, correlates with the onset of organized ureteral peristalsis in the embryo. Capsaicin-sensitive sensory afferents and the endogenous release of tachykinins and prostaglandins are involved in the maintenance of normal ureteral peristalsis.

LOSS OF INTERSTITIAL CELLS OF CAJAL AND GAP JUNCTION PROTEIN CONNEXIN 43 AT THE VESICOURETERAL JUNCTION IN CHILDREN WITH VESICOURETERAL REFLUX

PURPOSE

Symmetrical muscular contractions and unidirectional peristalsis are prerequisites for competent valve function at the ureterovesical junction. Interstitial cells of Cajal (ICCs) are pacemaker cells that create and coordinate peristaltic motility. We investigated ureteral endings immunohistochemically to elucidate the presence of c-kit positive ICCs as well as the occurrence of gap junction protein connexin 43 in children with vesicoureteral reflux (VUR) to identify a possible pathogenic factor of an insufficient antireflux mechanism.

MATERIALS AND METHODS

Distal ureteral specimens were obtained from 27 children undergoing antireflux surgery. Routine histological paraffin embedded sections were immunostained detecting the c-kit proto-oncogene to study the presence of ICCs as well as connexin 43 positive cells to determine the gap junction density within the ureteral wall. Age matched nonrefluxing ureteral endings served as controls. All investigations were done using high power field magnification for semiquantitative analysis and statistically analyzed.

RESULTS

ICCs were present in refluxing and nonrefluxing ureteral endings. Healthy individuals displayed significantly more ICCs than children with VUR. Connexin 43 immunoreactivity was significantly decreased in all refluxing ureteral specimens, whereas it was homogeneously distributed in normal controls.

CONCLUSIONS

C-kit positive ICCs are found at the ureterovesical junction. Refluxing ureteral endings significantly lack these pacemaker cells, implying a malfunctioning valve mechanism permitting VUR. A substantial decrease in gap junctions in this region adversely affects intercellular signaling, aggravating coordinated peristalsis, which is essential for a competent anti-reflux mechanism.

Interstitial cell of Cajal-like cells in the upper urinary tract

Autorhythmicity in the upper urinary tract (UUT) has long been considered to arise in specialized atypical smooth muscle cells (SMC) predominately situated in the most proximal regions of the pyeloureteric system. These atypical SMC pacemakers have been thought to trigger adjacent electrically-quiescent typical SMC to fire action potentials which allow an influx of Ca2+ and the generation of muscle contraction. More recently, the presence of cells with many of the morphological, electrical and immunohistochemical characteristics of interstitial cells of Cajal (ICC), the pacemaker cells of the gastrointestinal tract, have been located in many regions of both the upper and lower urinary tract. This article reviews the evidence from the literature and from our laboratory supporting a role of both atypical SMC and ICC-like cells in the initiation and propagation of pyeloureteric peristalsis in the UUT. We propose a new model in which there are 2 populations of pacemaker cells, high frequency atypical SMC and lower frequency ICC-like cells, both of which can drive electrically-quiescent typical SMC. The relative presence of these 2 populations of pacemaker cells and the relatively-long refractoriness of typical SMC determines the decreasing frequency of contraction with distance from the renal fornix. In the absence of the proximal pacemaker drive from atypical SMC after pyeloureteral/ureteral obstruction or surgery, ICC-like cell pacemaking provides a compensatory mechanism allowing the ureter to maintain rudimentary peristaltic waves and movement of urine from the pyelon towards the bladder.

Subset of cells immunopositive for neurokinin-1 receptor identified as arterial interstitial cells of Cajal in human large arteries

In the adventitia of large arteries, dendritic cells are located between nerve fibers, some of which contain substance P. The aim of the present study was to examine whether neurokinin 1 receptor (NK-1R) was expressed by dendritic cells in the arterial wall. Parallel sections of aortic and carotid artery segments were immunostained with anti-NK-1R and cell-type-specific antibodies. Dendritic cells in the arterial wall expressed NK-1R, albeit at a low level. Other cells, which intensely expressed NK-1R, were located along the border between the media and adventitia. They did not co-express any dendritic cell markers, including fascin, CD1a, S100, or Lag-antigen, and were negative for CD68, CD3, and mast cell tryptase. These NK-1R(+) cells were laser-capture microdissected and studied by means of electron-microscopic analysis. The microdissected cells were in direct contact with nerve endings, and their ultrastructure was typical of the interstitial cells of Cajal present in the gastrointestinal tract. Further systematic electron-microscopic analysis revealed that the cells displaying the features typical of interstitial cells of Cajal were a basic element of the human arterial wall architectonics. Arterial interstitial cells of Cajal were negative for c-kit but they expressed vasoactive intestinal peptide receptor 1 (VIPR1). Destructive alterations of contacts between arterial interstitial cells of Cajal and nerve endings were observed in arterial segments with atherosclerotic lesions. The functional significance of the arterial interstitial cells of Cajal and their possible involvement in atherosclerosis and other vascular diseases need clarification.

Cajal-like cells in the upper urinary tract: comparative study in various species

The interstitial cells of Cajal (ICC) play an important role in the control of gut motility. The recognition that the ICC cell membrane harbors the c-kit receptor (CD117) sparked rapid advancement in ICC research on the gut and certain pathologies using immunochemical and molecular methods. The question arises whether ICC exist in the upper urinary tract (UUT) and trigger motility. The present study analyzed the distribution of the c-kit receptor in the normal human UUT compared with various species. Immunohistochemistry (alkaline-phosphatase-anti-alkaline-phosphatase technique, immunofluorescence) was applied on serial sections using monoclonal and polyclonal antibodies recognizing the c-kit receptor. C-kit staining was compared with standard endothelial, epithelial, neurogenic, histiocytic, mast cell, and smooth muscle markers, as well as a negative control. Normal proximal, middle, and distal ureter segments were analyzed in rodents, carnivores, porcines, cow, and humans. In all species the c-kit receptor was detected in either round or spindle-shaped cells. Because of their antigenic profile, the round cells were identified as mast cells occurring in all layers of the ureteral wall except the urothelium and were more frequent in humans. In contrast, the population of spindle-shaped cells was marked only by anti-c-kit receptor antibodies, thus resembling ICC. These ICC-like cells were found among the inner and outer smooth muscle layers and in the lamina propria of all species. In humans, spindle-shaped cells were also found vertically oriented within the urothelium. Our morphological data present for the first time the distribution of ICC in the UUT of various species. The ubiquitous distribution in the entire pyeloureteral complex provides strong evidence that ICC generate electrical pacemaker activity within the UUT as an intrinsic system. Animal studies may help to understand the physiological importance of these ICC-like cells. The significance of these findings needs to be evaluated by functional studies and investigations of certain congenital pathologies with disturbance of the urinary outflow.