Contemporary disparities in progression to orchiopexy for cryptorchidism as reported in the Pediatric Health Information System (PHIS) database.

INTRODUCTION: When evaluating the timeliness of orchiopexy for cryptorchidism, health disparities are apparent among Hispanic and African American males and those with public insurance. Since the publication of these data, the COVID-19 pandemic has stressed our healthcare system and significantly affected the provision of pediatric urology care. OBJECTIVE: We sought to assess if certain groups were disproportionately affected in progression to orchiopexy after the diagnosis of cryptorchidism during and after the pandemic in US freestanding children's hospitals. STUDY DESIGN: Using the PHIS database, pediatric patients ≤5 years who underwent orchiopexy between January 2018 and December 2022 were retrospectively analyzed. Exclusion criteria included prematurity, retractile testes, and testicular torsion. Primary outcomes were age at orchiopexy and the proportion of individuals undergoing timely orchiopexy for cryptorchidism. RESULTS: Over the study period 3140 patients ≤5 years old underwent orchiopexy for cryptorchidism. Non-Hispanic Blacks and Hispanics were significantly less likely to have timely orchiopexy and underwent orchiopexy 2.13 and 3.60 months later compared to whites (p < 0.01). As compared to pre-COVID-19, during the pandemic the proportion of patients who had timely surgery was higher and the median age was significantly lower (p = 0.01 and p < 0.01, respectively) in white patients only. Over the study period, patients with public insurance were less likely to have timely orchiopexy and underwent orchiopexy 2.94 months later (p < 0.01) than patients with private insurance. Compared to during the pandemic, post-pandemic a significantly lower proportion of publicly insured patients have since undergone timely orchiopexy (p = 0.04). Patients in the West were less likely to have timely orchiopexy and had a higher age at time of orchiopexy (p < 0.01) than other regions. However, in the West during the pandemic, the proportion of children who had timely surgery was higher compared to pre-and post-COVID-19 (p < 0.01). DISCUSSION: Overall, regardless of insurance status, race, or location, a significant proportion of patients did not undergo timely orchiopexy. During the pandemic white patients had a lower median age and an increased proportion underwent timely orchiopexy, despite the number of orchiopexies remaining constant. Disparities in the post-COVID-19 era have been further exacerbated for publicly insured patients, who a significantly lower proportion of have since undergone timely orchiopexy. Specific efforts are required across the United States to increase timely orchiopexy for all boys. CONCLUSIONS: Progression to timely orchiopexy remains low for all boys in the era surrounding COVID-19; certain groups appear to be more adversely affected.

Gonadal tumors in a contemporary cohort of patients with differences in sex development undergoing surgery - A multi-site study from the Pediatric Urologic Oncology Working Group of the societies for pediatric urology.

BACKGROUND: Disturbances in gonadal development lead to increased risk of gonadal malignancy in some but not all patients with differences in sex development (DSD). However, the natural history of these tumors is poorly described, and the literature remains sparse. OBJECTIVE: The objective of this study was to describe the incidence of germ cell neoplasia in situ (GCNIS) and germ cell tumor (GCT) in a contemporary cohort of patients with DSD undergoing surgery and to provide long-term oncologic outcomes for these patients. STUDY DESIGN: Patients with DSD who have undergone gonadectomy or gonadal biopsy were identified at four institutions. Clinical characteristics, pathology, and treatment details were obtained retrospectively. Patients were stratified into risk categories based on DSD diagnosis. Oncologic treatment and outcomes were recorded. Descriptive statistics are reported using parametric methods. RESULTS: 83 patients were identified. Distribution of diagnoses is summarized in the summary table. 14 (16.9%) patients underwent gonadal biopsy, and 71 (85.5%) patients underwent gonadectomy (50/71 gonadectomies were bilateral). 8/83 (9.6%) patients had GCNIS or GCT (7 GCNIS, 1 GCT). Median age at surgery was 2.95 years (y) (interquartile range [IQR] 0.6-12.2) and 14y (IQR 0.85-16.9) in patients without and with GCNIS/GCT, respectively. All 8 patients with GCNIS/GCT had high or intermediate risk DSD diagnoses (4 mixed gonadal dysgenesis, 3 Turner with Y, 1 partial gonadal dysgenesis). Of the patients with high-risk diagnoses, 8/54 (15%) had GCNIS/GCT. No patient received adjuvant therapy, no patient had a recurrence, and all patients were living with mean follow up 6.4y. DISCUSSION: The risk of gonadal malignancy is heterogeneous in the DSD population and can vary based on DSD diagnosis as well as maturation, testicularization, and location of the gonads. The most recent consensus recommendations on gonadal management emphasize risk stratification and consideration of gonadal surveillance based on gender of rearing, but supporting literature remains sparse. In this contemporary cohort of DSD patients who underwent gonadal surgery, most patients did not have evidence of adverse pathology, all patients with malignant or premalignant pathology had a high/intermediate risk DSD diagnosis, and all patients with GCNIS/GCT were treated with surgery alone without recurrence. CONCLUSIONS: The distribution of patients with premalignant and malignant gonadal pathology and DSD in this cohort aligns with prior literature, and oncologic outcomes were excellent. These data add valuable information to the current literature and highlight the necessity to develop appropriate screening regimens for retained gonads.

Current Practice in Robotic Surgery Among Pediatric Urologists: A Survey Study.

Introduction: Since its introduction, robotic surgery has gained most traction among urologists. Pediatric urologists have been slower to adopt the technology than their adult counterparts. Our objectives were to understand current practice patterns for robotic surgery among pediatric urologists, to identify perceived barriers, and to identify factors associated with the use of robotic surgery. Methods: An anonymous online survey was administered using Research Electronic Data Capture (REDCap) to members of the Societies for Pediatric Urology (SPU) including questions about provider demographics and personal practice patterns. Comparisons were made using Pearson's chi-squared analysis. Results: Of 351 SPU members surveyed, 95 completed the survey (27%): 55 (58%) reported performing robotic surgery and 40 (42%) reported not performing robotic surgery. Twenty-seven (28%) reported receiving robotic training in residency, 26 (27%) in fellowship, 34 (36%) in a robotics course, and 30 (32%) with proctored surgery. Cited reasons for not performing robotic surgery were lack of training, referring to practice partners, and lack of benefit. Of those performing robotic surgery, most reported performing 0-1 or 2-4 per month. Thirty-one (56%) reported having selection criteria for use of the robot: 26 (47%) cited an age cutoff, 12 (22%) cited a weight cutoff, and 14 (26%) cited an abdominal size cutoff. Eighteen (33%) reported using hidden incisions endoscopic surgery (HIdES) approach and 40 (42%) reported using an assistant port. Factors associated with using the robot included surgeon age, years in practice, practice setting, having robotic training, and having practice partners who perform robotic surgery. Conclusions: Practice variation exists in the use and application of robotic surgery among pediatric urologists. The main self-reported barriers to performing robotic surgery are lack of training, referring to practice partners, and no perceived benefit to robotic surgery. Factors associated with performing robotic surgery were surgeon age, years in practice, practice setting, and having practice partners perform robotic surgery. There is no Clinical Trial Registration number associated with this study.

Presentation and Diagnosis of Ureteral Quadruplication: Case Report and Analysis of the Literature.

Ureteral quadruplication is exceedingly rare. All except for 2 cases were symptomatic and nearly all underwent intervention. We present the first case of asymptomatic ureteral quadruplication in the presence of ureteral cyst. The report is first to prove ureteral quadruplication, even with ureteral cyst, can have normal renal function and parenchyma without obstruction or reflux. The report analyzes differences between the 14 cases of ureteral quadruplication in the English literature. It is first to describe bilateral ureteral cysts with ureteral quadruplication and triplication, and is first to accurately characterize the appearance of quadruplicated ureters inside the kidney.

A novel urinary biomarker protein panel to identify children with ureteropelvic junction obstruction - A pilot study.

INTRODUCTION AND OBJECTIVE: Reliable urinary biomarker proteins would be invaluable in identifying children with ureteropelvic junction obstruction (UPJO) as the existing biomarker proteins are inconsistent in their predictive ability. Therefore, the aim of this study was to identify consistent and reliable urinary biomarker proteins in children with UPJO. METHODS: To identify candidate biomarker proteins, total protein from age-restricted (<2 years) and sex-matched (males) control (n = 22) and UPJO (n = 21) urine samples was analyzed by mass spectrometry. Proteins that were preferentially identified in UPJO samples were selected (2-step process) and ranked according to their diagnostic odds ratio value. The top ten proteins with highest odds ratio values were selected and tested individually by ELISA. The total amount of each protein was normalized to urine creatinine and the median with interquartile ranges for control and UPJO samples was determined. Additionally, fold change (UPJO/Control) of medians of the final panel of 5 proteins was also determined. Finally, we calculated the average + 3(SD) and average + 4(SD) values of each of the 5 proteins in the control samples and used it as an arbitrary cutoff to classify individual control and UPJO samples. RESULTS: In the first step of our selection process, we identified 171 proteins in UPJO samples that were not detected in the majority of the control samples (16/22 samples, or 72.7%). Of the 171 proteins, only 50 proteins were detected in at least 11/21 (52.4%) of the UPJO samples and hence were selected in the second step. Subsequently, these 50 proteins were ranked according to the odds ratio value and the top 10 ranked proteins were validated by ELISA. Five of the 10 proteins - prostaglandin-reductase-1, ficolin-2, nicotinate-nucleotide pyrophosphorylase [carboxylating], immunoglobulin superfamily-containing leucine-rich-repeat-protein and vascular cell adhesion molecule-1 were present at higher levels in the UPJO samples (fold-change of the median protein concentrations ranging from 2.9 to 9.4) and emerged as a panel of biomarkers to identify obstructive uropathy. Finally, the order of prevalence of the 5 proteins in UPJO samples is PTGR1>FCN2>QPRT>ISLR>VCAM1. CONCLUSION: In summary, this unique screening strategy led to the identification of previously unknown biomarker proteins that when screened collectively, may reliably distinguish between obstructed vs. non-obstructed infants and may prove useful in identifying informative biomarker panels for biological samples from many diseases.

Local Control of Perineal Rhabdomyosarcoma: Are Current Recommendations Adequate?

Rhabdomyosarcoma (RMS) is a rare malignancy that can develop in nearly any soft-tissue of the body. Location of the primary tumor affects treatment strategy and prognosis, and RMS of the perineal areas can be especially difficult to treat successfully. RMS is treated systemically with chemotherapy. Local control options include surgical excision, radiation treatment, or a combination of the 2. Treating RMS with radiation treatment can be challenging due to the absence of standardized dosage protocols, along with the presence of conflicting recommendations in the literature. Each case of perineal RMS may benefit from a more individualized treatment plan.

Future directions in risk stratification and therapy for advanced pediatric genitourinary rhabdomyosarcoma.

Rhabdomyosarcoma (RMS) represents the most common soft tissue sarcoma in infants and children and the third most common pediatric solid tumor, accounting for 5% to 15% of all childhood solid tumors. Of these, 15% to 20% arise from the genitourinary tract, with the most common sites originating from the prostate, bladder, and paratesticular regions, followed by the vagina and uterus. Although upfront radical surgery was used at the initiation of Intergroup RMS Study-I (1972-1978), the treatment paradigm has shifted to include initial biopsy with the goal of organ preservation, systemic chemotherapy for all patients, and local control involving surgical resection with or without radiation therapy for most patients. Collaborative group clinical trials have led to dramatic improvement in survival rates from 1960 to 1996 among patients with low- or intermediate-risk disease; however, outcomes appear to have plateaued in more recent years, and the prognosis for patients with metastatic or relapsed/refractory disease remains poor. Current management goals include minimizing toxicity while maintaining the excellent outcomes in low-risk disease, as well as improving outcomes in patients with intermediate- and high-risk disease. Advances in genetic analysis have allowed further refinement in risk stratification of patients. Perhaps the most significant recent development in RMS research was the discovery of an association of alveolar RMS (ARMS) with translocations t(2;13) and t(1;13). Translocation fusion-positive tumors comprise 80% of ARMS and are more aggressive. Fusion-negative ARMS may have a clinical course similar to embryonal RMS. Future Children's Oncology Group sarcoma studies will likely incorporate fusion status into risk stratification and treatment allocation. Newer radiotherapy modalities hold promise for providing local control of disease while minimizing morbidity. The addition of traditional cytotoxic chemotherapeutic agents does not seem to improve outcomes in high-risk patients. Ultimately, the most substantial progress may arise from further elucidation of genetic and molecular pathways involved in RMS tumor formation in an effort to identify novel, targeted therapeutic approaches.

Paratesticular inflammatory myofibroblastic tumor in a pediatric patient.

Although rare, paratesticular inflammatory myofibroblastic tumor (IMT) represents the second most common paratesticular mass after adenomatoid tumor and comprises roughly 6% of such lesions. Only approximately four cases have been reported in patients younger than 18 years of age. We report an incidentally discovered paratesticular IMT in a 17-year-old male successfully treated with wide excision and testis sparing. To our knowledge, no recurrence has been reported after complete excision of paratesticular IMT; however, continued follow-up is recommended.

Oncology: the role of partial nephrectomy in Wilms tumor.

Wilms tumor represents the most common pediatric renal malignancy and the fourth most common childhood cancer overall. Overall survival from Wilms tumor has increased to over 90 % secondary to multidisciplinary therapy and multi-institutional cooperative group trials. Recent therapeutic focus has shifted to reduction in treatment morbidity and renal preservation while maintaining the high survival rates. Partial nephrectomy is an integral component of the multimodal treatment protocols for Wilms tumor patients with bilateral disease, solitary kidney, or predisposing syndromes. Recent consideration has been given to utilization of nephron sparing surgery (NSS) in carefully selected patients with nonsyndromic unilateral Wilms tumor. While long-term, prospective data in this subgroup of patients is not yet available, case series demonstrate comparable oncologic outcomes after partial versus radical nephrectomy. The relative rarity of Wilms tumor, especially those amenable to upfront partial nephrectomy, presents a challenge to conducting controlled trials.

The need for additional procedures in patients undergoing proximal hypospadias repairs as reported in the pediatric health information system database.

PURPOSE: Using administrative data from freestanding pediatric hospitals in the United States, we characterized the frequency and type of additional procedures required in patients undergoing proximal hypospadias repair in a larger cohort than in published case series across multiple surgeons and institutions. MATERIALS AND METHODS: A search of the Pediatric Health Information System (PHIS) database by CPT code between January 1, 2005 and June 30, 2010 identified patients undergoing 1 or 2-stage repair for proximal hypospadias. Patient records with inconsistent coding or the suggestion of an alternate pathological condition were excluded from study. A forward query to June 30, 2011 identified additional hypospadias related interventions by CPT codes. RESULTS: We identified 1,679 patients from a total of 37 hospitals. Potential followup was 1 to 6.5 years. One-stage repair was performed in 85.7% of patients at a median age of 10 months. In patients undergoing 2-stage repair the median age at initial repair was 10 months and the median interval between stages was 6 months. Of all patients 26.2% required 1 or more additional interventions beyond definitive repair. Of all additional interventions 84.0% were open, 7.2% were endoscopic treatment for stricture, 0.4% were combined endoscopic and open interventions, and 8.4% were endoscopic evaluation. The median interval from definitive repair to the first intervention was 9 months. CONCLUSIONS: These data indicate that more than a quarter of patients who underwent proximal hypospadias repair at pediatric hospitals required additional intervention(s) after what was thought to be definitive repair. These data help create a broader context in a contemporary cohort of patients treated with proximal hypospadias repair.

Fetal hydronephrosis as a predictor of neonatal urologic outcomes.

OBJECTIVES: The ability to predict surgically relevant fetal renal hydronephrosis is limited. We sought to determine the most efficacious second- and third-trimester fetal renal pelvis anteroposterior diameter cutoffs to predict the need for postnatal surgery. METHODS: We retrospectively reviewed the medical records of mothers and neonates who had a prenatal sonographic examination in our Perinatal-Pediatric Urology Clinic and received follow-up care. Hydronephrosis was defined as a renal pelvis anteroposterior diameter of 5 mm or greater in the second trimester and 7 mm or greater in the third trimester. Hydronephrosis was subdivided into mild, moderate, and severe. RESULTS: Of 8453 fetuses, 96 met the criteria and were referred to our clinic. Isolated hydronephrosis was diagnosed in 74 fetuses, of which 53 received postnatal follow-up evaluations. The areas under the receiver operating characteristic curves for predicting postnatal surgery in the second and third trimesters were 0.770 and 0.899, respectively. The second-trimester renal anteroposterior diameter threshold that best predicted post-natal surgery was 9.5 mm (sensitivity, 71.4%; specificity, 81.1%). The third-trimester threshold that best predicted postnatal surgery was 15.0 mm (sensitivity, 85.7%; specificity, 94.6%). CONCLUSIONS: The fetal renal anteroposterior diameter on second- and third-trimester sonography is predictive of an increased risk for neonatal urologic surgery. Surgical risk is best predicted by a third-trimester renal anteroposterior diameter threshold of 15 mm.

Primary renal synovial sarcoma in a 13-year-old boy.

Primary renal synovial sarcoma is a rare entity with fewer than 40 cases reported in the literature. Its clinical presentation and radiographic features, namely, its often complex cystic appearance, make it difficult to differentiate from other benign or malignant renal lesions. Although there are certain consistent morphological and immunohistochemical features, diagnosis ultimately depends on molecular studies. Prognosis is poor, and there currently exists no defined treatment protocol. Herein, we describe the youngest reported case of primary renal synovial sarcoma in the literature.

Pediatric urologic oncology: organ-sparing surgery in kidney and testis.

Technological advances in imaging as well as increased knowledge of tumor-specific biology have promoted the role of organ-sparing approaches to pediatric renal and testicular tumors. Application of these techniques continues to evolve as data on long-term follow-up become available and as protocol-guided investigation provides answers to therapeutic outcomes of these approaches. Optimally, organ-sparing surgery will continue to provide increased potential for preservation of both renal function and fertility.

Infant communicating hydroceles--do they need immediate repair or might some clinically resolve?

PURPOSE: Infant hydroceles that are communicating by history (fluctuation in size) or examination (reducible fluid) are often repaired soon after presentation. We have followed a series of infant boys with such hydroceles and reviewed their early natural history. MATERIALS AND METHODS: Since 1998, we have followed 174 infant boys presenting with an apparent communicating hydrocele without immediate surgical repair. All boys were initially seen before 18 months of age and most (168) by 12 months. Most had been full term at delivery, although 32 had been premature (<37 weeks' gestational age) and 11 extremely so (<32 weeks). Most boys (120) had bilateral hydroceles at presentation. RESULTS: Of the 110 boys followed to disposition, 69 (62.7%) had complete resolution without surgery by a mean age of 11.7 months. Forty-one patients (37.3%) underwent surgery for correction at a mean age of 14 months because of persistence in size or development of a hernia. Six developed a hernia during observation, none of whom had any episode of incarceration. Only 2 patients with apparent resolution subsequently had recurrence with a hernia. Age at presentation and gestational age at birth showed no effect on resolution. The hydroceles of 64 boys had improved in size after a mean follow-up of 13.9 months when last seen. CONCLUSIONS: Many infant hydroceles that are communicating by history or examination do resolve clinically without surgery and deserve observation. Progression to hernia was rare in our experience and did not result in incarceration. Consequently, little risk is taken by initial observation.

Febrile urinary tract infection after ureteroneocystostomy: a contemporary assessment at a single institution.

PURPOSE: Febrile urinary tract infection represents significant morbidity in patients with vesicoureteral reflux, especially following open surgical or endoscopic treatment. The reported incidence of febrile urinary tract infection after ureteroneocystostomy varies from 10% to 24%. We investigated the incidence of febrile urinary tract infection following ureteroneocystostomy in a contemporary, single institution series. MATERIALS AND METHODS: We retrospectively reviewed medical records of 395 consecutive patients undergoing ureteroneocystostomy for primary vesicoureteral reflux at our institution between 2002 and 2007. We examined demographic, diagnostic and operative data, including presence of postoperative febrile urinary tract infection. A Cox proportional hazards model was performed to assess predictors of febrile urinary tract infection following ureteroneocystostomy. RESULTS: Ureteroneocystostomy was performed in 395 patients (673 ureters) at a mean age of 58 months. The most common reflux grade was III (41%). The incidence of postoperative febrile urinary tract infection was 4.6% at a mean followup of 15 months. Postoperative dysfunctional elimination syndrome was a significant predictor of febrile urinary tract infection (HR 3.8, 95% CI 1.2-12, p = 0.02), and was identified in 58 of 340 toilet trained children (15% overall). Age at diagnosis, initial presentation, age at surgery, indication for surgery, reflux grade, laterality, surgical technique and preoperative dysfunctional elimination syndrome were not predictive of postoperative febrile urinary tract infection. CONCLUSIONS: The incidence of febrile urinary tract infection following ureteroneocystostomy may be lower than previously reported. The presence of postoperative dysfunctional elimination syndrome is a significant predictor of postoperative febrile urinary tract infection.

Recruitment of bone marrow derived cells to the bladder after bladder outlet obstruction.

PURPOSE: Bladder fibrosis is an undesired end point of partial bladder outlet obstruction. In fibrotic disease of the lung, kidney, skin and heart chemokines recruit bone marrow derived cells to injured tissue. Blockade of chemokines like CCL2 results in decreased fibrosis in other organs. To our knowledge we present the first report of bone marrow derived cell recruitment to the bladder in a murine bladder outlet obstruction model. MATERIALS AND METHODS: We lethally irradiated WT female mice and reconstituted their bone marrow using fetal liver cells from transgenic mice ubiquitously expressing green fluorescent protein. Periurethral collagen injection was used for bladder outlet obstruction. Obstruction was assessed by urodynamics, and bladder and kidney histological changes. Bladders were harvested 1 to 12 weeks after bladder outlet obstruction and compared to those in nonobstructed controls. The chemokine CCL2 was compared between obstructed and nonobstructed mice with reverse transcriptase-polymerase chain reaction. Green fluorescent protein expressing bone marrow derived cells were identified with immunohistochemistry and fluorescence activated cell sorting. RESULTS: Bladders showed histological and urodynamic changes consistent with obstruction. CCL2 induction increased after obstruction compared to that in controls. After obstruction bone marrow derived cells were present in the urothelial and stromal layers. Activated epidermal growth factor receptor was found in cells associated with bone marrow derived cells. CONCLUSIONS: Bone marrow derived cells are recruited to the bladder by bladder outlet obstruction and are present in the urothelial and stromal layers. Stromal bone marrow derived cells may have a role in hypertrophy and fibrosis. Further study of the recruitment and function of bone marrow derived cells in the bladder may provide potential targets for antifibrotic therapy.

Pediatric ureteroscopic management of intrarenal calculi.

PURPOSE: Data addressing ureteroscopic management of intrarenal calculi in prepubertal children are limited. We reviewed our experience from January 2002 through December 2007. MATERIALS AND METHODS: We retrospectively reviewed ureteroscopic procedures for intrarenal calculi in children younger than 14 years. Stone-free status was determined with postoperative imaging. Multiple logistic regression analysis was used to assess the influence of preoperative factors on initial stone-free status and the need for additional procedures. RESULTS: Intrarenal calculi were managed ureteroscopically in 52 kidneys in 50 children with a mean age of 7.9 years (range 1.2 to 13.6). Mean stone size was 8 mm (range 1 to 16). Stone-free rate after a single ureteroscopic procedure was 50% (25 of 50 patients) on initial postoperative imaging and 58% (29 of 50) with extended followup. Initial stone-free status was dependent on preoperative stone size (p = 0.005) but not stone location. Additional stone procedures were required in 18 upper tracts. Younger patient age (p = 0.04) and larger preoperative stone size (p = 0.002) were associated with the need for additional procedures. Additional procedures were required in more than half of the stones 6 mm or larger but in no stone smaller than 6 mm. CONCLUSIONS: Ureteroscopy is a safe method for the treatment of intrarenal calculi in the prepubertal population. Our ureteroscopic stone-free rate for intrarenal stones is lower than that reported for ureteral stones. Parents should be informed that additional procedures will likely be required, especially in younger patients and those with stones larger than 6 mm.

Directed differentiation of bone marrow derived mesenchymal stem cells into bladder urothelium.

PURPOSE: We have previously reported that embryonic rat bladder mesenchyma has the appropriate inductive signals to direct pluripotent mouse embryonic stem cells toward endodermal derived urothelium and develop mature bladder tissue. We determined whether nonembryonic stem cells, specifically bone marrow derived mesenchymal stem cells, could serve as a source of pluripotent or multipotent progenitor cells. MATERIALS AND METHODS: Epithelium was separated from the mesenchymal shells of embryonic day 14 rat bladders. Mesenchymal stem cells were isolated from mouse femoral and tibial bone marrow. Heterospecific recombinant xenografts were created by combining the embryonic rat bladder mesenchyma shells with mesenchymal stem cells and grafting them into the renal subcapsular space of athymic nude mice. Grafts were harvested at time points of up to 42 days and stained for urothelial and stromal differentiation. RESULTS: Histological examination of xenografts comprising mouse mesenchymal stem cells and rat embryonic rat bladder mesenchyma yielded mature bladder structures showing normal microscopic architecture as well as proteins confirming functional characteristics. Specifically the induced urothelium expressed uroplakin, a highly selective marker of urothelial differentiation. These differentiated bladder structures demonstrated appropriate alpha-smooth muscle actin staining. Finally, Hoechst staining of the xenografts revealed nuclear architecture consistent with a mouse mesenchymal stem cell origin of the urothelium, supporting differentiated development of these cells. CONCLUSIONS: In the appropriate signaling environment bone marrow derived mesenchymal stem cells can undergo directed differentiation toward endodermal derived urothelium and develop into mature bladder tissue in a tissue recombination model. This model serves as an important tool for the study of bladder development with long-term application toward cell replacement therapies in the future.

Temporal-spatial protein expression in bladder tissue derived from embryonic stem cells.

PURPOSE: Identifying developmental proteins could lead to markers of bladder progenitor cells, which could be used to investigate bladder diseases. We recently reported a novel embryonic stem cell model in which to study differential protein expression patterns during bladder development. Differential and temporal expressions of the endodermal proteins known as forkhead box (Foxa1 and Foxa2) were observed. In the current study we further delineated these protein expression patterns. MATERIALS AND METHODS: Epithelium was removed from the underlying mesenchyma from embryonic day 18 rat bladders. Heterospecific recombinant xenografts were created by combining embryonic stem cells plus embryonic bladder mesenchyma and placed beneath the renal capsule of mouse hosts. Grafts were harvested at 16, 18, 21, 28, 35 and 42 days, and evaluated with hematoxylin and eosin, trichrome staining, and immunohistochemistry for uroplakin, smooth muscle alpha-actin, p63, Foxa1, Foxa2 and androgen receptor. RESULTS: At 16 days uroplakin was detectable and it seemed to correlate with the loss of Foxa2, while Foxa1 remained at all time points. Androgen receptor was first noted in stroma at day 16. It localized to urothelial nuclei at day 21 and was undetectable at 42 days. Adjacent to the urothelium alpha-smooth muscle actin was seen on day 16 and it was localized in bundles to the periphery of the graft at later time points. Staining for basilar urothelium with p63 confirmed basilar orientation at all time points. CONCLUSIONS: We report the temporal spatial expression of various genes in early bladder development. This suggests that some proteins may be potential markers of bladder progenitor cells. Characterizing these markers may potentially identify bladder progenitor cells that have been directed toward a lineage path destined to become urothelial cells. Ultimately these multipotential progenitor cells could be isolated and used to study and treat diseases that affect the bladder.