John M. Park

Expression of peroxisomal proliferator-activated receptors and retinoid X receptors in the kidney

The discovery that 15-deoxy-Delta12,14-prostaglandin J2 (15d-PGJ2) is a ligand for the gamma-isoform of peroxisome proliferator-activated receptor (PPAR) suggests nuclear signaling by prostaglandins. Studies were undertaken to determine the nephron localization of PPAR isoforms and their heterodimer partners, retinoid X receptors (RXR), and to evaluate the function of this system in the kidney. PPARalpha mRNA, determined by RT-PCR, was found predominately in cortex and further localized to proximal convoluted tubule (PCT); PPARgamma was abundant in renal inner medulla, localized to inner medullary collecting duct (IMCD) and renal medullary interstitial cells (RMIC); PPARbeta, the ubiquitous form of PPAR, was abundant in all nephron segments examined. RXRalpha was localized to PCT and IMCD, whereas RXRbeta was expressed in almost all nephron segments examined. mRNA expression of acyl-CoA synthase (ACS), a known PPAR target gene, was stimulated in renal cortex of rats fed with fenofibrate, but the expression was not significantly altered in either cortex or inner medulla of rats fed with troglitazone. In cultured RMIC cells, both troglitazone and 15d-PGJ2 significantly inhibited cell proliferation and dramatically altered cell shape by induction of cell process formation. We conclude that PPAR and RXR isoforms are expressed in a nephron segment-specific manner, suggesting distinct functions, with PPARalpha being involved in energy metabolism through regulating ACS in PCT and with PPARgamma being involved in modulating RMIC growth and differentiation.The discovery that 15-deoxy-Δ12,14-prostaglandin J2(15d-PGJ2) is a ligand for the γ-isoform of peroxisome proliferator-activated receptor (PPAR) suggests nuclear signaling by prostaglandins. Studies were undertaken to determine the nephron localization of PPAR isoforms and their heterodimer partners, retinoid X receptors (RXR), and to evaluate the function of this system in the kidney. PPARα mRNA, determined by RT-PCR, was found predominately in cortex and further localized to proximal convoluted tubule (PCT); PPARγ was abundant in renal inner medulla, localized to inner medullary collecting duct (IMCD) and renal medullary interstitial cells (RMIC); PPARβ, the ubiquitous form of PPAR, was abundant in all nephron segments examined. RXRα was localized to PCT and IMCD, whereas RXRβ was expressed in almost all nephron segments examined. mRNA expression of acyl-CoA synthase (ACS), a known PPAR target gene, was stimulated in renal cortex of rats fed with fenofibrate, but the expression was not significantly altered in either cortex or inner medulla of rats fed with troglitazone. In cultured RMIC cells, both troglitazone and 15d-PGJ2 significantly inhibited cell proliferation and dramatically altered cell shape by induction of cell process formation. We conclude that PPAR and RXR isoforms are expressed in a nephron segment-specific manner, suggesting distinct functions, with PPARα being involved in energy metabolism through regulating ACS in PCT and with PPARγ being involved in modulating RMIC growth and differentiation.

Kielin/chordin-like protein, a novel enhancer of BMP signaling, attenuates renal fibrotic disease

The bone morphogenetic proteins (BMPs) profoundly affect embryonic development, differentiation and disease. BMP signaling is suppressed by cysteine-rich domain proteins, such as chordin, that sequester ligands from the BMP receptor. We describe a novel protein, KCP, with 18 cysteine-rich domains. Unlike chordin, KCP enhances BMP signaling in a paracrine manner. Smad1-dependent transcription and phosphorylated Smad1 (P-Smad1) levels are increased, as KCP binds to BMP7 and enhances binding to the type I receptor. In vivo, Kcp−/− mice are viable and fertile. Because BMPs have a pivotal role in renal disease, we examined the phenotype of Kcp−/− mice in two different models of renal injury. Kcp−/− animals show reduced levels of P-Smad1, are more susceptible to developing renal interstitial fibrosis, are more sensitive to tubular injury and show substantial pathology after recovery. The data indicate an important role for KCP in attenuating the pathology of renal fibrotic disease.

Cyclooxygenase-2 is expressed in bladder during fetal development and stimulated by outlet obstruction

Studies were undertaken to assess expression of inducible cyclooxygenase (COX)-2 in bladder during fetal development and COX-1 and COX-2 expression after outlet obstruction. Bladder tissue or bladder progenitor tissue was harvested from CD-1 murine embryos at embryonic days 11.5( E11.5), E14.5, E17.5, E20.5 (newborn), and from adult. Bladder obstruction was created in adult female mice by ligating the urethra, and bladders were harvested after 3-24 h of obstruction. Gene expression was assessed by semiquantitative reverse transcription-polymerase chain reaction and Western blotting. COX-2 was highly expressed at the early stages of bladder development and declined progressively throughout gestation. In adult bladder, both COX-1 and COX-2 were detectable at low levels under basal conditions. An ∼30-fold increase in COX-2 mRNA was seen after 24 h of obstruction. In contrast, COX-1 did not change with obstruction. COX-2 mRNA levels peaked at 6 h of obstruction. In regional bladder-distention models, COX-2 induction was confined to the area of distention. Bladder outlet obstruction stimulates COX-2 expression dramatically, reactivating a gene that is highly expressed during fetal development.Studies were undertaken to assess expression of inducible cyclooxygenase (COX)-2 in bladder during fetal development and COX-1 and COX-2 expression after outlet obstruction. Bladder tissue or bladder progenitor tissue was harvested from CD-1 murine embryos at embryonic days 11.5 (E11.5), E14.5, E17.5, E20.5 (newborn), and from adult. Bladder obstruction was created in adult female mice by ligating the urethra, and bladders were harvested after 3-24 h of obstruction. Gene expression was assessed by semiquantitative reverse transcription-polymerase chain reaction and Western blotting. COX-2 was highly expressed at the early stages of bladder development and declined progressively throughout gestation. In adult bladder, both COX-1 and COX-2 were detectable at low levels under basal conditions. An approximately 30-fold increase in COX-2 mRNA was seen after 24 h of obstruction. In contrast, COX-1 did not change with obstruction. COX-2 mRNA levels peaked at 6 h of obstruction. In regional bladder-distention models, COX-2 induction was confined to the area of distention. Bladder outlet obstruction stimulates COX-2 expression dramatically, reactivating a gene that is highly expressed during fetal development.

Ketorolac suppresses postoperative bladder spasms after pediatric ureteral reimplantation.

We evaluated the efficacy of ketorolac in suppressing postoperative bladder spasms after ureteroneocystostomy (ureteral reimplantation). Twenty-four pediatric patients undergoing intravesical ureteroneocystostomy were enrolled prospectively to receive either ketorolac or placebo via double-blinded randomization. Twelve patients in each group shared similar preoperative characteristics. All were maintained on an epidural infusion of bupivacaine (0.1%) with fentanyl (2 &mgr;g/mL) throughout the study. Patients were given either ketorolac (0.5 mg · kg-1 · dose-1) or placebo (equivalent volume saline) IV after surgery and every 6 h thereafter for 48 h. Parents were instructed to record bladder spasm episodes prospectively by using a standardized time-flow diary. Three patients (25%) in the ketorolac group experienced bladder spasms, compared with 10 patients (83%) in the placebo group (two-sided P < 0.05). The median severity score for the ketorolac group was 1.2 (mild = 1.0, severe = 3.0), compared with 2.6 for the placebo group (P = 0.003). We conclude that IV ketorolac reduces the frequency and severity of postoperative bladder spasms after intravesical ureteroneocystostomy. Implications We studied the efficacy of ketorolac, a prostaglandin synthesis inhibitor, in the treatment of bladder spasm after ureteroneocystostomy (antireflux operation). Patients were randomized in a double-blinded manner to receive either ketorolac or placebo after the surgery. We demonstrate that ketorolac reduces the frequency and severity of postoperative bladder spasm.

Vesicoureteral Reflux: Current Trends in Diagnosis, Screening, and Treatment

CONTEXT Vesicoureteral reflux (VUR) is present in approximately 1% of children in North America and Europe and is associated with an increased risk of pyelonephritis and renal scarring. Despite its prevalence and potential morbidity, however, many aspects of VUR management are controversial. OBJECTIVE Review the evidence surrounding current controversies in VUR diagnosis, screening, and treatment. EVIDENCE ACQUISITION A systematic review was performed of Medline, Embase, Prospero, Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, clinicaltrials.gov, and the most recent guidelines of relevant medical specialty organizations. EVIDENCE SYNTHESIS We objectively assessed and summarized the published data, focusing on recent areas of controversy relating to VUR screening, diagnosis, and treatment. CONCLUSIONS The evidence base for many current management patterns in VUR is limited. Areas that could significantly benefit from additional future research include improved identification of children who are at risk for VUR-related renal morbidity, improved stratification tools for determining which children would benefit most from which VUR treatment option, and improved reporting of long-term outcomes of VUR treatments.

Percutaneous cystolithotomy using a laparoscopic entrapment sac

OBJECTIVES To describe a percutaneous approach that uses laparoscopic techniques and technology to achieve intact removal of bladder stones after augmentation cystoplasty. METHODS Percutaneous stone removal using a laparoscopic entrapment sac was performed in 4 patients with augmented bladders. Under endoscopic guidance, a 10-mm laparoscopic trocar was placed percutaneously into the augmented bladder using the previous suprapubic tube site. The stones were then maneuvered into a laparoscopic entrapment sac and extracted intact without lithotripsy. RESULTS Percutaneous removal of the entire stone burden (up to seven stones in 1 patient) was achieved in 3 of 4 patients. The total operative time was less than 1 hour in each of these cases. Partial conversion to open cystolithotomy was required in 1 patient, because of tearing of the entrapment sac. Three of 4 cases were performed on an outpatient basis and less than 24 hours of catheter drainage was required in all but 1 patient. CONCLUSIONS Percutaneous cystolithotomy using a laparoscopic entrapment sac is a safe, useful, and minimally invasive modification of contemporary percutaneous techniques. In patients with augmented bladders, application of this technique may minimize the risk of residual fragments and obviate the need for adjuvant lithotripsy.

Are stone protocol computed tomography scans mandatory for children with suspected urinary calculi

megalourethra and all cases had normal karyotype. Of seven liveborn babies, one died neonatally of pulmonary hypoplasia. All six infants alive at the time of writing had a dysfunctional urethra and three suffered from impaired or end-stage renal disease. Associated anomalies were found in half of the cases. Conclusion: Congenital megalourethra is caused by abnormal development or hypoplasia of the penile erectile tissue, secondary to distal urethral obstruction. When the amniotic fluid volume is normal, survival is possible. However, all liveborn infants have voiding and renal dysfunction and sexual dysfunction is expected. Megalourethra should be considered in all male fetuses presenting prenatally with megacystis and detailed fetal ultrasonography should look for an elongated and/or distended phallic structure as well as any associated anomalies.

EXTERNAL URETHRAL SPHINCTER DILATION FOR THE MANAGEMENT OF HIGH RISK MYELOMENINGOCELE: 15-YEAR EXPERIENCE

PURPOSE We investigate the long-term outcome using external urethral sphincter dilation for high risk myelomeningocele. MATERIALS AND METHODS Since 1984 external urethral sphincter dilation was performed in 25 patients with myelomeningocele who demonstrated passive leak point pressure greater than 40 cm. H2O and/or poor bladder compliance. Mean followup from the first dilation was 8.4 years. Overall 2.4 dilations were performed per patient (range 1 to 8). Cystometrography, imaging study and continence status were evaluated retrospectively. RESULTS Overall external urethral sphincter dilation produced durable improvements in mean leak point pressure (60.9 versus 34.4 cm. H2O), capacity (119.8 versus 233.3 ml.), initial compliance (11.5 versus 28.4 ml./cm. H2O) and terminal compliance (1.1 versus 7.7 ml./cm. H2O). Categorical analysis revealed 3 groups in terms of outcome. Group 1 consisted of 11 patients (44%) who demonstrated durable improvements in urodynamic parameters as well as preservation of the upper tracts. These patients demonstrated a 2-step compliance pattern on pre-dilation cystometrography, in which elevated leak point pressure was associated with excellent initial compliance. Group 2 consisted of 5 patients (20%) who failed to maintain safe leak point pressure and whose upper tracts deteriorated, including 4 who eventually underwent augmentation cystoplasty. This group demonstrated a 1-step hypertonicity in which elevated leak point pressure was associated with a steep pressure increase during early filling. Group 3 consisted of 9 patients (36%) who responded minimally in terms of leak point pressure reduction but whose upper tracts remained well preserved. They demonstrated a high pressure instability pattern associated with excellent baseline compliance. CONCLUSIONS External urethral sphincter dilation provides an effective long-term solution for select high risk myelomeningocele cases. Those who demonstrate elevated leak point pressure and poor bladder compliance at the time of external urethral sphincter dilation are less likely to respond, suggesting that the bladder may have already undergone irreversible changes due to high outlet resistance. Patients who demonstrate instability patterns are less likely to respond to external urethral sphincter dilation in terms of leak point pressure reduction but the upper tracts appear to be well preserved.

Mechanisms of Incontinence and Retention after Orthotopic Neobladder Diversion

OBJECTIVES To define the mechanism of incontinence and retention after orthotopic neobladder diversion. METHODS The results of urodynamic and endoscopic evaluations were assessed in 19 patients (15 men and 4 women). Mean age and postoperative follow-up were 58.3 years and 19.6 months, respectively. Seventeen patients (15 men, 2 women) presented with the sole complaint of nocturnal incontinence, and 2 women presented with retention. Evaluations included voiding and continence history, pelvic examination (for women), postvoid residual, uroflowmetry, triple-lumen video-urodynamic study, and cystourethroscopy. RESULTS Among patients with incontinence, 11 (65%) were found to have a primary failure-to-store problem as a result of either reservoir or sphincter failure. Four patients (24%) had a primary failure-to-empty problem, and 2 (11%) had features of both. The predominant etiology of voiding difficulty was the inability to relax the external urethral sphincter adequately during Valsalvas maneuver. Of the 2 women who presented with retention, one had obstructing mucosal folds at the neobladder opening and both demonstrated anterior vaginal wall prolapse on pelvic examination. CONCLUSIONS The mechanism of incontinence and retention after orthotopic neobladder diversion can vary. Carefully performed urodynamic and endoscopic assessments can define the underlying etiology and may serve as a guide for proper treatment selection.

Post-translational Processing and Renal Expression of Mouse Indian Hedgehog

The full-length mouse Indian hedgehog (Ihh) cDNA was cloned from an embryonic 17.5-day kidney library and was used to study the post-translational processing of the peptide and temporal and spatial expression of the transcript. Sequence analysis predicted two putative translation initiation sites. Ihh translation was initiated at both initiation sites when expressed in an in vitro transcription/translation system. Expression of an Ihh mutant demonstrated that the internal translation initiation site was sufficient to produce the mature forms of Ihh. Ihh post-translational processing proceeded in a fashion similar to Sonic and Drosophila hedgehog; the unprocessed form underwent signal peptide cleavage as well as internal proteolytic processing to form a 19-kDa amino-terminal peptide and a 26-kDa carboxyl-terminal peptide. This processing required His313 present in a conserved serine protease motif. Ihh transcript was detected by in situ RNA hybridization as early as 10 days postcoitum (dpc) in developing gut, as early as 14.5 dpc in the cartilage primordium, and in the developing urogenital sinus. In semiquantitative reverse transcription-polymerase chain reaction experiments, Indian hedgehog transcript was first detected in the mouse metanephros at 14.5 dpc; transcript abundance increased with gestational age, becoming maximal in adulthood. In adult kidney, Ihh transcript was detected only in the proximal convoluted tubule and proximal straight tubule.