Response of the newborn ureteropelvic junction complex to induced and later reversed partial ureteral obstruction in the rabbit model

Positive outcomes of phosphodiesterase type 5 inhibitor on histopathologic and biochemical changes induced by ureteral obstruction

OBJECTIVES

We examined the effects of tadalafil, one of the phosphodiesterase type 5 (PDE5) inhibitors, in a rat model of with partial and complete unilateral ureteral obstruction (UUO).

METHODS

The rats were divided into 5 groups: sham (n=6), partial unilateral ureteral obstruction (PUUO, n=6), PUUO with tadalafil treatment (PUUO+T; Cialis, 10 mg/72 h, intragastric; Lilly, Indianapolis, Indiana, USA), complete unilateral ureteral obstruction (CUUO, n=6), and CUUO with tadalafil treatment (CUUO+T).

RESULTS

Fifteen days after the UUO, the ureter presented changes in the layers of urothelium and significant infiltration of inflammatory cells in the PUUO and CUUO groups. Compared with the sham, PUUO and CUUO groups had severe increased inflammatory cell infiltration. The urothelial epithelium exhibited cell degeneration and loss because of the swollen, atrophic, and denuded epithelial cells in the PUUO and CUUO groups. In the PUUO+T and CUUO+T groups, the urothelium revealed less epithelial cell degeneration and loss.The expressions of α-smooth muscle actin (α-SMA) and transforming growth factor-β (TGF-β) exhibited up-regulation in the PUUO and CUUO groups. The expression of TGF-β decreased positively correlated with that of α-SMA in the tadalafil therapy groups, PUUO+T and CUUO+T.

CONCLUSION

The phosphodiesterase type 5 inhibitor's tadalafil reduced expressions of α-SMA and TGF-β in the obstructed ureters, measured by biochemical examinations. In addition, tadalafil decreased urothelium degeneration due to the decreased epithelial cell loss and inflammatory cell infiltration. Our results show that tadalafil prevents or slows down the onset of ureter inflammation and urothelial degeneration in rats with UUO.

Establishment and observation of a new and ideal reversible model of PUUO

Objective: We established a novel procedure to generate a reversible partial unilateral ureteral obstruction (PUUO) in rabbit. The method allows us to reliably measure the degree of ureteral obstruction in live animals, and thus could be a useful tool for studying kidney diseases.

Methods: Thirty rabbits of clean grade were divided randomly into sham control group and obstruction (PUUO) group. Each rabbit in this study received the same blocking surgery, in which the upper ureter was curvilinearly incised and inserted with two F6 ureteral catheters that were connected with a tee joint valve. Ureteral obstruction was created and released through the valve adjustment. Serum creatinine and ultrasonographic measurements were performed preoperatively, on the fifth and tenth days after obstruction surgery, and on the 10th and 20th day, respectively, after the relief of the obstruction. Pathological measurements were taken in two randomly chosen rabbits of each group on the 10th day after surgery and on the 20th day after obstruction relief.

Results: Data showed that the serum creatinine went transiently up and down in the early days and then remained a little bit higher in the following days after obstruction surgery. The morphology in obstructed kidney changed significantly on the 10th day postoperatively, compared to the sham control group. The obvious differences were also observed in pathology tests. After the relief of obstruction, the volume of renal pelvis (V), renal cortical thickness (RCT), and pathological impairment were partially reversed.

Conclusions: Those findings indicate our procedure generate a successful and reversible PUUO animal model. It is a reliable and simple procedure for generating an animal model for reversible PUUO. The feasibility and significance of the new method was confirmed through ultrasonographic and pathological results.

Study of the ureter structure in anencephalic fetuses

PURPOSE

The objective of this paper is to analyze the structure of the ureter in normal and anencephalic human fetuses.

MATERIALS AND METHODS

We studied 16 ureters from 8 human fetuses without congenital anomalies aged 16 to 27 weeks post-conception (WPC) and 14 ureters from 7 anencephalic fetuses aged 19 to 33 WPC. The ureters were dissected and embedded in paraffin, from which 5 μm thick sections were obtained and stained with Masson trichrome, to quantify smooth muscle cells (SMC) and to determine the ureteral lumen area, thickness and ureteral diameter. The samples were also stained with Weigert Resorcin Fucsin (to study elastic fibers) and Picro-Sirius Red with polarization and immunohistochemistry analysis of the collagen type III fibers to study collagen. Stereological analysis of collagen, elastic system fibers and SMC were performed on the sections. Data were expressed as volumetric density (Vv-%). The images were captured with an Olympus BX51 microscope and Olympus DP70 camera. The stereological analysis was done using the Image Pro and Image J programs. For biochemical analysis, samples were fixed in acetone, and collagen concentrations were expressed as micrograms of hydroxyproline per mg of dry tissue. Means were statistically compared using the unpaired t-test (p < 0.05).

RESULTS

The ureteral epithelium was well preserved in the anencephalic and control groups. We did not observe differences in the transitional epithelium in the anencephalic and control groups. There was no difference in elastic fibers and total collagen distribution in normal and anencephalic fetuses. SMC concentration did not differ significantly (p = 0.1215) in the anencephalic and control group. The ureteral lumen area (p = 0.0047), diameter (p = 0.0024) and thickness (p = 0.0144) were significantly smaller in anencephalic fetuses.

CONCLUSIONS

Fetuses with anencephaly showed smaller diameter, area and thickness. These differences could indicate that anencephalic fetal ureters tend to have significant structural alterations, probably due to cerebral lesions with consequent brain control damage of ureter nerves.

Nephron-sparing tumorectomy for a large benign renal mass: a case of massive bilateral renal angiomyolipomas associated with tuberous sclerosis

A case of massive bilateral angiomyolipomas (AML) associated with tuberous sclerosis in a 33-year-old woman is reported. She was hospitalized because she had been experiencing abdominal fullness and epigastralgia. Several imaging studies revealed massive bilateral renal tumors and she was diagnosed as having renal AML associated with tuberous sclerosis. Left nephrectomy was carried out after renal arterial embolization for intratumor hemorrhage. Two years after left nephrectomy, nephron-sparing surgery (tumorectomy) for right AML was done because of an increase in the size of the right renal AML and she hoped for a future pregnancy. The left kidney with AML weighed 5700 g and the right AML weighed 1700 g. Postoperative serous creatinine did not differ from that before operation and an increase in the size of the residual tumor was not observed 8 months after operation. We consider that tumorectomy is an effective therapy in patients with a very large tumor involving a solitary kidney.

Ureteral ischemia model: an explanation of ureteral dysfunction after chronic obstruction

BACKGROUND AND PURPOSE

Many models of smooth muscle ischemia have been developed to explain organ insufficiency or failure. Ureteral decompensation may also be described in these terms. We anticipate that ureteral ischemia will result from overdistention brought about by obstruction. A preliminary model to create an ischemic ureter is described herein.

MATERIALS AND METHODS

Six white New Zealand female rabbits were used for this study. All had their left ureters surgically ligated at the level of the urinary bladder. The right ureters served as controls. In the acute-phase group, the ureters were all reexplored 2 weeks postobstruction. Exploration of the other rabbits was delayed for 3 more weeks. A laser Doppler needle (Transonics Inc.) was used to measure tissue perfusion in the rental artery, renal vein, renal parenchyma, renal pelvis, ureteropelvic junction, upper ureter, mid ureter, lower ureter, and lateral wall of the bladder. Baseline and postobstructive measurements of tissue perfusion were collected and compared.

RESULTS

In both the acute and the chronic obstruction groups, there was a demonstrable drop-off in perfusion of the ureteral sidewall. A more notable loss of perfusion was seen in the distal ureter.

CONCLUSION

The increased wall tension in the obstructed ureter results in a significant decrease in smooth muscle perfusion. This ischemia may result in the same functional and histologic changes that occur in other smooth muscle organs. Ultimately, the poor outcomes of some restorative/reconstructive procedures on the ureter may be explained in terms of smooth muscle ischemia.

Ureteral ischemia model: an explanation of ureteral dysfunction after chronic obstruction

BACKGROUND AND PURPOSE

Many models of smooth muscle ischemia have been developed to explain organ insufficiency or failure. Ureteral decompensation may also be described in these terms. We anticipate that ureteral ischemia will result from overdistention brought about by obstruction. A preliminary model of an ischemic ureter is described herein.

MATERIALS AND METHODS

Six female New Zealand rabbits were used for this study. All had their left ureters surgically ligated at the level of the urinary bladder. The right ureters served as controls. In the acute-phase group, the ureters were reexplored 2 weeks after creation of obstruction. The other three rabbits were explored 3 weeks later. A laser Doppler needle was used to measure tissue perfusion with bilateral measurements of the renal artery and vein; renal parenchyma; renal pelvis; ureteropelvic junction; upper, mid, and lower ureter; and the lateral wall of the bladder. Baseline and postobstructive measurements of tissue perfusion were collected.

RESULTS

In both the acute and chronic obstruction groups, there was a demonstrable drop-off in perfusion of the ureteral wall.

CONCLUSION

The increased wall tension in the obstructed ureter results in a significant decrease in smooth muscle perfusion. This ischemia may result in the same functional and histologic changes that occur in other smooth muscle organs deprived of normal blood flow. Ultimately, poor outcomes of some restorative/reconstructive operations on the ureter may be explainable in terms of smooth muscle ischemia.

Angiotensin induces the urinary peristaltic machinery during the perinatal period

The embryonic development of mammalian kidneys is completed during the perinatal period with a dramatic increase in urine production, as the burden of eliminating nitrogenous metabolic waste shifts from the placenta to the kidney. This urine is normally removed by peristaltic contraction of the renal pelvis, a smooth muscle structure unique to placental mammals. Mutant mice completely lacking angiotensin type 1 receptor genes do not develop a renal pelvis, resulting in the buildup of urine and progressive kidney damage. In mutants the ureteral smooth muscle layer is hypoplastic and lacks peristaltic movements. We show that angiotensin can induce the ureteral smooth muscles in organ cultures of wild-type, but not mutant, ureteral tissues and that, in wild-type mice, expression of both renal angiotensin and the receptor are transiently upregulated at the renal outlet at birth. These results reveal a new role for angiotensin in the unique cellular adaptations of the mammalian kidney to the physiological stresses of postnatal life.

Tissue damage and regeneration of ureteric smooth muscle in rats with obstructive uropathy

OBJECTIVE

To investigate regeneration in obstructed ureters and to elucidate the role of hyperplasia in the thickening of the smooth muscle layer in the late stages of complete ureteric obstruction.

MATERIALS AND METHODS

The expression of Ki-67 antigen, c-Fos, c-Jun and c-Myc in the smooth muscle layer of obstructed ureters was determined using immunohistochemistry in 40 Sprague-Dawley rats. After unilateral ligation of the ureter, five rats each were killed for examination at 1, 3, 7, 10, 14, 21, 28 and 42 days after ligation: dive rats that underwent a sham operation were also examined as controls.

RESULTS

The severity of hydroureter and thickening of the smooth muscle layer progressed consistently in the ligated ureters, but no mitosis was detected in myocytes within 14 days of ligation. Fibrosis in the smooth muscle layer appeared 21 days after ligation and progressed. There was no expression of Ki-67 antigen and oncoproteins until 14 days after ligation. The expression of Ki-67 and c-Myc increased gradually to a peak after 28 days, then declined. However, the expression of c-Fos and c-Jun was low and transient.

CONCLUSION

Cell regeneration is impaired in the damaged muscle layer of obstructed ureters. Only hypertrophy and not hyperplasia of the smooth muscle layer developed during the course of complete ureteric obstruction in this rat model of obstructive uropathy.

Urinary tract obstruction in children

PURPOSE

Perinatal identification of children with congenital urinary obstruction has challenged our understanding of the pathophysiology and clinical treatment of many children with hydronephrosis.

MATERIALS AND METHODS

A critical review of recent reports relating to congenital urinary obstruction in children was performed in an attempt to integrate clinical and experimental information.

RESULTS

Several themes emerged from the many reports relating to congenital urinary obstruction that have not been previously emphasized. Congenital obstruction begins and evolves in a developing fetal kidney, indicating the importance of the effect of obstruction on renal growth and development, which is distinct from the postnatal renal response to obstruction. Variation in the ability of the developing kidney to compensate for obstruction may be an important factor in explaining variability in clinical and experimental reports. Clinical data show an unpredictable outcome of congenital hydronephrosis. Nonoperative management of hydronephrosis is supported by empirical evidence yet raises many questions regarding the certainty of outcome and the risks involved. It imposes on the practitioner a significant clinical obligation. The ability to differentiate between clinically significant and insignificant obstruction is the current challenge to be fulfilled by integrated clinical and experimental investigation.

CONCLUSIONS

The unique features of congenital urinary obstruction separate it from better understood acquired postnatal obstruction. Understanding the effects of obstruction on the developing kidney prenatally and postnatally is critical. A definition is proposed for congenital urinary obstruction in children, that is a condition of impaired urinary drainage which, if uncorrected, will limit the ultimate functional potential of a developing kidney.

Urinary tract obstruction in children

PURPOSE

Perinatal identification of children with congenital urinary obstruction has challenged our understanding of the pathophysiology and clinical treatment of many children with hydronephrosis.

MATERIALS AND METHODS

A critical review of recent reports relating to congenital urinary obstruction in children was performed in an attempt to integrate clinical and experimental information.

RESULTS

Several themes emerged from the many reports relating to congenital urinary obstruction that have not been previously emphasized. Congenital obstruction begins and evolves in a developing fetal kidney, indicating the importance of the effect of obstruction on renal growth and development, which is distinct from the postnatal renal response to obstruction. Variation in the ability of the developing kidney to compensate for obstruction may be an important factor in explaining variability in clinical and experimental reports. Clinical data show an unpredictable outcome of congenital hydronephrosis. Nonoperative management of hydronephrosis is supported by empirical evidence yet raises many questions regarding the certainty of outcome and the risks involved. It imposes on the practitioner a significant clinical obligation. The ability to differentiate between clinically significant and insignificant obstruction is the current challenge to be fulfilled by integrated clinical and experimental investigation.

CONCLUSIONS

The unique features of congenital urinary obstruction separate it from better understood acquired postnatal obstruction. Understanding the effects of obstruction on the developing kidney prenatally and postnatally is critical. A definition is proposed for congenital urinary obstruction in children, that is a condition of impaired urinary drainage which, if uncorrected, will limit the ultimate functional potential of a developing kidney.

The temporal relationship between the severity of hydroureter and the dynamic changes of obstructed ureters in a rat model

OBJECTIVE

To investigate dynamic changes in the obstructed rat ureter and to evaluate the usefulness of the rat model in the study of obstructive uropathy.

MATERIALS AND METHODS

Unilateral ligation of the ureter was performed in 26 rats. After ureteric ligation, four to seven rats were killed and examined after 1, 3, 7, 10, and 14 days. The severity of hydroureter and hydronephrosis was assessed by pyelography and the hydroureter-hydronephrosis index. The middle portion of the ureter was prepared for light and electron microscopic observation. Five rats which received a sham operation were also examined as controls.

RESULTS

The severity of hydroureter and hydronephrosis in the ligated ureters progressively increased during the period of obstruction (P < 0.005) and reached a maximum 10-14 days after ligation. Hypertrophy of the smooth muscle layer developed on the third day after ligation and proliferation of submucosal connective tissue occurred on the 10th day after ligation. The changes in smooth muscle and connective tissue layers also progressed consistently during ureteric obstruction (P < 0.001 and < 0.005, respectively). The number and size of granular endoplasmic reticulum and Golgi apparatus in the smooth muscle cells increased after ureteric ligation and then caveolae exocytosis developed. Deposition of collagen fibres between muscle cells became apparent later.

CONCLUSION

The rat model of hydrouropathy demonstrated a clear temporal relationship between the severity of hydroureter and the dynamic changes in the obstructed ureter and could be used as a conventional method for the study of obstructive ureter.