Renal structural and functional changes after unilateral ureteral obstruction in rabbits

Reduction in miRNA-125b-5p levels is associated with obstructive renal injury

Obstructive renal injury is a common disease that leads to progressive glomerulosclerosis, tubulointerstitial fibrosis and loss of renal function. MicroRNAs (miRNAs/miRs) are small non-coding molecules that may be involved in the progression of many renal diseases. The aim of the present study was to investigate the roles of miRNAs, including miR-125b, miR-326 and miR-324p, in obstructive renal injury. Blood samples were collected from 91 patients with ureteral obstruction and 76 controls to examine renal function. In addition, the levels of miR-125b, miR-326 and miR-324p in patients with ureteral obstruction and controls were determined by the reverse transcription-quantitative polymerase chain reaction. Furthermore, the relationship between miRNA levels and renal function was evaluated by the Mann-Whitney U test. Upregulated levels of serum creatinine (SCr) in patients with ureteral obstruction were observed, identifying the injury of renal function. Although the expression levels of miR-324-5p [1.003 (0.391-2.279) vs. 0.934 (0.579-1.539), P=0.300] and miR-326 [0.840 (0.180-2.020) vs. 0.949 (0.507-1.702), P=0.050] presented no significant difference, the levels of miR-125b-5p [0.755 (0.210-2.110) vs. 0.960 (0.390-1.770), P=0.002] in patients with ureteral obstruction were significantly lower than those in controls. These results indicated that there is a stronger correlation of miR-125b-5p with the occurrence of ureteral obstruction, especially for the female (P=0.0171) and elderly (P=0.0142). Furthermore, the levels of miR-125b-5p (r=-0.175, P=0.038) were closely associated with the serum levels of SCr, suggesting a key role of miR-125b-5p in renal dysfunction. Thus, these findings suggested that miR-125b-5p in patients with ureteral obstruction correlated with renal function, and may be a potential biomarker for obstructive renal injury.

Effects of preceding sialadenitis on the development of autoimmunity against salivary gland

OBJECTIVE

The mechanism underlying the onset and development of autoimmune diseases such as Sjogren's syndrome is not well understood. Here, we examined the effects of preceding inflammation of the salivary gland at the onset of autoimmunity against the salivary gland.

MATERIALS AND METHODS

One side of the submandibular gland duct was ligated in mice and the effect on the contralateral gland was investigated. After histological evaluation with hematoxylin and eosin staining, the presence of autoantibodies and immune compounds was examined.

RESULTS

In all five strains of mice that were used, the salivary gland of the ligated side showed severe inflammation and atrophic change. In two mouse strains (SJL/J and PL/J), mild sialadenitis was observed on the non-ligated side 8 weeks after ligation. Autoantibodies reacting to the salivary gland were detected in three mouse strains (C3H/He, SJL/J, and PL/J). Immune complex was also detected in the duct basement membrane.

CONCLUSION

The results indicate that the autoimmune mechanism is activated by the transient inflammation in the salivary gland under a specific genetic background.

How can we predict ureteral obstruction after gynecological surgery? The changes in Doppler resistive index and plasma creatinine and magnesium concentrations after surgical, unilateral ureteral obstruction in a rabbit model

The aim of this study is to evaluate the changes in Doppler resistive index (RI) and plasma creatinine and magnesium concentrations after unilateral ureteral obstruction in a rabbit model. Fourteen adult female rabbits were used in this study. In seven rabbits, the left ureter was ligated with silk suture, and the control group was sham operated. Before surgery and on the second and seventh days after surgery, blood samples were obtained to measure plasma creatinine and magnesium concentrations. Doppler RIs of both kidneys were also measured before surgery and on the second and seventh days after the surgical procedure. With regard to magnesium levels, there was a significant within-subjects sessions difference [F(2, 20) = 15.21, P= 0.001] indicating a decrease through sessions. Magnesium concentrations decreased significantly at the postoperative second and seventh days compared to preoperative baseline levels (P= 0.003 and P= 0.001, respectively). Multifactorial analysis of variance was applied for each session separately with laterality, and groups as factors. The Doppler RI and the creatinine level did not show any significant differences or interactions for all sessions (P > 0.05). The decreasing plasma magnesium concentration after surgery may indicate ureteral injury; however, Doppler studies and creatinine levels may not be useful as well.

Evidence that inhibition of tubular cell apoptosis protects against renal damage and development of fibrosis following ureteric obstruction

Ureteric obstruction is frequently encountered in primary care urology and can lead to damage to the ipsilateral kidney. Relief of all types of obstruction generally leads to the normalization of any deterioration in renal function noted at diagnosis. However, some evidence from animal models suggests that obstruction can cause progressive deleterious effects on renal function and blood pressure control, especially in the presence of preexisting pathologies such as essential hypertension. The last 10 years have seen a proliferation of studies in rodents wherein complete unilateral ureteric obstruction has been used as a model of renal fibrosis. However, the relevance of the findings to human obstructive uropathy has, in many cases, not been the primary aim. In this review, we outline the major events linking damage to the renal parenchyma and cell death to the evolution of fibrosis following obstruction. Special focus is given to the role of apoptosis as a major cause of cell death during and post-complete ureteric obstruction. Several interventions that reduce tubular apoptosis are discussed in terms of their ability to prevent subsequent progression to end-organ damage and fibrosis.

Voie excrétrice supérieure : physiologie, physiopathologie des obstructions et explorations fonctionnelles

The urine is transported from the renal papilla to the bladder through the upper urinary tract which allows this transport to be safe and comfortable, i.e., without any risk or pain for the kidney. This active transport depends on the smooth muscle contractile properties. The upper urinary tract is totally autonomous; this feature allows the preservation of its function after renal transplantation. However, despite its accessory role, the autonomous nervous system can modulate its activity. Upper urinary tract obstruction involves adaptative mechanisms which are different depending on the type (acute, chronic, acquired or congenital) of obstruction. Functional evaluations of the upper urinary tract are aimed at identify the urine transport conditions and the relationship between obstruction and clinical conditions such as hydronephrosis, pain or impaired renal function.

Renal pelvic pressure responds with augmented increases to increments in intraabdominal pressure

BACKGROUND/PURPOSE

Flow of a fluid through a collapsible tube is under the influence of various factors including the external compressing pressure. Because the intraabdominal pressure may compress the ureter, an experimental study has been planned to determine and compare the normal intraabdominal and renal pelvic pressures and the alterations in renal pelvic pressure in response to the increments in intraabdominal pressure in the rabbits.

METHODS

Eight adult rabbits were used for the experiment. Under general anesthesia, an urethral catheter, a nasogastric tube, and an intraperitoneal catheter were placed to measure intravesical (IVP), intragastric (IGP), and intraabdominal pressures (IAP), respectively. Intracranial pressure monitorization catheter was placed into the renal pelvis to monitor intrapelvic pressure (IPP). Basal pressure measurements have been recorded. The pressures have been recorded in every 5 minutes, and IAP has been increased gradually about 3 to 4 cm of water pressure in every step for 30-minute periods.

RESULTS

Increases in the intrapelvic pressure values have been significantly higher than the increases in the IAP (P < .001). A significant correlation has been found between IPP and IAP (P = .000, r = 0.866). By using linear regression analysis the relationship has been found to be IPP = 7.303 + 1.985 (IAP). Intragastric pressure values have been higher compared with IAP values (P < .001), whereas intravesical pressures have not differed from IAP (P > .05).

CONCLUSIONS

Elevations in IAP results in augmented increases in the IPP. Poiseuille and Laplace Laws suggest this augmented increase to resemble proximal ureteric obstruction. Increases in IAP may simulate proximal ureteric obstruction and may take part in the pathogenesis of hydronephrosis. J Pediatr Surg 36:901-904.

Free insulin-like growth factor-1 and unilateral complete ureteral obstruction in the rat

OBJECTIVES

To determine the effect of unilateral ureteral obstruction on renal free insulin-like growth factor-1 (IGF-1) content in the kidneys and the possible role of free IGF-1 in compensatory growth in the nonobstructed kidney in an experimental model.

METHODS

The content of free IGF-1 and total protein in the obstructed and nonobstructed kidneys were measured 7 days after unilateral ureteral obstruction. The weights of the kidneys were also determined. The results were compared with those of the sham-operated animals.

RESULTS

The mean renal free IGF-1 level of the obstructed kidneys was significantly lower than the mean renal free IGF-1 level of the sham-operated kidneys (P = 0.03), and the mean renal free IGF-1 level of the nonobstructed kidneys was significantly higher than the mean renal free IGF-1 level of the sham-operated kidneys (P <0.0001). The serum free IGF-1 levels in the two groups were not different. The mean weight of the obstructed and nonobstructed kidneys was significantly higher than those of the sham-operated kidneys (1.49 +/- 0.09 and 1.03 +/- 0.03 versus 0.88 +/- 0.02 g, P <0.0001 and P = 0.006, respectively). The obstructed kidneys had significantly lower mean protein content than the nonobstructed kidneys and had significantly higher mean protein content than the sham-operated kidneys (P <0.0001 and P = 0.0004, respectively).

CONCLUSIONS

Our results reveal that compensatory renal growth is driven by a rise in the free IGF-1 concentration after unilateral ureteral obstruction.

Resistance and pulsatility indices in acute renal obstruction

PURPOSE

The aim of this study was to evaluate the reliability of Doppler waveform alterations in diagnosing acute unilateral renal obstruction.

METHODS

From December 1993 to January 1996, 54 patients with unilateral renal obstruction were prospectively examined by conventional and duplex Doppler sonography. Seventy-eight patients with nonrenal abdominal problems comprised the control group. Doppler signals were obtained from interlobar arteries and arcuate arteries at the corticomedullary junction. From the waveform analysis, we calculated resistance (RI) and pulsatility (PI) indices. We also used the differences in RI and PI between the 2 kidneys in the same examinee (delta RI and delta PI) for further statistical analysis.

RESULTS

The mean RI and PI (+/- standard deviation) in the patients without renal impairment were 0.64 +/- 0.04 and 1.14 +/- 0.14, respectively. The mean delta RI and delta PI were 0.02 +/- 0.01 and 0.07 +/- 0.05, respectively. Both the RI and PI were significantly correlated with age (r = 0.74 and 0.69, respectively; p < 0.01). Acute renal obstruction significantly (p < 0.01) elevated the mean RI (0.72 +/- 0.04), delta RI (0.09 +/- 0.04), PI (1.42 +/- 0.17), and delta PI (0.33 +/- 0.18). Significant decreases in RI and delta RI were noted after relief of the obstruction. The best accuracy in diagnosing acute unilateral renal obstruction was achieved with the combination of delta RI > or = 0.06 and/or delta PI > or = 0.20, which had a sensitivity of 94% and specificity of 99%.

CONCLUSIONS

Renal Doppler indices are reliable parameters in the sonographic diagnosis of acute unilateral obstructive uropathy.

Interstitial fibrosis in obstructive nephropathy

Interstitial fibrosis and tubular basement membrane (TBM) thickening are evident within 16 days of unilateral ureteral obstruction (UUO) in the rabbit, and resemble the changes previously reported in hydronephrotic human kidneys. The cortical interstitial volume fraction in this rabbit model at 16 days is 43.3 +/- 6.1% (+/- 1 SD) in UUO kidneys, 4.9 +/- 3.1% in contralateral kidneys (CLK), and 2.8 +/- 0.8% in kidneys from sham-operated animals (ANOVA, P < 0.0001). Immunohistochemically, UUO is associated with increased interstitial collagens I and III, fibronectin, heparan sulfate proteoglycan and tubulointerstitial nephritis antigen. Aberrant collagen expression is also evident as interstitial collagen IV becomes prominent. Focal, peritubular accumulation of collagens I and II also appear to encircle the TBM. These changes are accompanied by an early, transient increase in renal cortical mRNA encoding the alpha 1 monomers of collagens I, III and IV, implicating increased matrix synthesis in the pathogenesis of obstructive nephropathy. In situ hybridization localized increased expression of alpha 1 (I) and alpha 1 (IV) mRNA to cells in the interstitial space, with clusters of alpha 1(I) positive cells associated with dilated tubules, muscular arteries and the periglomerular interstitium.

Pyeloureteral dynamics. Pelvic pressure and kidney function in partial long-term ureteric obstruction

In 10 pigs with reno-scintigraphically proven normal upper urinary tracts, a standardized partial obstruction of the left ureter was created at the lower kidney pole level. Three weeks later kidney function was scintigraphically reassessed and the pressure flow relationship in the flow range 0-20 ml/min outlined. The partially obstructed pelvic baseline pressure varied from 9.0 to 32.0 cmH2O. During perfusion small increases in pelvic pressure were seen at all flow rates in the individual cases and there was a linear relationship between pressure and flow. Compared to previous results of a similar but acute obstruction the results were identical in pressure ranges and pressure flow profile. This demonstrates, that a longitudinal stability in transport mechanism qualities is present also during the course of obstruction. The pelvic pressure at low flow rates was significantly correlated to kidney function depression, whereas perfusion pressures at high flow rates did not show any correlation, except at 20 ml/min. This clearly indicates, that the pelvic pressure at normal urine flow rate is an important factor in the pathogenesis of obstructive nephropathy.

Dimensional changes of proximal tubules and cortical capillaries in chronic obstructive renal disease. A light microscopic morphometric analysis

The study was carried out to determine the proximal tubular length, surface area and length of peritubular capillaries and the nephron numbers in kidneys with chronic nephropathy and varying increase in the cortical interstitial volume. Kidneys of pigs with varying chronic obstructive nephropathy were used for the experiments. Two subgroups of ureter-obstructed kidneys were defined arbitrarily according to the volume of cortical interstitium. One subgroup (I) comprised kidneys with a volume fraction of cortical interstitium less than 30% (mean 17.2%; mean of controls 9.7%). The other subgroup (II) consisted of kidneys with severe chronic nephropathy and with a volume fraction of interstitium more than 30% (mean 44.5%). Proximal tubular length and length and surface area of peritubular capillaries were assessed by conventional morphometric techniques on 1 micron thick sections of plastic embedded material. Nephron numbers were determined by a stereological method for counting glomeruli. The results demonstrated that proximal tubular length and capillary dimensions were significantly reduced in subgroup II, whereas no significant changes were observed in subgroup I. The mean number of glomeruli was not significantly different from control values in any of the subgroups. The results are in line with observations from previous quantitative analyses of proximal tubular cross-sections indicating that proximal tubular dimensions become reduced mainly at advanced stages of chronic nephropathy. The results also indicate that shortening of individual tubules rather than loss of entire nephrons is responsible for the observed reduction in total length of proximal tubules. Finally, the present observations suggest that reduced dimensions of the cortical capillary network may have pathogenetic significance for ongoing proximal tubular atrophy in chronic renal disease.

Quantitative ultrastructure of human proximal tubules and cortical interstitium in chronic renal disease (hydronephrosis)

Surgically removed perfusion-fixed human kidneys with chronic renal disease (hydronephrosis) were studied by electron microscopy in order to determine whether there is a quantitative relationship between ultrastructural changes in proximal tubules in atrophy and changes in the surrounding cortical interstitium. Morphometric techniques were applied to montages of electron micrographs each covering several tubular profiles in the cortical labyrinth and to montages representing cross-sections of individual proximal convoluted tubules at a higher magnification. In order to enable a quantification of the spatial relations between individual tubular cross-sections and adjacent peritubular capillaries a tubulo-capillary index (TCI) was defined. This index was based on the mean distances between individual tubular cross-sections and adjacent peritubular capillaries and on the fraction of tubular circumference facing capillaries. Normal tissue from similarly fixed human nephrectomy specimens, which had been removed mainly because of neoplastic disorders, served as control material. In the hydronephrotic kidneys the relative volume of cortical interstitium (excluding capillaries) covered a range from 19.2-70.3%. Inverse correlations were demonstrated between the relative volume of cortical interstitium and various structural variables of proximal convoluted tubules, including tubular wall volume, the volume of mitochondria and the surface area of basolateral membranes. The TCI showed positive correlations with these tubular variables. No significant correlation was found between the volume fractions of cortical interstitium and capillaries. Finally, it was found that an increase in the volume fraction of the cortical interstitium from 16.2% in controls to 24.7% in cortical areas of hydronephrotic kidneys was associated with a 40-50% reduction in the volume of mitochondria and in the surface area of basolateral membranes in proximal tubules. The results are consistent with a pathogenic interrelationship between tubular and interstitial changes. An important factor in this relationship might be disturbed topographic associations between tubules and blood capillaries caused by the increase in cortical interstitium. The results further show that even slight increases in the cortical interstitial volume are associated with significant quantitative changes in tubular fine structure suggesting impaired tubular functions.

Renal function in idiopathic hydronephrosis

In 11 patients who underwent Anderson-Hynes pyeloplasty for unilateral hydronephrosis, renal function was examined with split-clearance technique immediately after the operation and 2-5 years postoperatively. The studies shortly after pyeloplasty showed decreased glomerular filtration rate (GFR) and renal plasma flow (RPF) in most of the hydronephrotic kidneys. GFR improved slightly during the follow-up period, but RPF did not increase. The tubular dysfunction, expressed as moderately increased fractional excretion of electrolytes, showed significant improvement only as regards magnesium. The study indicates that reconstructive surgery is not warranted if the aim is to improve renal function in an asymptomatic patient with normal total GFR. On the other hand, patients with pain caused by the renal obstruction should always be subjected to surgery.