The elastic component of normal and dilated ureters in children: chemical and histochemical characterisation

Age- and region-related changes in the biomechanical properties and composition of the human ureter

The ureter has been largely overlooked heretofore in the study of the biomechanics of soft biological tissues, although there has been significant motivation to use its biomechanical properties as inputs to mathematical models of ureteral function. Herein, we used histological analysis for quantification of collagen contents and thickness/area of ureteral layers, with concomitant geometrical analysis of zero-stress and no-load states, and inflation/extension testing to biomechanically characterize with the Fung-type model the ureters from cadavers. The effects of age and gender on the regional distribution of those properties were examined. Tissue properties did not differ (p>0.05) between the left and right ureter. Regional heterogeneity was established that was profoundly age-related but seldom gender-related, based on the following evidence: 1) In younger subjects, the axial stress-circumferential strain curves of upper ureter were shifted to smaller stresses and model parameter a₂ representing axial stiffness was smallest (p<0.05), i.e. upper ureter was the least stiff region axially; 2) upper ureter underwent axial stiffening with advanced age, evidenced by the increasing (p<0.05) parameter a₂, and the stress-strain curves were uniformly exhibited along the ureter, evidenced by the non-varying (p>0.05) parameters C,a₁,a₂,anda₄; 3) aging raised (p<0.05) the collagen content of upper ureter to favor a near-uniform regional distribution; 4) wall thickness increased with age, unlike the opening angle and residual strains, reflecting the thickening of outer (muscular) vs. inner (mucosal) layers in aged subjects, with significant differences (p<0.05) in some regions; and 5) gender affected little (p>0.05) the opening angle and morphometry of no-load and zero-stress states.

A quantitative histologic analysis of collagen subtypes: the primary obstructed and refluxing megaureter of childhood

OBJECTIVES

To analyze and identify collagen subtypes in the primary obstructed and refluxing megaureter of childhood.

METHODS

Anticollagen monoclonal antibodies to collagen types I, III, and IV were used in control ureters (n = 4), obstructed (n = 7), and refluxing (n = 13) megaureters. Additionally, all were stained with Masson's trichrome to further define the extracellular matrix. After staining and serial sectioning, representative ureteral sections, focusing on the muscularis and lamina propria regions, were digitized and analyzed with a color image analysis system.

RESULTS

Immunohistochemical studies demonstrated increases in collagen types I and III for both obstructed and refluxing megaureters compared with controls (P <0.05). Collagen type IV was not detected in statistically significant amounts in any ureter. In control ureters most was type I (83% +/- 9%) collagen. Obstructed megaureters produced similar results with virtually all collagen being type I (84% +/- 26%) with very little type III collagen present, 5.3% +/- 3%. Refluxing megaureters contained only 55% +/- 15% type I collagen. However, there was an increase in type III collagen (16% +/- 4%) versus (4.5% +/- 2%) in controls (P <0.05).

CONCLUSIONS

These data suggest that the greater contribution of type III collagen may play a role in the pathophysiology of refluxing megaureters. Because type III collagen is a less distensible fiber, it may cause an intrinsically stiffer ureter and play a role in the lower surgical success in the reimplantation of refluxing megaureters.

A quantitative histological evaluation of the dilated ureter of childhood. II: Ectopia, posterior urethral valves and the prune belly syndrome

A quantitative histological study was performed on specimens of 33 ureters obtained from 14 male and 19 female patients 5 days to 14 years old (mean age 1.2 years). A high resolution color image video analysis system was used to quantify and compare collagen and smooth muscle components of the muscularis layers to normal control ureters from patients of similar ages. In comparing ureters with ectopia (7), ureters with ectopic ureteroceles (20) and control ureters (4) there was not a statistically different collagen-to-smooth muscle ratio among the groups. In the patients with posterior urethral valves the amount of collagen and smooth muscle was not statistically different from controls (p > 0.01), although the collagen-to-smooth muscle ratio was increased. The 4 patients with the prune belly syndrome had a collagen-to-smooth muscle ratio that was markedly elevated (1.21 versus 0.39) compared with controls. When this group was analyzed as 2 separate groups (obstructed versus refluxing ureters) the difference was more apparent (p < 0.004). Ureters with ectopia or ectopic ureteroceles and ureters associated with posterior urethral valves had similar quantitative amounts of smooth muscle (60%, 56% and 52%, respectively). In patients with the prune belly syndrome obstructed ureters had 65% muscle and refluxing ureters had 38% muscle on evaluation. The percentage of collagen was 33% in ureters with ectopia, 37% in those with ureteroceles and 48% in those associated with posterior urethral valves compared with 23% in controls. In the group with the prune belly syndrome there was 30% collagen in obstructed ureters and 62% collagen in refluxing ureters. Our findings demonstrate that while these dilated ureters had different etiologies the overall quantitative composition of collagen-to-smooth muscle ratios was similar except in refluxing ureters associated with the prune belly syndrome. Our study provides further insight into the pathological nature of such ureters and considerations for surgical repair.

A quantitative histological analysis of the dilated ureter of childhood

A quantitative histological study of the dilated ureter of childhood was performed on 26 ureters. The specimens were from 15 male and 11 female patients 10 days to 12 years old (mean age 2.0 years). A color image analysis system was used to examine and compare collagen and smooth muscle components of the muscularis layers to normal control ureters of similar age. In comparing primary obstructed (12) to primary refluxing (14) megaureters and control ureters (6), there was a statistically different collagen-to-smooth muscle ratio (p < 0.001) between the primary obstructed and primary refluxing megaureter groups. For patients with primary refluxing megaureter there was a 2-fold increase in the tissue matrix ratio of collagen-to-smooth muscle when compared to patients with primary obstructed megaureter. In the primary obstructed megaureters the amount of collagen and smooth muscle was not statistically different from controls (p > 0.01). The increased tissue matrix ratio of 2.0 +/- 0.35 (collagen-to-smooth muscle) in the refluxing megaureter group compared to 0.78 +/- 0.22 in the obstructed megaureter group and 0.52 +/- 0.12 in controls was found to be due not only to a marked increase in collagen but also a significant decrease in the smooth muscle component of the tissue. Primary obstructed and normal control ureters had similar quantitative amounts of smooth muscle with 60 +/- 5% and 61 +/- 6%, respectively, while refluxing megaureters had only 40 +/- 5% smooth muscle. The percentage collagen was 36 +/- 5 in the obstructed megaureter group and 30 +/- 5 in controls, with refluxing megaureters having 58 +/- 5% collagen on analysis. Our findings emphasize the significant differences in the structural components (collagen and smooth muscle) of the dilated ureter of childhood, and provide us with further insight into the pathological nature of these dilated ureters and their surgical repair.

Development of elastic fibres in the upper urinary tract

The development of elastic fibres in the upper urinary tract was studied in 31 fetuses ranging in ovulatory age from 10 to 24 weeks using special staining techniques for elastic fibres. The number, orientation and distribution of elastic fibres are described and correlated with age, ureteric level, and fetal weight. Significantly, before 10 weeks, elastic fibres were few in number, poorly developed, and randomly arranged. After 12 weeks, these fibres became more numerous at each level of the urinary tract, and were seen to develop specific orientation. The findings are described and potential clinical implications are discussed.

Elastin and collagen in the normal and obstructed urinary bladder

Histological and chemical studies were carried out on the elastin and collagen content of the normal and the obstructed urinary bladder wall. The observations were made on 3 different age groups: (1) 3-month-old children with vesical outlet obstruction, (2) children aged between 4 and 8 years with partial vesical obstruction, and (3) adults with a chronically obstructed bladder. An increase in elastic tissue was shown only in the newborn and in the adults. The collagen did not vary in any of the cases studied. The elastin showed an increase in polar amino acids in the pathological organs compared with the normal. A similar increase in elastin was observed in normal individuals as a result of the ageing process.

Structural evidence for insertion of collagen fibres to smooth muscle cells in the carotid arterial system of the giraffe (Giraffa camelopardalis)

Previous anatomical studies have failed to resolve the question relating to whether or not collagen fibers, like elastic fibres, are attached to smooth muscle cells in the arterial wall. The current ultrastructural study demonstrates the insertion of collagen fibres to the sarcolemmal dark areas in the smooth muscle cells of the carotid arterial system of the giraffe. It is concluded, therefore, that this morphological linkage between collagen and smooth muscle cells may facilitate transmission of the force of contraction between the cells and to the surrounding connective tissue framework since the myofilaments appear to be spatially placed in series with the extracellular collagen fibres at the sarcolemmal dark areas.

Primary obstructed megaureter

The clinical presentation and management of 57 primary obstructed megaureters in 46 patients, 35 of whom were children, are reported. Indications for operation include pain, infection, progressive pyelo-ureteric dilatation and reduction in the glomerular filtration rate. We have found that affected children cannot be managed successfully without operation. Conservative treatment may be employed effectively in adults in whom the condition is often stable and complications are less frequent. The preferred surgical technique is ureteric narrowing with reimplantation to the bladder by the Politano-Leadbetter method. The results of surgery are less satisfactory in adults than in children. This may be related to the reduced quantity of elastic tissue in the ureteric wall in adult cases.

The elastic tissue of the adult dilated ureter

Adult dilated ureters have been examined in order to calculate the amount of the elastic tissue. From the histological observations and by the chemical analyses performed on the extracted elastin a decrease of the elastic tissue, as compared to the normal adult ureters has been noted. In fact, in the adult normal ureters, the elastin accounts for 9% of the dry matter, while in the abnormal the elastin represents 6.5%.