Changes in the bladder morphological structure and function and the expression significance of transforming growth factor-beta1 pathway-related proteins in neurogenic bladder rats / 中华实用儿科临床杂志

ABSTRACT

Objective:To investigate changes in the bladder morphological structure and function and the expression of transforming growth factor-beta1 (TGF-β1) pathway-related proteins in the bilateral spinal nerve amputated neurogenic bladder(NB) rat.Methods:A total of 64 female SD rats were included, and 32 of them underwent bilateral spinal nerve L6+ S1 amputation to construct the NB model and the others were used as sham operation controls.Rats in both NB and control groups received bladder cystometry 3, 6, 12, 24 weeks after corresponding operation.Collagen fibers in their bladder tissues were detected by Masson staining and Sirius scarlet staining.TGF-β1, Smad2 and Smad6 proteins were checked by immunohistochemical staining.TGF-β1 receptor Ⅰ protein was measured by Western blot.Results:Bladders in the NB group were instable, with bladder leak point pressure(BLPP) and underactive voiding pressures.The basal pressure [(22.10±2.51), (18.20±1.52), (31.20±2.82), (41.10±3.41) cmH 2O(1 cmH 2O=0.098 kPa)] and bladder volume [(22.30±1.72), (49.10±5.54), (30.30±2.68), (13.50±1.52) mL] of the NB rats at 3, 6, 12 and 24 weeks were significantly higher than those of the sham operation controls[(3.51±0.45) cmH 2O and (0.52±0.04) mL], and the difference were significant(all P<0.05). The bladder size and thickness in the NB group firstly increased (3, 6 weeks) and then decreased (12, 24 weeks), but the bladder weight increased continuously.Masson staining showed disordered fibrous connective tissues, disintegrated layered bla-dder wall, hypertrophied smooth muscle tissues and deposited intramuscular collagen on the nerve-amputated bladder wall.Sirius scarlet staining suggested that 24 weeks after nerve amputation, collagen Ⅲ increased greatly, and the ratio of type Ⅲ/Ⅰ collagen fibers (3.14±0.71) was significantly higher than that in the sham group (0.88±0.21) ( t= 7.48, P<0.01). According to the immunohistochemical staining results, the expressions of TGF-1β and Smad2 increased while the pathway inhibitory protein Smad6 decreased with time in the NB group.Western blot showed that the expression of TGF-β1 receptor Ⅰ in the amputated bladder was 1.3 and 1.6 folds higher than that in the sham group 12 weeks and 24 weeks after operation( t=6.06, 14.45, all P<0.01). Conclusions:In NB rats with bilateral spinal nerve amputated, bladder contraction becomes paralysis, intravesical pressure increases, bladder normal structure disintegrates and the fibrosis pathway TGF-β1/Smads is activated.Therefore, the key step of development of pediatric NB is bladder fibrosis, which should be prevented as early as possibly in the clinical practice.