Preliminary study of a genetically engineered spinal cord implant on urinary bladder after experimental spinal cord injury in rats.

The objective of this study was to determine the effect of neurotrophin-secreting Schwann cell implants on the urinary bladder after spinal cord contusion. One hour after severe spinal cord contusion at the T8 to T11 level, carbon filaments containing nonsecreting Schwann cells, brain-derived neurotrophic factor (BDNF)-secreting Schwann cells, neurotrophin-3 (NT-3)-secreting Schwann cells, or Schwann cells secreting both BDNF and NT-3 were implanted into the spinal cord. Untreated spinal cord injured (SCI) rats and noncontused rats (C) were also studied. Two months after spinal cord injury, cystometry was performed and the bladders were studied using light microscopy. SCI rats had significantly increased bladder mass, thickness, and smooth muscle mass compared to C rats. Bladder capacity of SCI rats and rats with spinal cord implants were both significantly greater than that of C rats. This preliminary study suggests that neurotrophin-secreting Schwann cell implants may lead to improved bladder structure after spinal cord injury.

Collagen remodeling and suburethral inflammation might account for preserved anti-incontinence effects of cut polypropylene sling in rat model.

OBJECTIVES: To determine whether the inflammatory responses or collagen remodeling in suburethral tissue could have contributed to the preserved anti-incontinence effects of a cut polypropylene sling. METHODS: Stress urinary incontinence was created in 60 age-matched female Sprague-Dawley rats that were subsequently randomized into 3 equal-size groups according to surgical procedure: placement of a vaginal suburethral sling, placement of a vaginal suburethral sling in which the suburethral portion of the sling was immediately cut, and sham surgery without placement of the sling. In a previous study, the leak point pressure measurements were obtained on these rats 6 weeks after surgery. The rats were then killed, the urethrovaginal tissue was harvested (cross-section of the entire urethra and anterior vagina) from 30 animals (10 from each experimental group), and the tissue was stained with hematoxylin-eosin and Masson's trichrome for histopathologic studies and picrosirius red for collagen fibers. RESULTS: As previously published, the median leak point pressures were similarly and significantly increased in the rats in the intact and cut sling groups compared with those in the sham surgery group. The inflammatory mediators and interstitial edema were similarly increased in the intact and cut sling specimens compared with the sham surgery specimens. Under polarized light, picrosirius red-stained specimens from the sham surgery animals appeared to be composed of collagen that predominately birefringed red to yellow (typical of type I collagen). The picrosirius red-stained cut and intact sling specimens appeared to contain collagen fibers that predominately birefringed green (typical of type III collagen). CONCLUSIONS: Histologic changes, including inflammation, localized edema, and differential collagen remodeling, might contribute to the preserved anti-incontinence mechanisms of cut or intact polypropylene slings observed clinically.

Biocompatibility of nitinol and stainless steel in the bladder: an experimental study.

PURPOSE: We tested the biocompatibility of nitinol, a nickel titanium alloy, and stainless steel (SS) as bladder implant materials. MATERIALS AND METHODS: Rats received a nitinol implant, an SS implant or were sham controls. Two, 3, 6 and 8 weeks following implantation 24-hour voiding behavior studies were performed to investigate bladder irritation. All animals were sacrificed 8 weeks after implantation and a sample of urine was aspirated for culture. The bladders were examined by light microscopy and scanning electron microscopy (SEM). RESULTS: No visible encrustations or infections were noted in urine. Voiding frequency in the light period 6 weeks after implantation was significantly decreased in the 2 implant groups compared with sham controls. There were no other significant differences in frequency or mean volume per void in the light or dark periods at any time point. Light microscopy demonstrated similar implant tissue effects in all groups with little or no inflammation or fibrosis. Under SEM all implants showed a brittle, amorphous coating devoid of cells. The transition between the urothelium mucosa and the rod was smoother for SS than for nitinol, suggesting an affinity of SS for mucosa. In all nitinol rods discontinuity was present between the mucosa and rod. CONCLUSIONS: Nitinol and SS do not cause more irritation than the effects of surgery alone and the 2 materials seem to be biocompatible in the bladder. Nitinol may be more inert than SS based on SEM results.