Bladder Regeneration In A Canine Model Using Collagen Scaffolds Loaded With Collagen-binding Human Basic Fibroblast Growth Factor

Congenital abnormalities, cancer, inflammation, infection and trauma may result indisorders of the urinary bladder structure and function, which often require reconstructiveprocedures. Tradition enterocystoplasty by bowel segments will cause a series ofcomplications, such as infection, stones, and even malignant disease. Development of tissueengineering techniques has brought a new method for bladder reconstruction. Currently, theprimary problem of tissue engineering bladder is rapidly vascularization of the implantedbladder tissue, but the scaffolds loaded with the growth factors provide an option for therapid vascularization of implanted bladder tissue.Basic fibroblast growth factor (bFGF) plays a vital role in wound healing, tissue repairand angiogenesis, but the repair effect may be limited by factor diffusion because of theinfiltration and flow of body fluids after an adsorption of bFGF to materials andre-implantation. Thus, we enable the N-terminal collagen binding domian (CBD) to bindcollagen and keep releasing regenerative molecules signal at fixed points, at the same time,the exogenous collagen scaffold can provide a three-dimensional space for cell proliferationand tissue regeneration.The project uses large beagles in bladder reconstruction experiments, and the studyincludes two parts:Part I: produce beagle’s bladder injury model and reconstruct tissue engineeringbladder.CBD-bFGF and collagen scaffolds, provided by the Institute of Genetics andDevelopmental Biology, Chinese Academy of Sciences, prepare CBD-bFGF/Collagenmaterials and PBS/Collagen materials. Thirteen adult male beagles are divided into shamoperated group (n=3), PBS/Collagen group (n=5) and CBD-bFGF/Collagen group (n=5).Take the exposed bladder in the median incision on paramedian abdomen, remove50%to60%of the bladder, use CBD-bFGF/Collagen materials and PBS/Collagen materials in bladder reconstruction respectively. One month after the operation, there was one deathcase each in PBS/Collagen group and CBD-bFGF/Collagen group, the autopsy shows,severe bladder infection caused bladder rupture, and further caused abdominal infection anddeath. The remaining beagles in three groups survived with no urine leakage and infection.Part II: the performance of the two repair materials in beagle’s bladderreconstructionSix months after the operation, we conducted a detection of morphology, histology andfunction on all beagles’ bladder, in order to evaluate the reconstruction and repair effects ofthe two materials on beagles’ bladder. The analysis of urodynamic results shows: themaximum bladder capacity and compliance growed successively in the PBS/Collagen group,CBD-bFGF/Collagen group and Sham operated group, the differences among three groupshave statistical significance (P <0.05), whereas the differences in maximum detrusorpressure between CBD-bFGF/Collagen group and Sham operated group have no statisticalsignificance (P>0.05). Results of intravenous pyelography and cystography show: kidneyand ureter has normal development with clear bladder outline and normal morphology.Observations of gross specimens and histology show: diverticula and trabeculation eneratedin bladder in PBS/Collagen group, normal epithelial layer, submucosal tissue proliferation,bad muscular regeneration; while only a small amount of trabeculation generated inCBD-bFGF/Collagen group, and normal three-layer structure similar to Sham opratedgroup.In summary, in experiments of beagle’s bladder reconstruction and repair,CBD-bFGF/Collagen repair materials effectively promote bladder tissue regeneration andfunctional recovery, and the tissue engineered bladder constructed by CBD-bFGF/Collagenscaffolds can be an ideal biomaterial to replace and repair the bladder.