Bladder Regeneration Using Multiple Acellular Scaffolds with Growth Factors in a Bladder

Introduction: Tissue engineering may become an alternative to current bladder augmentation techniques. Large scaffolds are needed for clinically significant augmentation, but can result in fibrosis and graft shrinkage. The purpose of this study was to investigate the use of multiple scaffolds instead of one large scaffold, to enhance bladder tissue regeneration and bladder capacity. Second, acellular collagen, collagen-heparin, and collagen-heparin scaffolds with growth factors (GFs) were used and the biological activity of the different scaffolds was compared in a large animal model. Materials and Methods: Scaffolds were made of bovine type I collagen with or without heparin (O=3.2cm). Collagen-heparin scaffolds were loaded with GFs, vascular endothelial growth factor (VEGF), fibroblast growth factor 2 (FGF2), and heparin-binding epidermal growth factor (HB-EGF). Three identical scaffolds prepared from collagen (COL-group), collagen with heparin (COLHEP-group), or collagen-heparin with growth factors (COLHEPGF-group) were implanted in one porcine bladder. The outcome was compared with sham-operated animals (Sham-group), in which no scaffold was used. Urodynamic evaluation was performed before surgery and 3 months after bladder reconstruction, together with histological evaluation. Results: Survival rate was 92%, 12 animals completed the study, 3 of every group, 1 animal developed peritonitis due to urine leakage and was sacrificed. The regenerated area was largest in the COLHEP-group, and least in the COL-group (p=0.002). Histological evaluation revealed a normal urothelial layer and good angiogenesis in all groups, and comparable ingrowth of smooth muscle cells. Urodynamics showed no statistically significant differences in bladder capacity and compliance between groups. Bladder capacity and compliance was very high in this animal model, which made it impossible to study the increase due to augmentation. Conclusions: Implantation of multiple collagen-heparin scaffolds in one bladder is feasible in a porcine model, resulting in tissue almost indistinguishable from native tissue involving all cell layers of the bladder. Collagen scaffolds with heparin incorporated resulted in a larger area of regenerated tissue. To reach clinically significant augmentation, multiple larger collagen-heparin scaffolds, with or without GFs, need to be tested to study the largest possible diameter of scaffold and number of used scaffolds still resulting in well-vascularized tissue.