Manufacturing a Synthetic Scaffold for Urinary Bladder Tissue Engineering

We developed and characterized porous crosslinked biodegradable polyurethane compositions to be used in urinary bladder tissue engineering. The synthetic compositions are compatible with a sphere templated process previously developed in our research group to make biomaterials with highly controllable porosity. The polymer is a crosslinked poly(ester urethane) (PEU) synthesized using polycaprolactone triol (PCLT), lysine triisocyanate, and 1,1,1 tris(hydroxymethyl) propane as cross-linker. The materials developed possess a range of mechanical properties tunable by varying component ratios. We chose compositions with tensile strength similar to native human bladder tissue and highest ultimate strain.;No cytotoxic effects were found in cells seeded on the scaffolds. Products of degradation were also evaluated for cytotoxicity, no significant effects in cellular metabolic activity in vitro were found. Human urothelial cells and human bladder smooth muscle cells (SMCs) seeded in the scaffolds expand and increase their metabolic activity with time.;Two models of in vitro scaffold degradation were used to evaluate effects in mass loss and mechanical properties: enzymatic and accelerated degradation. Both methods show a progression of surface erosion and mass loss with increasing incubation time. Enzymatic degradation rate increases with higher PCLT concentration.;Porous PEU scaffold discs implanted subcutaneously in mice developed a thinner fibrous collagen capsule than solid PEU scaffolds. Porous scaffolds were vascularized as confirmed by immunohistochemistry. Mechanical characterization of rabbit urinary bladder tissue properties was performed to determine if rabbit bladder could potentially serve as a future animal model.;The ability to adsorb proteins on the scaffold surface improves cellular functions such as adhesion and proliferation. Protein concentration levels of vitronectin, collagen type I, and collagen type IV necessary to saturate porous PEU scaffold surfaces were identified (these proteins being fundamental in urinary system physiology).;A process to fabricate porous PEU spherical scaffolds was designed. Cell seeding of bladder urothelial cells and SMCs was performed on a spherical construct adsorbed with collagen type I. Histological analysis revealed cellular infiltration into the scaffold and layer formation at the surface of the scaffold.;Design of a bioreactor for 3D stimulation of seeded spherical scaffolds, animal implantation to assess tissue integration and in vivo degradation, and improvements on fabrication processes are some of the suggested future research directions.