Patients with a pathologic bladder have chronic medical problems with urinary incontinence, infections, and potential renal failure. Conventional surgical management of the pathologic bladder uses detubularized bowel as a patch (enterocystoplasty) to enlarge the bladder. Although enterocystoplasty provides functional improvement, it is associated with significant short- and long-term complications. Thus, alternative methods to enterocystoplasty have been explored through tissue engineering by seeding cultured bladder cells on bioscaffolds as an augmentation patch. With these techniques, marginal success has been noted but regeneration of fully functional normal bladder tissue has yet to be achieved. Several obstacles currently limit advancement in this research field including the choice of a relevant animal model; appropriate cell types for seeding, adequate neovascularization of the seeded graft, tissue innervation, and primitive bioscaffold design. Thus, alternative cell sources, advancements in bioscaffold design, and applicable animal models are needed to address these unmet clinical needs. Bone marrow stem/progenitor cells (BMSPCs) represent a highly defined population of cells that are easily accessible and may be used for bladder regeneration. BMSPCs are non-exclusively comprised of mesenchymal stem cells (MSCs) and hematopoietic stem/progenitor cells (HSPCs). MSCs have been shown to be capable of smooth muscle cell (SMC) differentiation and are involved in the bladder regenerative process, while HSPCs have demonstrated the ability to facilitate the growth of new blood vessels in regenerating tissue while aiding in peripheral nerve and urothelium regeneration. Recent developments in elastomer chemistry and scaffold design have allowed for the development of synthetic scaffolds that have controlled kinetic release of growth factors that are important for the regenerative process and that can mimic the mechanical properties of the bladder. Lastly, we have established a unique animal model of bladder augmentation in a nonhuman primate. This model is highly homologous to its human counterparts with regards to anatomy and physiology. This proposal will utilize these recent advancements in stem cell biology and elastomer chemistry along with our newly established bladder model to determine whether the use of autologous MSCs and HSPCs in conjunction with novel elastomer scaffolds can enhance current tissue engineering techniques to promote bladder regeneration. These include muscle and peripheral nerve regeneration, angiogenesis, and rapid urothelium growth. Preliminary data strongly suggests that these two cell types can accomplish these goals as demonstrated in vivo.
In patients that have abnormal bladders caused by birth defects, trauma, or disease, novel tissue engineering techniques that are successful in regenerating new bladder tissue for replacement therapy will be invaluable. Current tissue engineering techniques to regenerate bladder tissue have failed and are hampered by several problems including choice of appropriate cell types, inadequate development of new blood vessels to the regenerated tissue, tissue innervation, primitive bioscaffold design, and a poor animal model that lacks high homology to its human counterpart. This proposal aims to take advantages in recent advances in stem cell biology, elastomer chemistry and our newly established non-human primate model of bladder augmentation to address these problems and improve upon current tissue engineering techniques to make successful regeneration of bladder tissue a reality.
