Author Description

In this work, a porcine derived bladder acellular matrix (BAM) was investigated as a potential material for bladder augmentation. The in vivo response of BAM was evaluated in a porcine bladder augmentation model. Achievement of bladder compliance was assessed through the use of mechanical tensile testing of native and BAM tissue explants out to 22 weeks post-operative. A significant decrease in rupture strains, combined with a significant increase in tissue moduli for the explanted grafts provided quantitative evidence for a fibroproliferative tissue response. Histological observations supported mechanical property data. Central regions of the grafts displayed limited urothelial coverage and newly developed smooth muscle was limited within a dense fibrotic collagen matrix.Following in vitro characterization, BAM was modified to include the glycosaminoglycan hyaluronan (HA) and a biologically active peptide derived from the matricellular protein Secreted Protein, Acidic, Rich in Cysteine (SPARC), termed SP4.2. A thiol-modified form of HA was incorporated and cross-linked into BAM to produce a disulfide cross-linked HA/BAM construct. When utilized in the co-culture model, the HA/BAM scaffold exhibited a significantly higher degree of matrix contraction and gelatinase activity compared to unmodified BAM. In contrast, addition of SP4.2 to the BAM-only scaffold produced a negligible effect on contraction. Gelatinase activity was however significantly reduced. The trend of reduced gelatinase activity was consistent for HA+SP4.2 modified BAM. Unlike the BAM+SP4.2 scaffold, matrices containing both molecules displayed significant increases in matrix contraction compared to BAM alone. These in vitro results suggest that both HA and SP4.2 have potential to modify the processes associated with bladder repair following bladder augmentation with BAM.In order to address these unfavorable outcomes, an in vitro model for studying BAM-mediated fibroproliferative events was developed. Methods for culturing primary porcine bladder smooth muscle (SMC) and urothelial cells (UEC) were established and cell seeding experiments demonstrated the ability of BAM to support the growth of these cell types. SMC-mediated matrix contraction, as well as SMC invasiveness into BAM, was enhanced in co-culture with UECs. The contractile and invasive capacity of co-cultured SMCs appeared to be, at least partially, attributable to elevated levels of cell-secreted gelatinase activity.