Biaxial mechanical properties of muscle-derived cell seeded small intestinal submucosa for bladder wall reconstitution

Bladder wall replacement remains a challenging problem for urological surgery due to leakage, infection, stone formation, and extensive time needed for tissue regeneration. To explore the feasibility of producing a more functional biomaterial for bladder reconstitution, we incorporated muscle-derived cells (MDC) into small intestinal submucosa (SIS) scaffolds. MDC were harvested from mice hindleg muscle, transfected with a plasmid encoding for β-galactosidase, and placed into single-layer SIS cell culture inserts. Twenty-five MDC and/or SIS specimens were incubated at 37°C for either 10 or 20 days. After harvesting, mechanical properties were characterized using biaxial testing, and the areal strain under 1 MPa peak stress used to quantify tissue compliance. Histological results indicated that MDC migrated throughout the SIS after 20 days. The mean (±SE) areal strain of the 0 day control group was 0.182±0.027 (n=5). After 10 days incubation, the mean (±SE) areal strain in MDC/SIS was 0.247±0.014 (n=5) compared to 10 day control SIS 0.200±0.024 (n=6). After 20 days incubation, the mean areal strain of MDC/SIS was 0.255±0.019 (n=5) compared to control SIS 0.170±0.025 (n=5). Both 10 and 20 days seeded groups were significantly different (p=0.027) than that of incubated SIS alone, but were not different from each other. These results suggest that MDC growth was supported by SIS and that initial remodeling of the SIS ECM had occurred within the first 10 days of incubation, but may have slowed once the MDC had grown to confluence within the SIS.