In vivo degradation of ¹⁴C-labeled small intestinal submucosa (SIS) when used for urinary bladder repair

The rate of in vivo degradation was determined for a naturally occurring biomaterial derived from the extracellular matrix of the small intestinal submucosa (SIS). The SIS was labeled by giving weekly intravenous injections of 10μCi of ¹⁴C-proline to piglets from 3 weeks of age until the time of sacrifice at 26 weeks. The resultant SIS prepared from these pigs contained approximately 10³ fold more ¹⁴C than unlabeled tissues. The labeled SIS was used to repair experimental defects in the urinary bladder of 10 dogs. The animals were sacrificed at post-operative times ranging from 3 days to 1 year and the remodeled urinary bladder tissue was harvested for evaluation of ¹⁴C by a combination of liquid scintillation counting and accelerator mass spectrometry. The remodeled tissue contained less than 10% of the ¹⁴C (disintegrations per minute/gram tissue wet weight) at 3 months post-surgery compared to the SIS biomaterial that was originally implanted. The SIS scaffold was replaced by host tissue that resembled normal bladder both in structure and function. After implantation, ¹⁴C was detected in highest concentrations in the blood and the urine. The SIS bioscaffold provides a temporary scaffold for tissue remodeling with rapid host tissue remodeling, degradation, and elimination via the urine when used as a urinary bladder repair device.