Biocompatibility of two different types of extracellular matrix in bioartificial endocrine pancreas in dogs: A preliminary report

The biocompatibility of synthetic extracellular matrix (ECM) in the diffusion chamber of a bioartificial endocrine pancreas (Bio-AEP) was investigated in normal beagle dogs. Two different types of ECM were used in this study, type I collagen treated with pepsin to ensure lower antigenicity (type I LA) and reconstituted basement membrane matrix (Matrigel derived from Englbreth-Holm-Swarm mouse sarcoma. Bio-AEPs with type I LA or Matrigel without pancreatic endocrine cells were implanted into the abdominal cavities of beagle dogs (n=4). At 1 month after implantation, laparoscopy revealed no abnormalities in the Bio-AEPs with type I LA, whereas it revealed encapsulation of one of the Bio-AEPs with Matrigel with fibrous tissue, and in that case the Bio-AEP was removed. At 3 months after implantation, the remaining Bio-AEP with Matrigel was completely destroyed, whereas the Bio-AEPs with type I LA showed no abnormal findings. Microscopically, an invasion of red blood cells and macrophages into the chamber was observed in the Bio-AEPs with Matrigel. A proliferation of fibroblasts around the Matrigel was observed in one case. In contrast, light microscopic findings revealed no abnormal findings in the Bio-AEP with type I LA. These results suggest that the cell growth and differentiation factors and adhesion molecules in Matrigel may play an important role in fibrous encapsulation and may be incompatible with dogs, and that type I LA is more suitable for Bio-AEP.