Entrapment of dispersed pancreatic islet cells in CultiSpher-S macroporousgelatin microcarriers: Preparation, in vitro characterization, and microencapsulation

Immunoprotection of pancreatic islets for successful allo- or xenotransplan tation without chronic immunosuppression is an attractive, but still elusiv e, approach for curing type 1 diabetes. It was recently shown that, even in the absence of fibrotic overgrowth, other factors, mainly insufficient nut rition to the core of the islets, represent a major barrier for long-term s urvival of intraperitoneal microencapsulated islet grafts. The use of dispe rsed cells might contribute to solve this problem due to the conceivably ea sier nutritional support to the cells. In the present study, purified bovin e islets, prepared by collagenase digestion and density gradient purificati on, and dispersed bovine islet cells, obtained by trypsin and DNAsi (viabil ity > 90%), were entrapped into either 2% (w/v) sodium alginate (commonly u sed for encapsulation purposes) or (dispersed islet cells only) macroporous gelatin microcarriers (CulthiSpher-S, commonly used for the production of biologicals by animal cells). Insulin release studies in response to glucos e were performed within 1 week and after 1 month from preparation of the va rying systems and showed no capability of dispersed bovine islet cells with in sodium alginate microcapsules to sense glucose concentration changes. On the contrary, bovine islet cells entrapped in CulthiSpher-S microcarriers showed maintained capacity of increasing insulin secretion upon enhanced gl ucose concentration challenge. In this case, insulin release was approximat ely 60% of that from intact bovine islets within sodium alginate microcapsu les. MTT and hernatoxylineosin staining of islet cell-containing microcarri ers showed the presence of viable and metabolically active cells throughout the study period. This encouraging functional data prompted us to test whe ther the microcarriers could be immunoisolated for potential use in transpl antation. The microcarriers were embedded within 3% sodium alginate, which was then covered with a poly-L-lysine layer and a final outer alginate laye r. Maintained insulin secretion function of this system was observed, which raises the possibility of using microencapsulated CulthiSpher-S microcarri ers, containing dispersed pancreatic islet cells, in experimental transplan tation studies. (C) 2001 John Wiley & Sons, Inc.