Comparison of automated and manual methods for islet isolation

The authors used the principal features of a collagenase perfusion technique and an automated dissociation technique to determine if islets could be isolated from the large mammal pancreas and to compare the effects of the two methods on isolated islets. The pancreases of 16 dogs were cannulated and perfused with collagenase at 4 degrees C, then warmed to 37 degrees C. Group 1 (eight) pancreases were perfused at 37 degrees C until digested, then dissociated manually by teasing and trituration. Group 2 (eight) pancreases were transferred to a closed chamber for continued collagenase digestion and dissociation at 37 degrees C. Islets were purified using identical Ficoll gradients. Aliquots were stained with dithizone and evaluated for number, size and purity. Total islet volume was calculated. Group 2 pancreases were thoroughly digested leaving only a few residual ducts, but undigested fragments persisted in group 1 pancreases. Islet size was similar in both groups. There was a greater islet volume before and after Ficoll purification in group 2, but the difference was not significant. Purity was greater than 90% in both groups. Perifusion with 28 mM glucose elicited a biphasic insulin release from islets in both groups. The data show that the combined protocol enables mass isolation of purified islets from the canine pancreas. Compared with the manual technique, the automated protocol for pancreas dissociation tends to improve the yield of islets without compromising islet size and viability. It provides the advantages of a closed system with increased control over the extent of collagenase digestion.