A Combined Continuous Density/Osmolality Gradient for Supplemental Purification of Human Islets

Abstract

For islet transplantation, islet purification minimizes the risks associated with islet infusion through the portal vein. However, islet purification may result in decreased numbers of islets recovered from digested tissue. In this study, we evaluated the effectiveness of performing supplemental purification (SP) after regular purification (RP). We designed the densities of low-and high-density solutions based on the outcome of RP. Moreover, a combined continuous osmolality/continuous density gradient for the SP was used in this study. Low-density/osmolality (1.075–1.110 g/cm 3 /400–410 mOsm/kg) and high-density/osmolality (1.090–1.125 g/cm 3 /495–505 mOsm/kg) solutions were produced by changing the volumetric ratio of iodixanol, 1 HBSS, and RP solutions. The percentage of islet recovery (postpurification IE/prepurification IÉ 100) after RP was 77.3 ± 5.6%, and the percentage of islet recovery after addition of SP was 85.3 ± 5.4%. In vitro and in vivo assessments showed that islet viability and function were not altered by the additional purification step. These data suggest that the addition of SP could contribute approximately 8% to islet recovery with viability and potency comparable to that obtained by RP and, therefore, that usage of the combined continuous density and continuous osmolality gradient for SP could efficiently improve islet equivalents in the final preparation.