Transplantation of Purified Islet Cells in Diabetic Rats: II. Immunogenicity of Allografted Islet β-Cells

Abstract

This study examines whether the survival of allografted rat islet beta-cells is influenced by the presence of other pancreatic donor cells. Grafts (RT1u/l) of different cellular composition were intraportally transplanted in streptozocin-induced diabetic rats (RT1n/n). All grafts corrected the diabetic state within 3 days. Implants of freshly isolated islets contained various endocrine and nonendocrine cell types; they became diffusely infiltrated within 1 wk and were completely destroyed within 2 wk. A 4-day culture period did not lead to major changes in the cellular composition of the islets or in their survival as allograft. Islet cell aggregates prepared after islet dissociation and cell purification were less acutely infiltrated and less rapidly rejected. Aggregates composed of sorted MHC class II-negative cells maintained basal normoglycemia in 3 of 5 recipients for 5 wk but only in 1 of 5 for 20 wk. Aggregates of purified islet beta-cells remained relatively free of diffuse infiltrations during the 1st wk and preserved the normalized state in 7 of 13 recipients for 5 wk; after 20 wk, 6 of 13 were still aglucosuric, but 40% of the implants were diffusely infiltrated and depleted of insulin. Reaggregation of purified islet beta-cells with purified islet endocrine non-beta-cells promoted their long-term survival as allograft: 11 of 13 recipients of mixed islet endocrine cells maintained normal basal glycemia over 20 wk; their implants contained relatively constant insulin reserves and remained virtually devoid of diffuse infiltrations. These results demonstrate that techniques aiming at the elimination of surface MHC class II-positive cells are less successful in preparing rat islet allografts of low immunogenicity than methods of positive cell selection. Pure islet beta-cells are immunogenic as an allograft but illicit a milder and less-acute immune attack than undissociated islet tissue. Nonendocrine and damaged islet cells are suspected of enhancing the rapidity and intensity of the cytotoxic reaction. Survival of allografted beta-cells is markedly prolonged by the presence of islet endocrine non-beta-cells within the graft. The mechanisms underlying this effect have not yet been elucidated; they may involve immune and metabolic interactions of the endocrine non-beta-cells. We conclude that purification of islet endocrine cells represents a new and powerful method for preparing insulin-producing allografts that can survive in hosts without pharmacological immunosuppression.

Cell Loss during Pseudoislet Formation Hampers Profound Improvements in Islet Lentiviral Transduction Efficacy for Transplantation Purposes

“…Indeed, the gates to a mixture of cytokines in vitro and to immunecompetent NOD spleen cells in vivo, that the lentiviral essential secretory response of pancreatic β-cells is highly dependent on their aggregation and cell to cell gene transfer did not sensitize islet cells to cytokines nor induce antigenicity. Thus, the immune system does not communications with other β-cells and the presence of islet endocrine non-β-cells (15,25). become more activated in response to the lentiviral gene transfer, which confirms previous findings by Gallichan Different islet culture conditions were tested for optimal transduction efficiency and maintenance of islet cell et al (7).…”

α-cell loss from islet impairs its insulin secretion in vitro and in vivo

“…[17][18][19] In our study, diabetic C57BL/6 mice grafted with intact islets led to normoglycemia (glycemia level was reduced 70%), while mice grafted with α-cell deficient islets were still hyperglycemia (glycemia level was reduced 30%). Immunohistochemical examination confirmed the α-cell deficiency in hyperglycemic, but not in normoglycemic mice, with comparable insulin staining between the two groups.…”

“…13,16 In addition, the survival of allografted β-cells is markedly affected by the presence of islet endocrine non-β-cells within graft. [17][18][19] In view of the importance of α-cells in islet function, we investigated the effect of α-cell loss on the function of isolated human islets in vitro and in vivo. We addressed the following questions: (1) Does enzyme over-digestion during islet isolation induce α-cell loss from human islets?…”

Long-Term Metabolic Control by Rat Islet Grafts Depends on the Composition of the Implant

“…Pancreases and organs with islet implants were extracted for hormone assay or processed for histology (18).…”