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G S Korbutt

Publications and source records attributed to G S Korbutt.

At least 55 records · Page 3Linked to original sources
PubMed1997

Cotransplantation of allogeneic islets with allogeneic testicular cell aggregates allows long-term graft survival without systemic immunosuppression.

We prepared single-cell suspensions of Lewis rat ¿RT1(1/l)¿ testicular cells and cultured these in vitro for 48 h under conditions that promoted the formation of cellular aggregates. In the absence of systemic immunosuppression, the transplantation of a sufficient quantity of these aggregates (containing 11 x 10(6) cells, (75% Sertoli cells), together with 2,000 purified Lewis rat islets, reversed the diabetic state for >95 days in 100% (5/5) of the chemically diabetic Wistar-Furth ¿RT1(u/u)¿ recipients. Similar grafts consisting of islets alone or islets plus 50% fewer testicular cell aggregates survived for only 10 days. Functioning composite allografts harvested from normoglycemic animals at approximately 100 days showed healthy beta-cells in close association with Fas ligand-expressing Sertoli cells. Because no gene therapy protocol is required, the transplantation of composite grafts consisting of purified human allogeneic islets plus human allogeneic testicular cell aggregates can be applied in clinical islet transplantation as soon as it has been proven in a large animal model.

Animals↗
PubMed1996

Successful biolistic transformation of mouse pancreatic islets while preserving cellular function.

To utilize gene therapy, we required an efficient method to transfect intact islets before their use in transplantation. The biolistic method transforms cells by bombarding them with microprojectiles coated with DNA. Once internalized, the DNA is solubilized and expressed. We used the firefly luciferase gene driven by the human cytomegalovirus immediate early promoter as a reporter construct in freshly isolated BALB/c mouse islets to compare the transfection efficiency using either the biolistic method, lipofection, or recombinant adenoviral infection (n=4 in each case). The biolistic method achieved, on average, a 35-fold higher level of luciferase activity than the lipofection method (mean +/- SEM: 42.6 +/- 14.2 vs. 1.1 +/- 0.2 relative light units (RLU)/islet). Adenoviral infection achieved, on average, a further 25-fold higher level of luciferase activity than the biolistic method (1136.0 +/- 542.0 RLU/islet). The average proportion of islets recovered 48 hr after the biolistic blast was 53% (n=20). The average number of dissociated cells found to express the foreign gene product using beta-galactosidase as a reporter construct was 3% (n=6). Furthermore, nontransformed and biolistically transformed islets responded similarly to an in vitro glucose challenge (stimulation index of insulin release at 20.0 mM glucose/insulin release at 2.8 mM glucose = 2.8 and 3.0, respectively, P=0.9). Syngeneic, biolistically transfected islets functioned to reverse the diabetic state when transplanted (500 islets) beneath the renal capsule of alloxan-induced diabetic BALB/c recipients (n=7). This methodology can achieve efficient transfection of pancreatic islets while preserving their function and thus holds promise for ex vivo gene therapy of isolated islets prior to transplantation.

Animals↗
PubMed1996

Large scale isolation, growth, and function of porcine neonatal islet cells.

Based upon existing methods of isolating fetal porcine islet tissue, a simple, reliable procedure was developed for the preparation of porcine neonatal islet cell aggregates with a reproducible and defined cellular composition. After 9 d of in vitro culture, tissue from one neonatal pig pancreas yielded approximately 50,000 islet cell aggregates, consisting of primarily epithelial cells (57%) and pancreatic endocrine cells (35%). During the culture period, the total beta cell mass decreased initially, but subsequently increased 1.5-fold between days 3 and 9. Transplantation of grafts consisting of 3 x 10(5) beta cells (1,000 aggregated) under the kidney capsule of alloxan-diabetic nude mice corrected hyperglycemia in 75% (10/13) of the animals, whereas, 100% (20/20) of recipients implanted with 6 x 10(5) beta cells (2,000 aggregates) achieved euglycemia within 8 wk posttransplantation. Nephrectomy of the graft bearing kidney at 14 wk posttransplantation resulted in hyperglycemia in all recipients, and examination of the grafts revealed the presence of numerous well-granulated insulin- and glucagon-containing cells. The cellular insulin content of these grafts was 20 to 30-fold higher than at the time of transplantation. These results indicate that the neonatal porcine pancrease can be used as a source of large numbers of viable islet cells, which have the potential for growth both in vitro and in vivo, and exhibit the metabolic capacity to correct diabetes in nude mice.

Animals↗
PubMed1993

Rat pancreas preparation for cold storage and subsequent islet cell isolation.

Pancreatic islets can be isolated from cold-preserved organs. They contain 60% more beta cells when prepared from organs that were stored for 24 hr in Collins solution supplemented with albumin and benzamidine (CAB) instead of University of Wisconsin (UW) solution. Recovery from CAB-stored organs was similar when CAB was perfused in situ before organ removal or ex vivo after organ harvesting in UW. In situ flush with cold Ringers before ex vivo replacement by CAB resulted in 25% lower recovery of islet beta cells and in higher contamination with nonendocrine and damaged cells. Recovery of beta cells was 50% reduced when cold storage solution was not chased before collagenase digestion of the organ. It is concluded that the isolation of rat islets from cold-preserved organs can be improved by using UW or CAB instead of Ringers for situ perfusion, by cold storage in CAB, and by adequate chase of cold storage solution with physiologic medium before collagenase digestion. These conditions can be tested in current human islet isolation protocols.

Adenosine↗
PubMed1992

Prolonged exposure of human pancreatic islets to high glucose concentrations in vitro impairs the beta-cell function.

The aim of the present study was to clarify whether prolonged in vitro exposure of human pancreatic islets to high glucose concentrations impairs the function of these cells. For this purpose, islets isolated from adult cadaveric organ donors were cultured for seven days in RPMI 1640 medium supplemented with 10% fetal calf serum and containing either 5.6, 11, or 28 mM glucose. There was no glucose-induced decrease in islet DNA content or signs of morphological damage. However, islets cultured at 11 or 28 mM glucose showed a 45 or 60% decrease in insulin content, as compared to islets cultured at 5.6 mM glucose. Moreover, when such islets were submitted to a 60-min stimulation with a low (1.7 mM) followed by a high (16.7 mM) concentration of glucose, the islets cultured at 5.6 mM glucose showed a higher insulin response to glucose than those of the two other groups. Islets cultured at the two higher glucose concentrations showed increased rates of insulin release in the presence of low glucose, and a failure to enhance further the release in response to an elevated glucose level. Islets cultured at 28 mM glucose showed an absolute decrease in insulin release after stimulation with 16.7 mM glucose, as compared to islets cultured at 5.6 mM glucose. The rates of glucose oxidation, proinsulin biosynthesis, and total protein biosynthesis were similar in islets cultured at 5.6 or 11 mM glucose, but they were decreased in islets cultured at 28 mM glucose. These combined results suggest that lasting exposure to high glucose concentrations impairs the function of human pancreatic islets.

Adult↗
PubMed1992

Cold storage of rat pancreas before purification of islet beta-cells.

Allotransplantations in rats have demonstrated that aggregates of purified islet endocrine cells are less immunogenic than isolated islets. If purified islet cells are to be tested in humans, their preparation should be feasible from cold-preserved organs. We compared the yield in purified beta-cells from freshly harvested rat pancreases with that from cold-stored organs. After 24 h of preservation in Collins' solution or in University of Wisconsin (UW) solution, the number of purified beta-cells per pancreas was 40% lower (P less than 0.05) than that obtained from nonpreserved controls. Addition of 5 mM benzamidine/4% bovine serum albumin to Collins' solution resulted in similar recoveries as with freshly harvested organs; this addition did not increase the yield from UW solution-stored organs. When compared to preparations from fresh pancreases, islets and islet cells isolated from pancreases preserved in Collins' solution-bovine serum albumin-benzamidine were comparable in structural integrity, viability in culture, secretory responsiveness in vitro, and capability of correcting hyperglycemia in streptozocin-induced diabetic rats. We conclude that addition of benzamidine to Collins' preservation solution allows purification of islet beta-cells from 24-h-preserved rat pancreases in the same yield and quality as from freshly harvested organs. These results indicate that cold-preserved pancreases can be used for the preparation of purified islet cell grafts.

Adenosine↗
PubMedDate not supplied

Cold-preservation of pancreatic beta cells.

Clinical islet transplantation requires graft preservation conditions with a minimal loss in viable beta cells. The present study examines whether rat pancreatic beta cells survive a 96 h storage period at 4 degrees C. In a single cell viability assay, less than 20% viable cells were counted after 48 h storage in physiological HAM's F10 medium; cell survival was better in the high potassium solutions UW or Collins and further improved by supplementing Collins with albumin and benzamidine (CAB-77% viability after 96 h). Suspended beta cell aggregates were also well preserved during 4 days in CAB-4 degrees C as judged from DNA recovery and electron microscopy. After cold-storage in CAB, beta cells exhibited a higher insulin content than after culture in HAM's F10 at 20 degrees or 37 degrees C, but their capacity for subsequent insulin synthesis and release was comparable. When isolated islets were stored in CAB-4 degrees C for 96 h, they yielded slightly higher numbers of dissociated cells than after culture in HAM's F10 at 20 degrees C. Implantation of cold stored islets from 2 donor pancreata corrected hyperglycemia in streptozotocin-diabetic rats. It is concluded that rat beta cells can be stored in a supplemented Collins solution for at least 4 days at 4 degrees C, with preservation of initial cell number, hormone content and glucose responsiveness. During short-term periods, this new storage condition is at least equivalent to cultures at 20 degrees or 37 degrees C. Further studies are needed to assess any advantage for long-term storage of islet cell grafts.

Animals↗