P-248

Function and viability of human islets encapsulated in alginate sheets: in vitro and in vivo culture

M Lamb¹, R Storrs², S Li¹, K Laugenour¹, R Dorian², D Chapman¹, H Ichii¹, D Imagawa¹, C Foster¹, S King², J Lakey^1
1 University of California Irvine Medical Center, Surgery, Orange, USA; ² Islet Sheet Medical LLC, San Francisco, USA

Objective: Islet encapsulation in macroscopic polymer devices offers a means to protect transplanted islets and the ability to retrieve the transplanted graft. The aim of this study was to assess in vitro function and viability of human islets encapsulated in an alginate sheet and cultured over several weeks in tissue culture or in the subcutaneous space of rats.

Methods: Human islets were isolated from cadaveric organ donors at University of California, Irvine using enzyme (Vitacyte Inc)dissociation and continuous Ficoll-UWD (Mediatech Inc) purification. After overnight tissue culture, aliquots of islets were encapsulated in alginate sheets and either transplanted subcutaneously into Lewis rats or maintained in tissue culture at 37^oC and 5% CO₂. At 1, 2 and 4 weeks human islet sheets were retrieved and assessed for viability using FDA/PI and glucose stimulated insulin release using incubation for 1 hr in low (2.8mM), then high glucose (28mM), then to measure maximum insulin secretion, high (28mM) plus 50um IMBX (3-isobutyl-1-methylxanthine).

Results: Encapsulated human islets were 95 ± 0.2% viable (FDA/PI; mean ± SEM) after 1 week in culture. The initial stimulation index (SI, ratio of insulin produced in high over low glucose) was 3.8 ± 0.2 and the maximum secretion (MX, ratio of high glucose + IBMX over high glucose), when stimulated with IBMX, was 2.0. At 1-week post transplant, sheet integrity was maintained and viability was 90 ± 4%. Islet function was maintained with a SI of 3.0 ± 0.5 and MX of 2.1(p=ns, t test). At 2-weeks post transplant, explanted sheets were 85 ± 0.8% viable and still maintained glucose responsiveness with a SI of 3.0 ± 0.4, MX of 1.8.

Conclusions: These preliminary results suggest that encapsulated islets sheets can survive and maintain islet viability and function in vivo.

P-248

Function and viability of human islets encapsulated in alginate sheets: in vitro and in vivo culture

M Lamb¹, R Storrs², S Li¹, K Laugenour¹, R Dorian², D Chapman¹, H Ichii¹, D Imagawa¹, C Foster¹, S King², J Lakey^1
1 University of California Irvine Medical Center, Surgery, Orange, USA; ² Islet Sheet Medical LLC, San Francisco, USA

Objective: Islet encapsulation in macroscopic polymer devices offers a means to protect transplanted islets and the ability to retrieve the transplanted graft. The aim of this study was to assess in vitro function and viability of human islets encapsulated in an alginate sheet and cultured over several weeks in tissue culture or in the subcutaneous space of rats.

Methods: Human islets were isolated from cadaveric organ donors at University of California, Irvine using enzyme (Vitacyte Inc)dissociation and continuous Ficoll-UWD (Mediatech Inc) purification. After overnight tissue culture, aliquots of islets were encapsulated in alginate sheets and either transplanted subcutaneously into Lewis rats or maintained in tissue culture at 37^oC and 5% CO₂. At 1, 2 and 4 weeks human islet sheets were retrieved and assessed for viability using FDA/PI and glucose stimulated insulin release using incubation for 1 hr in low (2.8mM), then high glucose (28mM), then to measure maximum insulin secretion, high (28mM) plus 50um IMBX (3-isobutyl-1-methylxanthine).

Results: Encapsulated human islets were 95 ± 0.2% viable (FDA/PI; mean ± SEM) after 1 week in culture. The initial stimulation index (SI, ratio of insulin produced in high over low glucose) was 3.8 ± 0.2 and the maximum secretion (MX, ratio of high glucose + IBMX over high glucose), when stimulated with IBMX, was 2.0. At 1-week post transplant, sheet integrity was maintained and viability was 90 ± 4%. Islet function was maintained with a SI of 3.0 ± 0.5 and MX of 2.1(p=ns, t test). At 2-weeks post transplant, explanted sheets were 85 ± 0.8% viable and still maintained glucose responsiveness with a SI of 3.0 ± 0.4, MX of 1.8.

Conclusions: These preliminary results suggest that encapsulated islets sheets can survive and maintain islet viability and function in vivo.