Transplantation sites for human and murine islets

Rebecca A Stokes,Tom W Kay,Michael M Swarbrick,Wayne J Hawthorne,Kim Cheng,Amit Lalwani,Thomas Loudovaris,Jenny E Gunton,Philip J O’Connell,Helen E Thomas

doi:10.1007/s00125-017-4362-8

Abstract

Aims/hypothesisBeta cell replacement is a potential cure for type 1 diabetes. In humans, islet transplants are currently infused into the liver via the portal vein, although this site has disadvantages. Here, we investigated alternative transplantation sites for human and murine islets in recipient mice, comparing the portal vein with quadriceps muscle and kidney, liver and spleen capsules.MethodsMurine islets were isolated from C57BL6/J mice and transplanted into syngeneic recipients. Human islets were isolated and transplanted into either severe combined immunodeficiency (SCID) or recombination-activating gene 1 (RAG-1) immunodeficient recipient mice. All recipient mice were 8–12 weeks of age and had been rendered diabetic (defined as blood glucose concentrations ≥20 mmol/l on two consecutive days before transplantation) by alloxan tetrahydrate treatment. Islets were transplanted into five different sites (portal vein, quadriceps muscle, kidney, liver and spleen capsules). Blood glucose concentrations were monitored twice weekly until mice were killed. Dose–response studies were also performed to determine the minimum number of islets required to cure diabetes (‘cure’ is defined for this study as random fed blood glucose of <15 mmol/l).ResultsFor transplantation of murine islets into the different sites, the kidney yielded 100% success, followed by muscle (70%), portal vein (60%), spleen capsule (29%) and liver capsule (0%). For human islets, transplantation into the kidney cured diabetes in 75–80% of recipient mice. Transplantation into muscle and portal vein had intermediate success (both 29% at 2000 islet equivalents), while transplantation into liver and spleen capsule failed (0%). With increased islet mass, success rates for muscle grafts improved to 52–56%.Conclusions/interpretationFor both human and murine islets, equivalent or superior glucose lowering results were obtained for transplantation into skeletal muscle, compared with the portal vein. Unfortunately, kidney grafts are not feasible in human recipients. Skeletal muscle offers easier access and greater potential for protocol biopsies. This study suggests that human trials of muscle as a transplant site may be warranted.

Highlights

Pancreatic islet transplantation provides a potential cure for type 1 diabetes
In a non-diabetic individual, circulating nutrient concentrations increase postprandially and the nutrients are delivered to the pancreas where beta cells respond by secreting insulin
Two of seven mice (29%) receiving islets transplanted into the spleen subcapsular space were cured and none of the six mice receiving transplants into the liver subcapsular space were cured (Fig. 1a). For transplants into both spleen and liver, recipients had either hypoglycaemic readings from day 2–4 or repeated high blood glucose resulting in the need for euthanasia within 1–2 weeks post transplant

Summary

Introduction

MethodsPancreatic islet transplantation provides a potential cure for type 1 diabetes. Studies in mice reported success using the portal vein site [8] and subsequent refinements improved outcomes [3, 4, 9]. This site has disadvantages including the potential complications of portal hypertension, bleeding, portal vein thrombosis and hepatic ischaemia [10, 11]. These risks are low in the hands of experienced transplant centres with current protocols

Methods

Results

Conclusion