Long-Term Control of Diabetes in Immunosuppressed Nonhuman Primates (NHP) by the Transplantation of Adult Porcine Islets

Abstract

Pig islets are an alternative source for islet transplantation to treat type 1 diabetes (T1D), but reproducible curative potential in the pig-to-nonhuman primate (NHP) model has not been demonstrated. Here, we report that pig islet grafts survived and maintained normoglycemia for >6 months in four of five consecutive immunosuppressed NHPs. Pig islets were isolated from designated pathogen-free (DPF) miniature pigs and infused intraportally into streptozotocin-induced diabetic rhesus monkeys under pretreatment with cobra venom factor (CVF), anti-thymocyte globulin (ATG) induction and maintenance with anti-CD154 monoclonal antibody and low-dose sirolimus. Ex vivo expanded autologous regulatory T cells were adoptively transferred in three recipients. Blood glucose levels were promptly normalized in all five monkeys and normoglycemia (90-110 mg/dL) was maintained for >6 months in four cases, the longest currently up to 603 days. Intravenous glucose tolerance tests during the follow-up period showed excellent glucose disposal capacity and porcine C-peptide responses. Adoptive transfer of autologous regulatory T cells was likely to be associated with more stable and durable normoglycemia. Importantly, the recipients showed no serious adverse effects. Taken together, our results confirm the clinical feasibility of pig islet transplantation to treat T1D patients without the need for excessive immunosuppressive therapy.

Use of genetically-engineered pig donors in islet transplantation

“…This finding can explain the success in islet transplantation achieved by several groups, using Gal expressing adult pig islets transplanted into immunosuppressed nonhuman primate recipients [10,11,17] . In contrast, there is a higher expression of Gal on pig islets at birth and throughout the neonatal period than with adult islets [32] .…”

“…In many other ways, the pig is a suitable source of islets for xenotransplantation into human recipients. In the last decade, several groups from around the world have shown success in restoring insulin independence for a period > 6 mo in diabetic nonhuman primate recipients of pig islets, a breakthrough achievement in xenotransplantation [9][10][11][12][13][14][15][16][17] . While the results of pigto-nonhuman primate models cannot fully predict the pig-to-human results due to dissimilarities among the different donors and recipient species, they are necessary steps to reach clinical application [18,19] .…”

Pig-to-Nonhuman Primate (NHP) Naked Islet Xenotransplantation

“…For our pig-to-NHP islet xenotransplantation experiments, we performed three independent assays that included (1) islet cell viability test using β-cell specific fluorescent dye Fluozin-3, mitochondrial activity indicator Tetramethylrhodamine, Ethyl Ester (TMRE), and a fluorescence-activated cell sorting (FACS) machine, (2) glucose-stimulated insulin secretion (GSIS), and (3) nondiabetic obese severe combined immunodeficiency (NOD/SCID) mouse bioassay where four streptozotocin (STZ)-induced diabetic mice were transplanted with 2500 IEQ of porcine islets under the kidney subcapsule, and their BGL were monitored 2-3 times per week for at least 2 months (Figure 2). Our recent study showed that the isolated porcine islets were >90% pure, contained >80% healthy β-cells, and had >60% diabetes correction capacity, each demonstrated by dithizone staining, FACS analysis, and NOD/SCID bioassay, respectively [26]. Although the fold increase of insulin upon glucose stimulation of porcine islets overall reached >1, the results from GSIS assay were highly variable and did not reflect the potency of the isolated pig islets, unlike those from other species (data not shown).…”

“…There are two popular methods to transplant the islets via the portal vein: one is to infuse the islets through a jejunal vein after laparotomy [26]; and the other is to use percutaneous transhepatic portal catheterization guided by ultrasound technology [47]. The latter is less invasive than the former, but special equipment-such as ultrasound and C-arm-and the technique for ultrasound-guided percutaneous transhepatic portal vein catheterization are indispensable.…”

“…Follow-up should be for a period of at least 6 months in all cases and ideally for 12 months in one or two successful cases [24,25]. Recently, our group reported successful results where five consecutive diabetic monkeys achieved normoglycemia for at least 6 months after transplantation of adult porcine islets, with the longest survival day reaching to >603 days [26]. During a follow-up study, one monkey showed normoglycemia up to ~1000 days using a CD40-CD154 blockade such as anti-CD154 or anti-CD40 monoclonal antibody [27].…”