Successful Isolation and Transplantation of Nonhuman Primate Islets Using a Novel Purified Enzyme Blend

Implementation of a simplified method of islet isolation for allogeneic islet transplantation in cynomolgus monkeys

OBJECTIVES

The present study describes a simple and cost-effective islet isolation procedure. Using this method, allogeneic islets reverse diabetes in cynomolgus monkeys.

METHODS

Pancreatic tissue from 11 cynomolgus monkeys were digested, collected, and purified using a simplified method. Islet quantification, purity, viability, and glucose static incubation were conducted immediately after isolation. Five streptozotocin-induced monkeys with diabetes were transplanted intrahepatically, and liver biopsies from 3 of these monkeys were taken at different time points for histologic study.

RESULTS

The mean (SD) of viability, purity, and static glucose incubation stimulation index were 94.4% (2.3%), 91.8% (3.4%), and 2.6 (1.7), respectively. Monkeys who received a mean (SD) dose of 19,968 (2273) islet equivalent per kilogram (n = 4) from 2 to 3 donors who achieved prolonged normoglycemia (57-232 days), whereas the single monkey who received an islet dose of 8000 islet equivalent per kilogram did not experience diabetes reversal. Immunohistochemical assessment of the liver biopsies taken from the monkeys with normoglycemia revealed an insulin- and glucagon-positive islet graft for up to 6 months with minimal peri-islet inflammatory infiltration.

CONCLUSIONS

This study demonstrates that cynomolgus monkey islets can be successfully and efficiently harvested using a simple isolation method, and these islets can restore normoglycemia in monkeys with diabetes.

Xenofree enzymatic products for the isolation of human adipose-derived stromal/stem cells

Human adipose-derived stromal/stem cells (ASCs) are an abundant, readily available population of adult stem cells that reside in adipose tissue and that have a great potential utility for tissue engineering and regenerative medicine therapeutic applications. Several preclinical studies have shown that ASCs have therapeutic applicability, but a standardized isolation and expansion methodology for clinical cell therapy has yet to be established. ASC are typically isolated and expanded using reagents with xenogenic components and this may pose certain risks and safety issues, such as exposure to infectious agents and immune reactions, creating further obstacles to the translation of ASC-based therapies to clinical scenarios. The objective of this study was to determine the suitability and efficacy of various alternative enzymatic products, CLS1 (Worthington), CLSAFA (Worthington), NB4 (SERVA), and Liberase (Roche), for the digestion of adipose tissue and subsequent isolation of ASCs, assessing cell functionality concerning their proliferation and differentiation ability. Results show that there are no statistically significant differences on yield and proliferation of cells isolated after enzymatic digestion with any of the studied products. The differentiation potential of the cells was not affected, and cell surface marker expression was similar among all products. We concluded that clinical grade products can replace current research-grade products effectively in our cell isolation protocols without any negative effect in the yield or function of human ASCs.

Pancreatic islet transplantation

Pancreatic islet transplantation is a minimally invasive treatment that has the potential to prevent diabetes after total pancreatectomy for benign disease (islet autotransplantation) and to reverse diabetes in those with type 1 diabetes (islet allotransplantation). In both scenarios, the treatment involves extracting sufficient numbers of pancreatic islets from the resected or donor pancreas and infusing these through the portal vein into the patient's liver. The results for both forms of this treatment have been encouraging over recent years, with up to 85% of adult patients remaining insulin independent for at least 1 year after transplantation. However, there are a number of challenges that need to be overcome before these treatments can be used routinely in children. The aim of this review is to outline the rationale, methodology, and current results of islet allotransplantation, and to discuss the potential new developments that could enable this important treatment to be widely applicable to children. Although islet autotransplantation is not discussed in detail, the overall rationale and methods are similar. However, as the procedure involves the transplantation of the patient's own islets, and the indication for the procedure is not for autoimmune disease, there are none of the difficult immune challenges of allotransplantation.