Pancreatic islet transplantation: from dogs to humans and back again

Interim report on the effective intraperitoneal therapy of insulin-dependent diabetes mellitus in pet dogs using "Neo-Islets," aggregates of adipose stem and pancreatic islet cells (INAD 012-776)

We previously reported that allogeneic, intraperitoneally administered “Neo-Islets,” composed of cultured pancreatic islet cells co-aggregated with high numbers of immunoprotective and cytoprotective Adipose-derived Stem Cells, reestablished, through omental engraftment, redifferentiation and splenic and omental up-regulation of regulatory T-cells, normoglycemia in autoimmune Type-1 Diabetic Non-Obese Diabetic (NOD) mice without the use of immunosuppressive agents or encapsulation devices. Based on these observations, we are currently testing this Neo-Islet technology in an FDA guided pilot study (INAD 012–776) in insulin-dependent, spontaneously diabetic pet dogs by ultrasound-guided, intraperitoneal administration of 2x10e5 Neo-Islets/kilogram body weight to metabolically controlled (blood glucose, triglycerides, thyroid and adrenal functions) and sedated animals. We report here interim observations on the first 4 canine Neo-Islet-treated, insulin-dependent pet dogs that are now in the early to intermediate-term follow-up phase of the planned 3 year study (> 6 months post treatment). Current results from this translational study indicate that in dogs, Neo-Islets appear to engraft, redifferentiate and physiologically produce insulin, and are rejected by neither auto- nor allo-immune responses, as evidenced by (a) an absent IgG response to the allogeneic cells contained in the administered Neo-Islets, and (b) progressively improved glycemic control that achieves up to a 50% reduction in daily insulin needs paralleled by a statistically significant decrease in serum glucose concentrations. This is accomplished without the use of anti-rejection drugs or encapsulation devices. No adverse or serious adverse events related to the Neo-Islet administration have been observed to date. We conclude that this minimally invasive therapy has significant translational relevance to veterinary and clinical Type 1 diabetes mellitus by achieving complete and at this point partial glycemic control in two species, i.e., diabetic mice and dogs, respectively.

Production, Characterization, and Function of Pseudoislets from Perinatal Canine Pancreas

We evaluated the cell composition and function of canine pancreatic pseudoislets (PIs) produced from 42- to 55-day-old fetuses, 1- to 21-day-old pups, and an adult dog pancreas. After mild collagenase treatment, partially digested tissues were cultured for 2–3 weeks. PI production started on culture day 3, was marked for 6 to 9 days, and then stopped. PI production was greatest with the neonatal specimens, reaching about 12 million aggregates per litter (55-day-old fetus) or per pancreas (1-day-old pup). Cell composition at all stages was similar to that in adult pancreatic islets, with predominant β cells, scant α cells and, most importantly, presence of δ cells. Among pancreatic markers assessed by quantitative real-time PCR (qRT-PCR) mRNA assay, insulin showed the highest expression levels in PIs from newborn and adult pancreas, although these were more than 1000 times lower than in adult islets. Pdx1 mRNA expression was high in PIs from 55-day-old pancreases and was lower at later stages. Consistent with the qRT-PCR results, the insulin content was far lower than reported in adult dog pancreatic islets. However, insulin release by PIs from 1-day-old pups was demonstrated and was stimulated by a high-glucose medium. PIs were transplanted into euglycemic and diabetic SCID mice. In euglycemic animals, the transplant cell composition underwent maturation and transplants were still viable after 6 months. In diabetic mice, the PI transplants produced insulin and partially controlled the hyperglycemia. These data indicate that PIs can be produced ex vivo from canine fetal or postnatal pancreases. Although functional PIs can be obtained, the production yield is most likely insufficient to meet the requirements for diabetic dog transplantation without further innovation in cell culture amplification.

Selective Osmotic Shock for Islet Isolation in the Cadaveric Canine Pancreas

Currently, islet isolation is performed using harsh collagenases that cause nonspecific injury to both islets and exocrine tissue, negatively affecting the outcome of cell transplantation. We evaluated a novel islet isolation protocol utilizing high concentrations of glucose to cause selective osmotic shock (SOS). Islets have a membrane glucose transporter that allows adaptation to changes in glucose concentrations while exocrine tissue can be selectively destroyed by these osmolar shifts. Canine pancreata were obtained within 15 min after euthanasia from animals ( n = 6) euthanized for reasons unrelated to this study. Each pancreas was divided into 4 segments that were randomized to receive 300 mOsm glucose for 20 min (group 1), 600 mOsm for 20 min (group 2), 300 mOsm for 40 min (group 3), or 600 mOsm for 40 min (group 4). Islet yield, purity, and viability were compared between groups. Mean ± standard error of the mean islet yield for groups 1 to 4 was 428 ± 159, 560 ± 257, 878 ± 443, and 990 ± 394 islet equivalents per gram, respectively. Purity ranged from 37% to 45% without the use of density gradient centrifugation and was not significantly different between groups. Islet cell viability was excellent overall (89%) and did not differ between treatment protocol. Islet function was best in groups treated with 300 mOsm of glucose (stimulation index [SI] = 3.3), suggesting that the lower concentration of glucose may be preferred for use in canine islet isolation. SOS provides a widely available means for researchers to isolate canine islets for use in islet transplantation or in studies of canine islet physiology.

Improved yield of canine islet isolation from deceased donors

BACKGROUND

Canine diabetes is a strikingly prevalent and growing disease, and yet the standard treatment of a twice-daily insulin injection is both cumbersome to pet owners and only moderately effective. Islet transplantation has been performed with repeated success in canine research models, but has unfortunately not been made available to companion animals. Standard protocols for islet isolation, developed primarily for human islet transplantation, include beating-heart organ donation, vascular perfusion of preservation solutions, specialized equipment. Unfortunately, these processes are prohibitively complex and expensive for veterinary use. The aim of the study was to develop a simplified approach for isolating canine islets that is compatible with the financial and logistical restrictions inherent to veterinary medicine for the purpose of translating islet transplantation to a clinical treatment for canine diabetes.

RESULTS

Here, we describe simplified strategies for isolating quality islets from deceased canine donors without vascular preservation and with up to 90 min of cold ischemia time. An average of more than 1500 islet equivalents per kg of donor bodyweight was obtained with a purity of 70% (N = 6 animals). Islets were 95% viable and responsive to glucose stimulation for a week. We found that processing only the body and tail of the pancreas increased isolation efficiency without sacrificing islet total yield. Islet yield per gram of tissue increased from 773 to 1868 islet equivalents when the head of the pancreas was discarded (N = 3/group).

CONCLUSIONS

In summary, this study resulted in the development of an efficient and readily accessible method for obtaining viable and functional canine islets from deceased donors. These strategies provide an ethical means for obtaining donor islets.