Therapeutic Effects of a Non–β Cell Bioartificial Pancreas in Diabetic Mice

Abstract

Background Cell-based insulin therapies can potentially improve glycemic regulation in insulin dependent diabetes patients. Enteroendocrine cells engineered to secrete recombinant insulin have exhibited glycemic efficacy, but have been primarily studied as uncontrollable growth systems in immune incompetent mice. Furthermore, reports suggest that suboptimal insulin secretion remains a barrier to expanded application. Methods Genetic and tissue engineering strategies were applied to improve recombinant insulin secretion from intestinal L-cells on both a per-cell and per-graft basis. Transduction of insulin-expressing GLUTag L-cells with lentivirus carrying an additional human insulin gene enhanced secretion 2-fold. We infected cells with lentivirus expressing a luciferase reporter gene to track cell survival in vivo. To provide a growth-controlled and immune protective environment without affecting secretory capacity, cells were microencapsulated in barium alginate. Approximately 9×107 microencapsulated cells were injected intraperitoneally in immune competent streptozotocin-induced diabetic mice for therapeutic efficacy evaluation. Results Graft insulin secretion was increased to 16–24 mU insulin/day. Transient normoglycemia was achieved in treated mice two days after transplantation, and endogenous insulin was sufficient to sustain body weights of treated mice receiving minimal supplementation. Conclusions Glycemic efficacy of a bioartificial pancreas based on insulin-secreting enteroendocrine cells is insufficient as a standalone therapy, despite enhancement of graft insulin secretion capacity. Supplemental strategies to alleviate secretion limitations should be pursued.

The emerging field of pancreatic tissue engineering: A systematic review and evidence map of scaffold materials and scaffolding techniques for insulin-secreting cells

“…This relies on the basic concept of minimizing distances that limit oxygen and nutrient diffusion while retaining properties that prevent anoikis and immunological host-reactions and has commonly been used for in vivo studies in the reviewed literature. 18,56–59 The importance of diffusion distance for the viability and function of encapsulated ISC was shown experimentally by comparison of glucose-stimulated insulin secretion by free islets, microencapsulated islets in alginate (diameter = 700 µm), and encapsulated islets in larger alginate capsules (diameter = 1800 µm). The smaller microcapsules showed only a slightly delayed and decreased insulin secretion, whereas in the larger capsules the insulin secretion was > 40% decreased and the delay time was increased due to a larger diffusion distance.…”

“…61 The controllable generation of these droplets or the encapsulation of cells in general can be achieved by various techniques such as microfluidic devices (Figure 4(a)), pressure-based air jacket microencapsulation, vibrational jet flow technology, electrostatic droplet generation, or manual syringe-based extrusion into a chemical crosslinking solution (Figure 4(b)). 18,19,56,57,59,62–76 Most droplet-generation methods for cell encapsulation used extrusion-based systems, where a cell-containing hydrogel solution will be extruded through a needle. Depending on the viscosity of the hydrogel, the diameter of the needle, and the flow rate or extrusion pressure, a droplet will be generated.…”

“…Depending on the viscosity of the hydrogel, the diameter of the needle, and the flow rate or extrusion pressure, a droplet will be generated. 56,62,65,77 Once the droplet reaches critical size, it falls into a cross-linking solution or hardening bath. The adjustment of the above-described parameters defines the size and shape of the cell-encapsulating hydrogel.…”

Bioluminescence tracking of alginate micro-encapsulated cell transplants

“…In certain cases, these two measurements may differ. For example, in a recent study in which this BLI system was applied to therapeutic efficacy studies in diabetic mice transplanted with much higher cell numbers, explant BLI on day 17 was comparable to in vitro controls, but Alamar blue was significantly lower in explants relative to in vitro controls (Tiernan et al ., ). This discrepancy allowed the authors to identify hypoxia as a probable cause, since the cells appeared to remain alive but showed significantly lowered metabolic activity and insulin‐secretory function, perhaps due to prolonged exposure to hypoxic conditions.…”

Trichostatin A affects the secretion pathways of beta and intestinal endocrine cells

“…A genetic variant of GLUTag-INS, GLUTag-EINS (EINS), was also generated in our lab by lentiviral transduction of GLUTag-INS with the wild-type human insulin transgene (LV-WT-INS; Emory University; Dr. John Shires) to improve the level of secreted insulin. The development and characterization of this cell line are described in (14). …”