Bioluminescence tracking of alginate micro-encapsulated cell transplants

Abstract

Cell-based therapies to treat loss-of-function hormonal disorders such as diabetes and Parkinson's disease are routinely coupled with encapsulation strategies, but an understanding of when and why grafts fail in vivo is lacking. Consequently, investigators cannot clearly define the key factors that influence graft success. Although bioluminescence is a popular method to track the survival of free cells transplanted in preclinical models, little is known of the ability to use bioluminescence for real-time tracking of microencapsulated cells. Furthermore, the impact that dynamic imaging distances may have, due to freely-floating microcapsules in vivo, on cell survival monitoring is unknown. This work addresses these questions by applying bioluminescence to a pancreatic substitute based on microencapsulated cells. Recombinant insulin-secreting cells were transduced with a luciferase lentivirus and microencapsulated in Ba crosslinked alginate for in vitro and in vivo studies. In vitro quantitative bioluminescence monitoring was possible and viable microencapsulated cells were followed in real time under both normoxic and anoxic conditions. Although in vivo dispersion of freely-floating microcapsules in the peritoneal cavity limited the analysis to a qualitative bioluminescence evaluation, signals consistently four orders of magnitude above background were clear indicators of temporal cell survival. Strong agreement between in vivo and in vitro cell proliferation over time was discovered by making direct bioluminescence comparisons between explanted microcapsules and parallel in vitro cultures. Broader application of this bioluminescence approach to retrievable transplants, in supplement to currently used end-point physiological tests, could improve understanding and accelerate development of cell-based therapies for critical clinical applications. Copyright © 2014 John Wiley & Sons, Ltd.

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

“…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.…”

“…Scaffold size, mechanical stability, and diffusion distances affect the choice further. Among the in vivo studies included (n = 91) the ISC/scaffold construct was transplanted into subcutaneous locations (n = 31), 27,51,69,92–94,112,115,120,133,135,145,147,156,157,171,212–225 the peritoneal cavity (n = 19), 18,26,56,63,65–68,101,134,135,173,195,226–232 an omental pouch (n = 14), 57,59,81,118,119,163,174,225,233–238 the renal capsule (n = 18), 54,…”

“…18,56,62,65,73,77 The vibrating nozzle cuts the droplets into smaller pieces of uniform size. 73,77 Standard scaffold materials that can be applied for these manufacturing methods are alginate, 18,19,56,57,59,62,63,65,66,68,69,[72][73][74][75]78,79 PEG, 67 or PEGDA, 76 usually in combination with permselective poly-l-lysine and/or poly-l-ornithine to introduce positive charges on the hydrogel surface for potential further modifications, to influence the permeability for nutrients into the microcapsule, and to reinforce the mechanical durability of the microcapsules. 62,67 ECM components and growth factors are easy to include in such a microcapsule system.…”

“…Scaffold size, mechanical stability, and diffusion distances affect the choice further. Among the in vivo studies included (n = 91) the ISC/scaffold construct was transplanted into subcutaneous locations (n = 31), 27,51,69,[92][93][94]112,115,120,133,135,145,147,156,157,171,[212][213][214][215][216][217][218][219][220][221][222][223][224][225] the peritoneal cavity (n = 19), 18,26,56,63,[65][66][67][68]101,134,135,173,195,[226][227][228][229][230][231]…”

Critical Considerations in Bioluminescence Imaging of Transplanted Islets

“…In most in vivo studies, luciferin solution is administered IP or IV. Administration via IP is technically easier than IV, especially in small animals 69 . However, there is variability in the dynamics of the emitted bioluminescence among individual animals, presumably because of the inconsistent time required for the absorption of luciferin from the intraperitoneal space into the systemic circulation.…”