Improvement of the monitoring and biosafety of encapsulated cells using the SFGNESTGL triple reporter system

Abstract

Cell microencapsulation may represent a breakthrough to overcome problems associated with cell therapy. Advances in material biocompatibility and production protocols have put this field close to its clinical application. However, issues such as the possibility of tracking cell-containing microcapsules, monitoring cell viability, and discontinuation of the therapeutic activity when necessary, still remain unsolved. We demonstrate here simultaneous monitoring and pharmacological control of myoblasts-containing alginate microcapsules, injected in immunocompetent mice after transduction with the SFGNESTGL triple reporter retroviral vector, which contains green fluorescence protein (GFP), firefly luciferase and herpes simplex virus type 1 thymidine-kinase (HSV1-TK). Naked (as controls) or microencapsulated cells were subcutaneously injected in C57BL/6J mice and followed up by luminometry. Signal for naked cells disappeared 2 weeks after cell injection, whereas signal for microencapsulated cells remained strong for 8 months, thus demonstrating the presence of living cells. Treatment of mice with the thymidine-kinase substrate ganciclovir caused death of microencapsulated myoblasts, as seen by a drastic decay in the light emission and histological analysis. Hence, we conclude that incorporation of the SFGNESTGL vector into microencapsulated cells represents an accurate tool for controlling cell location and viability in a non-invasive way. Moreover, cell death can be induced by administration of ganciclovir, in case therapy needs to be interrupted. This system may represent a step forward in the control and biosafety of cell- and gene- therapy-based microencapsulation protocols.