Imaging grafted cells with [18F]FHBG using an optimized HSV1-TK mammalian expression vector in a brain injury rodent model

• Published in: PloS one 2017-09, Vol.12 (9), p.e0184630-e0184630
• Main Authors: Salabert, Anne-Sophie, Vaysse, Laurence, Beaurain, Marie, Alonso, Mathieu, Arribarat, Germain, Lotterie, Jean-Albert, Loubinoux, Isabelle, Tafani, Mathieu, Payoux, Pierre
• Format: Article
• Language: English
• Subjects: Animals; Biology and Life Sciences; Blood-brain barrier; Brain; Brain - diagnostic imaging; Brain cancer; Brain damage; Brain Injuries - diagnostic imaging; Brain Injuries - pathology; Brain injury; Calibration; Cell Line; Cell Transplantation; Computed tomography; Correlation analysis; Disease Models, Animal; Feasibility studies; Fluorine Radioisotopes - chemistry; Gene expression; Gene therapy; Genetic Vectors - genetics; Genetic Vectors - metabolism; Grafting; Guanine - analogs & derivatives; Guanine - chemical synthesis; Guanine - metabolism; Head injuries; Herpesvirus 1, Human - genetics; Humans; Image acquisition; In vivo methods and tests; Incubation; Injection; Kinases; Mammals; Medical imaging; Medical innovations; Medicine and Health Sciences; Mice; Neuroimaging; Physical Sciences; Positron emission; Positron emission tomography; Positron Emission Tomography Computed Tomography; Radiopharmaceuticals - chemical synthesis; Radiopharmaceuticals - metabolism; Rats; Rats, Sprague-Dawley; Research and Analysis Methods; Sensitivity analysis; Thymidine; Thymidine kinase; Thymidine Kinase - genetics; Thymidine Kinase - metabolism; TK gene; Tomography; Transplantation; Traumatic brain injury; Ultrasonic imaging
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0184630

Cell transplantation is an innovative therapeutic approach after brain injury to compensate for tissue damage. To have real-time longitudinal monitoring of intracerebrally grafted cells, we explored the feasibility of a molecular imaging approach using thymidine kinase HSV1-TK gene encoding and [18F]FHBG as a reporter probe to image enzyme expression. A stable neuronal cell line expressing HSV1-TK was developed with an optimised mammalian expression vector to ensure long-term transgene expression. After [18F]FHBG incubation under defined parameters, calibration ranges from 1 X 104 to 3 X 106 Neuro2A-TK cells were analysed by gamma counter or by PET-camera. In parallel, grafting with different quantities of [18F]FHBG prelabelled Neuro2A-TK cells was carried out in a rat brain injury model induced by stereotaxic injection of malonate toxin. Image acquisition of the rats was then performed with PET/CT camera to study the [18F]FHBG signal of transplanted cells in vivo. Under the optimised incubation conditions, [18F]FHBG cell uptake rate was around 2.52%. In-vitro calibration range analysis shows a clear linear correlation between the number of cells and the signal intensity. The PET signal emitted into rat brain correlated well with the number of cells injected and the number of surviving grafted cells was recorded via the in-vitro calibration range. PET/CT acquisitions also allowed validation of the stereotaxic injection procedure. Technique sensitivity was evaluated under 5 X 104 grafted cells in vivo. No [18F]FHBG or [18F]metabolite release was observed showing a stable cell uptake even 2 h post-graft. The development of this kind of approach will allow grafting to be controlled and ensure longitudinal follow-up of cell viability and biodistribution after intracerebral injection.