The use of gene-edited stem cells and in particular patient-derived iPSCs for cell replacement therapy is an appealing approach for genetic correction of a disease-associated gene mutation. If such therapies are pursued in future patients, it would be highly desirable to have non-invasive cell tracking techniques available that can report longitudinally on the distribution and survival of transplanted cells, in order to better understand their fate in vivo and to optimize personalized therapies. We have chosen amyotrophic lateral sclerosis (ALS), a devastating disease with near 100% mortality as an example of a target disease, in which loss of motor neurons is a key event leading to muscle paralysis. For familial forms of ALS, mutations in the gene superoxide dismutase 1 (SOD1) are known to be a causative factor for disease development. In this proposal, we aim to apply two novel experimental imaging modalities (MPI and PSMA-targeted 18F-DCFPyL PET) in conjunction with a clinically emerging technique (1H MRI) to answer several basic questions associated with the efficacy and safety of genome-edited cell therapy. These are complementary techniques, where MPI and PSMA- targeted 18F-DCFPyL PET can report on the whole-body distribution of administered cells, whereas MRI can report on real-time homing and immediate retention of cells. This three-pronged approach of imaging the same cell (labeled with SPIO for MPI and MRI, and 18F-DCFPyL for PET) will be applied for tracking of patient- derived native (39b-SOD1+/AV4) and genome-corrected (39b-SOD1+/+) iPSCs, with and without differentiation into motor neurons, in a transgenic SOD1G37R mouse model of ALS. Intra-arterial injection, an emerging cell delivery route, will be used to study the feasibility of real-time image-guided cell injections aimed at obtaining a more global cerebral cell distribution, while intraparenchymal injection in the spinal cord will be applied as a clinically effective delivery technique to deliver cells locally at the site of impaired motor neurons. If successful, this example imaging application of genome-corrected cells in ALS may encourage the use of MPI, MRI, and/or PMSA-based PET imaging to interrogate the fate of cells in other disease scenarios in vivo.

We aim to test novel and established non-invasive, clinically applicable cell tracking techniques using 18F PET, MPI, and 1H MRI. We will track induced pluripotent stem cells from ALS patients that have been genome- corrected for a gene commonly mutated in ALS. To this end, we will inject these cells in mice with a similar mutation as seen in this patient, and determine the whole-body distribution including the central nervous system after intra-arterial or intra-spinal cord injection.