Intrathecal delivery of human ESC-derived mesenchymal stem cell spheres promotes recovery of a primate EAE model

Nonhuman primate experimental autoimmune encephalomyelitis (EAE) is a valuable model for multiple sclerosis an inflammatory demyelinating disease in the central nervous system (CNS). Human embryonic stem cell-derived mesenchymal stem cells (EMSC) are effective in treating murine EAE. Yet, it remains unknown whether the EMSC efficacy is translatable to humans. Here we induced a primate EAE model in cynomolgus monkeys and transported EMSC in spheres (EMSCsp) to preserve the cell viability under ambient conditions. First, single cells dissociated from EMSCsp were intravenously infused into normal and EAE monkeys. The cells reached various organs including CNS but diminished rapidly. To increase the number and viability of EMSC in the CNS, we injected EMSCsp intrathecally (i.t.) into the subarachnoid cavity of EAE monkeys multiple times post-onset and upon relapses during a 3-month observation. The clinical symptoms in these animals relieved rapidly following the injections and eventually disappeared. Whereas, symptoms in a vehicle control-injected EAE monkey remained and reduced slowly. Consistently, reduced lesions and active regeneration were found in the CNS of the EMSCsp-treated monkeys compared to the control. EMSC were found in the CNS long after the i.t. injections and some of the cells had differentiated into neurons and oligodendrocytes. Supporting evidence demonstrated that EMSCsp cultured in cerebrospinal fluid from the EAE monkeys largely converted to neural cells with elevated expression of genes for neuronal markers, neurotropic factors, and neuronal myelination. Together, this study suggests that i.t. injection of ambiently transported EMSCsp can treat EAE in nonhuman primates via remyelination and transdifferentiation, which shall expedite the clinical application of EMSC in patients. This study for the first time demonstrates that EMSCsp, following ambient transportation, can be delivered directly via i.t. injection into the subarachnoid cavity of the spinal cord, and promote recovery in a NHP model of EAE. Spheroidal formation and i.t. injection may both enhance the cell number and survival of EMSC in the CNS, compared to peripheral administration of dissociated EMSC. Transdifferentiation of EMSC into neurons and oligodendrocytes as well as neural trophic effects of the transplanted cells may contribute to the efficacy of the cells as schemed in Fig. 7. Ideally more monkeys and EMSC lines could have been used to further verify the conclusions if the costs had not been so high. Nevertheless, the present study has extended our understanding of EMSC efficacy in the EAE models from mice to primates, and shall facilitate the translation of this potential cell therapy to humans.