Human Neural Stem Cells Ameliorate Autoimmune Encephalomyelitis in Non-human Primates Stefano Pluchino, MD, PhD, 1,2,11,§, * Angela Gritti, PhD, 3,§ Erwin Blezer, PhD, 4 Stefano Amadio, MD, 5 Elena Brambilla, BSc, 1 Giovanna Borsellino, MD, PhD, 6 Chiara Cossetti, BSc, 1,2,7,11 Ubaldo Del Carro, MD, 5 Giancarlo Comi, MD, 2,5 Bert ’t Hart, PhD, 8,9 Angelo Vescovi, PhD, 10,* and Gianvito Martino, MD 1,2,5, * Objective: Transplanted neural stem/precursor cells (NPCs) display peculiar therapeutic plasticity in vivo. Although the replace- ment of cells was first expected as the prime therapeutic mechanism of stem cells in regenerative medicine, it is now clear that transplanted NPCs simultaneously instruct several therapeutic mechanisms, among which replacement of cells might not nec- essarily prevail. A comprehensive understanding of the mechanism(s) by which NPCs exert their therapeutic plasticity is lacking. This study was designed as a preclinical approach to test the feasibility of human NPC transplantation in an outbreed nonhu- man primate experimental autoimmune encephalomyelitis (EAE) model approximating the clinical and complex neuropatho- logical situation of human multiple sclerosis (MS) more closely than EAE in the standard laboratory rodent. Methods: We examined the safety and efficacy of the intravenous (IV) and intrathecal (IT) administration of human NPCs in common marmosets affected by human myelin oligodendrocyte glycoprotein 1-125–induced EAE. Treatment commenced upon the occurrence of detectable brain lesions on a 4.7T spectrometer. Results: EAE marmosets injected IV or IT with NPCs accumulated lower disability and displayed increased survival, as com- pared with sham-treated controls. Transplanted NPCs persisted within the host central nervous system (CNS), but were also found in draining lymph nodes, for up to 3 months after transplantation and exhibited remarkable immune regulatory capacity in vitro. Interpretation: Herein, we provide the first evidence that human CNS stem cells ameliorate EAE in nonhuman primates without overt side effects. Immune regulation (rather than neural differentiation) is suggested as the major putative mechanism by which NPCs ameliorate EAE in vivo. Our findings represent a critical step toward the clinical use of human NPCs in MS. Ann Neurol 2009;66:343–354 Spontaneous neural tissue repair may occur in patients affected by acute and/or chronic inflammatory and de- generative disorders of the nervous system. However, this process is not robust enough to promote a func- tional and stable recovery of the nervous system archi- tecture. 1 Thus, the development of cell-based therapies designed to promote functional (direct vs indirect) neural cell replacement is anticipated . However, most (if not all) of the experimental cell therapies with neu- ral lineage-committed progenitors have failed to foster substantial repair in disease models where the anatom- ical and functional damage is widespread and an in- flamed and/or degenerative microenvironment coex- ists. 2 Conversely, the systemic injection of somatic as well as embryonic stem (ES) cell-derived neural stem/pre- cursor cells (NPCs) has provided a remarkable amelio- ration of the clinicopathological features of rodents with experimental autoimmune encephalomyelitis (EAE), the animal model of multiple sclerosis (MS). 3–5 From the 1 Neuroimmunology Unit, San Raffaele Scientific Insti- tute, Milan, Italy; 2 Institute of Experimental Neurology (InSpe), San Raffaele Scientific Institute, Milan, Italy; 3 Telethon Institute for Gene Therapy (TIGET), San Raffaele Scientific Institute, Milan, Italy; 4 Image Science Institute, University Medical Centre Utrecht, Utrecht, The Netherlands; 5 Department of Neurology and Clinical Neurophysiology, San Raffaele Scientific Institute, Milan, Italy; 6 Neuroimmunology Unit, European Brain Research Institute, Santa Lucia Foundation, via del Fosso di Fiorano, Rome, Italy; 7 Instituto de Cie ˆncias Biomedicas Abel Salazar (ICBAS), Universidade do Porto, Porto, Portugal; 8 Department of Immunobiology, Biomedi- cal Primate Research Center (BPRC), Rijswijk, The Netherlands; 9 Department of Immunology, Erasmus Medical Center, Rotterdam, The Netherlands; 10 Bioscience and Biotechnology Department and Unit of Cancer Stem Cell Biology, StemGen SpA, University of Milan-Bicocca, Milan, Italy; and 11 CNS Repair Unit, San Raffaele Scientific Institute, Milan, Italy. §, authors contributed equally. Address correspondence to Dr Pluchino, via Olgettina 58, Milano 20132, Italy. E-mail: pluchino.stefano@hsr.it; Dr Vescovi. E-mail: vescovi@tin.it; Dr Martino, E-mail: martino.gravito@hsr.it. Potential conflict of interest: Nothing to report. Additional Supporting Information may be found in the online ver- sion of this article. Received Jan 3, 2009, and in revised form Apr 9. Accepted for pub- lication May 1, 2009. Published online in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/ana.21745- © 2009 American Neurological Association 343