We previously demonstrated that human neural stem cells (hNSCs) and multipotent neural progenitor cells (hNPCs) grafted into sites of rodent spinal cord injury (SCI) survive, extend axons, form synapses, support host axon regeneration, and improve functional recovery (Lu et al., Cell, 2012; Lu et al., Neuron, 2014; Kadoya et al., Nat Med, 2016). We are translating this approach to non-human primates (Rhesus macaques).
Using the H9 human embryonic stem cell line, we generated neural stem cells using published protocols (Li et al., PNAS, 2011). Adult rhesus macaques underwent C7 lateral hemicontusions (N=2; Salegio et al., J Neurotrauma, 2016) or lateral hemisection lesions (N= 5; Rosenzweig et al., Nat Neuro 2010). H9-derived human NSCs were grafted into the SCI sites between 2 and 12 weeks after injury (2, 4, 6, 6, 8, and 12 wks). Subjects received 20 million GFP-expressing NSCs, suspended in a two-part fibrin matrix and growth factor cocktail (Lu et al., Cell, 2012). Subjects were immunosuppressed with prednisone, mycophenolate, and tacrolimus, and were sacrificed 3 – 21 weeks after grafting (3, 8, 16, 16, 18, 18, and 21 wks).
Five of the seven subjects (including both subjects with hemicontusions) had surviving grafts. All surviving grafts differentiated into both neurons and glia, and extended up to hundreds of thousands of new axons; some of these reached very long distances, up to 50 mm, in the host spinal cord. Graft filling of the lesion site varied, indicating the need for further optimization of the grafting method, immunosuppression protocol, or both.
These findings indicate that human neural stem cells can be grafted to sites of subacute to chronic primate SCI, survive, and extend remarkable numbers of axons over long distances. Grafting can be successfully accomplished in sites of contusive SCI, the most common mechanism of human injury. Further optimization of grafting methods is needed prior to potential human translation, highlighting the importance of utilization of larger animal models for methods development and safety assessments.
*E. S. ROSENZWEIG1, J. H. BROCK1,2, P. LU1,2, J. L. WEBER1, R. MOSEANKO3, S. HAWBECKER3, E. A. SALEGIO3, Y. S. NOUT4, L. A. HAVTON5, A. R. FERGUSON6, M. S. BEATTIE6, J. C. BRESNAHAN6, M. H. TUSZYNSKI1,2;
1Neurosciences, Univ. of California San Diego Dept. of Neurosciences, La Jolla, CA; 2VAMC, La Jolla, CA; 3California Natl. Primate Res. Center, Univ. Calif. Davis, Davis, CA; 4Col. of Vet. Med. and Biomed. Sciences, Colorado State Univ., Fort Collins, CO; 5Neurol., David Geffen Sch. of Medicine, Univ. of California, Los Angeles, Los Angeles, CA; 6Neurosurg., Univ. of California San Francisco, San Francisco, CA
E.S. Rosenzweig: None. J.H. Brock: None. P. Lu: None. J.L. Weber: None. R. Moseanko: None. S. Hawbecker: None. E.A. Salegio: None. Y.S. Nout: None. L.A. Havton: None. A.R. Ferguson: None. M.S. Beattie: None. J.C. Bresnahan: None. M.H. Tuszynski: None.