The transplanted cells had learn more extensive and ramified processes (

Figures 1C–1F). We estimate that ∼2.7% of transplanted MGE cells survived 1 month after transplantation (1380 ± 478 cells per animal, n = 5). However, given the likelihood that many cells were lost in the course of injection (cells remaining in the injection pipette, cell death in the course of the injection, cells trapped in the pia, etc.), it is likely that the MGE survival rate is significantly underestimated. The majority of the GFP+ cells (∼71%) were located in the deep dorsal horn of the spinal cord (laminae III-V), over ∼2.5 mm of the rostro-caudal lumbar enlargement, all ipsilateral to the injection side. We did not detect any GFP+ cells in the thoracic or cervical spinal cord. Most GFP+ cells colabeled for NeuN, a marker of neurons (89.4% ± 2.7%, Figures 2A–2C), but none for Iba1, a marker of microglia ( Figures 2D–2F), or glial fibrillary acid protein (GFAP), a marker of astrocytes ( Figures 2G–2I), indicating that the vast majority of MGE-derived cells differentiated into neurons. By following the grafted cells from 1 to 5 weeks after transplantation, we conclude that it takes at least 2 weeks

for the MGE-derived cells to acquire a neuronal (NeuN+) phenotype ( Figures 2J–2L). The majority of the GFP+ MGE cells expressed markers of subpopulations of cortical GABAergic interneurons, including GABA (75.1% ± 9.6%, Figures 3A–3C), neuropeptide Y (NPY; 33.4% ± 9.1%, Figures 3D–3F), parvalbumin (PV; 22.2 ± 2.3%, Figures 3G–3I), and somatostatin (40.1% ± 4.1%, Figures 3J–3L). The presence of somatostain (SST)-GFP-positive PF-01367338 ic50 neurons is of particular interest as this

neurochemical phenotype is characteristic of a large percentage (∼40%) of MGE-derived cortical GABAergic interneurons (Alvarez-Dolado et al., 2006). By contrast, GABA does not colocalize with SST in spinal cord interneurons; SST in fact marks a subpopulation of excitatory interneurons (Yasaka et al., 2010). These results provide evidence that the environment of the spinal cord does not alter the differentiation of MGE-derived cells into phenotypes similar to those observed in cortex. Taken together, these results indicate second that MGE transplants are viable in a foreign tissue environment (spinal cord versus cortex) and the majority of grafted cells differentiate into GABAergic neurons, which recapitulate the normal heterogeneity of cortical (but not spinal) GABAergic interneurons. As peripheral nerve injury induces a plethora of changes in the dorsal horn, including a profound activation of potentially phagocytic microglia, we next compared MGE graft survival in uninjured mice and others that underwent partial nerve injury (spared nerve injury, SNI). Survival rate of MGE cells in SNI animals (∼1.3%; 667 ± 267 cells per animal, n = 5) was in fact significantly lower (50% less) than in naive animals.