Long ‐term, dynamic synaptic reorganization after GABAergic precursor cell transplantation into adult mouse spinal cord

Abstract Transplanting embryonic precursors of GABAergic neurons from the medial ganglionic eminence (MGE) into adult mouse spinal cord ameliorates mechanical and thermal hypersensitivity in peripheral nerve injury models of neuropathic pain. Although Fos and transneuronal tracing studies strongly suggest that integration of MGE‐derived neurons into host spinal cord circuits underlies recovery of function, the extent to which there is synaptic integration of the transplanted cells has not been established. Here, we used electron microscopic immunocytochemistry to assess directly integration of GFP‐expressing MGE‐derived neuronal precursors into dorsal horn circuitry in intact, adult mice with short‐ (5–6 weeks) or long‐term (4–6 months) transplants. We detected GFP with pre‐embedding avidin–biotin‐peroxidase and GABA with post‐embedding immunogold labeling. At short and long times post‐transplant, we found host‐derived synapses on GFP‐immunoreactive MGE cells bodies and dendrites. The proportion of dendrites with synaptic input increased from 50% to 80% by 6 months. In all mice, MGE‐derived terminals formed synapses with GFP‐negative (host) cell bodies and dendrites and, unexpectedly, with some GFP‐positive (i.e., MGE‐derived) dendrites, possibly reflecting autoapses or cross talk among transplanted neurons. We also observed axoaxonic appositions between MGE and host terminals. Immunogold labeling for GABA confirmed that the transplanted ce...
Source: The Journal of Comparative Neurology - Category: Neurology Authors: Tags: RESEARCH ARTICLE Source Type: research