HUMAN EMBRYONIC SPINAL-CORD GRAFTS IN ADULT-RAT SPINAL-CORD CAVITIES - SURVIVAL, GROWTH, AND INTERACTIONS WITH THE HOST

The ability of solid pieces of transplanted human embryonic spinal cor d to survive, grow, and integrate with adult rat host spinal cord tiss ue was investigated. Unilateral cavities were surgically created at ve rtebral level T12-T13 in 10 athymic nude rats and 5 regular Sprague-Da wley rats. Seven of the athymic rats acutely received a human spinal c ord graft, while the remaining 8 rats served as controls, with cavitie s alone. After 6 months the morphological outcome was evaluated with c resyl violet and with immunohistochemistry using antibodies toward hum an-specific neurofilament (hNF), human-specific Thy-1 (Thy-1), neurofi lament, glial fibrillary acidic protein, serotonin (5-HT), and tyrosin e hydroxylase (TH). The in situ morphology of the human embryonic spin al cord was also investigated and compared with grafts that were six m onths older. Solid human embryonic spinal cord grafts showed a 100% su rvival rate, grew to fill the volume of the cavity in a noninvasive ma nner, and expressed human specific antigens 6 months postgrafting. Thy -1 immunoreactivity (IR) was demonstrated up to 8 mm rostral to the gr aft suggestive of graft-derived fiber outgrowth. hNF-IR fibers and 5-H T- and TH-IR fibers traversed the graft-host border for a few hundred micrometers, respectively. Finally, our findings suggest that grafted solid pieces of human embryonic spinal cord minimize cystic deformatio ns seen in the adult rat spinal cord with a unilateral cavity. (C) 199 8 Academic Press.