Engraftment of serotonergic precursors enhances locomotor function and attenuates chronic central pain behavior following spinal hemisection injury in the rat.

Spinal cord injury (SCI) results in abnormal locomotor and pain syndromes in humans. T13 spinal hemisection in the rat results in development of permanent mechanical allodynia and thermal hyperalgesia partially due to interruption of descending inhibitory modulators such as serotonin (5-HT). We hypothesize that lumbar transplantation of nonmitotic cells that tonically secrete antinociceptive and trophic compounds will reduce the pain-like behavior and enhance locomotor recovery after SCI. We used RN46A-B14 cells, a conditionally immortalized (SV40tsTag) rat neuronal cell line derived from E13 raphe bioengineered to secrete both 5-HT and BDNF in vitro at both permissive (33 degrees C) and nonpermissive (39 degrees C) temperatures. Three groups (n = 72) of 30-day-old male Sprague-Dawley rats were spinally hemisected at T13 and allowed 4 weeks for adequate recovery of locomotor function and development of allodynia and hyperalgesia. Immunosuppressed animals received either lumbar RN46A-B14 (n = 24) or control RN46A-V1 (n = 24) empty-vector transplants or no cell (n = 24) transplant. HPLC analysis of media and CSF demonstrated increases of both in vitro and in vivo 5-HT levels at 28 days in RN46A-B14 animals. ELISA demonstrated BDNF secretion in vitro and in vivo by RNA46A-B14 cells. Locomotor function (BBB scale) and nociceptive behaviors measured by paw withdrawals to von Frey filaments, radiant heat, and noxious pin stimuli were tested for 4 weeks posttransplant. Animals receiving RN46A-B14 cells demonstrated significantly improved locomotor function and reductions in both fore- and hindlimb mechanical allodynia and thermal hyperalgesia compared to controls receiving RN46A-V1 or no transplants. These effects were modulated by the 5-HT antagonist methysergide and reuptake inhibitor fluvoxamine. Bromodeoxyuridine and 5-HT immunoreactivity confirmed cell survival and graft location 4 weeks posttransplantation. These results support the therapeutic potential of bioengineered serotonin-secreting cell lines in reducing chronic central pain following spinal cord injury. Copyright 2001 Academic Press.