Lumbar transplant of neurons genetically modified to secrete galanin reverse pain-like behaviors after partial sciatic nerve injury

The use of cell lines as biologic "minipumps" to chronically deliver antino ciceptive molecules such as the peptide galanin near the pain processing ce nters of the spinal cord after nerve injury is a newly developing technolog y for the treatment of neuropathic pain. The neuronal rat cell line, RN33B, derived from E13 brainstem raphe and immortalized with the SV40 temperatur e-sensitive allele of large T antigen (tsTag), was transfected with rat pre progalanin (GAL) cDNA and the galanin-synthesizing and -secreting cell line , 33GAL.19, was isolated [1]. The 33GAL.19 cells transfected with the GAL g ene expressed immunoreactivity (ir) for the GAL protein and synthesized low levels of GAL-ir at permissive temperature (33 degrees C), when the cells were proliferating, and increased GAL-ir during terminal differentiation at non-permissive temperature (39 degrees C) in vitro. A control cell line: 3 3V.1, RN33B cells transfected with the pCEP4 vector alone and similarly iso lated by subcloning, contained no detectible GAL-ir at either temperature i n vitro. These cell lines were used as grafts in a model of chronic neuropa thic pain induced by unilateral chronic constriction injury (CCI) of the sc iatic nerve. Pain-related behaviors, including cold and tactile allodynia a nd thermal and mechanical hyperalgesia, were evaluated in the affected hind paw after CCI and transplants. The 33GAL.19 and 33V.1 cells transplanted in the lumbar subarachnoid space near the spinal cord one week after CCI, sur vived at least seven weeks on the pial surface around the spinal cord and o nly the 33GAL.19 cells expressed GAL-ir in vivo after transplant. Furthermo re, the tactile and cold allodynia and tactile and thermal hyperalgesia ind uced by CCI was significantly reduced or eliminated during the two to seven week period after grafts of 33GAL.19 cells. The maximal effect on chronic pain behaviors with the GAL grafts occurred one to three weeks after transp lantation. Transplants of 33V.1 control cells had no effect on the allodyni a and hyperalgesia induced by CCI, These data suggest that a chronically ap plied, low local dose of galanin supplied by transplanted cells near the lu mbar spinal dorsal horn was able to reverse the development of chronic neur opathic pain following CCI, The use of transplants of genetically modified neural cell lines that are able to deliver antinociceptive molecules, such as galanin, offers a safe and novel approach to pain management.