Lumbar transplants of immortalized serotonergic neurons alleviate chronic neuropathic pain

Abstract

The RN46A cell line was derived from embryonic day 13 rat medullary raphe cells by infection with a retrovirus encoding the temperature-sensitive mutant of SV40 large T antigen. This cell line is neuronally restricted and constitutively differentiates following a shift to non-permissive temperature. Brain-derived neurotrophic factor (BDNF) induced the serotonergic phenotype and increased the survival of RN46A cells in vitro. After transfection of the rat BDNF gene into RN46A cells, an autocrine BDNF-secreting cell line, 46A-B14, was isolated and transplanted into the rat CNS. Transplanted 46A-B14 cells had increased survival and enhanced serotonin (5HT) synthesis compared to 46A-V1 cells, RN46A cells transfected with vector-alone. When 46A-B14 cells were transplanted in the lumbar subarachnoid space of the spinal cord 1 week after a chronic constriction injury (CCI) of the sciatic nerve, they survived longer than 6 weeks on the pia mater. Furthermore, the tactile and cold allodynia and thermal hyperalgesia induced by CCI was significantly reduced during a 4-6- week period. The maximal effect occurred 1 week after transplantation. 46A-V1 cells, transplanted after CCI, did not survive beyond 2-3 weeks and had no effect on the allodynia and hyperalgesia induced by CCI. Acute intrathecal injection of the 5HT receptor antagonist methysergide decreased the antinociceptive effects of the 46A-B14 cells to pre-transplant levels. These data suggest that a chronically applied, low local dose of serotonin near the dorsal horn was able to reverse the development of chronic neuropathic pain following CCI. The use of neural cell lines that are able to deliver inhibitory neurotransmitters such as serotonin, in a model of chronic pain offers a novel approach to pain management.

Minocycline‐induced reduction of brain‐derived neurotrophic factor expression in relation to cancer‐induced bone pain in rats

“…Compelling evidence has demonstrated that the overexpression of BDNF is essential for development of neuropathic pain and inflammatory pain (Siuciak et al, 1994(Siuciak et al, , 1995Eaton et al, 1997;Thompson et al, 1999;Kerr et al, 1999;Mannion et al, 1999;Cejas et al, 2000;Deng et al, 2000;Ramer et al, 2000;Obata et al, 2003;Coull et al, 2005;Hayashida et al, 2008;Miletic and Miletic, 2008;Trang et al, 2009;Yang et al, 2009;Zhou et al, 2009;Geng et al, 2010;Valdes-Sanchez et al, 2010). We also show that i.t.…”

Amelioration of chronic neuropathic pain after partial nerve injury by adeno-associated viral (AAV) vector-mediated over-expression of BDNF in the rat spinal cord

“…BDNF has also been demonstrated to increase 5HT synthesis in raphe neurons in vitro by increasing expression of tryptophan hydroxylase (TPH; the rate-limiting enzyme for 5HT synthesis). 52 Lumbar subarachnoid grafts of cells that synthesized both BDNF and 5HT were able to reverse chronic neuropathic pain after CCI, 53 and neuropathic pain after dorsal hemisection injury of the spinal cord. 54,55 Serotonergic inhibition of primary afferents, 56 individual spinal neurons, 57 as well as the presence of ascending serotonergic sensory pathways, 58 suggest that changes in the serotonergic systems might facilitate or inhibit the development of chronic pain after PNS and CNS injury.…”

“…The ability to alter BDNF levels with chronic delivery of exogenous neurotrophic factors, such as BDNF to the CNS, is problematic as they will not cross the blood-brain barrier and must be directly injected or chronically infused. Chronic delivery of BDNF 69 and 5HT 53,54 from subdurally grafted bioengineered neuronal cells, functioning as cellular minipumps, resulted in an attenuation of the altered sensory behaviors in neuropathic pain. These findings suggest that a chronic source of BDNF alone might directly affect the reversal of those behaviors after partial nerve injury.…”

Sustained Morphine Administration Induces TRPM8-Dependent Cold Hyperalgesia

“…In fact, animals could be left 20 min on the plate with no signs of injury. 29 To further ensure that this protocol did not cause tissue injury, immediately after 5 min on the 5°C plate we assessed the surface temperature of the hind paws with an infrared thermometer (Fisher Scientific™ Traceable™ Noncontact Infrared Thermometers) in rats (n = 9) and mice (n = 6).…”