No abstract

The transcription factor nuclear factor kappa B (NF-κB) is a key regulator of inflammatory processes in reactive glial cells. We utilized a transgenic mouse model (GFAP-IκBα-dn) where the classical NF-κB pathway is inactivated by overexpression of a dominant negative (dn) form of the inhibitor of kappa B (IκBα) in glial fibrillary acidic protein (GFAP) expressing cells, which include astrocytes, Schwann cells, and satellite cells of the dorsal root ganglion (DRG) and sought to determine whether glial NF-κB inhibition leads to a reduction in pain behavior and inflammation following chronic constriction injury (CCI) of the sciatic nerve. As expected, following CCI nuclear translocation, and hence activation, of NF-κB was detected only in the in the sciatic nerve of wild type (WT) mice, and not in GFAP-IκBα-dn mice, while upregulation of GFAP was observed in the in sciatic nerve and DRGs of both WT and GFAP-IκBα-dn mice, indicative of glial activation. Following CCI, mechanical and thermal hyperalgesia were reduced in GFAP-IκBα-dn mice compared to WT, as well as gene and protein expression of CCL2, CCR2 and CXCL10 in the sciatic nerve. Additionally, gene expression of TNF, CCL2, and CCR2 was reduced in the DRGs of transgenic mice compared to WT after CCI. We can therefore conclude that transgenic inhibition of NF-κB in GFAP expressing glial cells attenuated pain and inflammation after peripheral nerve injury. These findings suggest that targeting the inflammatory response in Schwann cells and satellite cells may be important in treating neuropathic pain.

The use of human umbilical cord blood (hUCB)--a rich source of nonembryonic or adult stem cells--has recently been reported to ameliorate behavioral consequences of stroke. In this study, we tested whether human cord blood leukocytes also ameliorate behavioral impairments of spinal cord injury. Rats were divided into five groups: (1) laminectomy (without spinal cord injury) only; (2) laminectomy + cord blood infusion; (3) spinal cord injury + cord blood infused 1 day post injury; (4) spinal cord injury + cord blood infused 5 days post injury; and (5) spinal cord injury only. Spinal cord injury was induced by compressing the spinal cord for 1 min with an aneurysm clip calibrated to a closing pressure of 55 g. Open-field behavior was assessed 1, 2, and 3 weeks after intravenous injection of prelabeled human cord blood cells. Open-field test scores of spinal cord injured rats treated with human cord blood at 5 days were significantly improved as compared to scores of rats similarly injured but treated at day 1 as well as the otherwise untreated injured group. The results suggest that cord blood stem cells are beneficial in reversing the behavioral effects of spinal cord injury, even when infused 5 days after injury. Human cord blood-derived cells were observed in injured areas, but not in noninjured areas, of rat spinal cords, and were never seen in corresponding areas of spinal cord of noninjured animals. The results are consistent with the hypothesis that cord blood-derived stem cells migrate to and participate in the healing of neurological defects caused by traumatic assault.