STUDY DESIGN: The axonal growth potential of dorsal root ganglion (DRG) neurons in an organ culture system was investigated. OBJECTIVE: To examine the effects of neuronal injury and tumor necrosis factor-alpha (TNF-alpha) on the axonal growth potential of 2 types of nociceptive DRG neurons: nerve growth factor (NGF)-sensitive and glial cell line-derived neurotrophic factor (GDNF)-sensitive neurons. SUMMARY OF BACKGROUND DATA: Nerve ingrowth into the disc is recognized to be one of the causes of discogenic pain. Almost all of these disc-innervating neurons are NGF-sensitive. The axonal growth potential of NGF-sensitive neurons has not been investigated. METHODS: Adult Sprague-Dawley rats were used for immunohistochemistry (n = 7) and cell viability studies (n = 6). Bilateral L3-L5 DRGs, which were successfully removed without damage, were noncultured or cultured in serum-free medium containing TNF-alpha at 0, 0.01, 0.1, and 1 ng/mL for 48 hours (n = 5, each treatment). The DRGs were then immunostained for activating transcription factor 3 (ATF3, a marker for injured neurons) or double-stained for growth-associated protein 43 (GAP-43, a marker for axonal growth) with calcitonin gene-related peptide (CGRP, a marker for NGF-sensitive neurons) or isolectin B4 (IB4, a marker for GDNF-sensitive neurons). Cell viability was assessed by a lactate dehydrogenase (LDH) assay and an MTS assay (n = 6, each treatment). RESULTS: Immunoreactive evidence of injured neurons (ATF3 positive) was frequently observed in cultured DRGs, but never in noncultured DRGs. The percentage of neurons exhibiting axonal growth potential (GAP-43 immunoreactive) was significantly higher for NGF-sensitive neurons than for GDNF-sensitive neurons at any concentration of TNF-alpha. More than 95% of the cultured neurons were viable. CONCLUSIONS: The results suggest that the cultured DRG neurons exhibit pathologic changes similar to those found in injured neurons. NGF-sensitive neurons, which include disc-innervating neurons, may have a greater potential to extend their axons in response to neuronal injury under pathologic conditions in the presence of TNF-alpha than GDNF-sensitive neurons.
STUDY DESIGN: The axonal growth potential of dorsal root ganglion (DRG) neurons in an organ culture system was investigated. OBJECTIVE: To examine the effects of neuronal injury and tumor necrosis factor-alpha (TNF-alpha) on the axonal growth potential of 2 types of nociceptive DRG neurons: nerve growth factor (NGF)-sensitive and glial cell line-derived neurotrophic factor (GDNF)-sensitive neurons. SUMMARY OF BACKGROUND DATA: Nerve ingrowth into the disc is recognized to be one of the causes of discogenic pain. Almost all of these disc-innervating neurons are NGF-sensitive. The axonal growth potential of NGF-sensitive neurons has not been investigated. METHODS: Adult Sprague-Dawley rats were used for immunohistochemistry (n = 7) and cell viability studies (n = 6). Bilateral L3-L5 DRGs, which were successfully removed without damage, were noncultured or cultured in serum-free medium containing TNF-alpha at 0, 0.01, 0.1, and 1 ng/mL for 48 hours (n = 5, each treatment). The DRGs were then immunostained for activating transcription factor 3 (ATF3, a marker for injured neurons) or double-stained for growth-associated protein 43 (GAP-43, a marker for axonal growth) with calcitonin gene-related peptide (CGRP, a marker for NGF-sensitive neurons) or isolectin B4 (IB4, a marker for GDNF-sensitive neurons). Cell viability was assessed by a lactate dehydrogenase (LDH) assay and an MTS assay (n = 6, each treatment). RESULTS: Immunoreactive evidence of injured neurons (ATF3 positive) was frequently observed in cultured DRGs, but never in noncultured DRGs. The percentage of neurons exhibiting axonal growth potential (GAP-43 immunoreactive) was significantly higher for NGF-sensitive neurons than for GDNF-sensitive neurons at any concentration of TNF-alpha. More than 95% of the cultured neurons were viable. CONCLUSIONS: The results suggest that the cultured DRG neurons exhibit pathologic changes similar to those found in injured neurons. NGF-sensitive neurons, which include disc-innervating neurons, may have a greater potential to extend their axons in response to neuronal injury under pathologic conditions in the presence of TNF-alpha than GDNF-sensitive neurons.
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Authors: Eve Peeraer; An Van Lutsenborg; An Verheyen; Raf De Jongh; Rony Nuydens; Theo F Meert Journal: J Pain Res Date: 2011-02-14 Impact factor: 3.133