(206) Differential Transcriptome Analysis of Acutely Dissected and Cultured Human and Mouse Dorsal Root Ganglion

Abstract

Dorsal root ganglion (DRG) neurons detect sensory inputs and are crucial for pain processing. They are often studied under cultured conditions with the assumption that they model in vivo conditions. However, to our knowledge, no study has ever directly compared genome-wide transcriptomes of DRG tissue in vivo versus in vitro. We extracted lumbar DRG from C57BL6/J mice (Price and Gereau) and human organ donors (Gereau), and acutely froze one side and cultured the other. RNA was extracted and then sequenced using the NextSeq Illumina platform. Comparing native to cultured human DRG, we found that the overall expression level of many ion channels and GPCRs specifically expressed in neurons is markedly lower in culture, but still expressed at appreciable levels. This suggests that most pharmacological targets expressed in vivo are conserved in culture conditions; however, there were exceptions, such as the HTR1D gene encoding the 5-HT1D receptor which was completely shut off in DRG cultures. The reduced expression for neuronal genes in human DRG cultures was largely accounted for by increased expression of fibroblast genes, consistent with the mitotic status of these cells. We did find a subset of neuronal genes upregulated in human DRG cultures, including genes associated with nerve injury and/or inflammation in preclinical models such as BDNF, MMP9, GAL and ATF3. We also found a striking upregulation of a number of inflammation-associated genes including CXCL1, CCL7, IL6 and LIF in human DRG cultures suggesting a cellular environment conducive to studying inflammatory and/or neuropathic pain on human DRG neurons from organ donors without a history of a specific chronic pain disorder. Analysis of changes in mouse transcriptomes are being analyzed and will be presented to compare to human DRG findings, as well as between experimental sites. Funding: NIH grants T32DA007261 (LM); NS065926 and NS102161 (TJP); NS106953 and NS042595 (RWG).