Understanding Neuropathic Pain Mechanisms in the Human Dorsal Root Ganglion with Spatial Transcriptomics and Single-Cell RNA Analysis

Cellular heterogeneity in neuropathic pain mechanisms presents a significant challenge, as it involves diverse cell types within the dorsal root ganglion (DRG) of the peripheral nervous system (PNS). This complexity hinders understanding specific cell roles in pain. At the 2024 PNS Annual Meeting, Dr. Theodore Price, Professor of Neuroscience at the University of Texas at Dallas, focused on leveraging next-generation single-cell RNA sequencing technologies to gain a deeper understanding of neuropathic pain mechanisms in the human DRG. Additionally, he discussed the challenges and breakthroughs in analyzing human tissue transcriptomes, particularly of the dorsal ganglion, sympathetic ganglia, peripheral nerves, and spinal cord. Collaboration with organ procurement organizations and surgeons was essential for obtaining tissues. Dr. Price explained, "How do we understand what is happening in neuropathies? We have developed two ways to do this. One is to work with surgeons who do relatively rare surgeries where we can recover tissues. The other one is to improve our ability to get medical records from organ donors so that we know more about donors' medical history."

His lab developed protocols for sequencing these tissues, leading to the identification of neuron subtypes and the role of G protein-coupled receptors in decoding information. He expressed enthusiasm about the effectiveness of spatial sequencing technology, stating, "Spatial sequencing technology can give you very precise, deeply sequenced transcriptomes with specific areas within the tissue. We figured out how to do single nucleus sequencing from the DRG, where we would get a good representation of the neurons, and the new generation fixation of cells and nuclei kit from 10X Genomics worked really beautifully for this."

Using these advanced technologies, his team has identified 16 subtypes of cells in DRG neurons from deceased individuals who had not experienced pain. Dr. Price stated, "Humans have only peptidergic nociceptors, and each sensory neuron subset seems to have its own kind of peptidergic code." This state-of-the-art analysis has allowed for a clear examination of pain mechanisms. 'We mostly think about trying to preserve axons and regeneration, but there are subsets of sensory neurons that aren't undergoing axonal degeneration. We need to think about how to offer early and aggressive neuroprotection to prevent people from getting into irreversible disease.' Dr. Price highlighted the critical need for early and aggressive neuroprotection to prevent irreversible damage in neuropathic conditions. 

Two anecdotes illustrated the research potential of transcriptomics in studying mechanisms of neuropathy. The first one involved thoracic vertebrectomy, where DRGs removed during surgery revealed sex differences in pain-associated genes, with increased interferon signaling in females. The second anecdote focused on diabetic neuropathic pain, where Nageotte nodules were associated with diabetic neuropathy (DN) and other chronic pain types. Dr. Price's research demonstrated significant shifts in macrophage subsets, neuronal subsets, and adipocyte proliferation in DN DRGs, suggesting the need to reconsider diabetic peripheral neuropathy as a neurodegenerative disease.