Transcriptomic and Histological Characterization of Telocytes in the Human Dorsal Root Ganglion

Telocytes are interstitial cells characterized by long processes that span considerable distances within tissues, likely facilitating coordination and interaction with various cell types. Although present in central and peripheral neuronal tissues, their role remains elusive. Dorsal root ganglia (DRG) house pseudounipolar afferent neurons responsible for transmitting signals related to temperature, proprioception, and nociception. This study aimed to investigate the presence and function of telocytes in human DRG by examining their transcriptional profile, anatomical location, and ultrastructure. Combined expression of CD34 and PDGFRA is a marker gene set for telocytes, and our sequencing data revealed CD34 and PDGFRA expressing cells comprise roughly 1.5%-3% of DRG cells. Combined expression of CD34 and PDGFRA is a putative marker gene set for telocytes. Further analysis identified nine subclusters with enriched cluster-specific genes. Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology (GO) pathway analysis suggested vascular, immune, and connective tissue-associated putative telocyte subtypes, mapping over 3000 potential receptor-ligand interactions between sensory neurons and these CD34 and PDGFRA expressing putative telocytes were identified using a ligand-receptors interactome platform. Immunohistochemistry identified CD34+ve telocytes in the endoneural space of DRGs, next to neuron-satellite complexes, in perivascular spaces and in the endoneural space between nerve fiber bundles, consistent with pathway analysis. Transmission electron microscopy (TEM) confirmed their location identifying characteristic elongated nucleus, long and thin telopodes containing vesicles, often surrounded by a basal lamina. This study provides the first gene expression analysis of telocytes in complex human tissue, specifically the DRG, highlighting functional differences based on tissue location while revealing no significant ultrastructural variations.