Jennifer Mecklenburg, Sergey A Shein, Mostafa Malmir, Anahit H Hovhannisyan, Korri Weldon, Yi Zou, Zhao Lai, Yu-Fang Jin, Shivani Ruparel, Alexei V Tumanov, Armen N Akopian
Non-neuronal cells constitute 90%-95% of sensory ganglia. These cells, especially glial and immune cells, play critical roles in the modulation of sensory neurons. This study aimed to identify, profile, and summarize the types of trigeminal ganglion (TG) non-neuronal cells in naïve male mice using published and our own data generated by single-cell RNA sequencing, flow cytometry, and immunohistochemistry. TG has five types of non-neuronal cells, namely, glial, fibroblasts, smooth muscle, endothelial, and immune cells. There is an agreement among publications for glial, fibroblasts, smooth muscle, and endothelial cells. Based on gene profiles, glial cells were classified as myelinated and non-myelinated Schwann cells and satellite glial cells. has dominant expression in Schwann cells, and is specific for SCG. Two types of Col1a2 fibroblasts located throughout TG were distinguished. TG smooth muscle and endothelial cells in the blood vessels were detected using well-defined markers. Our study reported three types of macrophages (Mph) and four types of neutrophils (Neu) in TG. Mph were located in the neuronal bodies and nerve fibers and were sub-grouped by unique transcriptomic profiles with , , and as markers. A comparison of databases showed that type 1 Mph is similar to choroid plexus-low (CP) border-associated Mph (BAMs). Type 2 Mph has the highest prediction score with CP BAMs, while type 3 Mph is distinct. S100a8 Neu were located in the dura surrounding TG and were sub-grouped by clustering and expressions of , , , , and . Integrative analysis of published datasets indicated that Neu-1, Neu-2, and Neu-3 are similar to the brain Neu-1 group, while Neu-4 has a resemblance to the monocyte-derived cells. Overall, the generated and summarized datasets on non-neuronal TG cells showed a unique composition of myeloid cell types in TG and could provide essential and fundamental information for studies on cell plasticity, interactomic networks between neurons and non-neuronal cells, and function during a variety of pain conditions in the head and neck regions.
