Biology subjects

Hovhannisyan, A. H.

Publications and source records attributed to Hovhannisyan, A. H..

3 recordsLinked to original sources

bioRxiv2023

Transcriptional Profiles of Non-neuronal and Immune Cells in Mouse Trigeminal Ganglia

Non-neuronal cells constitute 90-95% of sensory ganglia. These cells play critical roles in modulation of nociceptive signal transmissions by sensory neurons. Accordingly, the aim of this review-study was to identify, profile and summarize TG non-neuronal cell types in naive male mice using published and our own data generated by single-cell RNA sequencing (scRNA-seq), flow cytometry (FC) and immunohistochemistry (IHC). TG contains 5 types of non-neuronal cells: glial, fibroblasts, smooth muscle, endothelial and immune cells. There is agreement among publications for glial, fibroblasts, smooth muscle and endothelial cells. Based on gene profiles, glial cells were classified as Schwann cells and satellite glial cells (SGC). Mpz had dominant expression in Schwann cells, and Fabp7 is specific for SCG. Two types of Col1a2+ fibroblasts located throughout TG were distinguished using gene profiles. TG smooth muscle and endothelial cells representing blood vessels were detected with well recognized markers. Our study split reported single TG immune cell group into 3 types of macrophages and 4 types of neutrophils. Macrophages were located among neuronal bodies and nerve fibers, and were sub-grouped by unique transcriptomic profiles and using Ccr2, Cx3cr1 and Iba1 as markers. S100a8+ neutrophils were located in dura surrounding TG and were sub-grouped by clustering and expressions of Csf3r, Ly6G, Ngp, Elane and Mpo. Overall, generated and summarized here dataset on non-neuronal TG cells could provide essential and fundamental information for studies on cell plasticity, interactomic network between neurons and non-neuronal cells and function during variety of pain conditions in the head and neck region.

neuroscience↗

bioRxiv2023

Association of inflammation and tissue damage inducedbiological processes in masseter muscle with the resolution of chronic myalgia

Biological processes linked to intramuscular inflammation during myogenous temporomandibular disorder (TMDM) are largely unknown. We mimicked this inflammation by intra-masseteric muscle (MM) injections of complete Freunds adjuvant (CFA) or collagenase type 2 (Col), which emulates tissue damage. CFA triggered mechanical hypersensitivity at 1d post-injection was mainly linked to processes controlling chemotactic activity of monocytes and neutrophils. At 5d post-CFA, when hypersensitivity was resolved, there was minimal inflammation whereas tissue repair processes were pronounced. Low dose Col (0.2U) also produced acute orofacial hypersensitivity that was linked to tissue repair, but not inflammatory processes. High dose Col (10U) triggered prolonged orofacial hypersensitivity with inflammatory processes dominating at 1d post-injection. At pre-resolution time point (6d), tissue repair processes were underway and a significant increase in pro-inflammatory gene expressions compared to 1d post-injection were detected. RNA-seq and flow cytometry showed that immune processes in MM were linked to accumulation of macrophages, natural killer and natural killer T cells, dendritic cells and T-cells. Altogether, CFA and Col treatments induced different immune processes in MM. Importantly, orofacial hypersensitivity resolution was preceded with repairs of muscle cell and extracellular matrix, an elevation in immune system gene expression and accumulation of distinct immune cells in MM.

neuroscience↗

bioRxiv2023

Sensory innervation of masseter, temporal and lateral pterygoid muscles in common marmosets

Myogenous temporomandibular disorders (TMDM) is associated with an increased responsiveness of nerves innervating the masseter (MM), temporal (TM), medial pterygoid (MPM) and lateral pterygoid muscles (LPM). This study aimed to examine sensory nerve types innervating MM, TM and LPM of adult non-human primate - common marmosets. Sensory nerves are localized in specific regions of these muscles. Pgp9.5, marker for all nerves, and NFH, a marker for A-fibers, showed that masticatory muscles were predominantly innervated with A-fibers. The proportion of C- to A-fibers was highest in LPM, and minimal (6-8%) in MM. All C-fibers (pgp9.5+/NFH-) observed in masticatory muscles were peptidergic (CGRP+) and lacked mrgprD, trpV1 and CHRNA3, a silent nociceptive marker. All fibers in masticatory muscles were labeled with GFAP+, a myelin sheath marker. There were substantially more peptidergic A-fibers (CGRP+/NFH+) in TM and LPM compared to MM. Almost all A-fibers in MM expressed trkC, with some of them having trkB and parvalbumin. In contrast, a lesser number of TM and LPM nerves expressed trkC, and lacked trkB. Tyrosine hydroxylase antibodies, which did not label TG, highlighted sympathetic fibers around blood vessels of the masticatory muscles. Overall, masticatory muscle types of marmosets have distinct and different innervation patterns.

neuroscience↗