Macrophage density in pharyngeal and laryngeal muscles greatly exceeds that in other striated muscles: an immunohistochemical study using elderly human cadavers

Abstract

Macrophages play an important role in aging-related muscle atrophy (i.e., sarcopenia). We examined macrophage density in six striated muscles (cricopharyngeus muscle, posterior cricoarytenoideus muscle, genioglossus muscle, masseter muscle, infraspinatus muscle, and external anal sphincter). We examined 14 donated male cadavers and utilized CD68 immunohistochemistry to clarify macrophage density in muscles. The numbers of macrophages per striated muscle fiber in the larynx and pharynx (0.34 and 0.31) were 5–6 times greater than those in the tongue, shoulder, and anus (0.05–0.07) with high statistical significance. Thick muscle fibers over 80 µm in diameter were seen in the pharynx, larynx, and anal sphincter of two limited specimens. Conversely, in the other sites or specimens, muscle fibers were thinner than 50 µm. We did not find any multinuclear muscle cells suggestive of regeneration. At the beginning of the study, we suspected that mucosal macrophages might have invaded into the muscle layer of the larynx and pharynx, but we found no evidence of inflammation in the mucosa. Likewise, the internal anal sphincter (a smooth muscle layer near the mucosa) usually contained fewer macrophages than the external sphincter. The present result suggest that, in elderly men, thinning and death of striated muscle fibers occur more frequently in the larynx and pharynx than in other parts of the body.

Fibroadipogenic Progenitors Regulate the Basal Proliferation of Satellite Cells and Homeostasis of Pharyngeal Muscles via HGF Secretion

“…In addition to results obtained from mice, we confirmed an increased HGF , PDGFRa , and PLAT transcript levels and CD90 + FAPs in human CP muscles. The increased HGF levels in CP is consistent with a previous report examining several craniofacial muscles, including CP muscles from 14 cadavers ( Rhee et al, 2016 ). These data indicate the translational potential of our data generated in mice.…”

Sarcopenia and dysphagia: Position paper by four professional organizations

“…A study of older human cadavers showed that the macrophage density in the pharyngeal and laryngeal muscles was five‐ to sixfold greater than that for the striated muscles of the tongue, shoulder and anus. Whereas the potential thinning and death of striated muscle fibers have been speculated to occur at greater rates in the pharyngeal and laryngeal muscles, macrophage migration is suspected to have possible protective effects on aging in these muscles through the actions of macrophage‐related cytokines …”

“…Whereas the potential thinning and death of striated muscle fibers have been speculated to occur at greater rates in the pharyngeal and laryngeal muscles, macrophage migration is suspected to have possible protective effects on aging in these muscles through the actions of macrophagerelated cytokines. 29 When dealing with sarcopenia of the swallowing-related muscles, careful and cautious discussion is critical; the embryological origin of the muscles and the characteristics of the special visceral muscles should be taken into consideration.…”

Oblique thyroarytenoid muscle in humans: An independent muscle or an accessory belly?

“…Glottal closure in the elderly can be mostly incomplete due to atrophic changes of the TA muscle with aging, especially in men . Atrophy of the vocal cords in the elderly results from the scarcity of elastic fibers and hyaluronic acid, and combined with atrophy of the vocal cord muscles could affect phonation . A cross‐innervation pattern to the TA muscle via the external branch of the superior laryngeal nerve and the classical recurrent laryngeal nerve further increases the challenge of understanding and treating dysfunction of the TA muscle .…”