Age-related changes in muscle fiber types in the human thyroarytenoid muscle: an immunohistochemical and stereological study using confocal laser scanning microscopy.
A decline in motor performance contributes to laryngeal dysfunction in the elderly, but the pathogenetic mechanisms are unknown. Quantitative 3-dimensional, age-related changes in the muscle fiber content of the human thyroarytenoid muscle were estimated from geometric probability (stereology) by use of a technique that provided a statistically unbiased sample of all possible section orientations and locations in the entire muscle volume. There was a preferential 27% age-related loss in the length density (L(V type, muscle)) of type 1 (slow) fibers in contrast to the selective type 2 (fast) fiber loss typical of aging limb muscles. In type 2 fibers there was no significant loss in the L(V), but there was an age-related decrease (P < 0.05) in the surface density (S(V type, muscle)) and an increase (P < 0.05) in the atrophy factor, an index of the content of very small, atrophic fibers. There was also an age-related increase in the length fraction (L(L type, all fibers)) of muscle fibers that coexpress both fast and slow myosin heavy-chain isoforms (P < 0.05). These findings demonstrate a type-specific fiber loss and atrophy that differs from that in aging limb muscles and an age-related increase in motor unit remodeling.
Malmgren
L T
LT
Department of Otolaryngology, SUNY Health Science Center at Syracuse, New York, USA.
Fisher
P J
PJ
Bookman
L M
LM
Uno
T
T
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D005260:Female; D019084:Fluorescent Antibody Technique, Indirect; D006801:Humans; D007821:Laryngeal Muscles / Q000473:pathology*; D008297:Male; D018613:Microscopy, Confocal; D008875:Middle Aged; D018656:Muscle Fibers, Fast-Twitch / Q000473:pathology*; D018657:Muscle Fibers, Slow-Twitch / Q000473:pathology*; D009133:Muscular Atrophy / Q000473:pathology; D018995:Myosin Heavy Chains / Q000032:analysis; D012016:Reference Values
D018995:Myosin Heavy Chains