Satellite cell regulation of muscle mass is altered at old age

• Published in: Journal of applied physiology (1985) 2004-09, Vol.97 (3), p.1082-1090
• Main Authors: Gallegly, Jason C, Turesky, Nicole A, Strotman, Beau A, Gurley, Cathy M, Peterson, Charlotte A, Dupont-Versteegden, Esther E
• Format: Article
• Language: English
• Subjects: Adaptation, Physiological; Aging; Aging - metabolism; Animals; Biological and medical sciences; Cells; Cellulose fibers; Female; Fundamental and applied biological sciences. Psychology; Hindlimb Suspension - adverse effects; Hindlimb Suspension - methods; Muscle, Skeletal - pathology; Muscle, Skeletal - physiopathology; Muscular Atrophy - etiology; Muscular Atrophy - pathology; Muscular Atrophy - physiopathology; Muscular system; Organ Size; Rats; Rats, Inbred F344; Recovery of Function; Satellite Cells, Skeletal Muscle - cytology; Satellite Cells, Skeletal Muscle - metabolism
• ISSN: 8750-7587; 1522-1601
• DOI: 10.1152/japplphysiol.00006.2004

Departments of 1 Geriatrics and 2 Physiology and Biophysics, University of Arkansas for Medical Sciences, and 3 Central Arkansas Veterans Health Care System, Little Rock, Arkansas 72205 Submitted 5 January 2004 ; accepted in final form 27 April 2004 Muscle mass is decreased with advancing age, likely due to altered regulation of muscle fiber size. This study was designed to investigate cellular mechanisms contributing to this process. Analysis of male Fischer 344 X Brown Norway rats at 6, 20, and 32 mo of age demonstrated that, even though significant atrophy had occurred in soleus muscle by old age, myofiber nuclear number did not change, resulting in a decreased myonuclear domain. Also, the number of centrally located nuclei was significantly elevated in soleus muscle of 32-mo-old rats, correlating with an increase in gene expression of MyoD and myogenin. Whereas total 5'-bromo-2'deoxyuridine (BrdU)-positive nuclei were decreased at older ages, BrdU-positive myofiber nuclei were increased. These results suggest that, with age, loss of muscle mass is accompanied by increased myofiber nuclear density that involves fusion of proliferative satellite cells, resembling ongoing regeneration. Interestingly, centrally located myofiber nuclei were not BrdU labeled. Rats were subjected to hindlimb suspension (HS) for 7 or 14 days and intermittent reloading during HS for 1 h each day (IR) to investigate how aging affects the response of soleus muscle to disuse and an atrophy-reducing intervention. After 14 days of HS, soleus muscle size was decreased to a similar extent at all three ages. However, myofiber nuclear number and the total number of BrdU-positive nuclei decreased with HS only in the young rats. IR was associated with an attenuation of atrophy in soleus muscles of 6- and 20- but not 32-mo-old rats. Furthermore, IR was associated with an increase in BrdU-positive myofiber nuclei only in young rats. These data indicate that altered satellite cell function with age contributes to the impaired response of soleus muscle to an intervention that attenuates muscle atrophy in young animals during imposed disuse. muscle atrophy; hindlimb suspension; satellite cells; myonuclear number Address for reprint requests and other correspondence: E. E. Dupont-Versteegden, Dept. of Geriatrics, Univ. of Arkansas for Medical Sciences, 4301 West Markham St. #807, Little Rock, AR 72205 (E-mail: dupontesthere{at}uams.edu ).