Evidence that satellite cell decrement contributes to preferential decline in nuclear number from large fibres during murine age-related muscle atrophy

Stem cells, ageing and the quest for immortality

Adult stem cells reside in most mammalian tissues, but the extent to which they contribute to normal homeostasis and repair varies widely. There is an overall decline in tissue regenerative potential with age, and the question arises as to whether this is due to the intrinsic ageing of stem cells or, rather, to the impairment of stem-cell function in the aged tissue environment. Unravelling these distinct contributions to the aged phenotype will be critical to the success of any therapeutic application of stem cells in the emerging field of regenerative medicine with respect to tissue injury, degenerative diseases or normal functional declines that accompany ageing.

Satellite-cell pool size does matter: defining the myogenic potency of aging skeletal muscle

The deteriorating in vivo environment is thought to play a major role in reduced stem cell function with age. The capacity of stem cells to support tissue maintenance depends not only on their response to cues from the surrounding niche, but also on their abundance. Here, we investigate satellite cell (myogenic stem cell) pool size and its potential to participate in muscle maintenance through old age. The numbers and performance of mouse satellite cells have been analyzed using molecular markers that exclusively characterize quiescent satellite cells and their progeny as they transit through proliferation, differentiation and generation of reserve cells. The study establishes that abundance of resident satellite cells declines with age in myofibers from both fast- and slow-twitch muscles. Nevertheless, the inherent myogenic potential of satellite cells does not diminish with age. Furthermore, the aging satellite cell niche retains the capacity to support effective myogenesis upon enrichment of the mitogenic milieu with FGF. Altogether, satellite cell abundance, but not myogenic potential, deteriorates with age. This study suggests that the population of satellite cells that participate in myofiber maintenance during routine muscle utilization is not fully replenished throughout life.

Dividing to keep muscle together: the role of satellite cells in aging skeletal muscle

The factors responsible for the atrophy of skeletal muscle with aging remain to be elucidated. Recent evidence points toward an important role for a population of cells located on the surface of skeletal muscle fibers, known as satellite cells, in maintaining the integrity of skeletal myocytes throughout the life span. This Perspective examines the role that these cells are thought to play in aging muscle atrophy, and highlights a recent study by Brack and colleagues that attempts to understand the role of satellite cells in maintaining the ratio of myonuclear number to cytoplasmic volume within myocytes as we age.