Serum from human burn victims impairs myogenesis and protein synthesis in primary myoblasts

Abstract

The pathophysiological response to a severe burn injury involves a robust increase in circulating inflammatory/endocrine factors and a hypermetabolic state, both of which contribute to prolonged skeletal muscle atrophy. In order to characterize the role of circulating factors in muscle atrophy following a burn injury, human skeletal muscle satellite cells were grown in culture and differentiated to myoblasts/myotubes in media containing serum from burn patients or healthy, age, and sex-matched controls. While incubation in burn serum did not affect NFκB signaling, cells incubated in burn serum displayed a transient increase in STAT3 phosphorlyation (Tyr705) after 48 h of treatment with burn serum (≈ + 70%; P < 0.01), with these levels returning to normal by 96 h. Muscle cells differentiated in burn serum displayed reduced myogenic fusion signaling (phospho-STAT6 (Tyr641), ≈−75%; ADAM12, ≈-20%; both P < 0.01), and reduced levels of myogenin (≈−75%; P < 0.05). Concomitantly, myotubes differentiated in burn serum demonstrated impaired myogenesis (assessed by number of nuclei/myotube). Incubation in burn serum for 96 h did not increase proteolytic signaling (assessed via caspase-3 and ubiquitin levels), but reduced anabolic signaling [p-p70S6k (Ser421/Thr424), −30%; p-rpS6 (Ser240/244), ≈-50%] and impaired protein synthesis (−24%) (P < 0.05). This resulted in a loss of total protein content (−18%) and reduced cell size (−33%) (P < 0.05). Overall, incubation of human muscle cells in serum from burn patients results in impaired myogenesis and reduced myotube size, indicating that circulating factors may play a significant role in muscle loss and impaired muscle recovery following burn injury.

Ribosome biogenesis may augment resistance training-induced myofiber hypertrophy and is required for myotube growth in vitro

“…Cover slips were mounted with Prolong Gold (Life Technologies, Carlsbad, CA) containing 4=,6-diamidino-2-phenylindole for nuclei labeling, and images were captured at ϫ4 magnification. Myotube size was assessed using Adobe Photoshop CS6 according to previously established procedures (12). A detailed protocol for this analysis is described (2).…”

Impaired regeneration: A role for the muscle microenvironment in cancer cachexia

“…In addition to denervation and disuse, other conditions of atrophy, such as chronic obstructive pulmonary disease (COPD) [87–92], chronic kidney disease [93, 94], burn injury [95, 96], diabetes [97–102], and cancer [103–107], have also been associated with the impairment of muscle regeneration. However, missing from these studies is an understanding of whether the impairment of muscle regeneration is simply a consequence of muscle atrophy, or instead a contributing factor leading to the loss of muscle mass and function.…”

Altered satellite cell dynamics accompany skeletal muscle atrophy during chronic illness, disuse, and aging

“…Findings from Corrick et al . further support that satellite cell terminal differentiation is impaired post-burn (20). When primary human skeletal muscle satellite cells were differentiated to myotubes in vitro and exposed to serum from burn patients, there was a reduction in myogenic fusion signaling and impairment of myogenesis (fewer nuclei per myotube) (20).…”

“…further support that satellite cell terminal differentiation is impaired post-burn (20). When primary human skeletal muscle satellite cells were differentiated to myotubes in vitro and exposed to serum from burn patients, there was a reduction in myogenic fusion signaling and impairment of myogenesis (fewer nuclei per myotube) (20). Diminished myonuclear accrual during differentiation was also associated with reduced myotube size, emphasizing the integral role of satellite cells in the recovery of lean muscle following a burn injury (20).…”

“…When primary human skeletal muscle satellite cells were differentiated to myotubes in vitro and exposed to serum from burn patients, there was a reduction in myogenic fusion signaling and impairment of myogenesis (fewer nuclei per myotube) (20). Diminished myonuclear accrual during differentiation was also associated with reduced myotube size, emphasizing the integral role of satellite cells in the recovery of lean muscle following a burn injury (20). Results from these recent studies highlight the need for a greater understanding of burn-induced dysregulation of satellite cell activity to identify targeted therapies to promote muscle recovery.…”