Role of insulin-like growth factor binding protein-3 (IGFBP-3) in the differentiation of primary human adult skeletal myoblasts

Foulstone, Emily, Savage, Paul B., Crown, Anna L., Holly, Jeff and Stewart, Claire E. (2003) Role of insulin-like growth factor binding protein-3 (IGFBP-3) in the differentiation of primary human adult skeletal myoblasts. Journal of Cellular Physiology, 195 (1). pp. 70-79. ISSN 1097-4652

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Abstract

Although muscle satellite cells were identified almost 40 years ago, little is known about the induction of their proliferation and differentiation in response to physiological/pathological stimuli or to growth factors/cytokines. In order to investigate the role of the insulin-like growth factor (IGF)/IGF binding protein (IGFBP) system in adult human myoblast differentiation we have developed a primary human skeletal muscle cell model. We show that under low serum media (LSM) differentiating conditions, the cells secrete IGF binding proteins-2, -3, -4 and -5. Intact IGFBP-5 was detected at days 1 and 2 but by day 7 in LSM it was removed by proteolysis. IGFBP-4 levels were also decreased at day 7 in the presence of IGF-I, potentially by proteolysis. In contrast, we observed that IGFBP-3 initially decreased on transfer of cells into LSM but then increased with myotube formation. Treatment with 20 ng/ml tumour necrosis factor-alpha (TNF), which inhibits myoblast differentiation, blocked IGFBP-3 production and secretion whereas 30 ng/ml IGF-I, which stimulates myoblast differentiation, increased IGFBP-3 secretion. The TNF-induced decrease in IGFBP-3 production and inhibition of differentiation could not be rescued by addition of IGF-I. LongR3IGF-I, which does not bind to the IGFBPs, had a similar effect on differentiation and IGFBP-3 secretion as IGF-I, both with and without TNF, confirming that increased IGFBP-3 is not purely due to increased stability conferred by binding to IGF-I. Furthermore reduction of IGFBP-3 secretion using antisense oligonucleotides led to an inhibition of differentiation. Taken together these data indicate that IGFBP-3 supports myoblast differentiation.