Intrauterine growth restriction (IUGR) is a leading cause of perinatal morbidity and mortality (Alisi et al., 2011). Skeletal muscle growth is disproportionately reduced in IUGR fetuses and offspring (Padoan et al. 2004; Yates et al. 2014). These individuals present with reduced muscle mass and increased risk for metabolic disorders at all stages of life (Godfrey and Barker, 2000; Yates et al. 2016.). Muscle growth requires proliferation, differentiation, and fusion of myoblasts (muscle stem cells) to form muscle fibers early in gestation and to increase myonuclear content of existing fibers during late gestation and after birth (Yates et al., 2014). These processes can be disrupted by inflammation, which is a potential factor in impaired muscle development in the IUGR fetus (Yates et al., 2012; Cadaret et al., 2017). Tumor necrosis factor-alpha (TNFα) and interleukin 6 (IL-6) are potent multifunctional cytokines involved in inflammatory and noninflammatory skeletal muscle disorders (Tüzün et al., 2006). We recently found that changes in gene expression of these cytokines and muscle sensitivity to them differed between IUGR and control rats (Cadaret et al., 2017), and that maternal inflammation induced fetal leukocyte adaptations, increasing gene expression of TNFα and its receptor TNFR1, but decreasing gene expression of IL-6 receptor. Both cytokines also regulate myoblast proliferation and differentiation outside of inflammatory states (Al-Shanti et al., 2008). These findings indicate TNFα and IL-6 are essential factors in proper growth and development of muscle, and thus, we postulate that expression and sensitivity changes contribute to decreased muscle growth capacity in IUGR fetuses. The objective of this study was to determine the effects of cytokines on fetal myoblast function and to determine if altered responsiveness is intrinsic in IUGR myoblasts, which would represent a potential adaptive mechanism for reduced muscle mass in IUGR offspring
