The process of myogenesis gradually deteriorates as the skeletal muscle ages, contributing to muscle mass loss. The aim of this study is to investigate the effect of senescence/aging on skeletal myogenesis, in vitro. A model of multiple cell divisions of C2C12 myoblasts was used to replicate cell senescence. Control and aged myoblasts were investigated during myogenesis, i.e., at days 0, 2, and 6of differentiation. SA-β-gal activity and comet assay were used as markers of aging and DNA damage. Flow cytometry was performed to characterize potential differences in cell cycle between control and aged cells. Alterations in the mRNA and/or protein expression of myogenic regulatory factors (MRFs), IGF-1 isoforms, apoptotic, atrophy, inflammatory, metabolic and aging-related factors were evaluated. Compared with the control cells, aged myoblasts exhibited G0/G1 cell cycle arrest, DNA damage, increased SA-β-gal activity, and increased expression of aging-related factors p16 and p21 during differentiation. Moreover, aged myoblasts showed a reduction in the expression of MRFs and metabolic/anabolic factors, along with an increased expression of apoptotic, atrophy and inflammatory factors. A diminished differentiation capacity characterized the aged myoblasts which, in combination with the induction of apoptotic and atrophy factors, indicated a disrupted myogenic lineage in the senescent muscle cells.
Background/Aim: Mechanical loading of differentiated myoblasts in vitro may mimic loading patterns of skeletal muscle in vivo. However, it is still uncharacterized the loading conditions that can produce the most effective muscle cells' biological responses, in vitro. This study investigated the effects of different loading protocols on the expression of myogenic regulatory factors, anabolic, atrophy and pro-apoptotic factors in skeletal myotubes. Materials and Methods: C2C12 myoblasts were differentiated and underwent various stretching protocols by altering their elongation, frequency and duration, utilizing an in vitro cell tension system. The loading-induced expression changes of MyoD, Myogenin, MRF4, IGF-1 isoforms, Murf1, Atrogin, Myostatin, Foxo and Fuca were measured by Real Time-PCR. Results: Stretching by 2% elongation at 0.25 Hz for 12 h was overall the most effective in inducing beneficial responses. Conclusion: A low strain, low frequency intermediate duration stretching can most effectively upregulate myogenic/anabolic factors and down-regulate proapoptotic and atrophy genes in myotubes.
Growth hormone (GH) and insulin-like growth factor 1 (IGF-1) have been proposed to play a pivotal role in male infertility due to their anabolic effects. The aim of this study was to investigate possible associations between seminal plasma levels of GH and IGF-1 and sperm parameters. Fifty men participated in this study. Semen analysis was performed, while cell-free seminal plasma was collected following sperm centrifugation. Seminal plasma concentrations of IGF-1 and GH were determined by enzyme-linked immunosorbent assay (ELISA). Due to the presence of asthenozoospermia in all participants who presented with abnormal sperm parameters, the participants were further subdivided into normal (group A), asthenozoospermic (group B) and asthenozoospermic plus at least one additional abnormal parameter (group C). A marginally nonsignificant statistical difference (p = 0.063) was revealed between the GH levels corresponding to the asthenozoospermic and the normal group with the latter presenting with higher GH levels. A statistically significant positive correlation (p < 0.05) was noted between levels of GH and IGF-1 in group C. The above relationship has also been observed in men with low sperm concentration, vitality, volume and abnormal morphology. These novel findings require further investigation in order for the biological significance of those associations to be clarified.
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