Caspase-3 is involved in nuclear remodeling of human satellite cells under stress conditions

Satellite cells (SC) proliferation and differentiation play a crucial role in skeletal muscle regeneration after damage and adaptation in response to hypertrophic stimuli. Skeletal muscle ageing affects SC proliferation and differentiation and rely on an enhanced expression of several pro-apoptotic factors. As previous researches demonstrated a modified expression of some genes associated with SC antioxidant and repair activity due to age, in the present project we aimed at assessing the occurrence of apoptotic features in human SCs. Cells were collected from Vastus Lateralis of 9 young (27.3 + 2.0 years old) and 9 old (71.1 + 1.8 years old) subjects and cultured in serum-free medium to be collected at 4-24-48 and 72 h. Apoptosis was investigated with Annexin V/PI staining, terminal deoxynucleotidyl transferase (TdT)-mediated nick-end labelling (TUNEL) technique, flow cytometry analysis of Caspase-8 activity and RT-PCR detection of transcripts of apoptotic genes. Interestingly, CAS9 and FOXO1 genes were found upregulated in aged SCs at all-time points tested. Furthermore, we showed the activation of caspase-3 enzyme after 72 h starvation in culture with a nice co-localization with myogenin and TUNEL-positive micronuclei in the elderly. Interestingly, after treatment for 24 h with a broad pan-caspase inhibitor Cbz-Val-Ala-Asp- fluoromethyl-ketone (z-VAD-fmk) no micronuclei neither myotube formation were revealed, suggesting the involvement of caspase enzymes in the nuclear remodelling occurring during myotube formation.