The age-dependent induction of apoptosis-inducing factor (AIF) in the human semitendinosus skeletal muscle

To assess the dependence on age of the expression of apoptosis regulatory proteins in the human semitendinosus muscle, we measured the expression levels of several apoptosis-related genes, including apoptosis-inducing factor (AIF), Bax, Bcl-2, caspase-3 and heat shock protein 70 (HSP70), using RT-PCR, immunohistochemistry and TUNEL assays. We found that the DNA fragmentation was proportional to the age of the tissues sample donors. The expression levels of AIF were significantly elevated (by 10 to 25%) in semitendinosus tissue samples from older individuals, but the Bax, Bcl-2, caspase-3 and HSP 70 levels remained almost constant. This data suggests that the morphological and functional changes observed in aged human semitendinosus muscle correlates with the apoptosis of muscle cells through the induction of AIF.