Comparative proteomic profile of rat sciatic nerve and gastrocnemius muscle tissues in ageing by 2-D DIGE

Ageing induces a progressive morphological change and functional decline in muscles and in nerves. Light and electron microscopy, 2-D DIGE and mass spectrometry were applied to profile the qualitative and quantitative differences in the proteome and morphology of rat gastocnemius muscle and sciatic nerve, in healthy 22-month-old rats. At muscle level, morphological changes are associated to fiber atrophy accompanied by myofibrillar loss and degeneration, disappearance of sarcomeres and sarcoplasmic reticulum dilatation, internal migration of nuclei, longitudinal fiber splitting, increment of subsarcolemmal mitochondria aggregates and increment of lipofuscin granules. Sciatic nerve shows myelin abnormalities like enfoldings, invaginations, onion bulbs, breakdowns and side axonal atrophy. Proteomic analysis identified changes correlated to morphological abnormalities in metabolic, contractile and cytoskeletal proteins, deregulation of iron homeostasis, change of Ca2+ balance and stress response proteins, accompanied by a deregulation of myelin membrane adhesion proteins and proteins regulating the neuronal caliber. By comparing proteomic results from the two tissues, 16 protein isoforms showed the same up and down regulation trend suggesting that there are changes implying a general process which may act as signal event of degeneration. Only β enolase and tropomyosin 1α were differentially expressed in the tissues.