Gene expression in medium- and long term-denervated rat tibialis anterior

Traumatic injuries, neurodegenerative diseases or aging may determine skeletal muscle denervation and induce an atrophy-dependent loss of fibers and a number of morphological, biochemical and physiological modifications. Upregulation of mRNAs encoding for myogenic transcriprtional factors and for the protein degradation machineryis well documented after medium-term denervation. We decided to evaluate by Real Time RT-PCR a number of mRNAs from rat skeletal muscles after medium- (2-3 months) or long- (9 months) term denervation, in order to extend the observations reported in literature to a longer time interval, and to include a number of previously undescribed mRNAs. Rat tibialis anterior muscles from the hind limbs were surgically denervated in aseptic conditions. Rats rapidly recovered and were stabulated in standard conditions before sacrifice. The muscles were removed from age-matched control rats and from rats that had undergone denervation. RNA was extracted by Tryzol© and quality controlled, then retrotrascribed and evaluated by Real Time PCR using Sybr Green dye. MCK RNA, a housekeeping gene, was used for standardization purposes. The folllowing mRNAs were evaluated: Myogenin, MyoD, Mrf4, PGC1-a, embryonal Myosin Chain 3 (Myh3), metalloproteinase-2, calsequestrin-2, HSP70, VEGF, VEGF-R2 (KDR). Main results can be summarised as follows: I) all examined mRNAs were found to be upregulated after 2-3 month denervation in respect to controls; ii) the amount of expression widely varied amoing different mRNAs, with muscle-specific transcription factors and Myh3 mRNAs being the higher expressed; for such genes, as well as for HSP70, VEGF and KDR, upragulation was maintained also aftrer long-term denervation. This observation may be of clinical interest in humans, were rehabilitation care is supplied months and even years from denervation.