Regolazione genica durante le prime fasi dopo la lesione del nervo periferico in modelli animali anziani ​

As a consequence of nerve damage, which is typically secondary to sudden stretch of a limb, laceration, compression, or ischemia, the body activates a response in order to restore the physiological condition: in particular, after an axonal injury, a degeneration of the axon trunk distal to the injured site occurs in a well-regulated, self-destructive process, called Wallerian degeneration. This process, together with other body functions, is affected by aging: indeed, many differences, concerning morphologic features of the peripheral nervous system, but also gene expression modulation, have been found to be altered in aged individuals. This research aims at evaluating the different expression levels of defined genes in rats immediately after nerve injury, emphasizing the comparison between old and young subjects. Specifically, we focused our attention on the expression, at short time points after injury (3, 6 and 24 hours), of genes involved in the degeneration and regeneration processes, also known as regeneration associated genes (RAGs). In order to evaluate gene expression levels, we firstly focused our attention on RNA expression quantification, by means of qRT-PCR. We reported a relative stronger upregulation in young rats compared to old ones of the transcription factors Krox20, c-Jun, Atf-3; the factor promoting Schwann cell dedifferentiation and survival Nrg1 type I-II, Nrg1-α, Nrg1-β, the proangiogenic factor Vegf and the receptor p75; in old rats the macrophage marker Iba1 was found to be upregulated. While many genes were differentially expressed between young and old rats, some showed no differences related to the age, in particular we reported a downregulation for ErbB3 and nNos, characterized by the same magnitude when comparing old and young rats relative to their healthy nerves. Additionally, we also performed western blot assay to evaluate the protein expression level. In conclusion, our results show that several genes, known to be strongly upregulated immediately after injury, are regulated both in young and in old rats, but this upregulation (relatively to the young and old healthy nerves), for several genes, is higher in young than in old individuals. This could be explained by a higher basal expression of these genes in old nerve cells, due to a basal inflammatory state, that partially masks the upregulation induced by nerve injury, or it could be explained by a reduced efficiency of old nerve cells to express regeneration associated genes; further studies are necessary to address these points. In particular, a higher number of samples will be necessary to increase the statistical power of these experiments.