Regeneration processes in the Pectoralis major muscles of broiler chickens selected for different growth-rates: the importance of vimentin and desmin

Intermediate filament proteins exert a relevant role in maintaining muscle cytoarchitecture. Among them, Desmin (DES) and Vimentin (VIM) have been deeply studied in myopathic and dystrophic muscles and are considered reliable marker of regeneration. In this context, in light of the similarities existing between the growth-related abnormalities affecting broilers Pectoralis major muscles (PMM) (i.e., white striping – WS and wooden breast – WB) and human myopathic disorders, the present study aimed at quantifying VIM and DES proteins in PMM of broiler chickens belonging to a fast- (FG) and a medium-growing (MG) genotype, with the first exhibiting features ascribable to WS and WB whereas the second considered as a control group. For this purpose, a total of 30 PMM were selected along different developmental ages (d) of the birds (i.e., at 28, 35 and 42 d) (5 PMM/genotype/sampling age) and VIM and DES quantified through Western Blot analysis. At each sampling, differences in VIM and DES content between the genotypes were assessed by using the non-parametric Mann-Whitney U test. Immunoblots revealed the presence of two bands: one ascribable to the native proteins (either VIM or DES), whereas the second associated to the development of an omo- or hetero-dimeric form at the Z-disk. At 28 d, a significantly higher (p<.01) VIM content was found in FG if compared to MG with the first exhibiting a 2- and a 3-fold increase in the content of the native and of the dimeric form, respectively. This finding corroborates the hypothesis of intense regenerative processes taking place within the PMM of FG as well as of mild regeneration ascribable to a physiological turnover in MG. On the other hand, no differences were observed in DES. Intriguingly, at 35 d, a remarkably lower (p<.01) VIM content was found in FG, either in the native (-63%) or in its the dimeric form (-65%). This was mirrored by a 2.5- and 5-fold increase (p<.01) in the content of the native and dimeric DES. These findings may be attributed to a progression of the regenerative processes that, at a later stage, require the synthesis of DES, replacing the pre-existing VIM-based network to support the sarcomere architecture. At last, no significant differences in VIM and DES between the genotypes were observed at 42 d. Overall, VIM and DES may be considered reliable markers for monitoring the occurrence and assessing the stage of the regenerative processes taking place in broilers PMM.