Gene expression analysis of Collagen type III coding gene in chicken breast muscles affected by wooden breast condition

Fibrillar collagen proteins composing the extracellular matrix (ECM) of chicken skeletal muscles exert pivotal roles in providing functional and structural support for muscle fibers. Among them, collagen type III is known to be predominantly expressed during the embryonic stage of muscle development, as well as in cellular response to muscle injury and inflammation. In the past few years, alterations in the ECM composition, especially referring to the collagen components, have been associated with the occurrence and progression of wooden breast (WB), a quality defect affecting the Pectoralis major muscle (PM) of broilers selected for rapid growth-rate and high breast-yield. The present study was aimed at assessing the level of expression of the Collagen type III alpha 1 chain (COL3A1) gene, encoding the homonymous protein, in PMs affected (WB) and not affected (NORM) by the WB defect, to address its potential involvement in the occurrence of this condition. To this purpose, ten PMs (n=5/group) from fast-growing broilers (45d-old; 3.0 kg of live weight) were collected 3h post-mortem and stored at -80°C until the PMs were used to perform Quantitative Real-Time PCR of COL3A1 mRNA using GAPDH as normalizing gene. After testing the normality of data distribution by means of the Shapiro-Wilk test, differences between groups were assessed by using the non-parametric Mann-Whitney U test. Statistical analyses were performed in R environment (v.4.3.2). As the outcome of the study, COL3A1 normalized gene expression was significantly higher in WB compared to NORM samples (P<0.05), which is in line with the abnormal collagen accumulation characterizing WB-affected breasts. Also, since collagen type III expression increases when muscular stress and injury occur, its higher expression at the gene level in WB samples might be considered directly related to the fibrosis condition occurring as a response to the injury status in myopathic muscles. Since collagen expression varies with age and this type of collagen is predominantly expressed during early muscle development, it is also possible that an abnormal regulation of its expression may be associated with a status of embryonic-like tissue in WB samples. Further analyses are warranted to elucidate whether its higher expression is directly related to the onset of this condition or a result of the fibrotic process characterizing this defect. Research supported by NextGenerationEU, National Grant PRIN2022 (Prot.n.2022EPWEPW).