Abstract
BACKGROUD: This study aimed to investigate changes in gene expression related to matrix synthesis in individuals with full-thickness rotator cuff tears (RCTs) and normal tendon tissues. The study also aimed to examine the differences in gene expression according to 4 distinct tear sizes. METHODS: A total of 12 patients with full-thickness RCTs were included in the study, all of whom underwent arthroscopic rotator cuff repair. The RCTs were stratified by size into small, medium, large, and massive. Tendon samples were harvested from the midpoint between the lateral end of the torn tendon and the musculotendinous junction. Subsequent analysis of the tissue samples revealed the mRNA expression levels of 11 collagen types, 6 proteoglycans, and 8 glycoproteins through real-time polymerase chain reaction techniques. For control purposes, supraspinatus tendon tissue was sourced from 3 patients who had proximal humerus fractures but did not present with RCTs. RESULTS: Among the 11 collagens and 14 non-collagenous protein (NCP) genes examined in this study, COL3A1 and COL10A1 showed a significant increase, whereas COL4A1 and COL14A1 showed a tendency to decrease compared to those in the normal group. ACAN significantly increased by 8.92-fold (p < 0.001) compared to that in the normal group, whereas DCN and LUM showed a tendency to decrease. FN1 and TNC increased significantly by 3.47-fold (p = 0.003) and 5.38-fold (p = 0.005), respectively, and the genes ELN, LAMA2, and THBS1 were all significantly reduced compared to those in the normal group. In the NCPs, almost all the genes with increased expression levels had the highest level in small size RCTs, and gene expression decreased as the size increased. The 3 proteoglycans (ACAN, BGN, and FMOD) showed the highest levels of expression in small size RCTs compared to those in the normal group, and 5 glycoproteins (COMP, FBN1, FN1, HAPLN1, and TNC) also showed the highest expression in small size RCTs. CONCLUSIONS: We confirmed that most of the detected extracellular matrix gene expression changes were related to the size of the full-thickness RCTs. In NCPs, gene expression was increased in small-size tears, and gene expression levels were significantly reduced when the size increased.