Gene expression analysis in calcific tendinopathy of the rotator cuff

We evaluated the expression of several genes involved in tissue remodelling and bone development in patients with calcific tendinopathy of the rotator cuff. Biopsies from calcified and non-calcified areas were obtained from 10 patients (8 women and 2 men; average age: 55 years; range: 40-68) with calcific tendinopathy of the rotator cuff. To evaluate the expression of selected genes, RNA extraction, cDNA synthesis and quantitative polymerase chain reaction (PCR) were performed. A significantly increased expression of tissue transglutaminase (tTG)2 and its substrate, osteopontin, was detected in the calcific areas compared to the levels observed in the normal tissue from the same subject with calcific tendinopathy, whereas a modest increase was observed for catepsin K. There was also a significant decrease in mRNA expression of Bone Morphogenetic Protein (BMP)4 and BMP6 in the calcific area. BMP-2, collagen V and vascular endothelial growth factor (VEGF) did not show significant differences. Collagen X and matrix metalloproteinase (MMP)-9 were not detectable. A variation in expression of these genes could be characteristic of this form tendinopathy, since an increased level of these genes has not been detected in other forms of tendon lesions.