Increased expression of collagens, transforming growth factor-β1, and -β3 in gluteal muscle contracture

BACKGROUND Gluteal muscle contracture (GMC) is a multi-factor human chronic fibrotic disease of the gluteal muscle. Fibrotic tissue is characterized by excessive accumulation of collagen in the muscle's extracellular matrix. Transforming growth factor (TGF)-beta1 and -beta2 are thought to play an important role in fibrogenesis, while TGF-beta3 is believed to have an anti-fibrotic function. We hypothesize that the expression of collagen and TGF-betas would be up-regulated in GMC patients. METHODS The expression of collagen type I, type III and TGF-betas were studied in 23 fibrotic samples and 23 normal/control samples in GMC patients using immunohistochemistry, reverse transcription and polymerase chain reaction (RT-PCR) and western bolt analysis. RESULTS Compared to the unaffected adjacent muscle, increased expression of TGF-beta1 and -beta3 was associated with deposition of collagen type I and type III in the fibrotic muscle of the GMC patients at the mRNA level. Strong up-regulation of these proteins in fibrotic muscle was confirmed by immunohistochemical staining and western blot analysis. TGF-beta2 was not up-regulated in relation to GMC. CONCLUSION This study confirmed our hypothesis that collagen types I, III, TGF-beta1 and TGF-beta3 were up-regulated in biopsy specimens obtained from patients with GMC. Complex interaction of TGF-beta1 with profibrotic function and TGF-beta3 with antifibrotic function may increase synthesis of collagens and thereby significantly contribute to the process of gluteal muscle scarring in patients with GMC.