ABSTRACT
BACKGROUND: Matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMP) are involved in the remodeling of extracellular matrix under normal or pathological conditions, and the positive expression of MMP-2 and MMP-9 has been shown to play important physiological and pathological roles in the denervated skeletal muscle. OBJECTIVE: To investigate the expression and effect of MMP-2 and MMP-9 and their tissue inhibitors (TIMP-1 and TIMP-2) in the denervated skeletal muscle. METHODS: The right sciatic nerve of rats was cut off to establish the model of denervated skeletal muscle, and the right skeletal muscle of rats was harvested after different intervals. The morphologic changes of the denervated skeletal muscle were detected through hematoxylin-eosin staining, immunohistochemical staining, and RT-PCR. The expression and change of MMP-2 and MMP-9 and TIMP-1 and TIMP-2 were compared with the sham operation group. RESULTS AND CONCLUSION: Atrophy and fibrosis were observed in the denervated skeletal muscle. There was a rapid increase of MMP-2 and TIMP-2 with double peaks at the 3rdand 56thdays after modeling; at the 3rdand 70thdays, the expression of MMP-9 increased significantly and reached the peak respectively; mRNA level of TIMP-1 only increased in the early stage, reached the peak at the 3rdday and gradual declined to normal level, without the second peak. To conclude, MMPs and TIMPs are involved in the tissue changes following denervation. TIMP-1 and TIMP-2 have a protective role in the remodeling progression. The altered balance between MMPs and TIMPs in the late stage of denervation may be responsible for extracellular matrix degradation leading to the atrophy and fibrosis progression.
ABSTRACT
The aim of this study was to investigate the mechanism of deposition of extracellular matrix induced by TGF-β1 in skeletal muscle-derived stem cells (MDSCs). Rat skeletal MDSCs were obtained by using preplate technique, and divided into four groups: group A (control group), group B (treated with TGF-β1, 10 ng/mL), group C (treated with TGF-β1 and anti-connective tissue growth factor (CTGF), both in 10 ng/mL), and group D (treated with anti-CTGF, 10 ng/mL). The expression of CTGF, collagen type-I (COL-I) and collagen type-III (COL-III) in MDSCs was examined by using RT-PCR, Western blot and immunofluorescent stain. It was found that one day after TGF-β1 treatment, the expression of CTGF, COL-I and COL-III was increased dramatically. CTGF expression reached the peak on the day 2, and then decreased rapidly to a level of control group on the day 5. COL-I and COL-III mRNA levels were overexpresed on the day 2 and 3 respectively, while their protein expression levels were up-regulated on the day 2 and reached the peak on the day 7. In group C, anti-CTGF could partly suppress the overexpression of COL-I and COL-II induced by TGF-β1 one day after adding CTGF antibody. It was concluded that TGF-β1 could induce MDSCs to express CTGF, and promote the production of COL-I and COL-III. In contrast, CTGF antibody could partially inhibit the effect of TGF-β1 on the MDSCs by reducing the expression of COL-I and COL-III. Taken together, we demonstrated that TGF-β1-CTGF signaling played a crucial role in MDSCs synthesizing collagen proteins in vitro, which provided theoretical basis for exploring the methods postponing skeletal muscle fibrosis after nerve injury.
ABSTRACT
The aim of this study was to investigate the mechanism of deposition of extracellular matrix induced by TGF-β1 in skeletal muscle-derived stem cells (MDSCs). Rat skeletal MDSCs were obtained by using preplate technique, and divided into four groups: group A (control group), group B (treated with TGF-β1, 10 ng/mL), group C (treated with TGF-β1 and anti-connective tissue growth factor (CTGF), both in 10 ng/mL), and group D (treated with anti-CTGF, 10 ng/mL). The expression of CTGF, collagen type-I (COL-I) and collagen type-III (COL-III) in MDSCs was examined by using RT-PCR, Western blot and immunofluorescent stain. It was found that one day after TGF-β1 treatment, the expression of CTGF, COL-I and COL-III was increased dramatically. CTGF expression reached the peak on the day 2, and then decreased rapidly to a level of control group on the day 5. COL-I and COL-III mRNA levels were overexpresed on the day 2 and 3 respectively, while their protein expression levels were up-regulated on the day 2 and reached the peak on the day 7. In group C, anti-CTGF could partly suppress the overexpression of COL-I and COL-II induced by TGF-β1 one day after adding CTGF antibody. It was concluded that TGF-β1 could induce MDSCs to express CTGF, and promote the production of COL-I and COL-III. In contrast, CTGF antibody could partially inhibit the effect of TGF-β1 on the MDSCs by reducing the expression of COL-I and COL-III. Taken together, we demonstrated that TGF-β1-CTGF signaling played a crucial role in MDSCs synthesizing collagen proteins in vitro, which provided theoretical basis for exploring the methods postponing skeletal muscle fibrosis after nerve injury.