Experimental study on the expression of II type collagen and MMP-7 in acetabular cartilage of developmental dysplasia of hip

Abstract

To detect the changes of expressions of II type collagen and matrix metalloproteinases-7 (MMP-7) of acetabular cartilage in early DDH (developmental dysplasia of hip) and to investigate the relevance between II type collagen and MMP-7 and the retrogression mechanism of acetabular cartilage. The animal model of DDH was successfully established in 8 rabbits by applying the method of knee extension in which left lower extremity as experimental group and right one as control group. And the stains of HE and toluidine blue were applied on the samples of acetabular cartilage to observe the changes of chondrocytes and extracellular matrix (ECM). The techniques of immunohistochemical staining and Western blot were employed to respectively qualify and quantitate the expression of II type collagen and MMP-7. Pathohistological observation indicated the signs of retrogressive changes of acetabular cartilage in experimental group, including a loss of ECM in toluidine blue stain and a cluster of chondrocytes in HE stain. The positive numbers of II type collagen and MMP-7 by immunohistochemical staining in experimental group were both higher than that of control group. The quantitative amounts of II type collagen and MMP-7 by Western blot in experimental group were both higher than that of control group. Both significant differences existed between two groups (P < 0.05). The expression of II type collagen and MMP-7 is correlated to a retrogression of acetabular cartilage and increases obviously in early DDH. The amount and intensity of II type collagen and MMP-7 are probably the rationale of differential retrogression of cartilage.