| Objective: To prepare a rat model of Developmental Dysplasia of the hip(DDH)using the straight-leg swaddling position,observe the morphological changes of the LabroAcetabular Complex(LAC),and verify the effect of straight leg swaddling on DDH acetabular labrum.The general morphology of acetabular cartilage,PCNA,Runx2,Col-II immunohistochemistry and TUNEL were observed to further investigate the pathological mechanism and the natural history of pathological changes of the LAC,and molecular biological changes in the abnormal development of acetabular cartilage complexes.Microarray was used to screen differential gene expression(DGE)and biological characteristics of DDH.The screened differential genes were verified by q RTPCR.Methods: The straight-leg swaddling position DDH model was prepared for Wistar newborn rats on the day of birth,and pelvic orthotopic radiographs were taken at 2,4,6,8,and 10 days after birth.Staining combined with Campbell’s DDH classification criteria,it can be divided into three types: I-acetabular dysplasia: acetabular dysplasia becomes shallower and the slope becomes larger,but the femoral head is still in the true acetabulum;II-subluxation: femoral head moves up,part is still in the true acetabulum;III-Complete dislocation: Dislocation of the femoral head moves up,forming a false acetabulum.Observe the morphological changes of the labrum on the coronal section of the hip joint and divide them into three types: I-No inversion occurred in the labrum;II-single labrum inversion,sacral branch acetabular labrum inversion;III-double labrum inversion,sciatic branch acetabular labrum with sacral branch acetabular labrum inversion.The differences in tissue structure,composition,proliferation and apoptosis between model groupe and normal groupe were determined by saffron-solid green staining,Masson staining,immunohistochemistry and TUNEL staining.The differential expression genes were screened and verified by q RT-PCR in the early DDH(2 days)and the late DDH(8 days)rats.Results: 1.With the extension of swaddling,the incidence of labial inversion increased gradually.It was 35%(14/40)on 2 days and 77.5%(31/4)on 4 days.40),73.68%(28/38)at 6 days,95%(38/40)at 8 days,100%(40/40)at 10 days,and the overall incidence of labrum inversion was 76.3%.A total of 198 in the experimental group Hip,according to Campbell’s orthopedic surgery DDH classification,16 cases with normal development(8.1%),28 cases with acetabular dysplasia(14.2%),48 cases with subluxation(24.2%),and 106 cases with complete dislocation(53.5%).The overall incidence of hip dysplasia caused by the straight-leg swaddling position was 91.9%(182/198).There was a positive correlation between the degree of glenolipid inversion and dislocation(rs=0.965,P <0.05).With the extension of swaddling,the I/U ratio increased,while The ratio of normal groupe decreased.2.Saffron-solid green staining of the coronal section of the hip joint showed that degenerative changes occurred early in the acetabulum of the experimental group.The volume of the labral chondrocytes increased and the stroma decreased.Masson staining showed that fibrosis in the experimental group increased;PCNA was in the acetabulum.The expression of the labrum is independent of time,but changes related to the degree of dislocation.The labrum fibrocartilage has a higher proliferative activity than hyaline cartilage;TUNEL in the experimental group shows that the cartilage intermediate layer and deep layer cells have more apoptosis than the control group,and The degree of apoptosis increases with time;when the acetabulum is underdeveloped or subluxed,the femoral head is still in the acetabulum and causes abnormal pressure on the upper and lower labrum.The expression of Runx2 in the experimental group is increased compared to the control group,and the expression position is mainly in the superficial area and the hip.In the acetabular labrum,the expression of both the upper and lower labrum was reduced when the dislocation occurred;the expression of Col-II in the experimental group was lower than that in the control group.3.In the early stage of maintaining the straight leg crest position,the screening conditions of the DDH experimental group compared with the control group were fold expression difference ≥ 2 or ≤ 0.5,and P value <0.05.There were 316 independent genes with known functions,of which up-regulated There were 223 genes and 93 down-regulated genes.Compared with the control group,there were 246 differentially expressed genes in the late DDH experimental group,of which 104 genes were up-regulated and 142 genes were down-regulated.Among them,the cartilage development-related gene Osr2 and the gene responsive to mechanical stimuli Junb were differentially expressed in early DDH,but neither gene was differentially expressed at 8 days.The q RT-PCR was used to verify the gene chip results.The results of the expression profile chip showed the same trend.Junb and Osr2 were differentially expressed between the experimental group and the control group.Conclusions: 1.The incidence of labrum inversion gradually increased with the prolonged maintenance of abnormal position,and the pathological changes of labial acetabular complex were gradually aggravated.2.The I / U ratio can be used as a radiological reference index for the DDH pup model with straight-leg swaddling position.3.The phenomenon of labrum inversion is caused by an abnormal labro-acetabular complex morphology,accompanied by proliferation,apoptosis,and differentiation abnormalities.4.Junb and Osr2 may regulate the development of acetabular cartilage complex chondrocytes in the early stage of DDH. |
