RESUMO
Objective To investigate the changes of microarchitecture and gene expression of subchondral bone in the initial stage of traumatic arthritis ,to explore the characteristics of subchondral bone remodeling and its role in the articular cartilage de‐generation .Methods The medial meniscal tear (MMT) was performed on the right knees of 13 SD rats to simulate the traumatic osteoarthritis ,while sham operation on the control group .Three weeks later ,all the rats were executed and dissected ,with proximal tibiae being kept and distributed into the two groups ,10 respectively .Micro‐computed tomography (micro‐CT) was adopted to re‐construct and analyze the subchondral bone .After being fixed by 4% paraformaldehyde ,all the samples were decalcified until six weeks passed ,followed by paraffin‐sectioning ,safranin O and fast green staining ,and examining and photographing under an ordina‐ry optical microscope .The RNA of another 3 SD rats′subchondral bone was extracted ,and a real‐time PCR test was carried out to illuminate the expression variation of bone‐formation marker genes (ALP ,RUNX2 ,and OCN) ,and bone‐resorption marker genes (TRAP ,CTSK and MMP9) ,between the two groups .Results Three weeks after MMT surgery ,subchondral bone disorders were observed among the experimental samples through micro‐CT scanning .There was lesser BV/TV ,Conn .D and Tb .Th(P<0 .05) and more Tb .Sp(P<0 .05) in the experimental group compared with the control group .In the pathological section ,arthritic degen‐eration was not spotted in both groups ,but trabeculae of the experimental group were found to be sparse .Compared with control group ,the level of mRNA expression of the bone‐formation marker genes of the experimental group was decreased(P<0 .05) ,while bone‐resorption related genes increased(P<0 .05) .Conclusion The model of initial traumatic osteoarthritis induced by MMT in rats′knees showed an active bone remodeling ,more bone absorbing than bone formation ,lowered bone volume ,and microarchitec‐ture changing of the subchondral bone .
RESUMO
Objective To investigate the function of CXCR4 and CXCR7 receptors expressed in bone marrow mesenchymal stem cells (BMSCs) membrane surface in process of cell migration,in order to provide a theoretical basis for bone trauma repair.Methods C57BL/6 mice were selected to collect BMSCs of second passage after using the adherence culture method.Expressions of CXCR4 and CXCR7 receptors on BMSCs membrane surface were detected using immunofluorescent staining and flow cytometry.In CXCL12-induced chemotaxis of BMSCs,the assay was divided into control group (cells were seeded in serum-free medium),CXCL12 group and (cells were seeded in serum-free medium containing CXCL12),and CXCR4-blocked group (cells were seeded in serum-free medium containing CXCL12 after the blockade of CXCR4).Migration of BMSCs was qualified and used to determine the chemotaxis role of CXCR4 and CXCR7.After the blockade of CXCR4,expression of CXCR7 was detected using the Western blot method.Results lmmunofluorescence showed overexpressions of CXCR4 and CXCR7 receptors on BMSCs membrane surface.Flow cytometry showed the positive rate of CXCR4 and CXCR7 on BMSCs membrane surface was 96.4％ and 97.3％ respectively.Cell migration assay showed amount of MBSCs migration was the highest in CXCL12 group,relative higher in CXCR4-blocked group and the lowest in control group (P ＜ 0.01).In CXCR4-blocked group,expression of CXCR7 increased.Conclusion CXCR4 and CXCR7 Receptors are expressed in BMSCs membrane surface,but CXCR4 play the major role in CXCL12-induced BMSCs migration to traumatic bone wounds.