Research Of The Tendon-to-bone Healing Of ACL Reconstruction In A Rabbit Model Using Autograft Seeded With PBMSCs Gel

Objective This study was conducted to analyze the effect of peripheral blood mesenchymal stem cells(PBMSCs) gel on the early period of tendon-to-bone healing after reconstruction of the anterior cruciate ligament(ACL) using autograft.Method Thirty-two New Zealand rabbits aged 3 to 4 months were randomly divided into two groups(n=16 per group): experimental and control. After rabbits from the experimental group were mobilized by subcutaneous injection of granulocyte colony stimulating factor(G-CSF) for 6 days, the PBMSCs were isolated from rabbit peripheral blood samples by combination of density gradient centrifugation and adhesive culture, morphology of cell proliferation was observed by microscopy and phenotypes of PBMSCs were detected by flow cytometry. A model of ACL reconstruction using autograft were performed in all of the rabbits, the experimental group received injection of PBMSCs gel into the femur tunnel and the control group received gel only. At 2, 4, 8 and 12 weeks, 4 animals in each group were euthanized, 1 for histologic assessment by Masson trichrome staining and 3 for biomechanical testing.Results Flow cytometry showed that the PBMSCs expressed CD29, CD90 positive, CD11 b, CD34 negative. According to the Masson trichrome staining, in the experimental group, collagen fibers were presented but have a disordered arrangement at 4 weeks after surgery. At 8 weeks after surgery, collagen fibers were obviously increased but irregularly arranged. At 12 weeks after surgery, collagen fibers wereformed in abundance and regularly arranged. The healing at tendon-bone interface of the experimental group was quicker than those of the control group. The maximum biomechanical pull-out strength of the autograft in the femur tunnel presented a rising trend with the prolong of repair time in both experimental and control groups, it was significantly higher in the experimental group at 8 and 12 weeks after surgery(P<0.01).Conclusion PBMSCs gel could enhance the early period of tendon-to-bone healing after reconstruction of the ACL using autograft.