| The meniscus is a fibrous cartilage tissue located in the knee joint,which has an important role of absorbing oscillation,conducting knee joint load,and lubricating joints.Meniscal injury can severely limit the function of the knee joint and increase the risk of knee osteoarthritis,and meniscus injury cases are clinically common.In recent years,tissue engineering has provided a new direction for meniscal injury repair therapy.The main steps of tissue engineering are to first prepare the scaffold,then inoculate the cells on the scaffold,and regulate the cell-scaffold complex by cytokines,mechanical stimulation,etc.,to produce extracellular matrix(ECM)and then transplant into the animal body.Due to the particularity of the meniscus anatomy,3D printing technology has great advantages in the preparation of tissue engineering meniscus scaffolds compared to other tissue engineering scaffold preparation techniques.Bone marrow mesenchymal stem cells is an ideal source of meniscal tissue engineered seed cells,but they often end up to hypertrophy when induced into cartilage.Many studies of tissue engineering meniscus have shown that although tissue engineered meniscus grafts can protect articular cartilage,it still causes articular cartilage damage and subchondral bone degeneration.Therefore,tissue engineering meniscus research should be focused on knee cartilage damage and subchondral bone degeneration.Parathyroid hormone(PTH)can inhibit the hypertrophy of BMSCs into the cartilage induction process,and can maintain the number of articular chondrocytes and the synthesis of extracellular matrix and maintain the subchondral bone structure.In order to evaluate the repair of tissue engineered meniscus transplantation on the meniscus defect by 3D printed meniscus composite composite BMSCs in vitro,and the auxiliary effect of PTH(1-34)on the remodeling and protection of joints in tissue engineering meniscus in this experiment,polycaprolactone(PCL)meniscus scaffold was prepared by 3D printing technique,the morphology and microstructure of the scaffold were observed by gross and scanning electron microscopy.The compressive modulus of the scaffold was determined by biomechanical test.The scaffold was evaluated by CCK-8 cytotoxicity test.The compatibility of the cells was induced,and the canine BMSCs were inoculated in vitro for 7,14,21,and 28 days.The growth of the cells on the scaffold was observed by inverted phase contrast microscopy.The glycosaminoglycan(GAG)was determined by different induction time.The content and the expression level of type II collagen were analyzed and compared with the effects of different in vitro induction time on matrix synthesis.Then,16 test dogs were randomly divided into 4 groups: PTH(1-34)combined group,engineering group,sham operation group and defect group.After constructing the medial meniscus defect model,tissue engineered meniscus was transplanted into the model dog knee.In the joints,PTH(1-34)was injected into the PTH(1-34)combined group for 3 weeks.The engineering group was injected with the same amount of normal saline.After 12 weeks,the general observation,knee function score,anatomy and histology were performed.The analysis assesses the regeneration of the implant and the degradation of the joint.The research results are as follows:1.The PCL scaffold prepared by 3D printing technology has higher degree of reduction of the natural anatomical shape of the meniscus,uniform pores and good inter-well connectivity,certain mechanical compressive properties and slow degradation rate,and cells inoculated thereon.The number showed an increasing trend.During the in vitro induction of BMSCs-scaffold complex,the cells proliferated continuously,and the synthesis of GAG and type II collagen increased with the induction time.The synthesis amount at 21 d was significantly higher than other induction time(P < 0.05).2.At the end of the 12 th week after surgery,most of the dogs in the PTH(1-34)combined group and the engineering group showed normal exercise performance,while the dogs in the defect group showed support during walking,and the performance of the upper and lower steps was difficult or even resisted,indicating the tissue engineering of 3D printing.Transplantation of the meniscus can improve knee function.The HE,Sirius Red,and Toluidine Blue of the neonatal meniscus showed that the neonatal meniscus of the PTH(1-34)combination group contained more chondrocytes than the engineering group,and had more similar histology to the natural meniscus.And more cartilage ECM formation.Knee anatomy and histological examination showed that the PTH(1-34)combined group and the engineering group meniscus grafts had protective effects on the joints of the canine medial meniscus resection model.The medial knee articular cartilage in the defect group was 12 w after operation.Degeneration occurred as a result of a large number of fissures on the surface of the articular cartilage,a decrease in cartilage thickness,and a loss of cartilage matrix staining.The structural degeneration of the articular cartilage in the engineering group and the loss of proteoglycans were all relieved to varying degrees,while in PTH(1-34),the surface of the articular cartilage is less worn and the cartilage matrix is evenly dyed,which is closer to the sham operation group,suggesting that PTH(1-34)has a certain maintenance effect on the balance of synthetic catabolism of articular chondrocytes and matrix.It is indicated that PTH(1-34)can enhance the protection effect of 3D printing tissue engineered meniscus on knee joint.In summary,this study prepared a scaffold suitable for the construction of tissue engineering meniscus in morphological structure,mechanical properties and cytocompatibility by 3D printing technology,and its complex with canine BMSCs was induced in the cartilage matrix in vitro for 21 d;3D printed scaffold composite canine BMSCs tissue engineered meniscus can form a new protective tissue on the knee joint,combined use of PTH(1-34)can enhance the regeneration of tissue engineered meniscus,it relieves the degeneration of articular cartilage and has an auxiliary effect on tissue engineered meniscus repairing meniscus defects in dogs. |
