Bone Marrow Stem Cells-Seeded Polyethylene Terephthalate Scaffold in Repair and Regeneration of Rabbit Achilles Tendon.

The objective of this study was to evaluate the effect of bone marrow stem cells (BMSCs)-seeded polyethylene terephthalate (PET) scaffold for Achilles tendon repair in a rabbit model. The allogeneic BMSCs were seeded onto the PET scaffold and cultured in vitro for 14 days. Sixteen mature New Zealand rabbits underwent surgery to establish a 2-cm Achilles tendon defect model. The BMSCs-seeded PET scaffold was implanted into the defect of one limb (BMSCs-PET group), while the PET scaffold without BMSCs was implanted into the defect of contralateral limb as the control (PET group). All rabbits were sacrificed at 6 and 12 weeks after surgery. At 12 weeks after surgery, macroscopic and histological results showed formation of tendon-like tissues, and the structure was more mature in the BMSCs-PET group. Immunohistochemical analysis and real-time polymerase chain reaction (RT-PCR) demonstrated that the collagen I and collagen III were significantly higher in the BMSCs-PET group compared with those in the PET group. Mechanically, both the failure load and the average stiffness were significantly higher in the BMSCs-PET group than those in the PET group. In conclusion, BMSCs-seeded PET scaffold could effectively facilitate the healing process after being implanted in a rabbit Achilles tendon defect model.

Enhanced Fibroblast Cellular Ligamentization Process to Polyethylene Terepthalate Artificial Ligament by Silk Fibroin Coating.

Artificial ligaments utilized in reconstruction of anterior cruciate ligament (ACL) are usually made of polyethylene terepthalate (PET) because of its good mechanical properties in vivo. However, it was found that the deficiencies in hydrophilicity and biocompatibility of PET hindered the process of ligamentization. Therefore, surface modification of the PET is deemed as a solution in resolving such problem. Silk fibroin (SF), which is characterized by good biocompatibility and low immunogenicity in clinical applications, was utilized to prepare a coating on the PET ligament (PET+SF) in this work. At first, decrease of hydrophobicity and appearance of amino groups were found on the surface of artificial PET ligament after coating with SF. Second, mouse fibroblasts were cultured on the two different kinds of ligament in order to clarify the possible effect of SF coating. It was proved that mouse fibroblasts display better adhesion and proliferation on PET+SF than PET ligament according to the results of several technical methods including SEM observation, cell adhesive force and spread area test, and mRNA analysis. Meanwhile, methylthiazolyldiphenyl-tetrazolium bromide and DNA content tests showed that biocompatibility of PET+SF is better than PET ligament. In addition, collagen deposition tests also indicated that the quantity of collagen in PET+SF is higher than PET ligament. Based on these results, it can be concluded that SF coating is suggested to be an effective approach to modify the surface of PET ligament and enhance the "ligamentization" process in vivo accordingly.

Biomineralizaion of hydroxyapatite on polyethylene terephthalate artificial ligaments promotes graft-bone healing after anterior cruciate ligament reconstruction: An in vitro and in vivo study.

The purpose of the present study is to modify the polyethylene terephthalate ligament with hydroxyapatite via biomineralization and to investigate its effect on graft-bone healing. After biomineralization of hydroxyapatite, the surface characterization of polyethylene terephthalate ligament was examined by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and water contact angle measurements. The compatibility and osteoinduction, along with the underlying signaling pathway involved of hydroxyapatite-polyethylene terephthalate ligament, were evaluated in vitro. Moreover, a rabbit anterior cruciate ligament reconstruction model was established, and the polyethylene terephthalate or hydroxyapatite-polyethylene terephthalate artificial ligament was implanted into the knee. The micro-computed tomography analysis, histological, and immunohistochemical examination as well as biomechanical test were performed to investigate the effect of hydroxyapatite coating in vivo. The results of scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction showed that the hydroxyapatite was successfully deposited on the polyethylene terephthalate ligament. Water contact angle of the hydroxyapatite-polyethylene terephthalate group was significantly smaller than that of the polyethylene terephthalate group. The in vitro study showed that hydroxyapatite coating significantly improved adhesion and proliferation of MC3T3-E1 cells. The osteogenic differentiation of cells was also enhanced through the activation of ERK1/2 pathway. The micro-computed tomography, histological, and immunohistochemical results showed that biomineralization of hydroxyapatite significantly promoted new bone and fibrocartilage tissue formation at 12 weeks postoperatively. Moreover, the failure load and stiffness in the hydroxyapatite-polyethylene terephthalate group were higher than that in the polyethylene terephthalate group. Therefore, biomineralizaion of hydroxyapatite enhances the biocompatibility and osseointegration of the polyethylene terephthalate artificial ligament, thus promoting graft-bone healing for anterior cruciate ligament reconstruction through the activation of ERK1/2 pathway.

The Effect of Remnant Preservation on Tibial Tunnel Enlargement in Anterior Cruciate Ligament Reconstruction with Polyethylene Terephthalate Artificial Ligament in a Large Animal Model.

An enlarged bone tunnel may affect the graft-bone integration and pose a problem for revision anterior cruciate ligament (ACL) surgery. The purpose of this study was to evaluate the effect of remnant preservation on tibial tunnel enlargement in ACL reconstruction with polyethylene terephthalate (PET) artificial ligament. Twenty-four skeletally mature male beagles underwent ACL reconstruction with PET artificial ligament for both knees. One knee was reconstructed with remnant preservation using sleeve technique (remnant group), while the contralateral was reconstructed without remnant preservation (control group). The animals were sacrificed at 1 day, 6 weeks, and 12 weeks after surgery for further evaluation including macroscopic observation, microcomputed tomography (micro-CT), histological assessment, and biomechanical testing. The remnant group had better synovial coverage than the control group at 6 and 12 weeks after surgery. The micro-CT analysis showed the tibial tunnel area (TTA) of the remnant group was significantly smaller and the bone volume/total volume fraction (BV/TV) value was higher than those of the control group at 6 and 12 weeks. Moreover, TTA and BV/TV at each time point were divided into three groups according to the different grade of synovial coverage. Significant association was observed between the synovial coverage degree and the TTA and BV/TV values. The histological assessment revealed that the interface width between the graft and host bone in the remnant group was smaller than that in the control group in the tibial tunnels at 6 and 12 weeks. Moreover, the remnant group had better failure load and stiffness than the control group at 12 weeks. The remnant preservation using sleeve technique could effectively promote the synovial coverage of the graft, decrease the risk of tibial tunnel enlargement by sealing the bone tunnel entrance, and enhance the biological environment for graft-bone healing after ACL reconstruction using PET artificial ligament. This technique provides a potential solution for bone tunnel enlargement following artificial ligament surgery for the acute ACL rupture in the clinical practice.

Electrospun PCL/Gel-aligned scaffolds enhance the biomechanical strength in tendon repair.

Tendons can transmit mechanical force from muscles to bones for movement. However, the mechanical strength of tendons is compromised after surgery, thus causing a high rate of tendon retear. Hence, the design and preparation of biodegradable materials with excellent mechanical properties have become an urgent demand for sports medicine. In this study, biomimetic polycaprolactone (PCL)/gelatin (Gel)-aligned scaffolds were fabricated for the mechanical restoration of the injured tendon in a rabbit model. The diameter of nanofibers was about 427.82 ± 56.99 nm, which was approximate to that of the native collagen fibrils; the directional consistency of the nanofibers in PCL/Gel-aligned scaffolds reached 77.33 ± 3.22%, which were ultrastructurally biomimetic. Compared to the observations for the control group, the in vitro mechanical results showed that the PCL/Gel-aligned scaffolds (P/G-A) were anisotropic in terms of failure load, tensile strength, and Young's modulus. After verifying their good cytocompatibility, the scaffolds were implanted into the rabbit patellar tendon in situ. The biomechanical properties of the repaired tendon in P/G-A reached 343.97 ± 65.30 N in failure load, 85.99 ± 16.33 MPa in tensile strength, 590.84 ± 201.87 MPa in Young's modulus, and 171.29 ± 61.50 N mm-1 in stiffness in vivo at 8 weeks post operation. In a word, our results demonstrated that P/G-A could support the regenerated tissue of injured patellar tendons to restore the biomechanical strength in a rabbit model. This suggested that the PCL/Gel-aligned scaffolds can pave a promising way to improve the healing of injured tendons in the clinic in the future.

Enhance the biocompatibility and osseointegration of polyethylene terephthalate ligament by plasma spraying with hydroxyapatite in vitro and in vivo.

PURPOSE: This study was designed to evaluate the biocompatibility and osseointegration of polyethylene terephthalate ligament after coating with hydroxyapatite (PET/HA) by using the plasma spraying technique in vitro and in vivo. METHODS: In this study, PET/HA sheets were prepared by using the plasma spraying technique. The characterization, the viability of bone marrow stromal cells (BMSCs), and the mRNA expression of bone formation-related genes were evaluated in vitro. The osseointegration in vivo was investigated in the rabbit anterior cruciate ligament (ACL) reconstruction model by micro-computed tomography (micro-CT) analysis, histological evaluation, and biomechanical tests. RESULTS: Scanning electron microscopy (SEM) results showed that the surface of polyethylene terephthalate (PET) becomes rough after spraying with hydroxyapatite (HA) nanoparticles, and the water contact angle was 75.4°±10.4° in the PET/HA-plasma group compared to 105.3°±10.9° in the control group (p<0.05). The cell counting kit-8 counting results showed that the number of BMSCs significantly increased in the PET/HA-plasma group (p<0.05). Reverse transcription polymerase chain reaction (RT-PCR) results showed that there was an upregulated mRNA expression of bone formation-related genes in the PET/HA-plasma group (p<0.05). Micro-CT results showed that the transactional area of tibial tunnels and femoral tunnels was smaller in the PET/HA-plasma group (p<0.05). The histological evaluation scores of the PET/HA-plasma group were significantly superior to those of the PET control group at 8 and 12 weeks (p<0.05). The biomechanical tests showed an increased maximum load to failure and stiffness in the PET/HA-plasma group compared to those in the control group at 8 and 12 weeks. CONCLUSION: Both in vitro and in vivo results demonstrated in this study suggest that the biocompatibility and osseointegration of PET/HA ligament were significantly improved by increasing the proliferation of cells and upregulating the expression of bone formation-related genes. In a word, the PET/HA-plasma ligament is a promising candidate for ACL reconstruction in future.

Surface modification of vascular endothelial growth factor-loaded silk fibroin to improve biological performance of ultra-high-molecular-weight polyethylene via promoting angiogenesis.

Ultra-high-molecular-weight polyethylene (UHMWPE) has been applied in orthopedics, as the materials of joint prosthesis, artificial ligaments, and sutures due to its advantages such as high tensile strength, good wear resistance, and chemical stability. However, postoperative osteolysis induced by UHMWPE wear particles and poor bone-implant healing interface due to scarcity of osseointegration is a significant problem and should be solved imperatively. In order to enhance its affinity to bone tissue, vascular endothelial growth factor (VEGF) was loaded on the surface of materials, the loading was performed by silk fibroin (SF) coating to achieve a controlled-release delivery. Several techniques including field emission scanning electron microscopy (FESEM) and attenuated total reflectance (ATR)-Fourier transform infrared (FTIR) and water contact angle measurement were used to validate the effectiveness of introduction of SF/VEGF. The result of ELISA demonstrated that the release of VEGF was well maintained up to 4 weeks. The modified UHMWPE was evaluated by both in vitro and in vivo experiments. According to the results of FESEM and cell counting kit-8 (CCK-8) assay, bone marrow mesenchymal stem cells cultured on the UHMWPE coated with SF/VEGF and SF exhibited a better proliferation performance than that of the pristine UHMWPE. The model rabbit of anterior cruciate ligament reconstruction was used to observe the graft-bone healing process in vivo. The results of histological evaluation, microcomputed tomography (micro-CT) analysis, and biomechanical tests performed at 6 and 12 weeks after surgery demonstrated that graft-bone healing could be significantly improved due to the effect of VEGF on angiogenesis, which was loaded on the surface by SF coating. This study showed that the method loading VEGF on UHMWPE by SF coating played an effective role on the biological performance of UHMWPE and displayed a great potential application for anterior cruciate ligament reconstruction.