ADORA2B, transcriptionally suppressing by MYC, promotes ferroptosis of chondrocytes via inhibition of the PI3K/Akt pathway in mice with osteoarthritis.

Recent studies have shown that chondrocyte ferroptosis contributes importantly to the pathogenesis of osteoarthritis (OA). However, it is largely unknown how it is regulated. In this study, the data sets GSE167852 and GSE190184 were downloaded from the Gene Expression Omnibus (GEO) database, and 161 differentially expressed genes (DEGs) related to ferroptosis were screened by bioinformatics analysis. Subsequently, ADORA2B was screened as a candidate gene from DEGs, which was significantly upregulated in palmitic acid (PA) treated chondrocytes. CCK-8, EdU, Western blotting, and ferroptosis-related kits assays demonstrated that knockdown of ADORA2B constrained ferroptosis and promoted viability of chondrocytes. Overexpression of ADORA2B promoted ferroptosis, while the PI3K/Akt pathway inhibitor LY294002 reversed the promotion of ADORA2B on ferroptosis. Dual-luciferase reporter gene assay and chromatin immunoprecipitation (ChIP) assays indicated MYC was a transcription suppressor of ADORA2B, and overexpression of MYC promoted the viability, and inhibited the ferroptosis of chondrocytes, while ADORA2B overexpression abated the promotion of MYC on chondrocyte viability and the inhibition on ferroptosis. In vivo experiments showed that MYC overexpression alleviated cartilage tissue damage in OA mice, which was able to reversed by ADORA2B overexpression. In summary, ADORA2B, transcriptionally suppressing by MYC, promotes ferroptosis of chondrocytes via inhibition of the PI3K/Akt pathway. Thus, ADORA2B can be used as a potential treatment target for ferroptosis-related diseases.

SLC9A2, suppressing by the transcription suppressor ETS1, restrains growth and invasion of osteosarcoma via inhibition of aerobic glycolysis.

Recent studies have shown that Solute Carrier Family 9 Member A2 (SLC9A2) could serve as a biomarker for cancer. However, its mechanism of action in osteosarcoma (OS) was still unclear. In this study, the data sets GSE154530 and GSE99671 were downloaded from the Gene Expression Omnibus (GEO) database, and 31 differentially expressed genes (DEGs) related to methylation were screened by bioinformatics analysis tools. Subsequently, SLC9A2 was screened as a candidate gene from DEGs, which was significantly downregulated in OS. CCK-8, transwell, western blotting and Seahorse XFe24 Cell Metabolic Analyzer assays demonstrated that overexpression of SLC9A2 could constrain OS cell proliferation, invasion, and aerobic glycolysis. Dual-luciferase reporter gene assay and chromatin immunoprecipitation (ChIP) assays indicated ETS proto-oncogene 1 (ETS1) was a transcription suppressor of SLC9A2, and overexpression of ETS1 could promote methylation levels in specific regions of the SLC9A2 promoter. ETS1 could promote the proliferation, invasion, and aerobic glycolysis ability of OS cells, as well as tumor growth in vivo by inhibiting the expression of SLC9A2. In addition, SLC9A2, suppressing by ETS1, restrains growth and invasion of OS via inhibition of aerobic glycolysis. Thus, SLC9A2 can function as a key inhibitory factor in the aerobic glycolysis to inhibit proliferation and invasion of OS. This indicated that SLC9A2 has a potential targeted therapeutic effect on OS.

Standardized 3D-printed trabecular titanium augment and cup for acetabular bone defects in revision hip arthroplasty: a mid-term follow-up study.

BACKGROUND: The aim of this study was to assess the feasibility and outcomes of standardized three-dimensional (3D)-printed trabecular titanium (TT) cups and augments to reconstruct most acetabular defects. METHODS: We included 58 patients with Paprosky type II and III acetabular bone defects who underwent revision hip arthroplasty between 2015 and 2018. Patients who were revised without 3D-printed augments, and cases who were lost to follow-up and died during follow-up were excluded. Radiographic and clinical outcomes were evaluated. A Kaplan-Meier survivorship curve was generated. The mean follow-up was 64.5 (range 49-84) months. RESULTS: In total, 48 (82.8%) acetabular revisions were performed using standardized 3D-printed TT cups and augments, and a retrospective review was conducted on 43 revisions. The average position of the vertical center of rotation and leg length discrepancy were significantly decreased from 42.4 ± 9.1 mm and 38.4 ± 10.7 mm to 22.8 ± 3.4 mm and 4.1 ± 3.0 mm, respectively. Non-progressive radiolucent lines were observed in 3 (7.5%) acetabular components with no indications for revision. The mean Harris hip score, Oxford hip score and EuroQol five-dimensional questionnaire score increased from 33.0 ± 10.7, 11.4 ± 3.4 and 0.29 ± 0.09 to 80.3 ± 8.8, 35.8 ± 2.4 and 0.71 ± 0.10, respectively. The revision-free survival rate of the acetabular component was 93.0% (40/43), with a rate of revision for aseptic loosening of 2.3% (1/43). CONCLUSION: Standardized 3D­printed TT augments and cups could be used to reconstruct the majority of Paprosky type II and III acetabular defects in revision hip arthroplasty and demonstrated encouraging results at mid-term follow-up.

Will previous antimicrobial therapy reduce the positivity rate of metagenomic next-generation sequencing in periprosthetic joint infections? A clinical study.

Background: Metagenomic next-generation sequencing (mNGS) is a culture-independent massively parallel DNA sequencing technology and it has been widely used for rapid etiological diagnosis with significantly high positivity rate. Currently, clinical studies on evaluating the influence of previous antimicrobial therapy on positivity rate of mNGS in PJIs are rarely reported. The present study aimed to investigate whether the positivity rate of mNGS is susceptible to previous antimicrobial therapy. Methods: We performed a prospective trial among patients who undergone hip or knee surgery due to periprosthetic joint infection (PJI) to compare the positivity rate of culture and mNGS between cases with and without previous antimicrobial therapy, and the positivity rates between cases with different antimicrobial-free intervals were also analysed. Results: Among 131 included PJIs, 91 (69.5%) had positive cultures and 115 (87.8%) had positive mNGS results. There was no significant difference in the positivity rate of deep-tissue culture and synovial fluid mNGS between cases with and without previous antimicrobial therapy. The positivity rate of synovial fluid culture was higher in cases with previous antimicrobial therapy. The positivity rates of mNGS in synovial fluid decreased as the antimicrobial-free interval ranged from 4 to 14 days to 0 to 3 days. Conclusion: mNGS is more advantageous than culture with a higher pathogen detection rate. However, our data suggested that antimicrobial agents may need to be discontinued more than 3 days before sampling to further increase the positivity rate of mNGS for PJIs.

Implementation of Photosensitive, Injectable, Interpenetrating, and Kartogenin-Modified GELMA/PEDGA Biomimetic Scaffolds to Restore Cartilage Integrity in a Full-Thickness Osteochondral Defect Model.

Cartilage defects caused by mechanical tear and wear are challenging clinical problems. Articular cartilage has unique load-bearing properties and limited self-repair ability. The current treatment methods, such as microfractures and autogenous cartilage transplantation to repair full-thickness cartilage defects, have apparent limitations. Tissue engineering technology has the potential to repair cartilage defects and directs current research development. To enhance the regenerative capacities of cartilage in weight-bearing areas, we attempted to develop a biomimetic scaffold loaded with a chondroprotective factor that can recreate structure, restore mechanical properties, and facilitate anabolic metabolism in larger joint defects. For enhanced spatial control over both bone and cartilage layers, it is envisioned that biomaterials that meet the needs of both tissue components are required for successful osteochondral repair. We used gelatin methacrylate (GELMA) and polyethylene glycol diacrylate (PEGDA) light-cured dual-network cross-linking modes that can significantly increase the mechanical properties of scaffolds and are capable of restoring function and prolonging the degradation time. Once the hydrogel complex was injected into the osteochondral defect, in situ UV light curing was applied to seamlessly connect the defect repair tissue with the surrounding normal cartilage tissue. The small molecule active substance kartogenin (KGN) can promote cartilage repair. We encapsulated KGN in biomimetic scaffolds so that, as the scaffold degrades, scaffold-loaded KGN was slowly released to induce endogenous mesenchymal stem cells to home and differentiate into chondrocytes to repair defective cartilage tissue. Our experiments have proven that, compared with the control group, GELMA/PEGDA + KGN repaired cartilage defects and restored cartilage to hyaline cartilage. Our study suggests that implementing photosensitive, injectable, interpenetrating, and kartogenin-modified GELMA/PEDGA biomimetic scaffolds may be a novel approach to restore cartilage integrity in full-thickness osteochondral defects.

Biomechanical Characteristics of the Femoral Isthmus during Total Hip Arthroplasty in Patients with Adult Osteoporosis and Developmental Dysplasia of the Hip: A Finite Element Analysis.

OBJECTIVE: This study investigated the underlying mechanisms of high fracture incidence in the femoral isthmus from a biomechanical perspective. METHODS: We retrospectively analyzed a total of 923 primary total hip arthroplasty (THA) patients and 355 osteoporosis (OP) patients admitted from January 2010 to January 2018. Through a series of screening conditions, 47 patients from each group were selected for inclusion in the study. The datasets on the unaffected side and affected side of the patients with unilateral developmental dysplasia of the hip (uDDH) were respectively classified as the normal group (Group I) and he tDDH group (Group II), and that of patients with osteoporosis were classified as the OP group (Group III). In this study, first, we collected computed tomography (CT) images and measured geometric parameters (inner and outer diameters) of the isthmus. Thereafter, to study biomechanical properties, we established six finite element models and calculated values of von Mises stress for each group with the methods of data conversion and grid processing. RESULTS: Compared with those of patients in the normal group, the values of the inner and outer diameters of femoral isthmus of patients in the DDH group were significantly lower (P < 0.001), while the inner diameters of patients in the OP group were significantly higher (P < 0.001) and the outer diameters of patients in the OP group showed no significant difference (P> 0.05). The cortical rates of patients in the normal group and the DDH group appeared insignificant (P > 0.05), and those of patients in normal group were significantly higher than those of patients in the OP group (P < 0.001). Moreover, patients in the DDH group showed a higher von Mises stress value than patients in the normal group (P < 0.001), but statistically speaking the values between patients in the OP and normal groups were insignificant (P > 0.05). CONCLUSIONS: The relatively shorter inner and outer diameters of the isthmus in DDH resulted in intensive von Mises stress under the torque of the hip location, and induced a high fracture incidence. However, in patients in the OP group, the geometric morphology exhibited no anatomical variation, and the fracture was not due to the intensity of von Mises stress.

Local hemodynamic analysis after coronary stent implantation based on Euler-Lagrange method.

Coronary stents are deployed to treat the coronary artery disease (CAD) by reopening stenotic regions in arteries to restore blood flow, but the risk of the in-stent restenosis (ISR) is high after stent implantation. One of the reasons is that stent implantation induces changes in local hemodynamic environment, so it is of vital importance to study the blood flow in stented arteries. Based on regarding the red blood cell (RBC) as a rigid solid particle and regarding the blood (including RBCs and plasma) as particle suspensions, a non-Newtonian particle suspensions model is proposed to simulate the realistic blood flow in this work. It considers the blood's flow pattern and non-Newtonian characteristic, the blood cell-cell interactions, and the additional effects owing to the bi-concave shape and rotation of the RBC. Then, it is compared with other four common hemodynamic models (Newtonian single-phase flow model, Newtonian Eulerian two-phase flow model, non-Newtonian single-phase flow model, non-Newtonian Eulerian two-phase flow model), and the comparison results indicate that the models with the non-Newtonian characteristic are more suitable to describe the realistic blood flow. Afterwards, based on the non-Newtonian particle suspensions model, the local hemodynamic environment in stented arteries is investigated. The result shows that the stent strut protrusion into the flow stream would be likely to produce the flow stagnation zone. And the stent implantation can make the pressure gradient distribution uneven. Besides, the wall shear stress (WSS) of the region adjacent to every stent strut is lower than 0.5 Pa, and along the flow direction, the low-WSS zone near the strut behind is larger than that near the front strut. What's more, in the regions near the struts in the proximal of the stent, the RBC particle stagnation zone is easy to be formed, and the erosion and deposition of RBCs are prone to occur. These hemodynamic analyses illustrate that the risk of ISR is high in the regions adjacent to the struts in the proximal and the distal ends of the stent when compared with struts in other positions of the stent. So the research can provide a suggestion on the stent design, which indicates that the strut structure in these positions of a stent should be optimized further.

Microalloying Design of Biodegradable Mg-2Zn-0.05Ca Promises Improved Bone-Implant Applications.

Mg and its alloys have been comprehensively studied and show huge potential for clinical orthopedic applications. However, balancing the mechanical strength and corrosion resistance of alloys is still a challenge. In light of this, micro-level contents of Zn and Ca were added to pure Mg to fabricate a Mg-2Zn-0.05Ca microalloy to expectedly enhance the mechanical strength and concurrently improve the corrosion resistance. The characteristics of the rolled Mg-2Zn-0.05Ca microalloy were explored using optical microscopy, X-ray diffraction, and tensile tests. The corrosion behavior and mechanical strength loss were explored using electrochemical and immersion tests. The effects of the microalloy extract on the proliferation, adhesion, and osteogenic differentiation of MC3T3-E1 cells were systematically studied. Moreover, implantations were done in femoral condyles of rabbits to study the degradation properties, osteogenic effect, mechanical strength loss, and biosafety of the microalloy. The ultimate tensile strength and yield strength of the rolled microalloy were found to be significantly elevated to 257 ± 2.74 and 237.6 ± 8.29 MPa, respectively. The microalloy showed a stable and gradual strength loss during degradation, both in vivo and in vitro. Concurrently, the microalloy exhibited improved corrosion resistance ability and especially, in vivo, the rolled microalloy exhibited a comparable degradation rate to that of rolled pure Mg within the initial 12 weeks of implantation. Additionally, the microalloy promoted osteogenesis, both in vitro and in vivo, and no short- and long-term toxicities of the microalloy were observed in rabbits. This study suggested that the rolled Mg-2Zn-0.05Ca microalloy effectively balanced the mechanical strength and corrosion resistance and showed potential application as bone implants.

A tricalcium phosphate/polyether ether ketone anchor bionic fixation device for anterior cruciate ligament reconstruction: Safety and efficacy in a beagle model.

The goal of this study was to develop a bionic fixation device based on the use of a tricalcium phosphate/polyether ether ketone anchor and harvesting of the ulnar carpal flexor muscle tendon for application as a ligament graft in a beagle anterior cruciate ligament (ACL) reconstruction model, with the goal of accelerating the ligament graft-to-bone tunnel healing and providing a robust stability through exploration of this new kind of autologous ligament graft. The safety and efficacy of this fixation device were explored 3 and 6 months after surgery in a beagle ACL reconstruction model using biomechanical tests and comprehensive histological observation. The data were compared using a two-tailed Student's t test and a paired t test. A p value <0.05 was defined as statistically significant. All the models were successfully established. This fixation device possessed the excellent mechanical properties for ACL reconstruction. A comprehensive histological observation revealed that a cartilage layer was visible in the transition zone between the tendon and bone interface at both 3 and 6 months postoperation. The trabecular of the new bone was observed six months after surgery and was found to be similar to a direct connection. This fixation technique provided not only a robust primary mechanical fixation but also a bionic fixation for long-term knee joint stability by accelerating the healing of the tendon to the bone tunnel, showing a high potential for use in clinical practice. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2018. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 554-563, 2019.

Special Biodegradable Fixation Device for Anterior Cruciate Ligament Reconstruction-Safety and Efficacy in a Beagle Model.

This study aimed to evaluate the safety and efficacy of the special WE43 magnesium alloy stretch plates (SPs) used as fixation device for anterior cruciate ligament (ACL) reconstruction in a beagle model. Eleven beagle dogs underwent ACL reconstruction using WE43 SPs to fix the ligament grafts with the femoral ends, whereas titanium interferences were employed in the tibia ends. Load-to-failure tests were conducted to evaluate the mechanical properties. A comprehensive set of histological observations was performed to observe the local tissue response and assess the status of the attachment between the bone tissue and ligament grafts. Microcomputed tomography and scanning electron microscopy in conjunction with energy spectrum analysis were conducted to evaluate the degradation rate in vivo and investigate the morphology of the cross-section of the SPs and the element distribution in vivo. Immersion tests were employed to investigate the corrosion properties in vitro. The special WE43 SPs showed not only good mechanical strength but also a suitable degradation rate in vivo. The results indicated the special WE43 SP could be considered as a novel fixation device for ACL reconstruction.

Identification of potential target genes associated with the pathogenesis of osteoarthritis using microarray based analysis.

The aim of the present study was to investigate the molecular circuitry of osteoarthritis (OA) and identify more potential target genes for OA treatment. Microarray data of GSE32317 was downloaded from the National Center for Biotechnology Information Gene Expression Omnibus database. Differentially expressed genes (DEGs) were identified in samples of synovial membrane from patients with early stage of knee OA (OA_Early) and late stage of knee OA (OA_End) that were compared with healthy specimens. Bioinformatics analysis was applied to analyze the significant functions and pathways that were enriched by the common DEGs identified in OA_Early and OA_End samples. Furthermore, a protein­protein interaction (PPI) network was constructed and significant modules were extracted. Transcription factors (TFs) that could regulate genes in the significant modules were identified. A total of 1,207 and 1,575 DEGs were identified in OA_Early and OA_End samples compared with healthy samples, respectively. A total of 740 genes were upregulated and 308 genes were downregulated across the OA_Early and OA_End samples. These common DEGs were enriched in different gene ontology terms and pathways, such as immune response. Angiotensinogen (AGT) and C­X­C motif chemokine ligand 12 (CXCL12) were identified to be hub proteins in the PPI network or in the selected module 1. In addition, the DEG lysine demethylase 2B (KDM2B) was identified as a TF that can regulate genes in the significant modules 2 and 3. In conclusion, the present study has identified AGT, CXCL12 and KDM2B as potentially essential genes associated with the pathogenesis of knee OA.

Morphological characteristics of cartilage-bone transitional structures in the human knee joint and CAD design of an osteochondral scaffold.

BACKGROUND: There is a lack of understanding of the morphological characteristics of the cartilage-bone interface. Materials that are currently being used in tissue engineering do not adequately support the regeneration of bone and cartilage tissues. The present study aimed to explore the morphological characteristics of cartilage-bone transitional structures in the human knee joint and to design a biomimetic osteochondral scaffold based on morphological data. METHODS: Histology, micro-computed tomography (micro-CT), and scanning electron microscopy (SEM) were used to investigate the microstructure of the cartilage-bone transitional structures. Morphological characteristics and their distribution were obtained and summarized into a biomimetic design. A three-dimensional model of a biomimetic osteochondral scaffold was CAD designed. A prototype of the resulting subchondral bone scaffold was constructed by stereolithography using resin. RESULTS: Micro-CT revealed that subchondral bone presented a gradually changing structure from the subchondral to spongy bone tissue. The subchondral bone plate was more compact with ~20 % porosity compared with ~60 % porosity for the spongy bone. Histology and SEM showed that cartilage was stabilized on the subchondral bone plate by conjunctions, imbedding, interlocking, and binding forces generated by collagen fibers. Some scattered defects allow blood vessel invasion and nutritional supply. CONCLUSIONS: The subchondral bone plate is not an intact plate between the cartilage and bone cavity, and some scattered defects exist that allow blood vessel invasion and nutritional supply. This characteristic was used to design an osteochondral scaffold. This could be used to construct an osteochondral complex that is similar to native bones.

Association between TRAIL gene polymorphisms and the susceptibility and severity of lumbar disc degeneration.

AIM: The aim of the present study was to investigate the association between tumor necrosis factor related apoptosis-inducing ligand (TRAIL) gene polymorphisms and the susceptibility and severity of lumbar disc degeneration (LDD) in the Chinese Han population. METHODS: A total of 153 patients with LDD and 131 healthy subjects were enrolled in the study. Four single-nucleotide polymorphisms (SNPs) in the 3' untranslated region (3'UTR) of TRAIL gene, including 1289 C/A, 1525 G/A, 1588 G/A and 1595 C/T, were genotyped with polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis. RESULTS: The genotypes and alleles frequencies of TRAIL at 1525 and 1595 positions in all subjects were the same. There was a significant association between TRAIL 1525/1595 polymorphisms and the susceptibility of LDD. The frequencies of 1525 GG /1595 CC genotype, and 1525 G/1595 C allele were higher in the patients group than that in the control group. In addition, we found patients with the 1525 AA /1595 TT genotype, as well as 1525 A/1595 T allele exhibit significantly low frequency of high grades of disc degeneration. However, there were no significant differences in the genotype or allele distribution of TRAIL 1289 C/A or 1588 G/A between the patients and the control group. CONCLUSION: TRAIL 1525/1595 polymorphisms were associated with the susceptibility and severity of LDD in the Chinese Han population.

The effect of interface microstructure on interfacial shear strength for osteochondral scaffolds based on biomimetic design and 3D printing.

Interface integration between chondral phase and osseous phase is crucial in engineered osteochondral scaffolds. However, the integration was poorly understood and commonly failed to meet the need of osteochondral scaffolds. In this paper, a biphasic polyethylene glycol (PEG)/ß-tricalcium phosphate (ß-TCP) scaffold with enhanced interfacial integration was developed. The chondral phase was a PEG hydrogel. The osseous phase was a ß-TCP ceramic scaffold. The PEG hydrogel was directly cured on the ceramic interface layer by layer to fabricate osteochondral scaffolds by 3D printing technology. Meanwhile, a series of interface structure were designed with different interface pore area percentages (0/10/20/30/40/50/60%), and interfacial shear test was applied for interface structure optimization (n=6 samples/group). The interfacial shear strength of 30% pore area group was nearly three folds improved compared with that of 0% pore area percentage group, and more than fifty folds improved compared with that of traditional integration (5.91±0.59 kPa). In conclusion, the biomimetic PEG/ß-TCP scaffolds with interface structure enhanced integration show promising potential application for osteochondral tissue engineering.

Cartilage repair and subchondral bone migration using 3D printing osteochondral composites: a one-year-period study in rabbit trochlea.

Increasing evidences show that subchondral bone may play a significant role in the repair or progression of cartilage damage in situ. However, the exact change of subchondral bone during osteochondral repair is still poorly understood. In this paper, biphasic osteochondral composite scaffolds were fabricated by 3D printing technology using PEG hydrogel and ß-TCP ceramic and then implanted in rabbit trochlea within a critical size defect model. Animals were euthanized at 1, 2, 4, 8, 16, 24, and 52 weeks after implantation. Histological results showed that hyaline-like cartilage formed along with white smooth surface and invisible margin at 24 weeks postoperatively, typical tidemark formation at 52 weeks. The repaired subchondral bone formed from 16 to 52 weeks in a "flow like" manner from surrounding bone to the defect center gradually. Statistical analysis illustrated that both subchondral bone volume and migration area percentage were highly correlated with the gross appearance Wayne score of repaired cartilage. Therefore, subchondral bone migration is related to cartilage repair for critical size osteochondral defects. Furthermore, the subchondral bone remodeling proceeds in a "flow like" manner and repaired cartilage with tidemark implies that the biphasic PEG/ß-TCP composites fabricated by 3D printing provides a feasible strategy for osteochondral tissue engineering application.

A novel silk-based artificial ligament and tricalcium phosphate/polyether ether ketone anchor for anterior cruciate ligament reconstruction - safety and efficacy in a porcine model.

Loss of ligament graft tension in early postoperative stages following anterior cruciate ligament (ACL) reconstruction can come from a variety of factors, with slow graft integration to bone being widely viewed as a chief culprit. Toward an off-the-shelf ACL graft that can rapidly integrate to host tissue, we have developed a silk-based ACL graft combined with a tricalcium phosphate (TCP)/polyether ether ketone anchor. In the present study we tested the safety and efficacy of this concept in a porcine model, with postoperative assessments at 3months (n=10) and 6months (n=4). Biomechanical tests were performed after euthanization, with ultimate tensile strengths at 3months of ∼370N and at 6months of ∼566N - comparable to autograft and allograft performance in this animal model. Comprehensive histological observations revealed that TCP substantially enhanced silk graft to bone attachment. Interdigitation of soft and hard tissues was observed, with regenerated fibrocartilage characterizing a transitional zone from silk graft to bone that was similar to native ligament bone attachments. We conclude that both initial stability and robust long-term biological attachment were consistently achieved using the tested construct, supporting a large potential for silk-TCP combinations in the repair of the torn ACL.

[Cartilage repair and subchondral bone reconstruction based on three-dimensional printing technique].

OBJECTIVE: To investigate whether subchondral bone microstructural parameters are related to cartilage repair during large osteochondral defect repairing based on three-dimensional (3-D) printing technique. METHODS: Biomimetic biphasic osteochondral composite scaffolds were fabricated by using 3-D printing technique. The right trochlea critical sized defects (4.8 mm in diameter, 7.5 mm in depth) were created in 40 New Zealand white rabbits (aged 6 months, weighing 2.5-3.5 kg). Biomimetic biphasic osteochondral composite scaffolds were implanted into the defects in the experimental group (n = 35), and no composite scaffolds implantation served as control group (n = 5); the left side had no defect as sham-operation group. Animals of experimental and sham-operation groups were euthanized at 1, 2, 4, 8, 16, 24, and 52 weeks after operation, while animals of control group were sampled at 24 weeks. Subchondral bone microstructural parameters and cartilage repair were quantitatively analyzed using Micro-CT and Wayne scoring system. Correlation analysis and regression analysis were applied to reveal the relationship between subchondral bone parameters and cartilage repair. The subchondral bone parameters included bone volume fraction (BV/TV), bone surface area fraction (BSA/BV), trabecular thickness (Tb.Th), trabecular number (Tb.N), and trabecular spacing (Tb.Sp). RESULTS: In the experimental group, articular cartilage repair was significantly improved at 52 weeks postoperatively, which was dominated by hyaline cartilage tissue, and tidal line formed. Wayne scores at 24 and 52 weeks were significantly higher than that at 16 weeks in the experimental group (P < 0.05), but no significant difference was found between at 24 and 52 weeks (P > 0.05); the scores of experimental group were significantly lower than those of sham-operation group at all time points (P < 0.05). In the experimental group, new subchondral bone migrated from the surrounding defect to the centre, and subchondral bony plate formed at 24 and 52 weeks. The microstructural parameters of repaired subchondral bone followed a "twin peaks" like discipline to which BV/TV, BSA/BV, and Tb.N increased at 2 and 16 weeks, and then they returned to normal level. The Tb.Sp showed reversed discipline compared to the former 3 parameters, no significant change was found for Tb.Th during the repair process. Correlation analysis showed that BV/TV, BSA/BV, Tb.Th, Tb.N, and Tb.Sp were all related with gross appearance score and histology score of repaired cartilage. CONCLUSION: Subchondral bone parameters are related with cartilage repair in critical size osteochondral repair in vivo. Microstructural parameters of repaired subchondral bone follow a "twin peaks" like discipline (osteoplasia-remodeling-osteoplasia-remodeling) to achieve reconstruction, 2nd week and 16th week are critical time points for subchondral bone functional restoration.

[Fabrication and in vivo implantation of ligament-bone composite scaffolds based on three-dimensional printing technique].

OBJECTIVE: To solve the fixation problem between ligament grafts and host bones in ligament reconstruction surgery by using ligament-bone composite scaffolds to repair the ligaments, to explore the fabrication method for ligament-bone composite scaffolds based on three-dimensional (3-D) printing technique, and to investigate their mechanical and biological properties in animal experiments. METHODS: The model of bone scaffolds was designed using CAD software, and the corresponding negative mould was created by boolean operation. 3-D printing techinique was employed to fabricate resin mold. Ceramic bone scaffolds were obtained by casting the ceramic slurry in the resin mould and sintering the dried ceramics-resin composites. Ligament scaffolds were obtained by weaving degummed silk fibers, and then assembled with bone scaffolds and bone anchors. The resultant ligament-bone composite scaffolds were implanted into 10 porcine left anterior cruciate ligament rupture models at the age of 4 months. Mechanical testing and histological examination were performed at 3 months postoperatively, and natural anterior cruciate ligaments of the right sides served as control. RESULTS: Biomechanical testing showed that the natural anterior cruciate ligament of control group can withstand maximum tensile force of (1 384 +/- 181) N and dynamic creep of (0.74 +/- 0.21) mm, while the regenerated ligament-bone scaffolds of experimental group can withstand maximum tensile force of (370 +/- 103) N and dynamic creep of (1.48 +/- 0.49) mm, showing significant differences (t = 11.617, P = 0.000; t = 2.991, P = 0.020). In experimental group, histological examination showed that new bone formed in bone scaffolds. A hierarchical transition structure regenerated between ligament-bone scaffolds and the host bones, which was similar to the structural organizations of natural ligament-bone interface. CONCLUSION: Ligament-bone composite scaffolds based on 3-D printing technique facilitates the regeneration of biomimetic ligament-bone interface. It is expected to achieve physical fixation between ligament grafts and host bone.

A novel silk-TCP-PEEK construct for anterior cruciate ligament reconstruction: an off-the shelf alternative to a bone-tendon-bone autograft.

Bone-tendon-bone autograft represents a gold-standard for anterior cruciate ligament (ACL) reconstruction but at the cost of a secondary surgical site that can be accompanied by functional impairment and discomfort. Although numerous in vitro and in vivo studies have investigated tissue engineering alternatives to autografting, the achievement of a functional histological transition between soft and hard tissue has remained elusive. To bridge this gap we developed and tested a novel multiphase scaffold of silk, tricalcium phosphate (TCP) and polyether ether ketone for ACL reconstruction. We present in vitro biomechanical tests demonstrating that the construct recapitulates native ACL function under typical physiological loads. A pilot in vivo experiment in two pigs with a three-month follow-up showed a robust histological transition between regenerated fibrous tissue and the margins of the bone tunnel, with histological features similar to the native ACL to bone insertion. These histological observations suggest that the construct was stably anchored until TCP incorporation to the host tissues. On the strength of these preliminary results, we conclude that the described approach may offer a promising alternative to autograft for ACL reconstruction. This study thus provides proof for a concept that warrants further development.

Reconstruction of comminuted long-bone fracture using CF/CPC scaffolds manufactured by rapid prototyping.

BACKGROUND: Stabilization and bone healing of fractures in weight-bearing long bones are challenging. This study was conducted to evaluate the effect of a scaffold composed of chitosan fiber and calcium phosphate ceramics (CF/CPC scaffold) on stability and fracture repair in weight-bearing long bones. MATERIAL/METHODS: Comminuted fractures of paired radiuses were created in 36 healthy, mature dogs. The left radius of each dog was classified in the experimental group and treated with CF/CPC scaffold, and the right one was not filled, and was used as a blank control. Of the 12 animals in each group that were killed at week 4, 8, and 12 after the operation, 6 were used for histological analysis, and the other 6 used were for biomechanical studies. Both radiuses from each animal were dissected free and stored for these analyses. All the animals underwent X-ray radiograph pre- and post-operatively. Computer-aided rapid-prototyping technologies were adopted for the fabrication of three-dimensional scaffolds with precise geometric control. RESULTS: X-ray showed that the bone fracture area in the experimental group was filled with callus at week 12 after surgery. Histological examination detected slow resorption of the cement and new bone formation since week 4. At week 12, the scaffold material partially degraded and was still present in all specimens. Mechanical testing revealed that the failure strength of the radiuses treated with CF/CPC scaffolds was about 3 times that of the radiuses without implanted scaffolds. CONCLUSIONS: The effect of using CF/CPC scaffold in treating comminuted weight-bearing long bone fractures is satisfactory.