Multimaterial Printing of Serpentine Microarchitectures with Synergistic Mechanical/Piezoelectric Stimulation for Enhanced Cardiac-Specific Functional Regeneration.

Recreating the natural heart's mechanical and electrical environment is crucial for engineering functional cardiac tissue and repairing infarcted myocardium in vivo. In this study, multimaterial-printed serpentine microarchitectures are presented with synergistic mechanical/piezoelectric stimulation, incorporating polycaprolactone (PCL) microfibers for mechanical support, polyvinylidene fluoride (PVDF) microfibers for piezoelectric stimulation, and magnetic PCL/Fe3O4 for controlled deformation via an external magnet. Rat cardiomyocytes in piezoelectric constructs, subjected to dynamic mechanical stimulation, exhibit advanced maturation, featuring superior sarcomeric structures, improved calcium transients, and upregulated maturation genes compared to non-piezoelectric constructs. Furthermore, these engineered piezoelectric cardiac constructs demonstrate significant structural and functional repair of infarcted myocardium, as evidenced by enhanced ejection and shortening fraction, reduced fibrosis and inflammation, and increased angiogenesis. The findings underscore the therapeutic potential of piezoelectric cardiac constructs for myocardial infarction therapy.

[Development and Challenges of Additive Manufactured Customized Implant].

Additive manufacturing (3D printing) technology aligns with the direction of precision and customization in future medicine, presenting a significant opportunity for innovative development in high-end medical devices. Currently, research and industrialization of 3D printed medical devices mainly focus on nondegradable implants and degradable implants. Primary areas including metallic orthopaedic implants, polyether-ether-ketone (PEEK) bone implants, and biodegradable implants have been developed for clinical and industrial application. Recent research achievements in these areas are reviewed, with a discussion on the additive manufacturing technologies and applications for customized implants. Challenges faced by different types of implants are analyzed from technological, application, and regulatory perspectives. Furthermore, prospects and suggestions for future development are outlined.

Electrohydrodynamic Printing of Microfibrous Architectures with Cell-Scale Spacing for Improved Cellular Migration and Neurite Outgrowth.

Electrohydrodynamic (EHD) printing provides unparalleled opportunities in fabricating microfibrous architectures to direct cellular orientation. However, it faces great challenges in depositing orderly microfibers with cell-scale spacing due to inherent fiber-fiber electrostatic interactions. Here a finite element method is established to analyze the electrostatic forces induced on the EHD-printed microfibers and the relationship between the fiber diameter and spacing for parallel deposition of EHD-printed microfibers is revealed theoretically and experimentally. It is found that uniform fiber arrangement can be achieved when the fiber spacing is five times larger than the fiber diameter. This finding enables the successful printing of parallel fibrous architectures with a fiber diameter of 4.9 ± 0.1 µm and a cell-scale fiber spacing of 25.6 ± 1.9 µm. The resultant microfibrous architectures exhibit unique capability to direct cellular alignment and enhance cellular density and migration as the fiber spacing decreases from 100 to 25 µm. The EHD-printed parallel microfibers with cell-scale spacing are found to improve the outgrowth length of neurites and accelerate the migration of Schwann cells from Dorsal Root Ganglion spheres, which facilitate the formation of densely-arranged and highly-aligned cellular constructs. The presented method is promising to produce biomimetic microfibrous architectures for functional nerve regeneration.

Deciphering Fluid Transport Within Leaf-Inspired Capillary Networks Based on a 3D Computational Model.

Leaf venation provides a promising template for engineering capillary-like vasculature in vitro due to its highly efficient fluid transport capability and remarkable similarities to native capillary networks. A key challenge in exploring the potential biological applications of leaf-inspired capillary networks (LICNs) is to accurately and quantitively understand its internal fluid transport characteristics. Here, a centerline-induced partition-assembly modeling strategy is proposed to establish a 3D computational model, which can accurately simulate the flow conditions in LICNs. Based on the 3D flow simulation, the authors demonstrate the excellent defect-resistant fluid transport capability of LICNs. Interestingly, structural defects in the primary channel can effectively accelerate the overall perfusion efficiency. Flow patterns in LICNs with multiple defects can be estimated by simple superposition of the simulation results derived from the corresponding single-defect models. The 3D computational model is further used to determine the optimal perfusion parameter for the in-vitro formation of endothelialized capillary networks by mimicking native microvascular flow conditions. The endothelialized networks can recapitulate the vascular colonization process and reveal a strong correlation between cancer cell adhesion and flow-induced shear stress. This study offers a quantitative tool to scrutinize the fluid and biological transport mechanisms within LICNs for various biomedical applications.

3D Bioprinting of Multifunctional Dynamic Nanocomposite Bioinks Incorporating Cu-Doped Mesoporous Bioactive Glass Nanoparticles for Bone Tissue Engineering.

Bioprinting has seen significant progress in recent years for the fabrication of bionic tissues with high complexity. However, it remains challenging to develop cell-laden bioinks exhibiting superior physiochemical properties and bio-functionality. In this study, a multifunctional nanocomposite bioink is developed based on amine-functionalized copper (Cu)-doped mesoporous bioactive glass nanoparticles (ACuMBGNs) and a hydrogel formulation relying on dynamic covalent chemistry composed of alginate dialdehyde (oxidized alginate) and gelatin, with favorable rheological properties, improved shape fidelity, and structural stability for extrusion-based bioprinting. The reversible dynamic microenvironment in combination with the impact of cell-adhesive ligands introduced by aminated particles enables the rapid spreading (within 3 days) and high survival (>90%) of embedded human osteosarcoma cells and immortalized mouse bone marrow-derived stroma cells. Osteogenic differentiation of primary mouse bone marrow stromal stem cells (BMSCs) and angiogenesis are promoted in the bioprinted alginate dialdehyde-gelatin (ADA-GEL or AG)-ACuMBGN scaffolds without additional growth factors in vitro, which is likely due to ion stimulation from the incorporated nanoparticles and possibly due to cell mechanosensing in the dynamic matrix. In conclusion, it is envisioned that these nanocomposite bioinks can serve as promising platforms for bioprinting complex 3D matrix environments providing superior physiochemical and biological performance for bone tissue engineering.

Application of Patient-Specific PEEK Implant for Aesthetic Considerations in Paranasal Augmentation.

The paranasal area is closely associated with midfacial esthetics. However, there is no special technique available to achieve ideal esthetics paranasal restoration. The present study aims to apply the 3D printed PolyEtherEtherKetone (PEEK) implants as an innovative solution for esthetic paranasal reconstruction. On the basis of the CT scan, the patient-specific PEEK implant and a surgical guiding plate were manufactured aided by a computer. Preoperative and postoperative CBCT data were utilized to evaluate esthetic outcomes. The average follow-up period was 13 months. All patients' wounds healed by first intention. The statistical analysis of preoperative and postoperative esthetic indices revealed light levels of postoperative paranasal depression ( P <0.001) and the wrinkle severity rating scale for nasolabial folds ( P <0.001). Moreover, the nasolabial angle increased ( P <0.05). The established 3D-printing PEEK implanted prosthesis can individually correct the depressed deformity of the paranasal region, and achieve favorable clinical esthetic outcomes.

Further Development of Magnetic Compression for Gastrojejunostomy in Rabbits.

BACKGROUND: Technical improvement of gastrojejunostomy is critical in bariatric and metabolic surgery. In this study, a novel magnetic compression approach for gastrojejunostomy was evaluated. MATERIALS AND METHODS: Both cylindrical and rectangular magnets were used in rabbits, and the magnets were named according to their location. All the magnets were perorally introduced into the stomach. The position of the jejunal magnet was controlled by a connecting line. When the jejunal magnet spontaneously entered the jejunum, the gastric magnet was introduced into the stomach. An extracorporeal magnet was used to guide these two magnets together, and the magnet pair was left to create a side-to-side anastomosis. The state of the animals and extrusion time of the magnets were observed. The anastomoses were evaluated by burst pressure and histology. RESULTS: Gastrojejunostomy was successfully established in all animals. Cylindrical and rectangular magnets spontaneously entered the jejunum through the pylorus within 2.4 ± 0.5 and 6.0 ± 0.8 d, respectively (P < 0.01). The cylindrical and rectangular magnet pairs fell off within 15.3 ± 0.8 and 11.9 ± 1.1 d, respectively (P < 0.01). The burst pressures were statistically similar between the two types of magnets (P > 0.05). Histological examination showed sealed anastomoses with mild inflammation of the mucosa and fibrosis within the submucosa. CONCLUSIONS: The feasibility and efficacy of establishing gastrojejunostomy by guidewire introduction of magnets, which were guided together with an extracorporeal magnet, were confirmed in rabbits. In humans, with the clinical use of this procedure, surgery would be greatly simplified.

The modified cross-suture technique for unilateral pulled-out anchor during all-inside meniscal repair.

BACKGROUND: Meniscal repair has received increasing attention, but for inexperienced doctors, unilateral suture anchor pulling out may occur during all-inside meniscal repair, and the treatment outcome may be affected. When the errors happened intraoperatively, how to minimize the loss under guaranteeing of treatment effectiveness is a topic worth studying. PURPOSE: To explore the practicability and effectiveness of the modified cross-suture method for arthroscopic remediation of unilateral suture anchor pulling out of an all-inside meniscal repair system. METHODS: From May 2014 to May 2017, 28 patients diagnosed with injuries of the meniscus and anterior cruciate ligaments (ACL) from the First Department of Orthopaedics of the Second Affiliated Hospital of Xi'an Jiaotong University were enrolled in the study as the observation group, including 18 males and 10 females with an average age of 25.5 ± 2.3 years (range 18-42 years). All patients underwent ACL reconstruction concurrently. All meniscus injuries were repaired with an all-inside meniscal repair technique, and 1-3 needles of unilateral suture anchor pulling out occurred intraoperatively. The modified cross-suture method was used to remedy the error of anchor pulling out and to eventually complete an effective repair. Another 30 patients who underwent ACL reconstruction and all-inside meniscal concurrently without unilateral suture anchor pulling out, including 20 males and 10 females with an average age of 26.3 ± 1.9 years (range 19-45 years), were enrolled as the control group. During postoperative follow-up, range of motion, Lachman test and pivot shift test were performed during the physical examination. The clinical healing of the meniscus was evaluated according to the Barrett standard. The meniscus healing status was also confirmed with magnetic resonance imaging (MRI). The function of the knee joint was evaluated according to the IKDC, Lysholm and Tegner scores. RESULTS: Twenty-five patients in the observation group and 28 patients in the control group completed the follow-up, with an average follow-up of 18.4 ± 5.2 months. All operations were performed by the same surgeon. At the follow-up 1 year after the operation, the average knee ROM of the two groups was 125.2 ± 4.3 degrees and 124.7 ± 3.8 degrees, the clinical healing rate of the meniscus of the two groups was 92.0% (23/25) and 92.9% (26/28), the MRI healing rate of the menniscus of the two groups was 72.0% (18/25) and 71.4% (20/28), and the IKDC, Lysholm and Tegner scores of the two groups were 90.52 ± 2.8, 89.17 ± 3.1, and 6.81 ± 1.7 and 91.42 ± 1.9, 90.32 ± 3.4, and 7.02 ± 1.4, respectively. The differences were not statistically significant (P > 0.05). CONCLUSIONS: The modified cross-suture method is practicable and effective for arthroscopic remediation of unilateral suture anchor pulling out in an all-inside meniscal repair system.

Microscale electrohydrodynamic printing of in situ reactive features for patterned ZnO nanorods.

Patterning of zinc oxide (ZnO) nanorods has attracted considerable interests to enhance the performance of ZnO-based functional devices. Most of the existing techniques for patterned ZnO nanorods are based on conventional microfabrication methods that commonly require cleanroom environment, high-cost equipment and complicated processes. In this study, electrohydrodynamic (EHD) printing strategy was accommodated to fabricate microscale ZnO nanorods patterns based on in situ reactive inks. Smaller working voltage and larger nozzle-to-collector distance facilitated the formation of thinner PEO-Zn(NO3)2 filaments, which were decomposed into ZnO nanoparticles to serve as the seeding template for the hydrothermal growth of ZnO nanorods. The resultant ZnO nanorods can be flexibly tuned by the EHD printed patterns. The effect of growth time on the size and morphology of ZnO nanorods was investigated. Compared with the spin-coating method, the photoelectrochemical property of patterned ZnO nanorods was well controlled and showed enhanced photoelectrochemical stability. The presented method provides a flexible and rapid way to customize patterned ZnO nanorods that can be potentially used in the fields of optical detectors, biosensors or solar-driven devices.

Gelatin-based perfusable, endothelial carotid artery model for the study of atherosclerosis.

BACKGROUND: Carotid artery geometry is important for recapitulating a pathophysiological microenvironment to study wall shear stress (WSS)-induced endothelial dysfunction in atherosclerosis. Endothelial cells (ECs) cultured with hydrogel have been shown to exhibit in vivo-like behaviours. However, to date, studies using hydrogel culture have not fully recapitulated the 3D geometry and blood flow patterns of real-life healthy or diseased carotid arteries. In this study, we developed a gelatin-patterned, endothelialized carotid artery model to study the endothelium response to WSS. RESULTS: Two representative regions were selected based on the computational fluid dynamics on the TF-shaped carotid artery: Region ECA (external carotid artery) and Region CS (carotid sinus). Progressive elongation and alignment of the ECs in the flow direction were observed in Region ECA after 8, 16 and 24 h. However, the F-actin cytoskeleton remained disorganized in Region CS after 24 h. Further investigation revealed that expression of vascular cell adhesion molecule-1 (VCAM-1) and intercellular adhesion molecule-1 (ICAM-1) was greatly increased in Region CS relative to that in Region ECA. The physiological WSS in the carotid artery system was found to stimulate nitric oxide (NO) and prostacyclin (PGI2) release and inhibit endothelin-1 (ET-1) release after 24-h perfusion experiments. The effective permeability (E.P) of fluorescein isothiocyanate (FITC)-dextran 40 kDa in Regions ECA and CS was monitored, and it was found that the turbulence WSS value (in Region CS) was less than 0.4 Pa, and there was a significant increase in the E.P relative to that in Region ECA, in which laminar WSS value was 1.56 Pa. The tight junction protein (ZO-1) production was shown that the low WSS in Region CS induced ZO-1-level downregulation compared with that in Region ECA. CONCLUSIONS: The results suggested that the gelatin-based perfusable, endothelial carotid artery model can be effective for studying the pathogenesis of atherosclerosis by which flow dynamics control the endothelium layer function in vitro.

Correction to: Effects of astrocyte on neuronal outgrowth in a layered 3D structure.

It was highlighted that the original article [1] contained an error in the Acknowledgments section.

Effects of astrocyte on neuronal outgrowth in a layered 3D structure.

BACKGROUND: Human brain models and pharmacological models of brain diseases are in high demand for drug screening because animal models have been found to be less than ideal for fully representing the human brain and are likely to fail during drug screening and testing; therefore, the construction of brain-like tissues is necessary. Due to the complexity of cortical tissue, the in vitro construction of brain-like tissue models has been restricted to mostly two-dimensional (2D) models and, on a limited scale, three-dimensional (3D) models. METHODS: In this study, 3D tissue blocks encapsulating neurons and astrocytes were constructed and cultured in vitro to mimic the cortex of the brain and to investigate the effects of astrocytes on the growth of neurons in a 3D culture. RESULTS: The results indicated that such methodology can provide a 3D culture environment suitable for neurons and astrocytes to live and function. When both cells were evenly mixed and cultured in a 3D manner, the astrocytes, which showed better outgrowth and a higher proliferation rate, benefited more than the neurons. On the other hand, the neurons benefited, showing longer axons and a denser network of dendrites, when they were accompanied by astrocytes at a certain distance. CONCLUSION: In conclusion, astrocytes stimulated the outgrowth of neurons in a 3D culture environment in vitro. Regardless, the spatial relationship between both types of cells should be controlled. Thus, culturing cells in a 3D manner is necessary to investigate the correlations between them. This study provides a foundation for biofabricating 3D neurons' cultures to allow for a deeper insight into the relationship between astrocytes or other glial cells and neurons in a 3D culture that is similar to the natural environment of the brain.

Quantitative assessment of cerebral connectivity deficiency and cognitive impairment in children with prenatal alcohol exposure.

It is common knowledge that alcohol consumption during pregnancy would cause cognitive impairment in children. However, recent works suggested that the risk of drinking during pregnancy may have been exaggerated. It is critical to determine whether and up to which amount the consumption of alcohol will affect the cognitive development of children. We evaluate time-varying functional connectivity using magnetoencephalogram data from somatosensory evoked response experiments for 19 teenage subjects with prenatal alcohol exposure and 21 healthy control teenage subjects using a new time-varying connectivity approach, combining renormalised partial directed coherence with state space modeling. Children exposed to alcohol prenatally are at risk of developing a Fetal Alcohol Spectrum Disorder (FASD) characterized by cerebral connectivity deficiency and impaired cognitive abilities. Through a comparison study of teenage subjects exposed to alcohol prenatally with healthy control subjects, we establish that the inter-hemispheric connectivity is deficient for the former, which may lead to disruption in the cortical inter-hemispheric connectivity and deficits in higher order cognitive functions as measured by an IQ test, for example. We provide quantitative evidence that the disruption is correlated with cognitive deficits. These findings could lead to a novel, highly sensitive biomarker for FASD and support a recommendation of no safe amount of alcohol consumption during pregnancy.

Activation of Sonic Hedgehog Signaling Is Associated with Human Osteosarcoma Cells Radioresistance Characterized by Increased Proliferation, Migration, and Invasion.

BACKGROUND Radioresistance restricts the application of radiotherapy in human osteosarcoma (OS). This study investigated the molecular mechanism of radioresistance in OS, which may provide clues to finding ideal targets for genetic therapy. MATERIAL AND METHODS The human OS cell line MG63 was employed as parent cells. After repeat low-dose X-ray irradiation of MG63, the radioresistant OS cell line MG63R was produced. Colony formation assay was used to assess the radioresistance. Cell viability was evaluated by CCK-8 assay. Flow cytometry was used to detect cell apoptosis, and wound healing assay was used to evaluate invasive capacity. The nuclear translocation was evaluated by fluorescent immunohistochemistry. Protein expression levels were assessed by Western blotting. Specific siRNA against Shh was used to silence Shh. RESULTS More survival colony formation, elevated cell viability, less cell apoptosis, and increased wound closure were found in MG63R than in MG63 cells exposed to irradiation. The nuclear translocation of Gli, expression levels of Shh, Smo, Ptch1, Bcl2, active MMP2, and active MMP9 were increased in MG63R cells compared with MG63 cells. Transfection of Shh-siRNA suppressed expression levels of Shh, Smo, Ptch1, Bcl2, active MMP2, and active MMP9, as well as the nuclear translocation of Gli in MG63R cells. The cell viability, survival colony formation, and wound closure were impaired, whereas cell apoptosis was increased, in siRNA-transfected MG63R cells than in control MG63R cells exposed to irradiation. CONCLUSIONS Activation of Shh signaling was involved in radioresistance of OS cells. Blocking this signaling can impair the radioresistance capacity of OS cells.

A study of cryogenic tissue-engineered liver slices in calcium alginate gel for drug testing.

To address issues such as transportation and the time-consuming nature of tissue-engineered liver for use as an effective drug metabolism and toxicity testing model, "ready-to-use" cryogenic tissue-engineered liver needs to be studied. The research developed a cryogenic tissue-engineered liver slice (TELS), which comprised of HepG2 cells and calcium alginate gel. Cell viability and liver-specific functions were examined after different cryopreservation and recovery culture times. Then, cryogenic TELSs were used as a drug-testing model and treated with Gefitinib. Cryogenic TELSs were stored at -80 °C to ensure high cell viability. During recovery in culture, the cells in the cryogenic TELS were evenly distributed, massively proliferated, and then formed spheroid-like aggregates from day 1 to day 13. The liver-specific functions in the cryogenic TELS were closely related to cryopreservation time and cell proliferation. As a reproducible drug-testing model, the cryogenic TELS showed an obvious drug reaction after treatment with the Gefitinib. The present study shows that the cryopreservation techniques can be used in drug-testing models.

A Method of Accurate Bone Tunnel Placement for Anterior Cruciate Ligament Reconstruction Based on 3-Dimensional Printing Technology: A Cadaveric Study.

PURPOSE: To explore a method of bone tunnel placement for anterior cruciate ligament (ACL) reconstruction based on 3-dimensional (3D) printing technology and to assess its accuracy. METHODS: Twenty human cadaveric knees were scanned by thin-layer computed tomography (CT). To obtain data on bones used to establish a knee joint model by computer software, customized bone anchors were installed before CT. The reference point was determined at the femoral and tibial footprint areas of the ACL. The site and direction of the bone tunnels of the femur and tibia were designed and calibrated on the knee joint model according to the reference point. The resin template was designed and printed by 3D printing. Placement of the bone tunnels was accomplished by use of templates, and the cadaveric knees were scanned again to compare the concordance of the internal opening of the bone tunnels and reference points. RESULTS: The twenty 3D printing templates were designed and printed successfully. CT data analysis between the planned and actual drilled tunnel positions showed mean deviations of 0.57 mm (range, 0-1.5 mm; standard deviation, 0.42 mm) at the femur and 0.58 mm (range, 0-1.5 mm; standard deviation, 0.47 mm) at the tibia. CONCLUSIONS: The accuracy of bone tunnel placement for ACL reconstruction in cadaveric adult knees based on 3D printing technology is high. CLINICAL RELEVANCE: This method can improve the accuracy of bone tunnel placement for ACL reconstruction in clinical sports medicine.

[Motion analysis on patients with knee osteoarthritis merged with varus deformity].

Aiming at comparing the pre-operative and post-operative gait characteristics and therefore establishing post-operative rehabilitation guidance for patients with end-stage knee osteoarthritis (KOA) merged with varus deformity, this study captured the level walking and sit-to-stand trials of 9 patients with 3-dimensional motion analysis system and after which musculoskeletal multi-body dynamic analysis was conducted. The study indicated that the average range of motion (ROM) of the proposed-surgical knee was 24.4°-57.6° and that of the non-surgical knee was 22.5°-71.5°. The knee ROM of control group during level walking was 7.2°-62.4°. When the unilateral KOA patients stood up from chair to complete the sit-to-stand movement, the ground reaction forces (GRFs) symmetry was 0.72-0.85, which means that the non-surgical limb bear the majority of body weight. The GRFs of the bilateral KOA patients were smallest during the sit-to-stand movement. The strategy that the non-surgical limb dominates in loading bearing taken by the unilateral KOA patients to cover most post-operative daily activities could increase the risk of KOA among non-surgical side joints as a result of long-term excessive loading-bearing. The study, on kinematics and biomechanical characteristics of patients with KOA merged with varus deformity, could help to understand the pathogenesis of KOA merged with varus deformity from the perspective of biomechanics and to provide strong clinic guidance for the pre-operative evaluation, prevention and post-operative recovery for patients.

Microscale Electro-Hydrodynamic Cell Printing with High Viability.

Cell printing has gained extensive attentions for the controlled fabrication of living cellular constructs in vitro. Various cell printing techniques are now being explored and developed for improved cell viability and printing resolution. Here an electro-hydrodynamic cell printing strategy is developed with microscale resolution (<100 µm) and high cellular viability (>95%). Unlike the existing electro-hydrodynamic cell jetting or printing explorations, insulating substrate is used to replace conventional semiconductive substrate as the collecting surface which significantly reduces the electrical current in the electro-hydrodynamic printing process from milliamperes (>0.5 mA) to microamperes (<10 µA). Additionally, the nozzle-to-collector distance is fixed as small as 100 µm for better control over filament deposition. These features ensure high cellular viability and normal postproliferative capability of the electro-hydrodynamically printed cells. The smallest width of the electro-hydrodynamically printed hydrogel filament is 82.4 ± 14.3 µm by optimizing process parameters. Multiple hydrogels or multilayer cell-laden constructs can be flexibly printed under cell-friendly conditions. The printed cells in multilayer hydrogels kept alive and gradually spread during 7-days culture in vitro. This exploration offers a novel and promising cell printing strategy which might benefit future biomedical innovations such as microscale tissue engineering, organ-on-a-chip systems, and nanomedicine.

Multi-frequency fringe projection profilometry based on wavelet transform.

Based on wavelet transforms (WTs), an alternative multi-frequency fringe projection profilometry is described. Fringe patterns with multiple frequencies are projected onto an object and the reflected patterns are recorded digitally. Phase information for every pattern is calculated by identifying the ridge that appears in WT results. Distinct from the phase unwrapping process, a peak searching algorithm is applied to obtain object height from the phases of the different frequency for a single point on the object. Thus, objects with large discontinuities can be profiled. In comparing methods, the height profiles obtained from the WTs have lower noise and higher measurement accuracy. Although measuring times are similar, the proposed method offers greater reliability.

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.