Recent Advances in Cell Sheet-Based Tissue Engineering for Bone Regeneration.

In conventional bone tissue engineering, cells are seeded onto scaffolds to create three-dimensional (3D) tissues, but the cells on the scaffolds are unable to effectively perform their physiological functions due to their low density and viability. Cell sheet (CS) engineering is expected to be free from this limitation. CS engineering uses the principles of self-assembly and self-organization of endothelial and mesenchymal stem cells to prepare CSs as building blocks for engineering bone grafts. This process recapitulates the native tissue development, thus attracting significant attention in the field of bone regeneration. However, the method is still in the prebasic experimental stage in bone defect repair. To make the method clinically applicable and valuable in personalized and precision medicine, current research is focused on the preparation of multifunctionalized building blocks using CS technologies, such as 3D layered CSs containing microvascular structures. Considering the great potential of CS engineering in repairing bone defects, in this review, the types of cell technologies are first outlined. We then summarize the various types of CSs as building blocks for engineering bone grafts. Furthermore, the specific applications of CSs in bone repair are discussed. Finally, we present specific suggestions for accelerating the application of CS engineering in the clinical treatment of bone defects.

A study on the mechanisms of teachers' academic emotions and motivational beliefs on learning engagement in the context of online training.

Introduction: In the context of digital transformation of education, online training is one of the important ways for teachers to improve their professionalism and promote the quality of education. However, studies have shown that teachers' online training suffers from insufficient learning engagement and other problems, so it is crucial to explore the factors influencing teachers' learning engagement and their mechanisms of action in the context of online training. Methods: Taking 589 teachers who participated in online training as the research subjects, the study used the methods of survey research and statistical analysis to explore the influence mechanism of teachers' academic emotions and motivational beliefs on online learning engagement based on the dual perspectives of control value theory and expectancy-value theory. Results: The study found that: (1) positive-high arousal academic emotions, training self-efficacy, and training task value significantly and positively predicted online learning engagement, respectively; (2) negative-high arousal and negative-low arousal academic emotions significantly and negatively predicted online learning engagement; (3) training self-efficacy and training task value mediated the relationship between positive-high arousal academic emotions, negative-high arousal academic emotions, negative-low arousal academic emotions and online learning engagement, respectively. Discussion: The study concluded that by creating an immersive learning environment based on the educational meta universe, personalized and precise training based on big data and adaptive technologies, and establishing a multi-dimensional and three-dimensional online learning support service system, which can effectively improve teachers' online learning engagement and enhance their online training quality and effectiveness.

The Role of Macrophage Phenotype in the Vascularization of Prevascularized Human Bone Marrow Mesenchymal Stem Cell Sheets.

With the development of tissue engineering and regenerative medicine, prevascularized bone marrow mesenchymal stem cell (BMSC) sheets have been regarded as a promising method for tissue regeneration. Furthermore, the inflammatory response is one of the main regulators of vascularization and the restoration of engineered tissue function; among them, macrophages and cytokines produced by them are considered to be the decisive factors of the downstream outcomes. This study investigated the effect of macrophages on the formation of microvascular-like structures of human umbilical vein endothelial cells (HUVECs) in BMSC sheets. First, a human monocytic leukemia cell line (THP-1 cells) was differentiated into derived macrophages (M0) with phorbol 12-myristate 13-acetate and further activated into proinflammatory macrophages (M1 macrophages) with interferon-γ and lipopolysaccharide or anti-inflammatory macrophages (M2 macrophages) with interleukin-4. Then, HUVECs and prevascularized sheets were treated with conditioned media (CM) from different macrophages, and the impact of macrophage phenotypes on vascularized network formation in prevascularized cell sheets was examined by hematoxylin and eosin staining, CD31 immunofluorescence staining and enzyme-linked immunosorbent assay. Our study showed that macrophages may guide the arrangement of endothelial cells through a paracrine pathway. Cell sheets that were cultured in the CM from M2 macrophages were thinner than those cultured in other media. At various time points, the levels of tumor necrosis factor alpha and vascular endothelial growth factor in prevascularized sheets cultured with CM(M1) was higher than that in sheets cultured with other media; however, the levels of platelet-derived growth factor in prevascularized sheets cultured with CM(M2) was higher than that in sheets cultured with other media. These findings suggest that the paracrine effect of macrophages can influence the formation of microvascular networks in prevascularized sheets by regulating the arrangement of cells, the thickness of the cell sheet and the secretion of cytokines related to angiogenesis. Macrophages with different phenotypes have unique effects on prevascularized sheets.

Large-Scale Plasma-Polymerized Hexamethyldisiloxane Thin Films: Role of Interelectrode Distance and Excellent Corrosion Resistance.

In comparison to the more traditional anticorrosion thin film coatings, the plasma polymerization approach offered a more efficient, dry, and straightforward procedure that made it possible to create dense films of several hundred nanometers in thickness, which has potential applications in metallic implant materials. In this paper, large-scale plasma polymerized hexamethyldisiloxane (ppHMDSO) thin film coatings were deposited on stainless steel substrates at different electrode distances to improve their corrosion resistance. The physicochemical properties and corrosion resistance of the ppHMDSO thin films as prepared at different electrode distances were characterized and gauged utilizing various characterization means. The results indicate that decreasing electrode distance accelerates monomer fragmentation and increases the oxidation process. The deposition rate and roughness of the ppHMDSO films both decreased as the electrode distance increased, while the carbonaceous group and hydrophobicity of the films enhanced. The ppHMDSO film prepared at an electrode distance of 40 mm obtained excellent elastic recovery and wear resistance and had an improved corrosion resistance, resulting in a reduction of 75% of the original corrosion behavior against the corrosion in Hank's solution. The resulting large-scale ppHMDSO thin film coatings can be further employed in implants for tissue engineering and biomaterials.

Long-term efficacy, safety, and medication compliance of roxadustat on peritoneal dialysis patients with renal anemia affected by the COVID-19 pandemic: a retrospective study.

BACKGROUND: Current studies have limited data on long-term treatment safety and medication compliance of roxadustat for renal anemia in peritoneal dialysis (PD) patients. We aimed to analyze the long-term efficacy, safety, and medication compliance of roxadustat in the treatment of renal anemia in patients with PD who discontinued recombinant human erythropoietin (rhEPO) treatment due to the corona virus disease 2019 (COVID-19) outbreak. METHODS: We retrospectively collected patients who were switched from rhEPO to roxadustat in our hospital due to the pandemic. The criteria for subject inclusion: aged >18 years with a dialysis vintage >3 months, without malignant tumor, no severe cardiovascular and cerebrovascular diseases, and not combined hemodialysis. Patients were followed up until the end of December 2021. Hemoglobin (Hb), red blood cell (RBC) and hematocrit (Hct) were recorded at baseline, month 1-12 and month 20, and iron parameters at baseline, 3, 6, 9, 12, and 20 months were collected. The Morisky Medication Adherence Scale-8 (MMAS-8) was used to score medication compliance during rhEPO treatment and roxadustat treatment, and adverse reactions occurred during treatment were collected. The efficacy and medication compliance of roxadustat were analyzed using Wilcoxon rank sum test or t-test. RESULTS: The median follow-up time was 21.1 (20.6, 21.7) months. After 1 month of treatment, the Hb level was significantly increased by 9.4 g/L (95% CI: 6.0-12.8 g/L) compared with the baseline, follow up at 20 months showed the Hb level had remained stable, increased by 20.7 g/L (95% CI: 15.9-25.4 g/L) compared with before treatment. At the beginning of treatment, total iron binding capacity increased, transferrin saturation and serum ferritin decreased, serum iron remained stable during treatment. During roxadustat treatment, no patient discontinued treatment due to the pandemic, and the Morisky score was improved compared with that during rhEPO treatment [5.75 (4.25, 6.00) vs. 6.75 (5.75, 7.00), P=0.000]. There were no serious adverse events associated with roxadustat were observed. CONCLUSIONS: Roxadustat can effectively improve anemia and had good tolerance in patients undergoing PD who have difficult using rhEPO, and the medication compliance was better than rhEPO during the COVID-19.

Comprehensive three-dimensional positional and morphological assessment of the temporomandibular joint in skeletal Class II patients with mandibular retrognathism in different vertical skeletal patterns.

BACKGROUND: Only a few studies have used 3D cone-beam computed tomography (CBCT) analysis to evaluate the positional and morphological characteristics of the temporomandibular joint (TMJ) in adults with skeletal Class II. No studies have focused on the case of skeletal Class II with mandibular retrognathism in different vertical skeletal patterns. As a result, this study aimed to evaluate and compare the position and morphology of TMJ in adults with skeletal Class II with mandibular retrognathism in different vertical skeletal patterns to the position and morphology of TMJ in the normal Chinese adult population in three dimensions. METHODS: This retrospective study analyzed CBCT images of 80 adult patients. Subjects with skeletal Class II with a normal sagittal position of the maxilla and mandibular retrognathism were classified according to the mandibular angle and facial height ratio into three groups of 20 subjects each: hypodivergent, normodivergent, and hyperdivergent groups, as well as a control group of 20 subjects. The following 3D measurements of TMJ were evaluated: (1) position, parameters, and inclination of the mandibular fossa; (2) position, parameters, and inclination of the mandibular condyle; (3) condyle centralization in their respective mandibular fossae; (4) anterior, posterior, superior, and medial joint spaces; and (5) 3D volumetric measurements of the TMJ spaces. Measurements were statistically analyzed by one-way ANOVA test, followed by Tukey's post hoc test. RESULTS: Significant differences were found in the hyperdivergent and hypodivergent groups compared with the normal group in the vertical and anteroposterior mandibular fossa position, vertical condylar inclination, and condylar width and length. The hyperdivergent group showed the significantly highest condylar inclination with the midsagittal plane; anterior and superior positioning of the condyle; smallest anterior, superior, and medial joint spaces; and largest volumetric total joint space relative to the two other groups. CONCLUSIONS: The condyle-fossa position and morphology differ with various vertical facial patterns in individuals with skeletal Class II mandibular retrognathism. These differences could be considered during TMD diagnosis and orthodontic treatment.

The effect of functional mandibular advancement for adolescent patients with skeletal class II malocclusion on the TMJ: a systematic review and meta-analysis.

OBJECTIVES: This study aimed to assess whether functional mandibular advancement (FMA) will cause temporomandibular joint disorders (TMD) or have side effects on temporomandibular joint (TMJ) in adolescent patients. METHODS: All searched databases, including PubMed, Web of Science, EMBASE, Cochrane Central Register of Controlled Trails and Scopus were searched. Gray literature and unpublished literature was also searched. Randomized controlled trails (RCT) and non-randomized studies of the effects of interventions (NRSI) directly observe the condition of adolescent patients' TMJ after finishing treatment will be considered to include in our study. According to Cochrane Handbook, Cochrane Collaboration risk of bias tool was used to assess the quality of included RCTs, and Risk of Bias In Non-randomized Studies of Interventions (ROBINS-I) tool was used to assess the quality of included NRSIs. RESULT: Finally 18 researches were evaluated as eligible to include in this study. 5 of the studies were RCTs, 8 were NRSIs and 5 were systematic reviews. The data of RCTs and NRSIs were statistically pooled in meta-analysis. The number of samples under investigated among primary studies was 579 individuals,there were 80 patients who developed temporomandibular symptoms during or after treatment. But all the subjective symptoms disappeared during follow-up time. The statistical outcomes proved that patients received FMA didn't show more tendency to develop temporomandibular symptoms [I2 = 27%, OR = 0.54, 95%CI (0.33,0.87), p = 0.01]. CONCLUSION: (1) TMJ symptoms may occur during the functional oral appliance wearing, but the symptoms will release or disappear after treatment or during the follow-up period. (2) Less convincing evidence indicates that slightly previous TMD and condyle-glenoid fossa relationship will be improved after treatment. (3) There is TMJ disc anterior displacement observed during treatment, but most of them will return to the normal position later. (4) Moderate evidence support that FMA will not have side effects on TMJ of adolescent patients.

Mechanical, antibacterial, biocompatible and microleakage evaluation of glass ionomer cement modified by nanohydroxyapatite/polyhexamethylene biguanide.

This study aims to look for the best concentration of nanohydroxyapatite (NHA) and polyhexamethylene biguanide (PHMB) incorporated into glass ionomer cement (GIC) in accordance with ISO:9917-1 and evaluate its mechanical, antibacterial, biocompatible and microleakages properties. NHA was incorporated into Fuji Ⅱ GIC powder at 0-8.00 wt% concentration and specimens were prepared; the best concentration was sifted out according to ISO9917-1. Based on best NHA proportion, 0-0.80% PHMB was dispersed into powder and samples were respectively prepared. Mechanical properties include net setting time (ST), compressive strength (CS), microhardness (VNH), solubility and scanning electron microscopy (SEM) observation. Those met ISO standard were qualified to continue microleakage observation, antibacterial activity, and biocompatibility test. The results suggested that GIC/6%NHA/0.2% PHMB and GIC/6%NHA/0.4%PHMB showed great performances in mechanical, antibacterial, and microleakage improvements, and the cytotoxicity of modified GIC showed no statistical difference with pure GIC.

Development of a decellularized porcine bone matrix for potential applications in bone tissue regeneration.

Aim: The objectives of this study were to develop a new decellularized bone matrix (DBM) and to investigate its effect on the in vitro cell behavior of human bone marrow-derived mesenchymal stem cells (hMSCs), compared with porous ß-tricalcium phosphate (ß-TCP) scaffolds. Materials & methods: Triton X-100 and deoxycholate sodium solution, combining DNase I and RNase, were used to decellularize porcine bones. The DBM were then characterized by DNA contents and matrix components. hMSCs were then seeded on the DBM and ß-TCP scaffolds to study cell behavior. Results: Results showed that most porcine cells were removed and the matrix components of the DBM were maintained. Cell culture results showed that DBM promoted cell attachment and proliferation of hMSCs but did not significantly promote the gene expression of osteogenic genes, compared with ß-TCP scaffolds. Conclusion: DBM has similar function on cell behavior to ß-TCP scaffolds that have promising potential in bone tissue regeneration.

[Construction of three-dimensional dermoid tissue based on cell sheets technology in vitro].

OBJECTIVE: To explore a new strategy for constructing three-dimensional dermoid tissue in vitro by using cell sheets technology. METHODS: Rabbit bone marrow mesenchymal stem cells (rBMSCs) were isolated from bone marrow of New Zealand white rabbits and cultured by whole bone marrow adherent method. Human dermal fibroblasts (HDFs) were cultured and passaged in vitro. The 2nd generation rBMSCs and the 3rd generation HDFs were cultured in a culture dish for 2 weeks with cell sheets conditioned medium respectively to obtain a monolayer cell sheets. Human umbilical vein endothelial cells (HUVECs) were inoculated on rBMSCs sheet to construct pre-vascularized cell sheet. During the culture period, the morphological changes of the cell sheet were observed under an inverted phase contrast microscope. At 1, 3, 7, and 14 days, HE staining and CD31 immunofluorescence staining were performed to observe the cell distribution and microvascular network formation. The rBMSCs sheet was used as control. The pre-vascularized cell sheet (experimental group) and rBMSCs sheet (control group) cultured for 7 days were placed in the middle of two HDFs sheets, respectively, to prepare three-dimensional dermoid tissues. After 24 hours of culture, CD31 immunofluorescence staining and collagen type Ⅰ and collagen type Ⅲ immunohistochemical stainings were performed to evaluate cell distribution and collagen expression. RESULTS: HDFs and rBMSCs sheets were successfully prepared after 2 weeks of cell culture. After inoculation of HUVECs on rBMSCs sheet for 3 days, HUVECs could be seen to rearrange on rBMSCs sheet and forming vacuoles. The reticular structure was visible at 7 days and more obvious at 14 days. The formation of vacuoles between the cell sheets was observed by HE staining, and the vacuoles became more and more obvious, the thickness of the membranes increased significantly with time. CD31 immunofluorescence staining showed the microvascular lumen formation. However, only the thickness of rBMSCs sheet increasing was observed, with no changes in cell morphology or cavitation structure. The three-dimensional dermoid tissue observation showed that the endothelial cells in the experimental group were positive expressions, and the rBMSCs, HDFs, and HUVECs cells were arranged neatly. The endothelial cells were negative expressions and randomly arranged in the control group. The collagen type Ⅰ and collagen type Ⅲ were positive expression in the experimental group and the control group. But compared with control group, experimental group presented a "honeycomb" network connection, where the matrix was distributed regularly, and cells were arranged tightly. The difference in the expression of collagen type Ⅰ and collagen type Ⅲ between the experimental group and the control group was not significant ( P>0.05). CONCLUSION: Three-dimensional dermoid tissue is successfully constructed by using cell sheet technology. The cell matrix distribution of the pre-vascularized cell sheet constructed by HUVECs and rBMSCs sheet is relatively regular, which has the potential to form tissue engineered dermis.

Controlling cell viability and bacterial attachment through fabricating extracellular matrix-like micro/nanostructured surface on titanium implant.

Good osseointegration and gingival epithelial sealing play a key role in preventing peri-implantitis of dental implants. In addition to antibacterial qualities, the transmucosal surface of the implant is beneficial to the growth of fibroblasts and epithelial cells, while its body surface is suitable for the growth of osteoblasts and is resistant to epithelial cells and fibroblasts. In this study, both microgrooves mimicking the extracellular matrix (ECM) and titanium (Ti) dioxide nanotubes with different parameter settings were produced on Ti surfaces. The behavior of MG63 osteoblasts, L929 fibroblasts, SCC epithelial cells and Porphyromonas gingivalis on these decorated Ti surfaces was detected to quantify their performances in terms of osseointegration, biological sealing and antimicrobial ability. Via a scoring method based on these results, we concluded that 100-50-20-10-5 µm width grooves arranged in the horizontal direction at 2 µm depth were the priority for the design of the implant's transmucosal surface. By changing the depth to 3.6 µm and further decorating with 55 nm nanotubes, a best surface design for the implant body was acquired. Hierarchical ECM-like micro/nano patterns could provide novel designs for dental implants to achieve excellent gingival epithelial sealing and osseointegration, which would facilitate the clinical application of dental implants.

Three-dimensional analysis of temporomandibular joint in Chinese adults with normal occlusion and harmonious skeleton.

OBJECTIVE: This study aimed to analyze the detailed three-dimensional measurements of temporomandibular joint (TMJ) in Chinese adults with normal occlusion and harmonious skeleton. METHODOLOGY: In 51 subjects 102 joints were analyzed using Anatomage Invivo dental 5.4. The measurements include: joints' parameters, position, angulation, and inclination of the condyle and articular fossa as well as 3D volumetric of the joint-spaces. All measurements were statistically analyzed by paired Student's t test to find out the differences between the left- and right sides. Pearson correlation coefficient test was done to figure out the relationship of the TMJ parts in the normal situation. RESULTS: The inter-condyle distances medially, geometrically, and laterally were 90.2 ± 5.2,107 ± 6.1, and 125 ± 5.5 mm, respectively. However, the 102 condyles were angulated on three planes 54.9º ± 11.2, 71.8º ± 7.3, and 12.5º ± 6.3 at vertical-, horizontal-, and midsagittal planes, respectively. The joint spaces measurements were 2.6 ± 0.7 mm, 2.5 ± 0.8 mm, 2.4 ± 0.7 mm, and 3.3 ± 0.7 mm for anterior-, medial-, posterior-, and superior joints, respectively. The total volume of the whole joint-space was 404.3 ± 71mm3. The left condyle position was on the centric position whereas the right condyle was eccentric (slightly anterior). CONCLUSION: Chinese subjects are characterized by wide inter-fossa distance and inter-condyle distance; however, no significant correlations with joint spaces in normal occlusion were found. The asymmetries between right- and left mandibular condyle were distinguished in angular and linear-vertical measurements. Finally, this study could be considered as reference data for upcoming research in the Chinese population.

Fabrication of vascularized and scaffold-free bone tissue using endothelial and osteogenic cells differentiated from bone marrow derived mesenchymal stem cells.

Over-dependence on existing synthetic scaffolds and insufficient vascularization limit the development of tissue engineered bone (TEB). The purpose of this study is to fabricate vascularized and scaffold-free bone tissue using cell sheet technology and to assess its feasibility to repair critical-sized calvarial defects in rats. Firstly, the pre-vascularized cell sheet was formed by seeding BMSC-derived endothelial cells (ECs) on an undifferentiated BMSCs cell sheet layer in vitro. After 3 days of co-culture, ECs migrated and rearranged to form lumens on the BMSC sheet. Secondly, osteogenic cell sheet was formed by inducing osteogenic differentiation of high density BMSCs. Then, the pre-vascularized cell sheet was stacked on BMSC-derived osteogenic cell sheet to fabricate a scaffold-free construct for bone regeneration. Finally, the scaffold-free construct with both angiogenic and osteogenic potential was implanted into critical-sized calvarial defects in adult Wistar rats. Results showed that more functional perfused blood vessels and new bone tissue formed in the pre-vascularized group than that in the controls (both empty and non-pre-vascularized cell sheet group). This study indicates a new promising strategy for bone tissue regeneration.

Engineering biomimetic periosteum with ß-TCP scaffolds to promote bone formation in calvarial defects of rats.

BACKGROUND: There is a critical need for the management of large bone defects. The purpose of this study was to engineer a biomimetic periosteum and to combine this with a macroporous ß-tricalcium phosphate (ß-TCP) scaffold for bone tissue regeneration. METHODS: Rat bone marrow-derived mesenchymal stem cells (rBMSCs) were harvested and cultured in different culture media to form undifferentiated rBMSC sheets (undifferentiated medium (UM)) and osteogenic cell sheets (osteogenic medium (OM)). Simultaneously, rBMSCs were differentiated to induced endothelial-like cells (iECs), and the iECs were further cultured on a UM to form a vascularized cell sheet. At the same time, flow cytometry was used to detect the conversion rates of rBMSCs to iECs. The pre-vascularized cell sheet (iECs/UM) and the osteogenic cell sheet (OM) were stacked together to form a biomimetic periosteum with two distinct layers, which mimicked the fibrous layer and cambium layer of native periosteum. The biomimetic periostea were wrapped onto porous ß-TCP scaffolds (BP/ß-TCP) and implanted in the calvarial bone defects of rats. As controls, autologous periostea with ß-TCP (AP/ß-TCP) and ß-TCP alone were implanted in the calvarial defects of rats, with a no implantation group as another control. At 2, 4, and 8 weeks post-surgery, implants were retrieved and X-ray, microcomputed tomography (micro-CT), histology, and immunohistochemistry staining analyses were performed. RESULTS: Flow cytometry results showed that rBMSCs were partially differentiated into iECs with a 35.1% conversion rate in terms of CD31. There were still 20.97% rBMSCs expressing CD90. Scanning electron microscopy (SEM) results indicated that cells from the wrapped cell sheet on the ß-TCP scaffold apparently migrated into the pores of the ß-TCP scaffold. The histology and immunohistochemistry staining results from in vivo implantation indicated that the BP/ß-TCP and AP/ß-TCP groups promoted the formation of blood vessels and new bone tissues in the bone defects more than the other two control groups. In addition, micro-CT showed that more new bone tissue formed in the BP/ß-TCP and AP/ß-TCP groups than the other groups. CONCLUSIONS: Inducing rBMSCs to iECs could be a good strategy to obtain an endothelial cell source for prevascularization. Our findings indicate that the biomimetic periosteum with porous ß-TCP scaffold has a similar ability to promote osteogenesis and angiogenesis in vivo compared to the autologous periosteum. This function could result from the double layers of biomimetic periosteum. The prevascularized cell sheet served a mimetic fibrous layer and the osteogenic cell sheet served a cambium layer of native periosteum. The biomimetic periosteum with a porous ceramic scaffold provides a new promising method for bone healing.

Effect of different cell sheet ECM microenvironment on the formation of vascular network.

The repair and reconstruction of large bone defects remains as a significant clinical challenge mainly due to the insufficient vascularization. The prefabrication of vascular network based on cell sheet technique brings a promising potential for sufficient vascularization due to rich extracellular matrix (ECM) of cell sheets. However, the effect of different cell sheet ECM micro-environment on the formation of a vascular network has not been well understood. Here our goal is to study the effect of different cell sheets on the formation of a vascular network. First we cultured human bone marrow mesenchymal stem cells (hBMSCs) under two culture conditions to obtain osteogenic differentiated cell sheet (ODCS) and undifferentiated cell sheet (UDCS), respectively. Then the human umbilical vein endothelial cells (HUVECs) were seeded onto the surface of the two sheets at different seeding densities to fabricate pre-vascularized cell sheets. Our results indicated that the two sheets facilitated the alignment of HUVECs and promoted the formation of vascular networks. Quantitative analysis showed that the number of networks in ODCS was higher than that in the UDCS. The ECM of the two sheets was remodeled and rearranged during the tubulogenesis process. Furthermore, results showed that the optimal seeding density of HUVECs was 5×10(4)cell/cm(2). In summary, these results suggest that the vascularized ODCS has a promising potential to construct pre-vascularized tissue for bone repair.

[DEVELOPMENT OF HYPOXIA-INDUCIBLE FACTOR 1α IN TISSUE ENGINEERED ANGIOGENESIS AND OSTEOGENESIS].

OBJECTIVE: To review the development and applications of hypoxia-inducible factor la (HIF-1α) in the strategy of tissue engineered angiogenesis and osteogenesis. METHODS: The literature about HIF-1α in tissue engineering technology was reviewed, analyzed, and summarized. RESULTS: HIF-1α plays a key role in arigiogenic-osteogenic coupling, and as an upstream regulator, HIF-1α can regulate the expressions of its target genes related with angiogenesis and osteogenesis. In addition, HIF-1α not only can control and improve the angiogenesis, but also has important significance in proliferation and differentiation of seed cells, especially stem cells, which is the foundation for bone healing. CONCLUSION: With the development of tissue engineering technology, the problems in the applications of HIF-1α, such as the effective dose of targeting controlled-release, pro-inflammatory effect, and carcinogenicity, will be explored and solved in the future, so it can be used better in clinical.

A new composite scaffold of bioactive glass nanoparticles/graphene: Synchronous improvements of cytocompatibility and mechanical property.

This study presents a simple method of synthesizing bioactive glass nanoparticles/graphene nanosheets composite (BGs/GNS) scaffolds using the sol-gel and mold-compressing strategies. Characterizations of BGs/GNS scaffold revealed that BGs with an average diameter of 28.75nm were densely anchored onto both sides of GNS. When the mass ratio of BGs to graphene oxide was set as 10, this scaffold showed better cytocompatibility and higher osseointegration ability with surrounding tissues than the other scaffolds. The introduction of GNS also significantly enhanced the hardness and Young's modulus of BGs. Given the excellent performance of this scaffold, it has potential applications in bone regeneration and implantation.

Prefabrication of axially vascularized bone by combining ß-tricalciumphosphate, arteriovenous loop, and cell sheet technique.

The repair of bone defects poses a great challenge for reconstructive surgeons. Although the development of tißsue engineering has exhibited promise in replacing damaged bone, the fabrication of large constructs with functional blood veßsels remains an obstacle. From the orthopedic surgeon's point of view, the generation of axially vascularized bone, which can anastomose with the recipient vessel, might be a solution to this medical problem. In this study, we aimed to prefabricate an axially vascularized bone by combining a ß-TCP scaffold, arteriovenous loop (AVL), and cell sheet in a bioreactor in vivo. Twelve rabbits were randomly allocated into two groups: the experimental group (presence of AVL) and the control group (absence of AVL). The constructs were explanted at 8 weeks postoperatively. The histomorphometric results showed 42.8±5.9% of the bone area in the AVL group and 26.6±3.5% in the control group. Similarly, vessel analysis revealed the average vessel density in the AVL group (12.5±3.3) was significantly more than that in the control group (6.1±1.5, p<0.05). Our research indicated that the combination of a ß-TCP scaffold, AVL and cell sheet might engineer vascularized bone. This prefabrication strategy might facilitate clinical translation of bone tissue engineering in reconstructing large bone defects.

[Three-dimensional Culture of Chondrocyte Using Methacrylic Alginate Gel Beads Cross-linked with Mixed Metal-cation].

This study was to explore a better three-dimensional (3-D) culture method of chondrocyte. The interpenetrating network (IPN) gel beads were developed through a photo-cross linking reaction with mixed barium ions and calcium ions at the ratio of 5:5 with the methacrylic alginate (MA), which was a chemically conjugated alginate with methacrylic groups. The second generation of primary cartilage cells was encapsulated in the MA gel beads for three weeks. In the designated timing, HE stain, Alamar blue method and Scanning electron microscopic were used to determine the cartilage cells growth, proliferation and the cell distribution in the scaffolds, respectively. The expression of type II collagen was investigated by an immunohistochemistry assay and the glycosaminoglycan content was quantitatively evaluated with the spectrophotometry of 1, 9 dimethylene blue assay. Compared to the alginate control group, the deposition of glycosaminoglycan was significantly upregulated in IPN-MA gel beads with higher cell proliferation. The secretion of extracellular matrix and proliferation of chondrocyte in methacrylic alginate gel beads were higher than that in Alginate beads. Cells were able to attach, to grow well on the scaffolds under scanning electron microscopy. The result of immunohistochemistry staining of collagen type II was positive, confirming the maintenance of chondrocyte phenotype in methacrylic alginate gel beads. This study shows a great potential for three-dimensional culture of cartilage.

[DEVELOPMENT OF CELL SHEET ENGINEERING TECHNOLOGY IN ENGINEERING VASCULARIZED TISSUE].

OBJECTIVE: To review the development of cell sheet engineering technology in engineering vascularized tissue. METHODS: The literature about cell sheet engineering technology and engineering vascularized tissue was reviewed, analyzed, and summarized. RESULTS: Although there are many methods to engineer vascularized tissue, cell sheet engineering technology provides a promising potential to develop a vascularized tissue. Recently, cell sheet engineering technology has become a hot topic in engineering vascularized tissue. Co-culturing endothelial cells on a cell sheet, endothelial cells are able to form three-dimensional prevascularized networks and microvascular cavities in the cell sheet, which facilitate the formation of functional vascular networks in the transplanted tissue. CONCLUSION: Cell sheet engineering technology is a promising strategy to engineer vascularized tissue, which is still being studied to explore more potential.