Semaphorin3C identified as mediator of neuroinflammation and microglia polarization after spinal cord injury.

Excessive neuroinflammation after spinal cord injury (SCI) is a major hurdle during nerve repair. Although proinflammatory macrophage/microglia-mediated neuroinflammation plays important roles, the underlying mechanism that triggers neuroinflammation and aggravating factors remain unclear. The present study identified a proinflammatory role of semaphorin3C (SEMA3C) in immunoregulation after SCI. SEMA3C expression level peaked 7 days post-injury (dpi) and decreased by 14 dpi. In vivo and in vitro studies revealed that macrophages/microglia expressed SEMA3C in the local microenvironment, which induced neuroinflammation and conversion of proinflammatory macrophage/microglia. Mechanistic experiments revealed that RAGE/NF-κB was downstream target of SEMA3C. Inhibiting SEMA3C-mediated RAGE signaling considerably suppressed proinflammatory cytokine production, reversed polarization of macrophages/microglia shortly after SCI. In addition, inhibition of SEMA3C-mediated RAGE signaling suggested that the SEMA3C/RAGE axis is a feasible target to preserve axons from neuroinflammation. Taken together, our study provides the first experimental evidence of an immunoregulatory role for SEMA3C in SCI via an autocrine mechanism.

Tensile Stress-Activated and Exosome-Transferred YAP/TAZ-Notch Circuit Specifies Type H Endothelial Cell for Segmental Bone Regeneration.

The Ilizarov technique has been continuously innovated to utilize tensile stress (TS) for inducing a bone development-like regenerative process, aiming to achieve skeletal elongation and reconstruction. However, it remains uncertain whether this distraction osteogenesis (DO) process induced by TS involves the pivotal coupling of angiogenesis and osteogenesis mediated by type H endothelial cells (THECs). In this study, it is demonstrated that the Ilizarov technique induces the formation of a metaphysis-like architecture composed of THECs, leading to segmental bone regeneration during the DO process. Mechanistically, cell-matrix interactions-mediated activation of yes-associated protein (YAP)/transcriptional co-activator with PDZ-binding motif (TAZ) transcriptionally upregulates the expression of Notch1 and Delta-like ligand 4, which act as direct positive regulators of THECs phenotype, in bone marrow endothelial cells (BMECs) upon TS stimulation. Simultaneously, the Notch intracellular domain enhances YAP/TAZ activity by transcriptionally upregulating YAP expression and stabilizing TAZ protein, thus establishing the YAP/TAZ-Notch circuit. Additionally, TS-stimulated BMECs secrete exosomes enriched with vital molecules in this positive feedback pathway, which can be utilized to promote segmental bone defect healing, mimicking the therapeutic effects of Ilizarov technique. The findings advance the understanding of TS-induced segmental bone regeneration and establish the foundation for innovative biological therapeutic strategies aimed at activating THECs.

Black Phosphorus/MnO2 Nanocomposite Disrupting Bacterial Thermotolerance for Efficient Mild-Temperature Photothermal Therapy.

The emergence of multi-drug resistant (MDR) pathogens is a major public health concern, posing a substantial global economic burden. Photothermal therapy (PTT) at mild temperature presents a promising alternative to traditional antibiotics due to its biological safety and ability to circumvent drug resistance. However, the efficacy of mild PTT is limited by bacterial thermotolerance. Herein, a nanocomposite, BP@Mn-NC, comprising black phosphorus nanosheets and a manganese-based nanozyme (Mn-NZ) is developed, which possesses both photothermal and catalytic properties. Mn-NZ imparts glucose oxidase- and peroxidase-like properties to BP@Mn-NC, generating reactive oxygen species (ROS) that induce lipid peroxidation and malondialdehyde accumulation across the bacterial cell membrane. This process disrupts unprotected respiratory chain complexes exposed on the bacterial cell membrane, leading to a reduction in the intracellular adenosine triphosphate (ATP) content. Consequently, mild PTT mediated by BP@Mn-NC effectively eliminates MDR infections by specifically impairing bacterial thermotolerance because of the dependence of bacterial heat shock proteins (HSPs) on ATP molecules for their proper functioning. This study paves the way for the development of a novel photothermal strategy to eradicate MDR pathogens, which targets bacterial HSPs through ROS-mediated inhibition of bacterial respiratory chain activity.

Biomimetic hydrogel derived from decellularized dermal matrix facilitates skin wounds healing.

Cutaneous wound healing affecting millions of people worldwide represents an unsolvable clinical issue that is frequently challenged by scar formation with dramatical pain, impaired mobility and disfigurement. Herein, we prepared a kind of light-sensitive decellularized dermal extracellular matrix-derived hydrogel with fast gelling performance, biomimetic porous microstructure and abundant bioactive functions. On account of its excellent cell biocompatibility, this ECM-derived hydrogel could induce a marked cellular infiltration and enhance the tube formation of HUVECs. In vivo experiments based upon excisional wound splinting model showed that the hydrogel prominently imparted skin wound healing, as evidenced by notably increased skin appendages and well-organized collagen expression, coupled with significantly enhanced angiogenesis. Moreover, the skin regeneration mediated by this bioactive hydrogel was promoted by an accelerated M1-to-M2 macrophage phenotype transition. Consequently, the decellularized dermal matrix-derived bioactive hydrogel orchestrates the entire skin healing microenvironment to promote wound healing and will be of high value in treatment of cutaneous wound healing. As such, this biomimetic ddECMMA hydrogel provides a promising versatile opinion for the clinical translation.

A spatiotemporal release hydrogel based on an M1-to-M2 immunoenvironment for wound management.

Cutaneous wounds remain a major clinical challenge that urgently requires the development of advanced and functional wound dressings. During the wound healing process, macrophages are well known to exhibit temporal dynamics with a pro-inflammatory phenotype at early stages and a pro-healing phenotype at late stages, thus playing an important role in regulating inflammatory responses and tissue regeneration. Meanwhile, disrupted temporal dynamics of macrophages caused by poor wound local conditions and deficiency of macrophage function always impair the wound-healing progression. Here in this work, we proposed a novel controllable strategy to construct a spatiotemporal dynamical immune-microenvironment for the treatment of cutaneous wounds. To achieve this goal, a concentric decellularized dermal hydrogel was constructed with the combination of type 1 and type 2 macrophage-associated cytokine complexes in the sheath portion and core portion, respectively. The in vitro degradation experiment exhibited a sequential cascade release of pro-inflammatory cytokines and pro-healing cytokines. The enhanced cell biocompatibility and tube formation of HUVECs were confirmed. A full-thickness skin defect model of rats was developed to analyze the effect of the spatiotemporal dynamical bioactive hydrogels on wound healing. Remarkable angiogenesis, rapid wound restoration, moderate extracellular matrix deposition and obvious skin appendage neogenesis were identified at different time points after treatment with the macrophage cytokine-based decellularized hydrogels. Consequently, the concentric decellularized hydrogels with spatiotemporal dynamics of immune cytokines have considerable potential for cell-free therapy for wound healing.

Cobalt-Doped Mesoporous Silica Coated Magnetic Nanoparticles Promoting Accelerated Bone Healing in Distraction Osteogenesis.

Introduction: Large bone abnormalities are commonly treated using distraction osteogenesis (DO), but it is not suitable for a long-term application; therefore, there is an urgent need for adjuvant therapy that can accelerate bone repair. Methods: We have synthesized mesoporous silica-coated magnetic nanoparticles doped with cobalt ions (Co-MMSNs) and assessed their capacity to quicken bone regrowth in a mouse model of DO. Furthermore, local injection of the Co-MMSNs significantly accelerated bone healing in DO, as demonstrated by X-ray imaging, micro-CT, mechanical tests, histological evaluation, and immunochemical analysis. Results: In vitro, the Co-MMSNs exhibited good biocompatibility and induced angiogenic gene expression and osteogenic development in bone mesenchymal stem cells. And the Co-MMSNs can promote bone regeneration in a rat DO model. Discussion: This study demonstrated the significant potential of Co-MMSNs to shorten the DO treatment duration and effectively reduce the incidence of complications.

Bacterial Contamination of Open Fractures: Pathogens and Antibiotic Resistance Patterns in East China.

Bacterial contamination of soft tissue in open fractures leads to high infection rates. Pathogens and their resistance against therapeutic agents change with time and vary in different regions. The purpose of this study was to characterize the bacterial spectrum present in open fractures and analyze the bacterial resistance to antibiotic agents based on five trauma centers in East China. A retrospective multicenter cohort study was conducted in six major trauma centers in East China from January 2015 to December 2017. Patients who sustained open fractures of the lower extremities were included. The data collected included the mechanism of injury, the Gustilo-Anderson classification, the isolated pathogens and their resistance against therapeutic agents, as well as the prophylactic antibiotics administered. In total, 1348 patients were included in our study, all of whom received antibiotic prophylaxis (cefotiam or cefuroxime) during the first debridement at the emergency room. Wound cultures were taken in 1187 patients (85.8%); the results showed that the positive rate of open fracture was 54.8% (651/1187), and 59% of the bacterial detections occurred in grade III fractures. Most pathogens (72.7%) were sensitive to prophylactic antibiotics, according to the EAST guideline. Quinolones and cotrimoxazole showed the lowest rates of resistance. The updated EAST guidelines for antibiotic prophylaxis in open fracture (2011) have been proven to be adequate for a large portion of patients, and we would like to suggest additional Gram-negative coverage for patients with grade II open fractures based on the results obtained in this setting in East China.

Epidemiological updates of post-traumatic related limb osteomyelitis in china: a 10 years multicentre cohort study.

BACKGROUND: Post-traumatic related limb osteomyelitis (PTRLO) is a complex bone infection. Currently, there are no available microbial data on a national scale that can guide appropriate antibiotic selection, and explore the dynamic changes in dominant pathogens over time. This study aimed to conduct a comprehensive epidemiological analysis of PTRLO in China. METHODS: The study was approved by the Institutional Research Board (IRB), and 3526 PTRLO patients were identified from 212 394 traumatic limb fracture patients at 21 hospitals between 1 January 2008 and 31 December 2017. A retrospective analysis was conducted to investigate the epidemiology of PTRLO, including changes in infection rate (IR), pathogens, infection risk factors and antibiotic resistance and sensitivity. RESULTS: The IR of PTRLO increased gradually from 0.93 to 2.16% (Z=14.392, P <0.001). Monomicrobial infection (82.6%) was significantly higher than polymicrobial infection (17.4%) ( P <0.001). The IR of Gram-positive (GP) and Gram-negative (GN) pathogens showed a significant increase from the lowest 0.41% to the highest 1.15% (GP) or 1.62% (GN), respectively. However, the longitudinal trend of GP vs. GN's composition did not show any significance (Z=±1.1918, P >0.05). The most prevalent GP strains were Methicillin-sensitive Staphylococcus aureus (MSSA) (17.03%), Methicillin-resistant Staphylococcus aureus (MRSA) (10.46%), E. faecalis (5.19%) and S. epidermidis (4.87%). In contrast, the dominant strains GN strains were Pseudomonas Aeruginosa (10.92%), E. cloacae (10.34%), E. coli (9.47%), Acinetobacter Baumannii (7.92%) and Klebsiella Pneumoniae (3.33%). In general, the high-risk factors for polymicrobial infection include opened-fracture (odds ratio, 2.223), hypoproteinemia (odds ratio, 2.328), and multiple fractures (odds ratio, 1.465). It is important to note that the antibiotics resistance and sensitivity analysis of the pathogens may be influenced by complications or comorbidities. CONCLUSIONS: This study provides the latest data of PTRLO in China and offers trustworthy guidelines for clinical practice. (China Clinical Trials.gov number, ChiCTR1800017597).

Masquelet technique with radical debridement and alternative fixation in treatment of infected bone nonunion.

Background: Infected bone nonunion is the toughest problem in fracture-related infection, leading to high disability and recurrence. The aim of this study was to evaluate the effectiveness of the Masquelet technique with radical debridement and alternative fixation in the management of infected bone nonunion. Patients and Methods: A retrospective study of prospectively collected data in two trauma centers was performed from 2016 to 2020. Patients diagnosed as infected bone nonunion were included in this study. The initial implant was removed and all patients received a two-stage Masquelet procedure with radical debridement and alternative fixation. The disappearance of inflammatory manifestations and regression of infection indicators (such as interleukin-6 (IL-6), C-reactive protein, white blood cell count) to the normal range were regarded as radical debridement. The alternative fixation depended on local soft tissue conditions. Results were evaluated according to clinical and radiographic assessment and patient satisfaction. Results: A total of 23 patients were included in our study. Six of them received internal fixation, while the other 17 received external fixation. Of the 23 cases, 21 were successfully reconstructed without infection recurrence, except 2 reinfected cases. Mean full weight bearing time was 6.6 months follow-up post last surgery. Out of the 23, 20 cases had satisfactory functional outcomes without additional bone or soft tissue comorbidities. Discrepancies in leg length and joint stiffness were observed in three cases and marked as unsatisfied results. Conclusions: Infected bone nonunion can be successfully managed using the Masquelet technique under radical debridement combined with an alternative fixation method.

In vivo prevascularization strategy enhances neovascularization of ß-tricalcium phosphate scaffolds in bone regeneration.

Background: Neovascularization is critical for bone regeneration. Numerous studies have explored prevascularization preimplant strategies, ranging from calcium phosphate cement (CPC) scaffolds to co-culturing CPCs with stem cells. The aim of the present study was to evaluate an alternative in vivo prevascularization approach, using preimplant-prepared macroporous beta-tricalcium phosphate (ß-TCP) scaffolds and subsequent transplantation in bone defect model. Methods: The morphology of ß-TCPs was characterized by scanning electron microscopy. After 3 weeks of prevascularization within a muscle pouch at the lateral size of rat tibia, we transplanted prevascularized macroporous ß-TCPs in segmental tibia defects, using blank ß-TCPs as a control. Extent of neovascularization was determined by angiography and immunohistochemical (IHC) evaluations. Tibia samples were collected at different time points for biomechanical, radiological, and histological analyses. RT-PCR and western blotting were used to evaluate angio- and osteo-specific markers. Results: With macroporous ß-TCPs, we documented more vascular and supporting tissue invasion in the macroporous ß-TCPs with prior in vivo prevascularization. Radiography, biomechanical, IHC, and histological analyses revealed considerably more vascularity and bone consolidation in ß-TCP scaffolds that had undergone the prevascularization step compared to the blank ß-TCP scaffolds. Moreover, the prevascularization treatment remarkably upregulated mRNA and protein expression of BMP2 and vascular endothelial growth factor (VEGF) during bone regeneration. Conclusion: This novel in vivo prevascularization strategy successfully accelerated vascular formation to bone regeneration. Our findings indicate that prevascularized tissue-engineered bone grafts have promising potential in clinical applications. The translational potential of this article: This study indicates a novel in vivo prevascularization strategy for growing vasculature on ß-TCP scaffolds to be used for repair of large segmental bone defects, might serve as a promising tissue-engineered bone grafts in the future.

A Photoannealed Granular Hydrogel Facilitating Hyaline Cartilage Regeneration via Improving Chondrogenic Phenotype.

Hydrogel-based chondrocyte implantation presents a promising tissue engineering strategy for cartilage repair. However, the widely used elastic hydrogels usually restrict cell volume expansion and induce the dedifferentiation of encapsulated chondrocytes. To address this limitation, a photoannealed granular hydrogel (GH) composed of hyaluronic acid, polyethylene glycol, and gelatin was formulated for cartilage regeneration in this study. The unannealed GH prepared by Diels-Alder cross-linked microgels could be mixed with chondrocytes and delivered to cartilage defects by injection, after which light was introduced to anneal the scaffold, leading to the formation of a stable and microporous chondrocyte deploying scaffold. The in vitro studies showed that GH could promote the volume expansion and morphology recovery of chondrocytes and significantly improve their chondrogenic phenotype compared to the nongranular hydrogel (nGH) with similar compositions. Further in vivo studies of subcutaneous culture and the rat full-thickness cartilage defect model proved that chondrocyte loaded GH could significantly stimulate hyaline cartilage matrix deposition and connection, therefore facilitating hyaline-like cartilage regeneration. Finally, the mechanistic study revealed that GH might improve chondrogenic phenotype via activating the AMP-activated protein kinase/glycolysis axis. This study proves the great feasibility of GHs as in situ chondrocyte deploying scaffolds for cartilage regeneration and brings new insights in designing hydrogel scaffold for cartilage tissue engineering.

Tumor microenvironment-responsive nanohybrid for hypoxia amelioration with photodynamic and near-infrared II photothermal combination therapy.

Phototherapy, particularly photothermal therapy (PTT) and photodynamic therapy (PDT), has been widely investigated for tumor treatment. However, the limited tissue penetration depth of light in the near-infrared I (NIR-I) region and the hypoxic tumor microenvironment (TME) severely constrain their clinical applications. To address these challenges, in the present study, we developed a chlorin e6 (Ce6) and MnO2-coloaded, hyaluronic acid (HA)-coated single-walled carbon nanohorns (SWNHs) nanohybrid (HA-Ce6-MnO2@SWNHs) for PDT and PTT combination therapy of tumor. HA-Ce6-MnO2@SWNHs responded to the mild acidic TME to ameliorate tumor hypoxia, thus enhancing tumor PDT. Moreover, HA-Ce6-MnO2@SWNHs had a high photothermal conversion efficiency at 1064 nm (55.48%), which enabled deep tissue penetration (3.05 cm) and allowed for highly efficient tumor PTT in near-infrared II (NIR-II) window. PDT and PTT combination therapy with HA-Ce6-MnO2@SWNHs achieved a good therapeutic efficacy on 4T1 tumor-bearing mice, eradicating the primary tumors and suppressing cancer recurrence. Our study provides a promising strategy for developing a hypoxia relief and deep tissue penetration phototherapy platform by using SWNHs for highly effective tumor PDT and NIR-II PTT combination therapy. STATEMENT OF SIGNIFICANCE: The hypoxic tumor microenvironment (TME) and the limited penetration of the NIR-I light in biological tissues compromise the efficacy of photothermal therapy (PTT) and photodynamic therapy (PDT) on tumors. Here, we developed a chlorin e6 (Ce6) and MnO2-coloaded, hyaluronic acid (HA)-coated single-walled carbon nanohorns (SWNHs) nanohybrid (HA-Ce6-MnO2@SWNHs) for PDT and PTT combination therapy of tumors. The nanohybrid could efficiently accumulate in tumors through CD44-mediated active targeting. The sequential MnO2-enhanced PDT and efficient NIR-II PTT had a remarkable therapeutic effect by eliminating the primary tumor and simultaneously inhibiting tumor recurrence.

miR-199a-5p Plays a Pivotal Role on Wound Healing via Suppressing VEGFA and ROCK1 in Diabetic Ulcer Foot.

Diabetes mellitus (DM) is a growing health problem. As a common complication of DM, diabetic foot ulcer (DFU) results in delayed wound healing and is a leading cause of nontraumatic amputation. miR-199a-5p, a short noncoding RNA, had abnormal expression in DFU wound tissues. The expression of miR-199a-5p was significantly increased in DFU wound tissues, skin tissues of diabetic rats, and high glucose-induced cells. Vascular endothelial growth factor A (VEGFA) and Rho-associated kinase 1 (ROCK1) are directly targets of miR-199a-5p. Inhibiting the expression of miR-199a-5p alleviated the inhibition of VEGFA and ROCK1, thereby rescued impaired proliferation and migration of HG-induced cells, and restored the normal function of the cells to some extent. In diabetic rats, inhibition of miR-199a-5p significantly increased the expression of VEGFA and ROCK1, significantly promoted wound healing, and rescued impaired wound healing. miR-199a-5p and its targets showed therapeutic effect on diabetic wounds.

Identification and comprehensive analysis of circRNA-miRNA-mRNA regulatory networks in osteoarthritis.

Osteoarthritis (OA) is a common orthopedic degenerative disease, leading to high disability in activities of daily living. There remains an urgent need to identify the underlying mechanisms and identify new therapeutic targets in OA diagnosis and treatment. Circular RNAs (circRNAs) play a role in the development of multiple diseases. Many studies have reported that circRNAs regulate microRNAs (miRNAs) through an endogenous competitive mechanism. However, it remains unclear if an interplay between circRNAs, miRNAs, and target genes plays a deeper regulatory role in OA. Four datasets were downloaded from the GEO database, and differentially expressed circRNAs (DECs), differentially expressed miRNAs (DEMs), and differentially expressed genes (DEGs) were identified. Functional annotation and pathway enrichment analysis of DEGs and DECs were carried out to determine the main associated mechanism in OA. A protein-protein network (PPI) was constructed to analyze the function of, and to screen out, hub DEGs in OA. Based on the artificial intelligence prediction of protein crystal structures of two hub DEGs, TOP2A and PLK1, digitoxin and oxytetracycline were found to have the strongest affinity, respectively, with molecular docking. Subsequently, overlapping DEMs and miRNAs targeted by DECs obtained target DEMs (DETMs). Intersection of DEGs and genes targeted by DEMs obtained target DEGs (DETGs). Thus, a circRNA-miRNA-mRNA regulatory network was constructed from 16 circRNAs, 32 miRNAs, and 97 mRNAs. Three hub DECs have the largest number of regulated miRNAs and were verified through in vitro experiments. In addition, the expression level of 16 DECs was validated by RT-PCR. In conclusion, we constructed a circRNA-miRNA-mRNA regulatory network in OA and three new hub DECs, hsa_circ_0027914, hsa_circ_0101125, and hsa_circ_0102564, were identified as novel biomarkers for OA.

N klA Case Report on a IV-degree Thermal Crush Injury of Right Upper Arm: The Application of Functional Prosthesis Implantation Technology.

Severe IV-degree thermal crush injury of limbs involved the subcutaneous fascia, muscle and bone, which may lead to amputation and has a great impact on the patient's quality of life. We can repair wounds with pedicle flaps or even free flaps, However, there are still huge challenges in bone defect of extremities and functional reconstruction. In recent years, with the development of functional prostheses, we have reconstructed limb functions in many patients helping them to complete their daily lives. We report a case where the right upper arm was injured by thermal crush, leading severe burns to the skin, fascia, muscle and bone. We applied a pedicled latissimus dorsi flap and a free anterolateral thigh flap to repair the wound, and realized the function of limb salvage and movement of the right upper arm by implanting 3D printed scapula, upper arm, and elbow joint prostheses. This case illustrates that IV-degree burns involving bones have new technologies to repair and achieve mobility now.

Strontium doped mesoporous silica nanoparticles accelerate osteogenesis and angiogenesis in distraction osteogenesis by activation of Wnt pathway.

Distraction osteogenesis (DO) is a powerful method to reconstruct segmented bone defects in the extremities. However, the main shortcoming of DO is the time-consuming consolidation period. To shorten the consolidation process, two biocompatible inorganic ions, strontium and silicone, were applied to design a biocompatible material to enhance bone mineralization ability during DO. In the present study, we integrated strontium into a one-pot synthesis of mesoporous silica nanoparticles to obtain strontium-doped mesoporous silica nanoparticles characterized by a homogeneous spherical morphology and uniform ion-releasing dynamics. This dual-ion releasing osteogenic and angiogenic drug delivery system was investigated to accelerate mineralization in DO. Osteogenesis was promoted by activation of the Wnt/ß-catenin pathway, while bone resorption was inhibited by reduction of the osteoclastogenic factor RANKL/OPG. In addition, angiogenesis may have been enhanced indirectly by secretion of vascular endothelial growth factor (VEGF) from bone marrow stem cells. Therefore, strontium-doped mesoporous silica nanoparticles could be a potential biomaterial candidate for accelerating consolidation during DO.

Bony Hypertrophy in Vascularized Fibular Grafts.

Background: Vascularized fibula graft (VFG) transfer is an established method of repairing large skeletal defects resulting from trauma, tumor resection, or infection. It obviates the process of creeping substitution that conventional bone grafts undergo and therefore exhibits better healing and improved strength. The aim of this study is to evaluate hypertrophy in VFG. Methods: We retrospectively reviewed patients undergoing VFG and studied immediate and late postoperative radiographs. Orthogonal views were measured for width of graft cortex and intramedullary canal, as well as adjacent recipient bone. Changes were measured for total cross sectional area, cortical area, intramedullary area, and graft width. Results: Thirty patients were included in the analysis, with recipient sites including 3 forearm, 4 humerus, 12 tibia, and 11 femur. Mean follow-up was 7.6 years (0.5-24.9 years). Patients' mean age was 31 (16-59 years). Average hypertrophy was 254% in early postoperative period and 340% in the late postoperative period. There was rapid graft hypertrophy in early postoperative period that plateaued with time. The width of the graft increased over time but didn't exceed the width of the adjacent recipient bone. In the later postoperative period, the size of graft intramedullary canal increased. Upper and lower extremity grafts showed similar hypertrophy. Conclusions: Using VFG to treat large skeletal defects is an attractive option in part due to the graft's ability to hypertrophy. We describe an early period of periosteal hypertrophy, followed by endosteal hypertrophy. These processes have relevance to function, mechanical strength, and surgical decision-making.

Tunable and Controlled Release of Cobalt Ions from Metal-Organic Framework Hydrogel Nanocomposites Enhances Bone Regeneration.

Cobalt (Co) ions, which can mimic hypoxia to promote angiogenesis, exhibit great potential for bone repair. However, a key point for the use of Co ions is that their release profile should be controllable and, more importantly, suitable for the bone regeneration process. Here, 2-ethylimidazole (eIm) was introduced into zeolitic imidazolate framework-67 (ZIF-67) to slow down Co-ion release and fabricate eIm-doped ZIF-67 (eIm/ZIF-67), which was combined into gelatin methacrylate (GelMA) to obtain an in situ photo-cross-linking nanocomposite hydrogel as a tunable Co-ion controlled release system. A tunable and controlled release of Co ions from the nanocomposite hydrogel was achieved by variation of linker composition, and GelMA with 75% eIm/ZIF-67 (with 75% eIm in the precursor solutions) could maintain a 21-day sustained release of Co ions, which is matched with early-stage angiogenesis during the bone formation process. Our in vitro study also showed that the GelMA@eIm/ZIF-67 hydrogel could reduce cytotoxicity and effectively promote the angiogenic activity of human umbilical vein endothelial cells (HUVECs) and osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs). Moreover, an in vivo rat calvarial defect model demonstrated that the GelMA@eIm/ZIF-67 hydrogel exhibited remarkably enhanced bone formation and neovascularization abilities and had good biocompatibility as shown in organ histopathological examinations. Therefore, this novel nanocomposite hydrogel has strong therapeutic potential as a desirable Co-ion controlled release system and a powerful proangiogenic/osteogenic agent for the treatment of bone defects.

In Situ Prevascularization Strategy with Three-Dimensional Porous Conduits for Neural Tissue Engineering.

Neovascularization is crucial for peripheral nerve regeneration and long-term functional restoration. Previous studies have emphasized strategies that enhance axonal repair over vascularization. Here, we describe the development and application of an in situ prevascularization strategy that uses 3D porous nerve guidance conduits (NGCs) to achieve angiogenesis-mediated neural regeneration. The optimal porosity of the NGC is a critical feature for achieving neovascularization and nerve growth patency. Hollow silk fibroin/poly(l-lactic acid-co-ε-caprolactone) NGCs with 3D sponge-like walls were fabricated using electrospinning and freeze-drying. In vitro results showed that 3D porous NGC favored cell biocompatibility had neuroregeneration potential and, most importantly, had angiogenic activity. Results from our mechanistic studies suggest that activation of HIF-1α signaling might be associated with this process. We also tested in situ prevascularized 3D porous NGCs in vivo by transplanting them into a 10 mm rat sciatic nerve defect model with the aim of regenerating the severed nerve. The prevascularized 3D porous NGCs greatly enhanced intraneural angiogenesis, resulting in demonstrable neurogenesis. Eight weeks after transplantation, the performance of the prevascularized 3D NGCs was similar to that of traditional autografts in terms of improved anatomical structure, morphology, and neural function. In conclusion, combining a reasonably fabricated 3D-pore conduit structure with in situ prevascularization promoted functional nerve regeneration, suggesting an alternative strategy for achieving functional recovery after peripheral nerve trauma.

EGFL6 regulates angiogenesis and osteogenesis in distraction osteogenesis via Wnt/ß-catenin signaling.

BACKGROUND: Osteogenesis is tightly coupled with angiogenesis during bone repair and regeneration. However, the underlying mechanisms linking these processes remain largely undefined. The present study aimed to test the hypothesis that epidermal growth factor-like domain-containing protein 6 (EGFL6), an angiogenic factor, also functions in bone marrow mesenchymal stem cells (BMSCs), playing a key role in the interaction between osteogenesis and angiogenesis. METHODS: We evaluated how EGFL6 affects angiogenic activity of human umbilical cord vein endothelial cells (HUVECs) via proliferation, transwell migration, wound healing, and tube-formation assays. Alkaline phosphatase (ALP) and Alizarin Red S (AR-S) were used to assay the osteogenic potential of BMSCs. qRT-PCR, western blotting, and immunocytochemistry were used to evaluate angio- and osteo-specific markers and pathway-related genes and proteins. In order to determine how EGFL6 affects angiogenesis and osteogenesis in vivo, EGFL6 was injected into fracture gaps in a rat tibia distraction osteogenesis (DO) model. Radiography, histology, and histomorphometry were used to quantitatively evaluate angiogenesis and osteogenesis. RESULTS: EGFL6 stimulated both angiogenesis and osteogenic differentiation through Wnt/ß-catenin signaling in vitro. Administration of EGFL6 in the rat DO model promoted CD31hiEMCNhi type H-positive capillary formation associated with enhanced bone formation. Type H vessels were the referred subtype involved during DO stimulated by EGFL6. CONCLUSION: EGFL6 enhanced the osteogenic differentiation potential of BMSCs and accelerated bone regeneration by stimulating angiogenesis. Thus, increasing EGFL6 secretion appeared to underpin the therapeutic benefit by promoting angiogenesis-coupled bone formation. These results imply that boosting local concentrations of EGFL6 may represent a new strategy for the treatment of compromised fracture healing and bone defect restoration.