Netrin-1 Promotes Inflammation Resolution to Achieve Endothelialization of Small-Diameter Tissue Engineering Blood Vessels by Improving Endothelial Progenitor Cells Function In Situ

Netrin-1 co-cross-linked hydrogel accelerates diabetic wound healing in situ by modulating macrophage heterogeneity and promoting angiogenesis

Diabetic wounds, characterized by prolonged inflammation and impaired vascularization, are a serious complication of diabetes. This study aimed to design a gelatin methacrylate (GelMA) hydrogel for the sustained release of netrin-1 and evaluate its potential as a scaffold to promote diabetic wound healing. The results showed that netrin-1 was highly expressed during the inflammation and proliferation phases of normal wounds, whereas it synchronously exhibited aberrantly low expression in diabetic wounds. Neutralization of netrin-1 inhibited normal wound healing, and the topical application of netrin-1 accelerated diabetic wound healing. Mechanistic studies demonstrated that netrin-1 regulated macrophage heterogeneity via the A2bR/STAT/PPARγ signaling pathway and promoted the function of endothelial cells, thus accelerating diabetic wound healing. These data suggest that netrin-1 is a potential therapeutic target for diabetic wounds.

Gelatin/heparin coated bio-inspired polyurethane composite fibers to construct small-caliber artificial blood vessel grafts

Long-term patency and ability for revascularization remain challenges for small-caliber blood vessel grafts to treat cardiovascular diseases clinically. Here, a gelatin/heparin coated bio-inspired polyurethane composite fibers-based artificial blood vessel with continuous release of NO and biopeptides to regulate vascular tissue repair and maintain long-term patency is fabricated. A biodegradable polyurethane elastomer that can catalyze S-nitrosothiols in the blood to release NO is synthesized (NPU). Then, the NPU core-shell structured nanofiber grafts with requisite mechanical properties and biopeptide release for inflammation manipulation are fabricated by electrospinning and lyophilization. Finally, the surface of tubular NPU nanofiber grafts is coated with heparin/gelatin and crosslinked with glutaraldehyde to obtain small-caliber artificial blood vessels (ABVs) with the ability of vascular revascularization. We demonstrate that artificial blood vessel grafts promote the growth of endothelial cells but inhibit the growth of smooth muscle cells by the continuous release of NO; vascular grafts can regulate inflammatory balance for vascular tissue remodel without excessive collagen deposition through the release of biological peptides. Vascular grafts prevent thrombus and vascular stenosis to obtain long-term patency. Hence, our work paves a new way to develop small-caliber artificial blood vessel grafts that can maintain long-term patency in vivo and remodel vascular tissue successfully.

Precise Engineering of Growth Factor Presentation Using Extracellular Microenvironment-Mimicking Microfluidic Microparticles

One of the main challenges in tissue engineering is finding a way to deliver specific growth factors (GFs) with precise spatiotemporal control over their presentation. Here, we report a novel strategy for generating microscale carriers with enhanced affinity for high content loading suitable for the sustained and localized delivery of GFs. Our developed microparticles can be injected locally and sustainably release encapsulated growth factors for up to 28 days. Fine-tuning of particles' size, affinity, microstructures, and release kinetics is achieved using a microfluidic system along with bioconjugation techniques. We also describe an innovative 3D micromixer platform to control the formation of core-shell particles based on superaffinity using a polymer-peptide conjugate for further tuning of release kinetics and delayed degradation. Chitosan shells block the burst release of encapsulated GFs and enable their sustained delivery for up to 10 days. The matched release profiles and degradation provide the local tissues with biomimetic, developmental-biologic-compatible signals to maximize regenerative effects. The versatility of this approach is verified using three different therapeutic proteins, including human bone morphogenetic protein-2 (rhBMP-2), vascular endothelial growth factor (VEGF), and stromal cell-derived factor 1 (SDF-1α). As in vivo morphogenesis is typically driven by the combined action of several growth factors, the proposed technique can be developed to generate a library of GF-loaded particles with designated release profiles.

Systemwide effects of ER-intracellular membrane contact site disturbance in primary endothelial cells

Membrane contact sites (MCS) make up a crucial route of inter-organelle non-vesicular transport within the cell. Multiple proteins are involved in this process, which includes the ER-resident proteins vesicle associated membrane protein associated protein A and -B (VAPA/B) that form MCS between the ER and other membrane compartments. Currently most functional data on VAP depleted phenotypes have shown alterations in lipid homeostasis, induction of ER stress, dysfunction of UPR and autophagy, as well as neurodegeneration. Literature on concurrent silencing of VAPA/B is still sparse; therefore, we investigated how it affects the macromolecule pools of primary endothelial cells. Our transcriptomics results showed significant upregulation in genes related to inflammation, ER and Golgi dysfunction, ER stress, cell adhesion, as well as Coat Protein Complex-I and -II (COP-I, COP-II) vesicle transport. Genes related to cellular division were downregulated, as well as key genes of lipid and sterol biosynthesis. Lipidomics analyses revealed reductions in cholesteryl esters, very long chain highly unsaturated and saturated lipids, whereas increases in free cholesterol and relatively short chain unsaturated lipids were evident. Furthermore, the knockdown resulted in an inhibition of angiogenesis in vitro. We speculate that ER MCS depletion has led to multifaceted outcomes, which include elevated ER free cholesterol content and ER stress, alterations in lipid metabolism, ER-Golgi function and vesicle transport, which have led to a reduction in angiogenesis. The silencing also induced an inflammatory response, consistent with upregulation of markers of early atherogenesis. To conclude, ER MCS mediated by VAPA/B play a crucial role in maintaining cholesterol traffic and sustain normal endothelial functions.

Cellular energy supply for promoting vascular remodeling of small-diameter vascular grafts: a preliminary study of a new strategy for vascular graft development

Rapid endothelialization is extremely essential for the success of small-diameter tissue-engineered vascular graft (TEVG) (<6 mm) transplantation. However, severe inflammation in situ often causes cellular energy decline of endothelial cells. The cellular energy supply involved in vascular graft therapy remains unclear, and whether promoting energy supply would be helpful in the regeneration of vascular grafts needs to be established. In our work, we generated an AMPK activator (5-aminoimidazole-4-carboxamide ribonucleotide, AICAR) immobilized vascular graft. AICAR-modified vascular grafts were successfully generated by the co-electrospinning technique. In vitro results indicated that AICAR could upregulate energy supply in endothelial cells and reprogram macrophages (MΦ) to assume an anti-inflammatory phenotype. Furthermore, endothelial cells (ECs) co-cultured with AICAR achieved higher survival rates, better migration, and angiogenic capacity than the controls. Concurrently, a rabbit carotid artery transplantation model was used to investigate AICAR-modified vascular grafts at different time points. The results showed that AICAR-modified vascular grafts had higher patency rates (92.9% and 85.7% at 6 and 12 weeks, respectively) than those of the untreated group (11.1% and 0%). In conclusion, AICAR strengthened the cellular energy state and attenuated the adverse effects of inflammation. AICAR-modified vascular grafts achieved better vascular remodeling. This study provides a new perspective on promoting the regeneration of small-diameter vascular grafts.

The Regulatory Effect of Braided Silk Fiber Skeletons with Differential Porosities on In Vivo Vascular Tissue Regeneration and Long-Term Patency

The development of small-diameter vascular grafts that can meet the long-term patency required for implementation in clinical practice presents a key challenge to the research field. Although techniques such as the braiding of scaffolds can offer a tunable platform for fabricating vascular grafts, the effects of braided silk fiber skeletons on the porosity, remodeling, and patency in vivo have not been thoroughly investigated. Here, we used finite element analysis of simulated deformation and compliance to design vascular grafts comprised of braided silk fiber skeletons with three different degrees of porosity. Following the synthesis of low-, medium-, and high-porosity silk fiber skeletons, we coated them with hemocompatible sulfated silk fibroin sponges and then evaluated the mechanical and biological functions of the resultant silk tubes with different porosities. Our data showed that high-porosity grafts exhibited higher elastic moduli and compliance but lower suture retention strength, which contrasted with low-porosity grafts. Medium-porosity grafts offered a favorable balance of mechanical properties. Short-term in vivo implantation in rats indicated that porosity served as an effective means to regulate blood leakage, cell infiltration, and neointima formation. High-porosity grafts were susceptible to blood leakage, while low-porosity grafts hindered graft cellularization and tended to induce intimal hyperplasia. Medium-porosity grafts closely mimicked the biomechanical behaviors of native blood vessels and facilitated vascular smooth muscle layer regeneration and polarization of infiltrated macrophages to the M2 phenotype. Due to their superior performance and lack of occlusion, the medium-porosity vascular grafts were evaluated in long-term (24-months) in vivo implantation. The medium-porosity grafts regenerated the vascular smooth muscle cell layers and collagen extracellular matrix, which were circumferentially aligned and resembled the native artery. Furthermore, the formed neoarteries pulsed synchronously with the adjacent native artery and demonstrated contractile function. Overall, our study underscores the importance of braided silk fiber skeleton porosity on long-term vascular graft performance and will help to guide the design of next-generation vascular grafts.

Construction of enzyme-laden vascular scaffolds based on hyaluronic acid oligosaccharides-modified collagen nanofibers for antithrombosis and in-situ endothelialization of tissue-engineered blood vessels

The current use of synthetic grafts often yields low patency in the reconstruction of small-diameter blood vessels owing to the deposition of thrombi and imperfect coverage of the endothelium on the graft lumen. Therefore, the design of vascular scaffolds with antithrombotic performance and endothelialization is greatly required. Herein, we developed an enzyme-laden scaffold based on hyaluronic acid oligosaccharides-modified collagen nanofibers (labeled HA-COL) to improve the anti-platelet capacity and endothelialization of vascular grafts. In this study, HA-COL nanofibers not only encouraged the endothelialization of vascular scaffolds, but acted as an antiplatelet enzyme-laden platform. Apyrase (Apy) and 5'-nucleotidase (5'-NT) were covalently grafted onto the nanofibers, which in turn converted the platelet-sensitive substance: adenosine diphosphate (ADP) into adenosine monophosphate (AMP) and adenosine, thereby, improving the antithrombotic performance of the scaffolds. Notably, the catalytic end-product: adenosine would work in coordination with HA-COL to synergistically enhance the endothelialization of the vascular scaffolds. The results demonstrated that the enzyme-laden scaffolds maintained catalytic performance, reduced platelet adhesion and aggregation, and guaranteed higher patency after 1-month in situ transplantation. Moreover, these scaffolds showed optimal cytocompatibility, tissue compatibility, scaffold biodegradability and tissue regenerative capability during in vivo implantation. Overall, these engineered vascular scaffolds demonstrated their capacity for endothelialization and antithrombotic performance, suggesting their potential for small-diameter vascular tissue engineering applications. STATEMENT OF SIGNIFICANCE: Considering the critical problems in small-diameter vascular reconstruction, the enzyme-laden vascular scaffolds were prepared for improving in-situ endothelialization and antithrombotic performances of artificial blood vessels. The electrospun HA-COL nanofibers were used as the main matrix materials, which provided favorable structural templates for the regeneration of vasculature and functioned as a platform for the loading of enzymes. The enzyme-laden scaffolds with the biomimetic cascading reaction would convert ADP into adenosine, thereby, decreasing the sensitivity of platelets and improving the antithrombotic performance of tissue-engineered blood vessels (TEBVs). The nanofibrous scaffolds exhibited optimal cytocompatibility, tissue compatibility and regenerative capability, working together with catalytic products of dual-enzyme reaction that would synergistically contribute to TEBVs endothelialization. This study provides a new method for the improvement of in-situ endothelialization of small-diameter TEBVs while qualified with antithrombotic performance.

Quercetin improves rapid endothelialization and inflammatory microenvironment in electrospun vascular grafts

There is a great need for small diameter vascular grafts among patients with cardiovascular diseases annually. However, continuous foreign body reactions and fibrosis capsules brought by biomaterials are both prone to poor vascular tissue regeneration. To address this problem, we fabricated a polycaprolactone (PCL) vascular graft incorporated with quercetin (PCL/QCT graft) in this study. In vitro cell assay showed that quercetin reduced the expressions of pro-inflammatory genes of macrophages while increased the expressions of anti-inflammatory genes. Furthermore, in vivo implantation was performed in a rat abdominal aorta replacement model. Upon implantation, the grafts exhibited sustained quercetin release and effectively enhanced the regeneration of vascular tissue. The results revealed that quercetin improved endothelial layer formation along the lumen of the vascular grafts at 4 weeks. Furthermore, the thickness of vascular smooth muscle layers significantly increased in PCL/QCT group compared with PCL group. More importantly, the presence of quercetin stimulated the infiltration of a large amount of M2 phenotype macrophages into the grafts. Collectively, the above data reinforced our hypothesis that the incorporation of quercetin may be in favor of modulating the inflammatory microenvironment and improving vascular tissue regeneration and remodeling in vascular grafts.

Programming of Regulatory T Cells In Situ for Nerve Regeneration and Long-Term Patency of Vascular Grafts

Rapid integration into the host tissue is critical for long-term patency after small diameter tissue engineering vascular grafts (sdTEVGs) transplantation. Neural recognition may be required for host integration and functionalization of the graft. However, immune rejection and inflammation hinder nerve regeneration of sdTEVGs. Here, a CRISPR/dCas9-nanocarrier was used for targeted programming of regulatory T cells (Treg cells) in situ to promote nerve regeneration of sdTEVGs by preventing excessive inflammation. Treg cells and (C-C chemokine receptor) CCR2+ macrophage recruitment occurred after transplantation. The nanodelivery system upregulated ten eleven translocation (TET2) in Treg cells in vitro. Reprogrammed Treg cells upregulated anti-inflammatory cytokines and decreased the proportion of CCR2+ macrophages. IL-6 concentrations decreased to the levels required for nerve regeneration. Implantation of CRISPR/dCas9 nanodelivery system-modified sdTEVGs in rats resulted in Treg cell editing, control of excessive inflammation, and promoted nerve regeneration. After 3 months, nerve regeneration was similar to that observed in normal blood vessels; good immune homeostasis, consistency of hemodynamics, and matrix regeneration were observed. Neural recognition promotes further integration of the graft into the host, with unobstructed blood vessels without intimal hyperplasia. Our findings provide new insights into vascular implant functionalization by the host.

Adhesive hydrogel wrap loaded with Netrin-1-modified adipose-derived stem cells: An effective approach against periarterial inflammation after endovascular intervention

Endovascular interventions, such as balloon dilation and stent implantation, are currently recommended as the primary treatment for patients with peripheral artery disease (PAD), greatly improving patient prognosis. However, the consequent lumen restenosis that occurs after endovascular interventions has become an important clinical problem. Inflammation has been proven to be crucial to postoperative restenosis. In previous studies we have identified that Netrin-1-modified adipose-derived stem cells (N-ADSCs) transplantation is an effective anti-inflammatory strategy to repair vascular damage. Nevertheless, it remained to be explored how one could constantly deliver N-ADSCs onto damaged arteries. Therefore, we developed an adhesive double network (DN) hydrogel wrap loaded with N-ADSCs for sustained perivascular delivery. Inspired by the adhesion mechanism of mussels, we developed an adhesive and tough polyacrylamide/calcium-alginate/reduced graphene oxide/polydopamine (PAM/CA/rGO/PDA) hydrogel. Dopamine was attached to graphene sheets and limitedly oxidized to generate free catechol groups. The hydrogel could wrap damaged arteries and induce anti-inflammatory effects through N-ADSCs. In vitro experiments demonstrated that N-ADSCs significantly promoted the M2 polarization of macrophages to anti-inflammatory phenotypes and reduced the expression of inflammatory factors. In vivo experiments in a rat carotid artery guidewire injury model showed that the adhesive hydrogel wrap loaded with N-ADSCs could significantly reduce arterial inflammation, inhibit intimal hyperplasia and improve re-endothelialization. Altogether, this newly developed N-ADSCs-loaded hydrogel wrap provides an effective slow-releasing system, which may be a promising way to prevent and treat restenosis after endovascular interventions.

LincRNA‑EPS increases TGF‑β expression to inhibit the Wnt/β‑catenin pathway, VSMC osteoblastic differentiation and vascular calcification in diabetic mice

In patients with diabetes, the Wnt/β-catenin pathway in vascular smooth muscle cells (VSMCs) is continuously activated by low-intensity inflammation, which leads to the osteoblastic differentiation of these cells and the deposition of calcium and phosphorus in blood vessels. The aim of the present study was to determine whether long intergenic non-coding RNA-erythroid pro-survival (lincRNA-EPS) was able to ameliorate vascular calcification (VC) associated with diabetes. VSMCs isolated from C57BL/6 mice were transfected with lincRNA-EPS overexpression vector in vitro and their osteoblastic differentiation was evaluated under high-glucose conditions. In addition, a mouse model of diabetes was established, which included a lincRNA-EPS knockout group and a lincRNA-EPS high expression group. Blood vessel samples from the mice were examined to determine the degree of calcification. The levels of inflammatory factors in serum were also detected. The VSMCs transfected with lincRNA-EPS overexpression vector exhibited less osteoblastic differentiation and migration and significantly lower levels of Wnt pathway-associated proteins than those transfected with empty control. Furthermore, the in vivo experiments revealed that the overexpression of lincRNA-EPS significantly reduced VC in diabetic mice. Therefore, on the basis of these findings, it is suggested that lincRNA-EPS overexpression may provide a novel and effective method for the treatment of VC in patients with diabetes.

In Situ Fabrication and Perfusion of Tissue-Engineered Blood Vessel Microphysiological System

Human tissue-engineered blood vessels (TEBVs) that exhibit vasoactivity can be used to test drug toxicity, modulate pro-inflammatory cytokines, and model disease states in vitro. We developed a novel device to fabricate arteriole-scale human endothelialized TEBVs in situ with smaller volumes and higher throughput than previously reported. Both primary and induced pluripotent stem cell (iPSC)-derived cells can be used. Four collagen TEBVs with 600μm inner diameter and 2.9 mm outer diameter are fabricated by pipetting a solution of collagen and medial cells into a three-layer acrylic mold. After gelation, the TEBVs are released from the mold and dehydrated. After suturing the TEBVs in place and changing the mold parts to form a perfusion chamber, the TEBVs are endothelialized in situ, and then media is perfused through the lumen. By removing 90% of the water after gelation, the TEBVs become mechanically strong enough for perfusion at the physiological shear stress of 0.4 Pa within 24 h of fabrication and maintain function for at least 5 weeks.

Programmable dual responsive system reconstructing nerve interaction with small-diameter tissue-engineered vascular grafts and inhibiting intimal hyperplasia in diabetes

Small-diameter tissue-engineered vascular grafts (sdTEVGs) with hyperglycemia resistance have not been constructed. The intimal hyperplasia caused by hyperglycemia remains problem to hinder the patency of sdTEVGs. Here, inspired by bionic regulation of nerve on vascular, we found the released neural exosomes could inhibit the abnormal phenotype transformation of vascular smooth muscle cells (VSMCs). The transformation was a prime culprit causing the intimal hyperplasia of sdTEVGs. To address this concern, sdTEVGs were modified with an on-demand programmable dual-responsive system of ultrathin hydrogels. An external primary Reactive Oxygen Species (ROS)-responsive Netrin-1 system was initially triggered by local inflammation to induce nerve remolding of the sdTEVGs overcoming the difficulty of nerve regeneration under hyperglycemia. Then, the internal secondary ATP-responsive DENND1A (guanine nucleotide exchange factor) system was turned on by the neurotransmitter ATP from the immigrated nerve fibers to stimulate effective release of neural exosomes. The results showed nerve fibers grow into the sdTEVGs in diabetic rats 30 days after transplantation. At day 90, the abnormal VSMCs phenotype was not detected in the sdTEVGs, which maintained long-time patency without intima hyperplasia. Our study provides new insights to construct vascular grafts resisting hyperglycemia damage.

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VSMCs undergo a phenotypic transformation under high glucose, which lead to intimal hyperplasia in sdTEVGs.

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Neural exosomes could inhibit the abnormal phenotype transformation of VSMCs from contractile to synthetic.

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SdTEVGs with on-demand programmable dual responsive system inhibited intimal hyperplasia in diabetes.

The expression of Netrin-1 in the MIA-induced osteoarthritic temporomandibular joint in mice

Subchondral bone degeneration is the main pathological change during temporomandibular joint (TMJ) osteoarthritis (OA) development. Netrin-1, an axon-guiding factor, might play roles in OA development and pain. The purpose of this study was to investigate the expression of Netrin-1 in TMJ OA and its possible role in the progression of TMJ OA and pain. The synovial fluids of temporomandibular joint disorders (TMDs) patients were collected for Netrin-1 by enzyme linked immunosorbent assay (ELISA). TMJ OA model was built by MIA joint injection, and then the von Frey test, hematoxylin & eosin (H&E) staining, toluidine blue (TB) staining, immunohistochemical (IHC) staining and micro-CT were performed. After induction of osteoclast differentiation of raw264.7 cells, immunofluorescence (IF) was used to detect the Netrin-1 and its receptors on osteoclast membrane. The concentration of Netrin-1 increased in the synovial fluid of TMJ OA patients. After MIA injection to TMJ, the head withdrawal threshold (HWT) was significantly decreased. Microscopically, the structural disorder of subchondral bone was the most obvious at the 2nd week after MIA injection. In addition, Netrin-1 expression increased in the subchondral bone at the 2nd week after MIA injection. In vitro, the expressions of Netrin-1 and its receptor Unc5B were upregulated on the osteoclast membrane. Netrin-1 might be an important regulator during bone degeneration and pain in the process of TMJ OA.

Digital 3D Topographic Microscopy: Bridging the Gaps Between Macroscopy, Microscopy and Scanning Electron Microscopy

Re-endothelialization of vascular lumen after endovascular procedures is a critical healing milestone and is subjected to routine pathological evaluation during preclinical safety assessment of new cardiovascular devices. Gross evaluation, microscopic evaluation, and scanning electron microscopy (SEM) are the methods of choice for evaluation of vascular surfaces. In this article, we present a new digital imaging approach of surface topography herein referred to as topographical digital microscopy (TDM) that is able to meet the objectives of endovascular healing assessment in a single instrumental platform combined with the same sample preparation techniques as for histology or SEM. This platform is taking advantage of digitally managed illumination, X-Y stitching, and Z-stacking to enable direct optical imaging of tissue surfaces at levels of details ranging from the macroscopic to the cellular level. This technique is enabled by advances in digital optical microscopy and provides images in color and 3 dimensions that can help in the analysis, especially in distinguishing biologically meaningful observations from technical preparation artifacts and in visualizing surface topography.

Netrin-1 and its receptor Unc5b as markers of periodontal disease

OBJECTIVES

The aim of this present study was to evaluate the levels of Netrin-1 and Unc5b in periodontal health and disease.

BACKGROUND

Netrin-1, acting via its receptor UNC5b, regulates the inflammatory response and takes apart in bone destructive diseases.

METHODS

Samples of gingival crevicular fluid (GCF), whole saliva, and serum were taken from systemically healthy, nonsmoking 20 periodontitis , 20 gingivitis patients, and 20 periodontally healthy subjects at baseline and 4 weeks after nonsurgical periodontal treatment (NSPT). Whole-mouth and site-specific clinical periodontal parameters were recorded. Netrin-1 and Unc5b levels were measured by enzyme-linked immunosorbent assay. Data were analyzed by nonparametric tests.

RESULTS

Total amount of Netrin-1 in GCF was significantly higher in periodontitis than the others, and the levels were significantly reduced after NSPT. Salivary and serum concentrations of Netrin-1 were significantly different among the study groups (P = .000), and NSPT significantly increased the concentration levels of both salivary and serum Netrin-1 (P < .05). Healthy subjects had significantly lower GCF (P = .001) and conversely, higher salivary and serum levels of Unc5b than the other groups (P = .002). The GCF levels of Unc5b were significantly reduced (P < .01), and conversely, serum concentrations were significantly increased after NSPT (P < .05). GCF Netrin-1 and Unc5b total amounts were positively correlated with clinical parameters (P < .01 and P < .05) whereas salivary Netrin-1 and Unc5b concentrations were negatively correlated with clinical parameters (P < .01 and P < .05).

CONCLUSIONS

The results of this study indicate that Netrin-1 and its receptor Unc5b may have essential roles in periodontal inflammation and those can be assumed as useful therapeutic agent to control inflammation and periodontal breakdown.

Regulation of the inflammatory response by vascular grafts modified with Aspirin-Triggered Resolvin D1 promotes blood vessel regeneration

The unabated inflammatory response is often the cause for inhibited vascular regeneration of transplanted small-diameter vascular grafts (diameter <6 mm) in vascular replacement therapies. We proposed that stimulating inflammatory resolution could be an effective approach for treatment of chronic vascular graft inflammation after transplantation. Aspirin-Triggered Resolvin D1 (AT-RvD1) plays critical roles in driving cellular processes toward the resolution of inflammation and suppressing downstream inflammatory signaling pathways. With the aim to facilitate vascular regeneration, we developed a polycaprolactone (PCL) vascular graft loaded with AT-RvD1. The results showed that AT-RvD1 promoted macrophage polarization into M2 macrophages in vitro. Macrophages pretreated with AT-RvD1 conditioned medium promoted endothelial cell tube formation. Furthermore, in vivo implantation was performed by replacing rat abdominal aorta. We observed fast endothelialization and enhanced smooth muscle regeneration in rats that received the AT-RvD1-containing graft implants. The presence of AT-RvD1 induced infiltration of a large number of M2 macrophages and integrin α4-positive (CD49d⁺) neutrophils into the graft wall after implantation. Vascular graft RNA-Seq analysis revealed that AT-RvD1 inhibited leukocyte and neutrophil migration and activation. Results also indicated that macrophage polarization to the M2 phenotype was promoted on day 7 post-implantation. These results demonstrated the ability of locally delivered AT-RvD1 to increase pro-regenerative immune subpopulations and promote vascular tissue regeneration. STATEMENT OF SIGNIFICANCE: Chronic inflammation is a key deciding factor in the failure of vascular regeneration of transplanted small-diameter vascular grafts (diameter <6 mm). Aspirin-triggered Resolvin D1 (AT-RvD1) is a critical driving force in cellular resolution inflammation and suppresses inflammatory signaling. Herein, we developed an electrospun polycaprolactone (PCL) vascular graft loaded with AT-RvD1. In vivo implantation was performed by replacing rat abdominal aorta and AT-RvD1-loaded grafts showed rapid endothelialization, enhanced capillary formation, and excellent smooth muscle regeneration by regulating inflammatory reaction and promoting its rapid resolution. Thus, our study provided new perspectives for long-term vascular graft survival and integration with the host tissue. We believe that AT-RvD1 can be widely applied in tissue engineering owing to its anti-inflammatory and therapeutic effects.

Evaluation of a simple off-the-shelf bi-layered vascular scaffold based on poly(L-lactide-co-ε-caprolactone)/silk fibroin in vitro and in vivo

Purpose: In the field of small-caliber vascular scaffold research, excellent vascular remodeling is the key to ensuring anticoagulant function. We prepared an off-the-shelf bi-layered vascular scaffold with a dense inner layer and a loose outer layer and evaluated its remodeling capabilities by in vivo transplantation.

Materials and Methods: Based on poly(L-lactide-co-ε-caprolactone) (PLCL), silk fibroin(SF), and heparin (Hep), PLCL/SF/Hep bi-layered scaffolds and PLCL/Hep bi-layered scaffolds were prepared by electrospinning. The inner layer was a PLCL/SF/Hep or PLCL/Hep nanofiber membrane, and the outer layer was PLCL/SF nano yarn. The in vitro tests included a hydrophilicity test, mechanical properties test, and blood and cell compatibility evaluation. The in vivo evaluation was conducted via single rabbit carotid artery replacement and subsequent examinations, including ultrasound imaging, immunoglobulin assays, and tissue section staining.

Results: Compared to the PLCL/Hep nanofiber membrane, the hydrophilicity of the PLCL/SF/Hep nanofiber membrane was significantly improved. The mechanical strength met application requirements. Both the blood and cell compatibility were optimal. Most importantly, the PLCL/SF/Hep scaffolds maintained lumen patency for 3 months after carotid artery transplantation in live rabbits. At the same time, CD31 and α-SMA immunofluorescence staining confirmed bionic endothelial and smooth muscle layers remodeling.

Conclusion: Using this hybrid strategy, PLCL and SF were combined to manufacture bi-layered small-caliber vascular scaffolds; these PLCL/SF/Hep scaffolds showed satisfactory vascular remodeling.

lncRNA GAS5 promotes M1 macrophage polarization via miR-455-5p/SOCS3 pathway in childhood pneumonia

OBJECTIVES

We herein aimed to explore whether growth arrest-specific 5 (GAS5) promotes M1 macrophage polarization in childhood pneumonia and to investigate the underlying mechanism.

METHODS

Relative GAS5 and miR-455-5p expression and suppressor of cytokine signaling 3 (SOCS3) messenger RNA level were examined using quantitative reverse transcription polymerase chain reaction. Protein expression of SOCS3 and the Janus kinase 2/signal transducer and activator of transcription 3 (JAK2/STAT3) pathway-related proteins was detected using western blot analysis. Luciferase activity assay was performed to test whether miR-455-5p could bind to GAS5 or SOCS3. The macrophage phenotype was determined using flow cytometry analysis and enzyme-linked immunosorbent assay.

RESULTS

The macrophage polarization toward the M2 phenotype was observed in peripheral blood from pneumonia children. Furthermore, GAS5 and SOCS3 expression were upregulated but miR-455-5p downregulated in human monocyte-derived macrophages from pneumonia children compared with the control group. Furthermore, GAS5 acted as a sponge for miR-455-5p to facilitate SOCS3 expression. Moreover, miR-455-5p mimic and SOCS3 knockdown significantly reversed the GAS5 overexpression-mediated suppression of the JAK2/STAT3 signaling and promotion of M1 polarization.

CONCLUSION

GAS5 promotes M1 macrophage polarization by acting as a competing endogenous RNA of miR-455-5p to facilitate SOCS3 expression in childhood pneumonia.

Construction of a small-caliber tissue-engineered blood vessel using icariin-loaded β-cyclodextrin sulfate for in situ anticoagulation and endothelialization

The rapid endothelialization of tissue-engineered blood vessels (TEBVs) can effectively prevent thrombosis and inhibit intimal hyperplasia. The traditional Chinese medicine ingredient icariin is highly promising for the treatment of cardiovascular diseases. β-cyclodextrin sulfate is a type of hollow molecule that has good biocompatibility and anticoagulation properties and exhibits a sustained release of icariin. We studied whether icariin-loaded β-cyclodextrin sulfate can promote the endothelialization of TEBVs. The experimental results showed that icariin could significantly promote the proliferation and migration of endothelial progenitor cells; at the same time, icariin could promote the migration of rat vascular endothelial cells (RAVECs). Subsequently, we used an electrostatic force to modify the surface of the TEBVs with icariin-loaded β-cyclodextrin sulfate, and these vessels were implanted into the rat common carotid artery. After 3 months, micro-CT results showed that the TEBVs modified using icariin-loaded β-cyclodextrin sulfate had a greater patency rate. Scanning electron microscopy (SEM) and CD31 immunofluorescence results showed a better degree of endothelialization. Taken together, icariin-loaded β-cyclodextrin sulfate can achieve anticoagulation and rapid endothelialization of TEBVs to ensure their long-term patency.

The Host Response in Tissue Engineering: Crosstalk Between Immune cells and Cell-laden Scaffolds

Implantation of cell-laden scaffolds is a promising strategy for regenerating tissue that has been damaged due to injury or disease. However, the act of implantation initiates an acute inflammatory response. If the scaffold is non-biologic (i.e., a modified biologic scaffold or synthetic-based scaffold), inflammation will be prolonged through the foreign body response (FBR), which eventually forms a fibrous capsule and walls off the implant from the surrounding host tissue. This host response, from a cellular perspective, can create a harsh environment leading to long-lasting effects on the tissue engineering outcome. At the same time, cells embedded within the scaffold can respond to this environment and influence the interrogating immune cells (e.g., macrophages). This crosstalk, depending on the type of cell, can dramatically influence the host response. This review provides an overview of the FBR and highlights important and recent advancements in the host response to cell-laden scaffolds with a focus on the impact of the communication between immune cells and cells embedded within a scaffold. Understanding this complex interplay between the immune cells, notably macrophages, and the tissue engineering cells is a critically important component to a successful in vivo tissue engineering therapy.