Melt-electrowriting-enabled anisotropic scaffolds loaded with valve interstitial cells for heart valve tissue Engineering.

Tissue engineered heart valves (TEHVs) demonstrates the potential for tissue growth and remodel, offering particular benefit for pediatric patients. A significant challenge in designing functional TEHV lies in replicating the anisotropic mechanical properties of native valve leaflets. To establish a biomimetic TEHV model, we employed melt-electrowriting (MEW) technology to fabricate an anisotropic PCL scaffold. By integrating the anisotropic MEW-PCL scaffold with bioactive hydrogels (GelMA/ChsMA), we successfully crafted an elastic scaffold with tunable mechanical properties closely mirroring the structure and mechanical characteristics of natural heart valves. This scaffold not only supports the growth of valvular interstitial cells (VICs) within a 3D culture but also fosters the remodeling of extracellular matrix of VICs. The in vitro experiments demonstrated that the introduction of ChsMA improved the hemocompatibility and endothelialization of TEHV scaffold. The in vivo experiments revealed that, compared to their non-hydrogel counterparts, the PCL-GelMA/ChsMA scaffold, when implanted into SD rats, significantly suppressed immune reactions and calcification. In comparison with the PCL scaffold, the PCL-GelMA/ChsMA scaffold exhibited higher bioactivity and superior biocompatibility. The amalgamation of MEW technology and biomimetic design approaches provides a new paradigm for manufacturing scaffolds with highly controllable microstructures, biocompatibility, and anisotropic mechanical properties required for the fabrication of TEHVs.

The mediating role of electronic word-of-mouth in the relationship between CSR initiative and consumer satisfaction.

The importance of CSR in today's business environment cannot be ignored, especially more and more enterprises realize that when consumers perceive CSR, it will affect consumer behavior and then affect corporate efficiency and reputation. With the widespread application of social media, corporate social responsibility behaviors are easy to be participated and discussed by consumers on the Internet, forming electronic word-of-mouth. Therefore, this paper discusses the influence of electronic word-of-mouth between CSR and consumer satisfaction, taking China's largest Internet enterprise Tencent and its consumers and users as the research object. The overall purpose of this study is to explore the mediating role of electronic word-of-mouth in CSR and consumer satisfaction. This study uses Stimulus-Organism-Response (SOR) theory as the theoretical framework to explain the relationship between CSR initiatives, eWOM and consumer satisfaction. Using the quantitative method of questionnaire survey, taking China's enterprise Tencent as an example, a total of 490 valid questionnaires from Tencent WeChat users from four different levels of cities were received. The PLS-SEM model was used to deeply study the impact of CSR on consumer satisfaction and electronic word-of-mouth. The study found that philanthropic responsibility has a significant impact on consumer satisfaction, but environmental responsibility has no significant impact on satisfaction. At the same time, electronic word-of-mouth plays a key mediating role between the dimension of charitable responsibility and consumer satisfaction, but there is no mediating relationship between the dimension of environmental responsibility and consumer satisfaction. This study is beneficial to other enterprises in the formulation and planning of social responsibility, helps enterprises better understand consumer demands under different CSR dimensions, and provides a useful reference for the formulation of more accurate CSR strategies.

Chondroitin Sulfate Derivative Cross-Linking of Decellularized Heart Valve for the Improvement of Mechanical Properties, Hemocompatibility, and Endothelialization.

Tissue-engineered heart valve (TEHV) has emerged as a prospective alternative to conventional valve prostheses. The decellularized heart valve (DHV) represents a promising TEHV scaffold that preserves the natural three-dimensional structure and retains essential biological activity. However, the limited mechanical strength, fast degradation, poor hemocompatibility, and lack of endothelialization of DHV restrict its clinical use, which is necessary for ensuring its long-term durability. Herein, we used oxidized chondroitin sulfate (ChS), one of the main components of the extracellular matrix with various biological activities, to cross-link DHV to overcome the above problems. In addition, the ChS-adipic dihydrazide was used to react with residual aldehyde groups, thus preventing potential calcification. The results indicated notable enhancements in mechanical properties and resilience against elastase and collagenase degradation in vitro as well as the ability to withstand extended periods of storage without compromising the structural integrity of valve scaffolds. Additionally, the newly cross-linked valves exhibited favorable hemocompatibility in vitro and in vivo, thereby demonstrating exceptional biocompatibility. Furthermore, the scaffolds exhibited traits of gradual degradation and resistance to calcification through a rat subcutaneous implantation model. In the rat abdominal aorta implantation model, the scaffolds demonstrated favorable endothelialization, commendable patency, and a diminished pro-inflammatory response. As a result, the newly constructed DHV scaffold offers a compelling alternative to traditional valve prostheses, which potentially advances the field of TEHV.

Functional Oxidized Hyaluronic Acid Cross-Linked Decellularized Heart Valves for Improved Immunomodulation, Anti-Calcification, and Recellularization.

Tissue engineering heart valves (TEHVs) are expected to address the limitations of mechanical and bioprosthetic valves used in clinical practice. Decellularized heart valve (DHV) is an important scaffold of TEHVs due to its natural three-dimensional structure and bioactive extracellular matrix, but its mechanical properties and hemocompatibility are impaired. In this study, DHV is cross-linked with three different molecular weights of oxidized hyaluronic acid (OHA) by a Schiff base reaction and presented enhanced stability and hemocompatibility, which could be mediated by the molecular weight of OHA. Notably, DHV cross-linked with middle- and high-molecular-weight OHA could drive the macrophage polarization toward the M2 phenotype in vitro. Moreover, DHV cross-linked with middle-molecular-weight OHA scaffolds are further modified with RGD-PHSRN peptide (RPF-OHA/DHV) to block the residual aldehyde groups of the unreacted OHA. The results show that RPF-OHA/DHV not only exhibits anti-calcification properties, but also facilitates endothelial cell adhesion and proliferation in vitro. Furthermore, RPF-OHA/DHV shows excellent performance under an in vivo hemodynamic environment with favorable recellularization and immune regulation without calcification. The optimistic results demonstrate that OHA with different molecular weights has different cross-linking effects on DHV and that RPF-OHA/DHV scaffold with enhanced immune regulation, anti-calcification, and recellularization properties for clinical transformation.

Facile engineering of interactive double network hydrogels for heart valve regeneration.

Regenerative heart valve prostheses are essential for treating valvular heart disease, which requested interactive materials that can adapt to the tissue remodeling process. Such materials typically involves intricate designs with multiple active components, limiting their translational potential. This study introduces a facile method to engineer interactive materials for heart valve regeneration using 1,1'-thiocarbonyldiimidazole (TCDI) chemistry. TCDI crosslinking forms cleavable thiourea and thiocarbamate linkages which could gradually release H2S during degradation, therefore regulates the immune microenvironment and accelerates tissue remodeling. By employing this approach, a double network hydrogel was formed on decellularized heart valves (DHVs), showcasing robust anti-calcification and anti-thrombosis properties post fatigue testing. Post-implantation, the DHVs could adaptively degrade during recellularization, releasing H2S to further support tissue regeneration. Therefore, the comprehensive endothelial cell coverage and notable extracellular matrix remodeling could be clearly observed. This accessible and integrated strategy effectively overcomes various limitations of bioprosthetic valves, showing promise as an attractive approach for immune modulation of biomaterials.

Neutralizing Potency of Prototype and Omicron RBD mRNA Vaccines Against Omicron Variant.

The newly emerged Omicron variant of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) contains more than 30 mutations on the spike protein, 15 of which are located within the receptor binding domain (RBD). Consequently, Omicron is able to extensively escape existing neutralizing antibodies and may therefore compromise the efficacy of current vaccines based on the original strain, highlighting the importance and urgency of developing effective vaccines against Omicron. Here we report the rapid generation and evaluation of an mRNA vaccine candidate specific to Omicron, and explore the feasibility of heterologous immunization with WT and Omicron RBD vaccines. This mRNA vaccine encodes the RBD of Omicron (designated as RBD-O) and is formulated with lipid nanoparticle. Two doses of the RBD-O mRNA vaccine efficiently induce neutralizing antibodies in mice; however, the antisera are effective only on the Omicron variant but not on the wildtype and Delta strains, indicating a narrow neutralization spectrum. It is noted that the neutralization profile of the RBD-O mRNA vaccine is opposite to that observed for the mRNA vaccine expressing the wildtype RBD (RBD-WT). Importantly, booster with RBD-O mRNA vaccine after two doses of RBD-WT mRNA vaccine can significantly increase neutralization titers against Omicron. Additionally, an obvious increase in IFN-γ, IL-2, and TNF-α-expressing RBD-specific CD4+ T cell responses was observed after immunization with the RBD-WT and/or RBD-O mRNA vaccine. Together, our work demonstrates the feasibility and potency of an RBD-based mRNA vaccine specific to Omicron, providing important information for further development of heterologous immunization program or bivalent/multivalent SARS-CoV-2 vaccines with broad-spectrum efficacy.

Molecular mechanism of antibody neutralization of coxsackievirus A16.

Coxsackievirus A16 (CVA16) causes hand, foot and mouth disease in infants and young children. However, no vaccine or anti-viral agent is currently available for CVA16. Here, the functions and working mechanisms of two CVA16-specific neutralizing monoclonal antibodies (MAbs), 9B5 and 8C4, are comprehensively investigated. Both 9B5 and 8C4 display potent neutralization in vitro and prophylactic and therapeutic efficacy in a mouse model of CVA16 infection. Mechanistically, 9B5 exerts neutralization primarily through inhibiting CVA16 attachment to cell surface via blockade of CVA16 binding to its attachment receptor, heparan sulfate, whereas 8C4 functions mainly at the post-attachment stage of CVA16 entry by interfering with the interaction between CVA16 and its uncoating receptor SCARB2. Cryo-EM studies show that 9B5 and 8C4 target distinct epitopes located at the 5-fold and 3-fold protrusions of CVA16 capsids, respectively, and exhibit differential binding preference to three forms of naturally occurring CVA16 particles. Moreover, 9B5 and 8C4 are compatible in formulating an antibody cocktail which displays the ability to prevent virus escape seen with individual MAbs. Together, our work elucidates the functional and structural basis of CVA16 antibody-mediated neutralization and protection, providing important information for design and development of effective CVA16 vaccines and antibody therapies.

Small-diameter polyurethane vascular graft with high strength and excellent compliance.

In this study, a polyurethane vascular graft with excellent strength and compliance for clinical application was designed and fabricated by preparing three small-diameter vascular graft layers via the textile techniques of wet spinning and knitting. The polyurethane filament that was fabricated by wet spinning formed the inner layer. The polyurethane tubular fabric was used as the middle layer. The outer layer was prepared by spraying polyurethane solution. The three layers of the polyurethane vascular graft have uniform wall thickness, high strength, excellent compliance, and good puncture resistance compared with clinical poly(ethylene terephthalate) (PET) and expanded polytetrafluoroethylene (ePTFE) vascular graft. Therefore, these layers can have potential clinical applications in the replacement of the conventional artificial vascular graft prepared from PET and ePTFE.

Effect of poly (lactic acid) porous membrane prepared via phase inversion induced by water droplets on 3T3 cell behavior.

Phase inversion induced by water droplets has garnered attention in the field of polymer science as a novel method for preparing porous membranes. This study investigates the effect of the porous structure of poly (lactic acid) (PLA) membranes prepared through phase inversion induced by water droplets at four different temperatures (25, 50, 75, and 100 °C) on the morphology and proliferation of 3T3 cells. The surface properties of the PLA porous membrane, including pore size, pore size distribution, surface roughness, surface hydrophilicity, and cytocompatibility with 3T3 cells, were evaluated. The results indicated that the synthesized PLA membrane had two surfaces with different structures. The upper surface in contact with the water droplets during preparation contained uniformly distributed micropores, whereas the bottom surface was smooth and composed of small particles in contacted with the mold. The upper surface showed high cytocompatibility with 3T3 cells, and the 3T3 cells migrated and grew within the pores at 25 °C. In contrast, the bottom surface exhibited low biocompatibility with the 3T3 cells. Our study has wide-ranging implications and will improve the fabrication and implementation of 3D cultured scaffolds with excellent cytocompatibility.

A riboflavin-ultraviolet light A-crosslinked decellularized heart valve for improved biomechanical properties, stability, and biocompatibility.

Tissue-engineered heart valves are a promising alternative to current valve substitutes. As the main scaffold of tissue-engineered heart valves, the decellularized heart valve (DHV) has problems such as biomechanical property damage and rapid degradation. In this study, we applied a photo-crosslinking reaction induced by riboflavin and ultraviolet light A (UVA) in the DHV for improving its biomechanical properties and stability. The results showed that the biomechanical properties of the DHV significantly improved following riboflavin-UVA (R-UVA) crosslinking. Moreover, the R-UVA-crosslinked DHV (R-UV-DHV) showed better resistance to enzymatic degradation in vitro, with significantly higher thermal denaturation temperature compared to that of the untreated DHV, indicating that the stability of the R-UV-DHV improved. Histological staining and scanning electron microscopy showed that the leaflet ultrastructure was preserved better after R-UVA crosslinking compared to a glutaraldehyde-crosslinked DHV. In addition, we found that the R-UV-DHV exhibited excellent human umbilical vein endothelial cell adhesion and cells could readily grow on its surface. In an in vitro anti-calcification experiment, the R-UV-DHV demonstrated non-calcifying properties in a simulated body fluid. Furthermore, the R-UV-DHV showed characteristics of slow degradation, non-calcification, and reduced pro-inflammatory response through a rat subcutaneous implantation model. As a result, R-UVA can effectively crosslink the DHV and the R-UV-DHV possessed satisfactory biocompatibility. R-UVA crosslinking can be a new approach for improving the performance of the DHV to prepare a better scaffold for tissue-engineered valves.

Effect of temperature on the thermal property and crystallization behavior of poly (lactic acid) porous membrane prepared via phase separation induced by water microdroplets.

Poly (lactic acid) (PLA)-based porous membrane were fabricated through phase separation induced by water microdroplets at different ambient temperature to unravel the relationship between the physical properties (including thermal properties and crystallization) and preparation temperature. Cross-sectional scanning electron micrographs revealed that the thickness of the membrane decreases with increasing temperature between 25 °C and 100 °C. In the bilayer structure, each layer has a different morphology. Differential scanning calorimetry (DSC) and X-ray diffraction studies indicate that the preparation temperature influences the ratio between imperfect and perfect crystals in the membrane, leading to a bimodal melting peak in the DSC thermogram. The change in the initial decomposition temperature in the thermogravimetric analysis curve is weak, suggesting a negligible effect of the preparation temperature on the thermal stability of the membranes. Thus, PLA porous membranes can be prepared with better crystallinity by controlling the ambient temperature during the phase separation induced by water microdroplets.

Sequential hydrophile and lipophile solubilization as an efficient method for decellularization of porcine aortic valve leaflets: Structure, mechanical property and biocompatibility study.

Antigenicity of xenogeneic tissues is the major obstacle to increased use of these materials in clinical medicine. Residual xenoantigens in decellularized tissue elicit the immune response after implantation, causing graft failure. With this in mind, the potential use is proposed of three protein solubilization-based protocols for porcine aortic valve leaflets decellularization. It was demonstrated that hydrophile solubilization alone achieved incomplete decellularization; lipophile solubilization alone (LSA) completely removed all cells and two most critical xenoantigens - galactose-α(1,3)-galactose (α-Gal) and major histocompatibility complex I (MHC I) - but caused severe alterations of the structure and mechanical properties; sequential hydrophile and lipophile solubilization (SHLS) resulted in a complete removal of cells, α-Gal and MHC I, and good preservation of the structure and mechanical properties. In contrast, a previously reported method using Triton X-100, sodium deoxycholate and IGEPAL CA-630 resulted in a complete removal of all cells and MHC I, but with remaining α-Gal epitope. LSA- and SHLS-treated leaflets showed significantly reduced leucocyte activation (polymorphonuclear elastase) upon interaction with human blood in vitro. When implanted subdermally in rats for 6 weeks, LSA- or SHLS-treated leaflets were presented with more biocompatible implants and all four decellularized leaflets were highly resistant to calcification. These findings illustrate that the SHLS protocol could be considered as a promising decellularization method for the decellularization of xenogeneic tissues in tissue engineering and regenerative medicine. Copyright © 2016 John Wiley & Sons, Ltd.