Orthotopic equine study confirms the pivotal importance of structural reinforcement over the pre-culture of cartilage implants

In articular cartilage (AC), the collagen arcades provide the tissue with its extraordinary mechanical properties. As these structures cannot be restored once damaged, functional restoration of AC defects remains a major challenge. We report that the use of a converged bioprinted, osteochondral implant, based on a gelatin methacryloyl cartilage phase, reinforced with precisely patterned melt electrowritten polycaprolactone micrometer-scale fibers in a zonal fashion, inspired by native collagen architecture, can provide long-term mechanically stable neo-tissue in an orthotopic large animal model. The design of this novel implant was achieved via state-of-the-art converging of extrusion-based ceramic printing, melt electrowriting, and extrusion-based bioprinting. Interestingly, the cell-free implants, used as a control in this study, showed abundant cell ingrowth and similar favorable results as the cell-containing implants. Our findings underscore the hypothesis that mechanical stability is more determining for the successful survival of the implant than the presence of cells and pre-cultured extracellular matrix. This observation is of great translational importance and highlights the aptness of advanced 3D (bio)fabrication technologies for functional tissue restoration in the harsh articular joint mechanical environment.</p

Convergence of melt electrowriting and extrusion-based bioprinting for vascular patterning of a myocardial construct

To progress cardiac tissue engineering strategies closer to the clinic, thicker constructs are required to meet the functional need following a cardiac event. Consequently, pre-vascularization of these constructs needs to be investigated to ensure survival and optimal performance of implantable engineered heart tissue. The aim of this research is to investigate the potential of combining extrusion-based bioprinting (EBB) and melt electrowriting for the fabrication of a myocardial construct with a precisely patterned pre-vascular pathway. Gelatin methacryloyl (GelMA) was investigated as a base hydrogel for the respective myocardial and vascular bioinks with collagen, Matrigel and fibrinogen as interpenetrating polymers to support myocardial functionality. Subsequently, extrusion-based printability and viability were investigated to determine the optimal processing parameters for printing into melt electrowritten meshes. Finally, an anatomically inspired vascular pathway was implemented in a dual EBB set-up into melt electrowritten meshes, creating a patterned pre-vascularized myocardial construct. It was determined that a blend of 5% GelMA and 0.8 mg·ml -1collagen with a low crosslinked density was optimal for myocardial cellular arrangement and alignment within the constructs. For the vascular fraction, the optimized formulation consisted of 5% GelMA, 0.8 mg·ml -1collagen and 1 mg·ml -1fibrinogen with a higher crosslinked density, which led to enhanced vascular cell connectivity. Printability assessment confirmed that the optimized bioinks could effectively fill the microfiber mesh while supporting cell viability (∼70%). Finally, the two bioinks were applied using a dual EBB system for the fabrication of a pre-vascular pathway with the shape of a left anterior descending artery within a myocardial construct, whereby the distinct cell populations could be visualized in their respective patterns up to D14. This research investigated the first step towards developing a thick engineered cardiac tissue construct in which a pre-vascularization pathway is fabricated within a myocardial construct. </p

Convergence of melt electrowriting and extrusion-based bioprinting for vascular patterning of a myocardial construct

To progress cardiac tissue engineering strategies closer to the clinic, thicker constructs are required to meet the functional need following a cardiac event. Consequently, pre-vascularization of these constructs needs to be investigated to ensure survival and optimal performance of implantable engineered heart tissue. The aim of this research is to investigate the potential of combining extrusion-based bioprinting (EBB) and melt electrowriting for the fabrication of a myocardial construct with a precisely patterned pre-vascular pathway. Gelatin methacryloyl (GelMA) was investigated as a base hydrogel for the respective myocardial and vascular bioinks with collagen, Matrigel and fibrinogen as interpenetrating polymers to support myocardial functionality. Subsequently, extrusion-based printability and viability were investigated to determine the optimal processing parameters for printing into melt electrowritten meshes. Finally, an anatomically inspired vascular pathway was implemented in a dual EBB set-up into melt electrowritten meshes, creating a patterned pre-vascularized myocardial construct. It was determined that a blend of 5% GelMA and 0.8 mg·ml -1collagen with a low crosslinked density was optimal for myocardial cellular arrangement and alignment within the constructs. For the vascular fraction, the optimized formulation consisted of 5% GelMA, 0.8 mg·ml -1collagen and 1 mg·ml -1fibrinogen with a higher crosslinked density, which led to enhanced vascular cell connectivity. Printability assessment confirmed that the optimized bioinks could effectively fill the microfiber mesh while supporting cell viability (∼70%). Finally, the two bioinks were applied using a dual EBB system for the fabrication of a pre-vascular pathway with the shape of a left anterior descending artery within a myocardial construct, whereby the distinct cell populations could be visualized in their respective patterns up to D14. This research investigated the first step towards developing a thick engineered cardiac tissue construct in which a pre-vascularization pathway is fabricated within a myocardial construct

Simultaneous micropatterning of fibrous meshes and bioinks for the fabrication of living tissue constructs

\u3cp\u3eFabrication of biomimetic tissues holds much promise for the regeneration of cells or organs that are lost or damaged due to injury or disease. To enable the generation of complex, multicellular tissues on demand, the ability to design and incorporate different materials and cell types needs to be improved. Two techniques are combined: extrusion-based bioprinting, which enables printing of cell-encapsulated hydrogels; and melt electrowriting (MEW), which enables fabrication of aligned (sub)-micrometer fibers into a single-step biofabrication process. Composite structures generated by infusion of MEW fiber structures with hydrogels have resulted in mechanically and biologically competent constructs; however, their preparation involves a two-step fabrication procedure that limits freedom of design of microfiber architectures and the use of multiple materials and cell types. How convergence of MEW and extrusion-based bioprinting allows fabrication of mechanically stable constructs with the spatial distributions of different cell types without compromising cell viability and chondrogenic differentiation of mesenchymal stromal cells is demonstrated for the first time. Moreover, this converged printing approach improves freedom of design of the MEW fibers, enabling 3D fiber deposition. This is an important step toward biofabrication of voluminous and complex hierarchical structures that can better resemble the characteristics of functional biological tissues.\u3c/p\u3

The burden of disease of fatal and non-fatal burn injuries for the full spectrum of care in the Netherlands

Abstract Background A comprehensive overview of the burden of disease of burns for the full spectrum of care is not available. Therefore, we estimated the burden of disease of burns for the full spectrum in the Netherlands in 2018, and explored whether the burden of disease changed over the past 5 years (2014-2018). Methods Data were collected at four levels: general practice, emergency department, hospital, and mortality data. For each level, years lived with disability (YLD), years of life lost (YLL), and disability-adjusted life-years (DALY) were estimated using a tailored methodology. Results Burns resulted in a total of 9278 DALYs in the Netherlands in 2018, comprising of 7385 YLDs (80%) and 1892 YLLs (20%). Burn patients who visited the general practice contributed most DALYs (64%), followed by deceased burn patients (20%), burn patients admitted to hospital (14%) and those treated at the emergency department (2%). The burden of disease was comparable in both sexes (4734 DALYs (51%) for females; 4544 DALYs (49%) for males), though the distribution of DALYs by level of care varied; females contributed more DALYs at the general practice level, and males at all other levels of care. Among children boys 0-4 years had the highest burden of disease (784 DALYs (9%)), and among adults, females 18-34 years old (1319 DALYs (14.2%)) had the highest burden of disease. Between 2014 and 2018 there was a marginal increase of 0.8% in the number of DALYs. Conclusions Burns cause a substantial burden of disease, with burns requiring care at the general practice level contributing most DALYs. Information on burden of burns by the full level of care as well as by subgroup is important for the development of tailored burn prevention strategies, and the updated figures are recommended to be used for priority setting and resource allocation

Additional file 1: of Predictors of health-related quality of life after burn injuries: a systematic review

Search strategy. (DOCX 24 kb

Additional file 2: of Predictors of health-related quality of life after burn injuries: a systematic review

Summary of 19 multivariable predictive studies of HRQL in adult burn patients according to time assessment points. (DOCX 43 kb

Rapid and cytocompatible cell-laden silk hydrogel formation: Via riboflavin-mediated crosslinking

Bioactive hydrogels based on naturally-derived polymers are of great interest for regenerative medicine applications. Among naturally-derived polymers, silk fibroin has been extensively explored as a biomaterial for tissue engineering due to its unique mechanical properties. Here, we demonstrate the rapid gelation of cell-laden silk fibroin hydrogels by visible light-induced crosslinking using riboflavin as a photo-initiator, in presence of an electron acceptor. The gelation kinetics were monitored by in situ photo-rheometry. Gelation was achieved in minutes and could be tuned owing to its direct proportionality to the electron acceptor concentration. The concentration of the electron acceptor did not affect the elastic modulus of the hydrogels, which could be altered by varying the polymer content. Further, the biocompatible riboflavin photo-initiator combined with sodium persulfate allowed for the encapsulation of cells within silk fibroin hydrogels. To confirm the cytocompatibility of the silk fibroin formulations, three cell types (articular cartilage-derived progenitor cells, mesenchymal stem cells and dental-pulp-derived stem cells) were encapsulated within the hydrogels, which associated with a viability >80% for all cell types. These results demonstrated that fast gelation of silk fibroin can be achieved by combining it with riboflavin and electron acceptors, which results in a hydrogel that can be used in tissue engineering and cell delivery applications. This journal i

NEXT GENERATION BIOENGINEERED HUMAN MYOCARDIUM

Cardiac patches consisting of induced pluripotent stem cell‐derived cardiomyocytes (iPSC‐CMs) show beneficial effects when placed on the infarcted heart and the first human clinical trials have been approved. However, current patches do not replicate myocardial tissue, lacking 3D organization, mechanical properties, cellular maturity, and relevant thickness, and thereby fail to provide real contractile support to the failing heart. Previously, we have shown that melt electrowritten (MEW) hexagonal fiber scaffolds can be used to generate contractile cardiac patches that mimic native mechanical properties, thereby inducing iPSC‐CM maturation and tissue organization.[1] Although a huge step forward, these constructs do not yet fully replicate myocardial cellular and ECM composition and organization, and myocardial 3D fiber alignment. To tackle these hurdles, we have investigated the incorporation of additional cardiac cell types like iPSC‐derived cardiac fibroblasts (cFBs) and endothelial cells (ECs), the use of various myocardial and EC‐optimized bioinks for extrusion‐based bioprinting to allow for strategic cell‐type arrangement, and introducing 3D myocardial fiber‐angle orientation by stacking hexagonal MEW scaffolds. We found that the addition of cFBs, the optimization of hydrogel/ECM composition and stiffness (Collagen‐GelMA), and increasing thickness (1cm) and fiber organization by strategically stacking hexagonal meshes, led to the formation of a thick synchronously contracting myocardial tissue‐like construct. Our constructs showed a multi‐layered 3D fiber organization, with cells aligning with the hexagonal microarchitectures and an increase in maturation. Taken together, we have developed a next‐generation bioengineered myocardium with a more native‐like muscle structure and the potential to provide real functional support to the injured heart