Author Correction: Rapid fabrication of reinforced and cell-laden vascular grafts structurally inspired by human coronary arteries.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Rapid fabrication of reinforced and cell-laden vascular grafts structurally inspired by human coronary arteries.

Design strategies for small diameter vascular grafts are converging toward native-inspired tissue engineered grafts. A new automated technology is presented that combines a dip-spinning methodology for depositioning concentric cell-laden hydrogel layers, with an adapted solution blow spinning (SBS) device for intercalated placement of aligned reinforcement nanofibres. This additive manufacture approach allows the assembly of bio-inspired structural configurations of concentric cell patterns with fibres at specific angles and wavy arrangements. The middle and outer layers were tuned to structurally mimic the media and adventitia layers of native arteries, enabling the fabrication of small bore grafts that exhibit the J-shape mechanical response and compliance of human coronary arteries. This scalable automated system can fabricate cellularized multilayer grafts within 30 min. Grafts were evaluated by hemocompatibility studies and a preliminary in vivo carotid rabbit model. The dip-spinning-SBS technology generates constructs with native mechanical properties and cell-derived biological activities, critical for clinical bypass applications.

Cold-adaptation of a methacrylamide gelatin towards the expansion of the biomaterial toolbox for specialized functionalities in tissue engineering.

Tissue regeneration is witnessing a significant surge in advanced medicine. It requires the interaction of scaffolds with different cell types for efficient tissue formation post-implantation. The presence of tissue subtypes in more complex organs demands the co-existence of different biomaterials showing different hydrolysis rate for specialized cell-dependent remodeling. To expand the available toolbox of biomaterials with sufficient mechanical strength and variable rate of enzymatic degradation, a cold-adapted methacrylamide gelatin was developed from salmon skin. Compared with mammalian methacrylamide gelatin (GelMA), hydrogels derived from salmon GelMA displayed similar mechanical properties than the former. Nevertheless, salmon gelatin and salmon GelMA-derived hydrogels presented characteristics common of cold-adaptation, such as reduced activation energy for collagenase, increased enzymatic hydrolysis turnover of hydrogels, increased interconnected polypeptides molecular mobility and lower physical gelation capability. These properties resulted in increased cell-remodeling rate in vitro and in vivo, proving the potential and biological tolerance of this mechanically adequate cold-adapted biomaterial as alternative scaffold subtypes with improved cell invasion and tissue fusion capacity.

Layer-by-layer approach for a uniformed fabrication of a cell patterned vessel-like construct.

Successful tissue engineered small diameter blood vessels (SDBV) require manufacturing systems capable of precisely controlling different key elements, such as material composition, geometry and spatial location of specialized biomaterials and cells types. We report in this work an automated methodology that enables the manufacture of multilayer cylindrical constructs for SDBV fabrication that uses a layer-by-layer deposition approach while controlling variables such as dipping and spinning speed of a rod and biomaterial viscosity. Different biomaterials including methacrylated gelatin, alginate and chitosan were tested using this procedure to build different parts of the constructs. The system was capable of controlling dimensions of lumen from 0.5 mm up to 6 mm diameter and individual layers from 1 µm up to 400 µm thick. A cellular component was successfully added to the biomaterial in the absence of significant cytotoxic effect which was assessed by viability and proliferation assays. Additionally, cells showed a homogenous distribution with well-defined concentric patterns across the multilayer vessel grafts. The challenging generation of inner endothelial cells of approximately 20-30 µm of thickness was achieved. Preliminary experimental evidences of microstructural alignment of the biomaterial were obtained when the dipping approach was combined with the rod rotation. The study demonstrated the wide versatility and scalability of the automated system to easily and rapidly fabricate complex cellularized multilayer vascular grafts with structural configuration that resembles natural blood vessels.

Comparative metabolic analysis of CHO cell clones obtained through cell engineering, for IgG productivity, growth and cell longevity.

Cell engineering has been used to improve animal cells' central carbon metabolism. Due to the central carbon metabolism's inefficiency and limiting input of carbons into the TCA cycle, key reactions belonging to these pathways have been targeted to improve cultures' performance. Previous works have shown the positive effects of overexpressing PYC2, MDH II and fructose transporter. Since each of these modifications was performed in different cell lines and culture conditions, no comparisons between these modifications can be made. In this work we aim at contrasting the effect of each of the modifications by comparing pools of transfected IgG producing CHO cells cultivated in batch cultures. Results of the culture performance of engineered clones indicate that even though all studied clones had a more efficient metabolism, not all of them showed the expected improvement on cell proliferation and/or specific productivity. CHO cells overexpressing PYC2 were able to improve their exponential growth rate but IgG synthesis was decreased, MDH II overexpression lead to a reduction in cell growth and protein production, and cells transfected with the fructose transporter gene were able to increase cell density and reach the same volumetric protein production as parental CHO cells in glucose. We propose that a redox unbalance caused by the new metabolic flux distribution could affect IgG assembly and protein secretion. In addition to reaction dynamics, thermodynamic aspects of metabolism are also discussed to further understand the effect of these modifications over central carbon metabolism.