Engineering of viable implants

Tissue engineering has promised to overcome the current limitations of conventional implants. By creating viable constructs based on an autologous cell sources, the implant should be non-immunogenic and should have the potential to remodel, to self-repair and even to grow specifically interesting in the field of pediatric applications. Furthermore, providing a viable epithelium or endothelium could decrease the risk of implant-related infections. Tissue engineering is based on four major aspects: (i) the selection of the optimal cell source, (ii) the selection and design of the biomaterial as scaffold for creating the 3D architecture and (iii) the physical and/or biochemical stimulation leading to a functional tissue development. Furthermore, (iv) the development of (prototypical) production processes for tissue-engineered constructs is attracting an increasing attention. Specifically, the last aspect seems to be important because not many tissue-engineered implants have found their way into clinical application. Important research work has been done in the last two decades demonstrating the proof of principle and the superiority of different tissue-engineered constructs in preclinical trials, but it has ignored the aspects of good manufacturing practice crucially for clinical translation. The production aspect in tissue engineering is rapidly developing supported by the current hype in biofabrication. In our previous highlight issue “Biomaterials & Artificial Tissue” in 2016 we have reported about the important progress in biomaterials development and processing [1, 2, 6, 8]. The current journal of Biomedical Engineering/ Biomedizinische Technik is highlighting innovations in tissue engineering and scaffold development from different perspectives. This gives the reader an excellent view in the four major fields of research at the border of life sciences, engineering and medicine. The manuscript by Malischewski et al. deals with the selection of the optimal cell source for mitral valve tissue engineering. The group compared the use of venous vs. arterial cells from umbilical cell source. The amount and organization of the extracellular matrix protein elastin produced during the in vitro cultivation by human umbilical vein cells is remarkable. Elastin plays an important role in the biomechanics of heart valve leaflets, which has been observed rarely in tissue-engineered heart valves in the past [4]. The scaffold plays an important role in the cell-to-cell interaction and in the 3D configuration of tissueengineered constructs. It serves as permanent or temporary support structure for an optimal integration of the viable tissue. Schilling et al. describe the technology to engineer biodegradable magnesium alloy scaffolds to stabilize biological myocardial grafts. The group demonstrates that the adaptation of the alloy composition, coating and structural geometry allows the manufacturing of clinically applicable magnesium scaffolds for myocardial tissue engineering [7]. Beside the biomechanical properties, the loading of scaffold with drugs towards a bioactive device is addressed by Yang et al. The paper deals with the evaluation of the therapeutic potential of bioactive scaffolds to support the bone-healing process. The group describes a nano-bioglass/phosphatidylserine/collagen scaffold loaded with steroidal saponins. The preliminary biological evaluation has demonstrated a positive effect on the secretion of nerve growth factor, which can stimulate the bone healing. The aspect of biomechanical stimulation by the development of a novel bioreactor system for cartilage tissue engineering is addressed by the group of Princz et al. The automation is an important aspect with regard to the translation of regenerative medicine into the clinical environment [5]. Using freeform-fabrication methods for the creation of individualized implants is a further important translational aspect. Liu et al. [3] have used this method for the automatized production of highresolution osteogenic scaffolds with using polycaprolactone as biomaterial. The publications cover the broad aspects of tissue engineering and scaffold development. I hope that they will support your research and stimulate further investigations.