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Skeletal muscle is capable of regeneration following minor damage, more significant volumetric muscle loss (VML) however results in permanent functional impairment. Current multimodal treatment methodologies yield variable functional recovery, with reconstructive surgical approaches restricted by limited donor tissue and significant donor morbidity. Tissue-engineered skeletal muscle constructs promise the potential to revolutionise the treatment of VML through the regeneration of functional skeletal muscle. Herein, we review the current status of tissue engineering approaches to VML; firstly the design of biocompatible tissue scaffolds, including recent developments with electroconductive materials. Secondly, we review the progenitor cell populations used to seed scaffolds and their relative merits. Thirdly we review in vitro methods of scaffold functional maturation including the use of three-dimensional bioprinting and bioreactors. Finally, we discuss the technical, regulatory and ethical barriers to clinical translation of this technology. Despite significant advances in areas, such as electroactive scaffolds and three-dimensional bioprinting, along with several promising in vivo studies, there remain multiple technical hurdles before translation into clinically impactful therapies can be achieved. Novel strategies for graft vascularisation, and in vitro functional maturation will be of particular importance in order to develop tissue-engineered constructs capable of significant clinical impact.

Chronic wound management is an enormous economic strain and quality-of-life issue for patients. Current treatments are ineffective or expensive and invasive. Materials (native and artificial) can act as the basis to enhance wound repair but often fall short of complete healing. The therapeutic index of materials have often been enhanced by combining them with drug or biologic elution technologies. Combination of materials with living drugs (cells) presents a new paradigm for enhancing therapy. Cell material interaction and therapeutic output will depend on variables ascribed to the living drug as well as variables ascribed to the underlying matrix. In this article, we review medical matrices currently approved by the US Food and Drug Administration (FDA) that would likely be the first generation of materials to be used in this manner. Currently there are hundreds of different materials on the market. Identification of the right combinations would benefit from a classification scheme to group materials with similar composition or derivation. We provide a classification scheme and FDA documentation references that should provide researchers and clinicians a starting point for testing these materials in the laboratory and rapidly transitioning cell therapies to the bedside., (Copyright © 2019 Mayo Foundation for Medical Education and Research. Published by Elsevier Inc. All rights reserved.)

Several procedures have been proposed to achieve maxillary ridge augmentation. These require bone replacement materials to be manually cut, shaped, and formed at the time of implantation, resulting in an expensive and time-consuming process. In the present study, we describe a technique for the design and fabrication of custom-made scaffolds for maxillary ridge augmentation, using three-dimensional computerized tomography (3D CT) and computer-aided design/computer-aided manufacturing (CAD/CAM). CT images of the atrophic maxillary ridge of 10 patients were acquired and modified into 3D reconstruction models. These models were transferred as stereolithographic files to a CAD program, where a virtual 3D reconstruction of the alveolar ridge was generated, producing anatomically shaped, custom-made scaffolds. CAM software generated a set of tool-paths for manufacture by a computer-numerical-control milling machine into the exact shape of the reconstruction, starting from porous hydroxyapatite blocks. The custom-made scaffolds were of satisfactory size, shape, and appearance; they matched the defect area, suited the surgeon's requirements, and were easily implanted during surgery. This helped reduce the time for surgery and contributed to the good healing of the defects.

Delineation of the mechanisms that establish and maintain the polarity of epithelial tissues is essential to understanding morphogenesis, tissue specificity and cancer. Three-dimensional culture assays provide a useful platform for dissecting these processes but, as discussed in a recent study in BMC Biology on the culture of mammary gland epithelial cells, multiple parameters that influence the model must be taken into account.