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A bioengineered skeletal muscle construct that mimics structural and functional characteristics of native skeletal muscle is a promising therapeutic option to treat extensive muscle defect injuries. We previously showed that bioprinted human skeletal muscle constructs were able to form multi-layered bundles with aligned myofibers. In this study, we investigate the effects of neural cell integration into the bioprinted skeletal muscle construct to accelerate functional muscle regeneration in vivo. Neural input into this bioprinted skeletal muscle construct shows the improvement of myofiber formation, long-term survival, and neuromuscular junction formation in vitro. More importantly, the bioprinted constructs with neural cell integration facilitate rapid innervation and mature into organized muscle tissue that restores normal muscle weight and function in a rodent model of muscle defect injury. These results suggest that the 3D bioprinted human neural-skeletal muscle constructs can be rapidly integrated with the host neural network, resulting in accelerated muscle function restoration., 3D bioprinting of skeletal muscle using primary human muscle progenitor cells results in correct muscle architecture, but functional restoration in rodent models is limited. Here the authors include human neural stem cells into bioprinted skeletal muscle and observe improved architecture and function in vivo.

A bioengineered skeletal muscle tissue as an alternative for autologous tissue flaps, which mimics the structural and functional characteristics of the native tissue, is needed for reconstructive surgery. Rapid progress in the cell-based tissue engineering principle has enabled in vitro creation of cellularized muscle-like constructs; however, the current fabrication methods are still limited to build a three-dimensional (3D) muscle construct with a highly viable, organized cellular structure with the potential for a future human trial. Here, we applied 3D bioprinting strategy to fabricate an implantable, bioengineered skeletal muscle tissue composed of human primary muscle progenitor cells (hMPCs). The bioprinted skeletal muscle tissue showed a highly organized multi-layered muscle bundle made by viable, densely packed, and aligned myofiber-like structures. Our in vivo study presented that the bioprinted muscle constructs reached 82% of functional recovery in a rodent model of tibialis anterior (TA) muscle defect at 8 weeks of post-implantation. In addition, histological and immunohistological examinations indicated that the bioprinted muscle constructs were well integrated with host vascular and neural networks. We demonstrated the potential of the use of the 3D bioprinted skeletal muscle with a spatially organized structure that can reconstruct the extensive muscle defects. Wake Forest Clinical and Translational Science Institute [UL1 TR001420]; Army; Navy; NIH; Air Force; VA; Health Affairs [W81XWH-14-2-0004]; U.S. Army Medical Research Acquisition Activity, Fort Detrick MD [21702-5014]; Basic Science Research Program through the National Research Foundation of Korea (NRF) - Ministry of Education, Science, and Technology [2012R1A6A3A03040684] We thank H. S. Kim, J. S. Lee, and T. Bledsoe for a surgical procedure, Regenerative Medicine Clinical Center (RMCC) for hMPCs isolation, M. Devarasetty for imaging, and Y. M. Ju for technical assistance. The authors thank K. Klein at the Wake Forest Clinical and Translational Science Institute (UL1 TR001420) for editorial assistance. This work was supported by the Army, Navy, NIH, Air Force, VA and Health Affairs to support the AFIRM II effort under Award No. W81XWH-14-2-0004. The U.S. Army Medical Research Acquisition Activity, 820 Chandler Street, Fort Detrick MD 21702-5014 is the awarding and administering acquisition office. Opinions, interpretations, conclusions, and recommendations are those of the author and are not necessarily endorsed by the Department of Defense. J.H.K. was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science, and Technology (2012R1A6A3A03040684).

Many finite element (FE) models have been designed based on geometric information from computed tomography (CT) data, and validated via comparison with experimental results for human cadaver ossicular bones. Here, we describe a novel method for developing and analyzing the biomimetic ceramic ossicles (BCO) in combination with 3D printing technology, and we establish an FE model of the BCO for analyzing vibration performance. Novel biomimetic ceramic ossicles (BCO) made of hydroxyapatite (HA) were fabricated using 3D printing technology, and their vibration properties were measured. We created a 3D model of the BCO using computer-aided design, which corresponds to the ossicular structure and geometry, and created an FE model of the human ossicles via a comparison of experimental and simulated vibrations to investigate the characteristics of the ossicular chain. The FE model was established based on the displacements of the malleus, incus, and stapes, which was analyzed using an externally applied vibrational force.

INTRODUCTION AND OBJECTIVE:Organ-on-a-chip is a microengineered biomimetic system containing microfluidic channels and tissue-specific cell types, which replicate functional units of living organs ...

Skin injury to the face remains one of the greatest challenges in wound care due to the varied contours and complex movement of the face. Current treatment strategies for extensive facial burns are limited to the use of autografts, allografts, and skin substitutes, and these often result in scarring, infection, and graft failure. Development of an effective treatment modality will greatly improve the quality of life and social integration of the affected individuals. In this proof of concept study, we developed a novel strategy, called "BioMask", which is a customized bioengineered skin substitute combined with a wound dressing layer that snugly fits onto the facial wounds. To achieve this goal, three-dimensional (3D) bioprinting principle was used to fabricate the BioMask that could be customized by patients' clinical images such as computed tomography (CT) data. Based on a face CT image, a wound dressing material and cell-laden hydrogels were precisely dispensed and placed in a layer-by-layer fashion by the control of air pressure and 3-axis stage. The resulted miniature BioMask consisted of three layers; a porous polyurethane (PU) layer, a keratinocyte-laden hydrogel layer, and a fibroblast-laden hydrogel layer. To validate this novel concept, the bioprinted BioMask was applied to a skin wound on a pre-fabricated face-shaped structure in mice. Through this in vivo study using the 3D BioMask, skin contraction and histological examination showed the regeneration of skin tissue, consisting of epidermis and dermis layers, on the complex facial wounds. Consequently, effective and rapid restoration of aesthetic and functional facial skin would be a significant improvement to the current issues a facial wound patient experience.

Many drugs have progressed through preclinical and clinical trials and have been available - for years in some cases -before being recalled by the FDA for unanticipated toxicity in humans. One reason for such poor translation from drug candidate to successful use is a lack of model systems that accurately recapitulate normal tissue function of human organs and their response to drug compounds. Moreover, tissues in the body do not exist in isolation, but reside in a highly integrated and dynamically interactive environment, in which actions in one tissue can affect other downstream tissues. Few engineered model systems, including the growing variety of organoid and organ-on-a-chip platforms, have so far reflected the interactive nature of the human body. To address this challenge, we have developed an assortment of bioengineered tissue organoids and tissue constructs that are integrated in a closed circulatory perfusion system, facilitating inter-organ responses. We describe a three-tissue organ-on-a-chip system, comprised of liver, heart, and lung, and highlight examples of inter-organ responses to drug administration. We observe drug responses that depend on inter-tissue interaction, illustrating the value of multiple tissue integration for in vitro study of both the efficacy of and side effects associated with candidate drugs. Defense Threat Reduction Agency (DTRA) under Space and Naval Warfare Systems Center Pacific (SSC PACIFIC) [N6601-13-C-2027]; Comprehensive Cancer Center of Wake Forest University NCI CCSG [P30CA012197] The authors gratefully thank Dr. Pedro Baptista for aid in the drug metabolism studies, Steven Forsythe and Meiei Wan for technical aid in maintaining liver and cardiac organoid viability, and Dipasri Konar and Katherine Crowell for technical aid in the lung-on-a-chip operation. The authors gratefully acknowledge funding by the Defense Threat Reduction Agency (DTRA) under Space and Naval Warfare Systems Center Pacific (SSC PACIFIC) Contract No. N6601-13-C-2027. The publication of this material does not constitute approval by the government of the findings or conclusions herein. Proteomics and Metabolomics Core Lab services are supported by the Comprehensive Cancer Center of Wake Forest University NCI CCSG P30CA012197 grant.

Bioprinting has emerged as a versatile biofabrication approach for creating tissue engineered organ constructs. These constructs have potential use as organ replacements for implantation in patients, and also, when created on a smaller size scale as model "organoids" that can be used in in vitro systems for drug and toxicology screening. Despite development of a wide variety of bioprinting devices, application of bioprinting technology can be limited by the availability of materials that both expedite bioprinting procedures and support cell viability and function by providing tissue-specific cues. Here we describe a versatile hyaluronic acid (HA) and gelatin-based hydrogel system comprised of a multi-crosslinker, 2-stage crosslinking protocol, which can provide tissue specific biochemical signals and mimic the mechanical properties of in vivo tissues. Biochemical factors are provided by incorporating tissue-derived extracellular matrix materials, which include potent growth factors. Tissue mechanical properties are controlled combinations of PEG-based crosslinkers with varying molecular weights, geometries (linear or multi-arm), and functional groups to yield extrudable bioinks and final construct shear stiffness values over a wide range (100 Pa to 20 kPa). Using these parameters, hydrogel bioinks were used to bioprint primary liver spheroids in a liver-specific bioink to create in vitro liver constructs with high cell viability and measurable functional albumin and urea output. This methodology provides a general framework that can be adapted for future customization of hydrogels for biofabrication of a wide range of tissue construct types.

Three-dimensional (3D) bioprinting technology has been utilized as a method to engineer complex tissues and organs. This rapidly growing technology allows for precise placement of multiple types of cells, biomaterials, and biomolecules in spatially predefined locations within 3D structures. Many researchers are focusing on the further development of bioprinting technology and its applications. In this chapter, we introduce the general principles and limitations of widely used bioprinting systems and applications for tissue and organ regeneration. In addition, the current challenges facing the clinical applications of bioprinting technology are addressed.

The online version of the original article can be found at http://dx.doi.org/10.1007/s12541-016-0198-2

Three-dimensional integrated organ printing (IOP) technology seeks to fabricate tissue constructs that can mimic the structural and functional properties of native tissues. This technology is particularly useful for complex tissues such as those in the musculoskeletal system, which possess regional differences in cell types and mechanical properties. Here, we present the use of our IOP system for the processing and deposition of four different components for the fabrication of a single integrated muscle-tendon unit (MTU) construct. Thermoplastic polyurethane (PU) was co-printed with C2C12 cell-laden hydrogel-based bioink for elasticity and muscle development on one side, while poly(ϵ-caprolactone) (PCL) was co-printed with NIH/3T3 cell-laden hydrogel-based bioink for stiffness and tendon development on the other. The final construct was elastic on the PU-C2C12 muscle side (E = 0.39 ± 0.05 MPa), stiff on the PCL-NIH/3T3 tendon side (E = 46.67 ± 2.67 MPa) and intermediate in the interface region (E = 1.03 ± 0.14 MPa). These constructs exhibited >80% cell viability at 1 and 7 d after printing, as well as initial tissue development and differentiation. This study demonstrates the versatility of the IOP system to create integrated tissue constructs with region-specific biological and mechanical characteristics for MTU engineering.