4D Bioprinting via Molecular Network Contraction for Membranous Tissue Fabrication

Osteoblast-Mesenchymal Stem Cell Coculture Drives In Vitro Osteogenesis in 3D Bioprinted Periosteum

The periosteum serves as a local source of osteoprogenitor cells and vasculature, therefore influencing the key processes of osteogenesis and neovascularization during bone healing. However, it is often not considered in traditional bone tissue engineering strategies. The periosteum consists of two stratified cell layers, including an inner cambium layer, which serves as a local source of osteoblasts (OBs) and osteoprogenitor cells, and an outer fibrous layer, which hosts vasculature, collagen fibers, and support cells. While several studies have investigated different methodologies to produce tissue-engineered periosteum (TEP) substitutes, few have evaluated the roles of specific cell types within the inner cambium layer and their patterning in 3D environments on underlying bone tissue development. Therefore, we sought to investigate whether mesenchymal stem cells (MSCs) alone, OBs alone, or a 1:1 mixture of the two would result in increased osteogenic differentiation of bone layer MSCs in a 3D bioprinted periosteum-bone coculture model in vitro. We first evaluated these effects in a 2D transwell model, demonstrating that OB-containing cultures, either alone or in a mixed population with MSCs, upregulated alkaline phosphatase activity and runt-related transcription factor 2 (RUNX2) expression. In the 3D bioprinted model, the mixed population showed higher levels of RUNX2 expression and calcium deposition, indicating increased osteogenic differentiation within the bone layer. Results obtained from this study provide evidence that a mixed population of MSCs and OBs within the inner cambium layer of TEP can increase bone regeneration.

A self-hygroscopic, rapidly self-gelling polysaccharide-based sponge with robust wet adhesion for non-compressible hemorrhage control and infected wounds healing

Uncontrollable non-compressible hemorrhage and traumatic infection have been major causes of mortality and disability in both civilian and military populations. A dressing designed for point-of-care control of non-compressible hemorrhage and prevention of traumatic infections represents an urgent medical need. Here, a novel self-gelling sponge OHN@ε-pL is developed, integrating N-succinimidyl ester oxidized hyaluronic acid (OHN) and ε-poly-L-lysine (ε-pL). Upon application to the wound site, the sponge can rapidly absorb interfacial fluids and undergo a phase transition from sponge to gel. The transformed gel facilitates robust tissue adhesion and achieves synergistic hemostasis by enriching coagulation factors within the sponge phase and providing a barrier effect in the gel phase. The in vitro and in vivo studies revealed that the optimized OHN@ε-pL3 sponge possesses self-gelling capability, tissue adhesion, enhanced coagulation ability, and exhibits excellent biocompatibility and antibacterial efficacy. In hemostasis, OHN@ε-pL3 sponges exhibited reduced blood loss and decreased hemostatic time compared to commercial hemostatic agents, as demonstrated in rat liver, femoral vein, and tail truncation bleeding models. Furthermore, the OHN@ε-pL3 sponge exhibited superior performance in accelerating wound closure and healing of S. aureus-infected wounds. Collectively, OHN@ε-pL sponges represent a promising candidate for medical dressings, specifically for managing uncontrollable non-compressible hemorrhage and traumatic infections.

From lab to life: advances inin-situbioprinting and bioink technology

Bioprinting has the potential to revolutionize tissue engineering and regenerative medicine, offering innovative solutions for complex medical challenges and addressing unmet clinical needs. However, traditionalin vitrobioprinting techniques face significant limitations, including difficulties in fabricating and implanting scaffolds with irregular shapes, as well as limited accessibility for rapid clinical application. To overcome these challenges,in-situbioprinting has emerged as a groundbreaking approach that enables the direct deposition of cells, biomaterials, and bioactive factors onto damaged organs or tissues, eliminating the need for pre-fabricated 3D constructs. This method promises a personalized, patient-specific approach to treatment, aligning well with the principles of precision medicine. The success ofin-situbioprinting largely depends on the advancement of bioinks, which are essential for maintaining cell viability and supporting tissue development. Recent innovations in hand-held bioprinting devices and robotic arms have further enhanced the flexibility ofin-situbioprinting, making it applicable to various tissue types, such as skin, hair, muscle, bone, cartilage, and composite tissues. This review examinesin-situbioprinting techniques, the development of smart, multifunctional bioinks, and their essential properties for promoting cell viability and tissue growth. It highlights the versatility and recent advancements inin-situbioprinting methods and their applications in regenerating a wide range of tissues and organs. Furthermore, it addresses the key challenges that must be overcome for broader clinical adoption and propose strategies to advance these technologies toward mainstream medical practice.

Comparison of cation and anion-mediated resolution enhancement of bioprinted hydrogels for membranous tissue fabrication

Fabrication of engineered thin membranous tissues (TMTs) presents a significant challenge to researchers, as these structures are small in scale, but present complex anatomies containing multiple stratified cell layers. While numerous methodologies exist to fabricate such tissues, many are limited by poor mechanical properties, need for post-fabrication, or lack of cytocompatibility. Extrusion bioprinting can address these issues, but lacks the resolution necessary to generate biomimetic, microscale TMT structures. Therefore, our goal was to develop a strategy that enhances bioprinting resolution below its traditional limit of 150 μm and delivers a viable cell population. We have generated a system to effectively shrink printed gels via electrostatic interactions between anionic and cationic polymers. Base hydrogels are composed of gelatin methacrylate type A (cationic), or B (anionic) treated with anionic alginate, and cationic poly-L-lysine, respectively. Through a complex coacervation-like mechanism, the charges attract, causing compaction of the base GelMA network, leading to reduced sample dimensions. In this work, we evaluate the role of both base hydrogel and shrinking polymer charge on effective print resolution and cell viability. The alginate anion-mediated system demonstrated the ability to reach bioprinting resolutions of 70 μm, while maintaining a viable cell population. To our knowledge, this is the first study that has produced such significant enhancement in extrusion bioprinting capabilities, while also remaining cytocompatible.

Advancements in Polymer Biomaterials as Scaffolds for Corneal Endothelium Tissue Engineering

Corneal endothelial dysfunction is a leading cause of vision loss globally, frequently requiring corneal transplantation. However, the limited availability of donor tissues, particularly in developing countries, has spurred on the exploration of tissue engineering strategies, with a focus on polymer biomaterials as scaffolds for corneal endotlhelium regeneration. This review provides a comprehensive overview of the advancements in polymer biomaterials, focusing on their role in supporting the growth, differentiation, and functional maintenance of human corneal endothelial cells (CECs). Key properties of scaffold materials, including optical clarity, biocompatibility, biodegradability, mechanical stability, permeability, and surface wettability, are discussed in detail. The review also explores the latest innovations in micro- and nano-topological morphologies, fabrication techniques such as electrospinning and 3D/4D bioprinting, and the integration of drug delivery systems into scaffolds. Despite significant progress, challenges remain in translating these technologies to clinical applications. Future directions for research are highlighted, including the need for improved biomaterial combinations, a deeper understanding of CEC biology, and the development of scalable manufacturing processes. This review aims to serve as a resource for researchers and clinician-scientists seeking to advance the field of corneal endothelium tissue engineering.

MAGIC matrices: freeform bioprinting materials to support complex and reproducible organoid morphogenesis

Organoids are powerful models of tissue physiology, yet their applications remain limited due to their relatively simple morphology and high organoid-to-organoid structural variability. To address these limitations we developed a soft, composite yield-stress extracellular matrix that supports optimal organoid morphogenesis following freeform 3D bioprinting of cell slurries at tissue-like densities. The material is designed with two temperature regimes: at 4 °C it exhibits reversible yield-stress behavior to support long printing times without compromising cell viability. When transferred to cell culture at 37 °C, the material cross-links and exhibits similar viscoelasticity and plasticity to basement membrane extracts such as Matrigel. We first characterize the rheological properties of MAGIC matrices that optimize organoid morphogenesis, including low stiffness and high stress relaxation. Next, we combine this material with a custom piezoelectric printhead that allows more reproducible and robust self-organization from uniform and spatially organized tissue "seeds." We apply MAGIC matrix bioprinting for high-throughput generation of intestinal, mammary, vascular, salivary gland, and brain organoid arrays that are structurally similar to those grown in pure Matrigel, but exhibit dramatically improved homogeneity in organoid size, shape, maturation time, and efficiency of morphogenesis. The flexibility of this method and material enabled fabrication of fully 3D microphysiological systems, including perfusable organoid tubes that experience cyclic 3D strain in response to pressurization. Furthermore, the reproducibility of organoid structure increased the statistical power of a drug response assay by up to 8 orders-of-magnitude for a given number of comparisons. Combined, these advances lay the foundation for the efficient fabrication of complex tissue morphologies by canalizing their self-organization in both space and time.

Advances in 3D printing for the repair of tympanic membrane perforation: a comprehensive review

Tympanic membrane perforation (TMP) is one of the most common conditions in otolaryngology worldwide, and hearing damage caused by inadequate or prolonged healing can be distressing for patients. This article examines the rationale for utilizing three-dimensional (3D) printing to produce scaffolds for repairing TMP, compares the advantages and disadvantages of 3D printed and bioprinted grafts with traditional autologous materials and other tissue engineering materials in TMP repair, and highlights the practical and clinical significance of 3D printing in TMP repair while discussing the current progress and promising future of 3D printing and bioprinting. There is a limited number of reviews specifically dedicated to 3D printing for TMP repair. The majority of reviews offer a general overview of the applications of 3D printing in the broader realm of tissue regeneration, with some mention of TMP repair. Alternatively, they explore the biopolymers, cells, and drug molecules utilized for TMP repair. However, more in-depth analysis is needed on the strategies for selecting bio-inks that integrate biopolymers, cells, and drug molecules for tympanic membrane repair.

4D bioprinting of programmed dynamic tissues

Setting time as the fourth dimension, 4D printing allows us to construct dynamic structures that can change their shape, property, or functionality over time under stimuli, leading to a wave of innovations in various fields. Recently, 4D printing of smart biomaterials, biological components, and living cells into dynamic living 3D constructs with 4D effects has led to an exciting field of 4D bioprinting. 4D bioprinting has gained increasing attention and is being applied to create programmed and dynamic cell-laden constructs such as bone, cartilage, and vasculature. This review presents an overview on 4D bioprinting for engineering dynamic tissues and organs, followed by a discussion on the approaches, bioprinting technologies, smart biomaterials and smart design, bioink requirements, and applications. While much progress has been achieved, 4D bioprinting as a complex process is facing challenges that need to be addressed by transdisciplinary strategies to unleash the full potential of this advanced biofabrication technology. Finally, we present future perspectives on the rapidly evolving field of 4D bioprinting, in view of its potential, increasingly important roles in the development of advanced dynamic tissues for basic research, pharmaceutics, and regenerative medicine.

Engineering Innervated Musculoskeletal Tissues for Regenerative Orthopedics and Disease Modeling

Musculoskeletal (MSK) disorders significantly burden patients and society, resulting in high healthcare costs and productivity loss. These disorders are the leading cause of physical disability, and their prevalence is expected to increase as sedentary lifestyles become common and the global population of the elderly increases. Proper innervation is critical to maintaining MSK function, and nerve damage or dysfunction underlies various MSK disorders, underscoring the potential of restoring nerve function in MSK disorder treatment. However, most MSK tissue engineering strategies have overlooked the significance of innervation. This review first expounds upon innervation in the MSK system and its importance in maintaining MSK homeostasis and functions. This will be followed by strategies for engineering MSK tissues that induce post-implantation in situ innervation or are pre-innervated. Subsequently, research progress in modeling MSK disorders using innervated MSK organoids and organs-on-chips (OoCs) is analyzed. Finally, the future development of engineering innervated MSK tissues to treat MSK disorders and recapitulate disease mechanisms is discussed. This review provides valuable insights into the underlying principles, engineering methods, and applications of innervated MSK tissues, paving the way for the development of targeted, efficacious therapies for various MSK conditions.