From Medical Imaging to Bioprinted Tissues: The Importance of Workflow Optimisation for Improved Cell Function

Biomaterial-based 3D bioprinting strategy for orthopedic tissue engineering.

The burden of musculoskeletal diseases in the United States.

Over the past decade, three-dimensional (3D) bioprinting has made significant progress, transforming into a key innovation in tissue engineering. Despite the early strides, critical challenges remain in 3D bioprinting that must be addressed to accelerate clinical translation. In particular, there is still a long way to go before functionally-mature, clinically-relevant tissue equivalents are developed. Current limitations range from the sub-optimal bioink properties and degree of biomimicry of bioprintable architectures, to the lack of stem/progenitor cells for massive cell expansion, and fundamental knowledge regardingin vitroculturing conditions. In addition to these problems, the absence of guidelines and well-regulated international standards is creating uncertainty among the biofabrication community stakeholders regarding the reliable and scalable production processes. This review aims at exploring the latest developments in 3D bioprinting approaches, including various additive manufacturing techniques and their applications. A thorough discussion of common bioprinting techniques and recent progresses are compiled along with notable recent studies. Later we discuss the current challenges in clinical application of 3D bioprinting and the major bottlenecks in the commercialization of 3D bioprinted tissue equivalents, including the longevity of bioprinted organs, meeting biomechanical requirements, and the often underrated ethical and legal aspects. Amidst the progress of regulatory efforts for regenerative medicine, we also present an overview of the current regulatory concerns which should be taken into account to translate bioprinted tissues into clinical practice. At last, this review emphasizes future directions in 3D bioprinting that includes the transformative ideas such as bioprinting in microgravity and the integration of artificial intelligence. The study concludes with a discussion on the need for collaborative efforts in resolving the technical and regulatory constraints to improve the quality, reliability, and reproducibility of bioprinted tissue equivalents to ultimately accomplish their successful clinical implementation.

Three-dimensional (3D) bioprinting technologies have great attention in different researching areas such as tissue engineering, medicine, etc. due to its maximum mimetic property of natural biomaterials by providing cell combination, growth factors, and other biomaterials. Bioprinting of tissues, organs, or drug delivery systems emerged layer-by-layer deposition of bioinks. 3D bioprinting technique has some complexity such as choice of bioink combination, cell type, growth, and differentiation. In this study, a composite material in 3D bioprinting studies has been developed for biofabrication of the cell carrying scaffolds namely cryogenic scaffolds. Cryogenic scaffolds are highly elastic and have a continuous interconnected macroporous structure in 3D biomaterials that enable the cell attachment, viability, and proliferation. Freeze-drying cryogelation process for the formation of cryogel scaffolds has been achieved firstly among 3D bioprinting studies. Cryogenic gelatin–hyaluronic acid (Gel–HA)-based 3D-bioprinted scaffolds have been fabricated and characterized by scanning electron microscope (SEM), optical microscope images, tensile tests, determination of swelling degree, and porosity. Then, L929 cells from mouse C3H/An have been attached to cryogenic Gel–HA scaffolds. Cell attachment, viability, and proliferation on cryogenic scaffolds have been investigated for 7 days. The results showed that a combination of 3D bioprinting technologies and cryogenic process provided a new direction on biomedical scaffolds.

The field of tissue engineering has progressed tremendously over the past few decades in its ability to fabricate functional tissue substitutes for regenerative medicine and pharmaceutical research. Conventional scaffold-based approaches are limited in their capacity to produce constructs with the functionality and complexity of native tissue. Three-dimensional (3D) bioprinting offers exciting prospects for scaffolds fabrication, as it allows precise placement of cells, biochemical factors, and biomaterials in a layer-by-layer process. Compared with traditional scaffold fabrication approaches, 3D bioprinting is better to mimic the complex microstructures of biological tissues and accurately control the distribution of cells. Here, we describe recent technological advances in bio-fabrication focusing on 3D bioprinting processes for tissue engineering from data processing to bioprinting, mainly inkjet, laser, and extrusion-based technique. We then review the associated bioink formulation for 3D bioprinting of human tissues, including biomaterials, cells, and growth factors selection. The key bioink properties for successful bioprinting of human tissue were summarized. After bioprinting, the cells are generally devoid of any exposure to fluid mechanical cues, such as fluid shear stress, tension, and compression, which are crucial for tissue development and function in health and disease. The bioreactor can serve as a simulator to aid in the development of engineering human tissues from in vitro maturation of 3D cell-laden scaffolds. We then describe some of the most common bioreactors found in the engineering of several functional tissues, such as bone, cartilage, and cardiovascular applications. In the end, we conclude with a brief insight into present limitations and future developments on the application of 3D bioprinting and bioreactor systems for engineering human tissue.

The area of regenerative therapy will undergo a revolution thanks to 3D bioprinting, which holds enormous potential for the bioprinting of artificial tissue and organs. The present research explores the potential synergies between 3D bioprinting and current developments in tissue engineering and regenerative medicine. Before 3D bioprinting is extensively used in organotypic structures for regenerative medicine, a number of obstacles must be solved. This places a significant burden on society in terms of providing care for those who have deteriorating organs and debilitating diseases. Researchers and medical experts are developing medications and technology that can repair tissues and even generate fresh ones in order to solve this problem. Tissue engineering and regenerative medicine strive to create new tissues and organs while also curing damaged or sick ones by fusing technology and biological principles. substantial breakthroughs in these domains have a substantial influence on 3D bioprinting of tissues and organs. The area of regenerative medicine might undergo a radical transformation thanks to the use of 3D bioprinting, which makes it possible to build new tissues and organs. The relationship between recent developments in tissue engineering, 3D bioprinting, and regenerative medicine is investigated in this paper. Before 3D bioprinting can be widely used to produce organotypic structures for regenerative medicine, a number of problems must be overcome

Cardiovascular diseases (CVDs) are known as the major cause of death worldwide. In spite of tremendous advancements in medical therapy, the gold standard for CVD treatment is still transplantation. Tissue engineering, on the other hand, has emerged as a pioneering field of study with promising results in tissue regeneration using cells, biological cues, and scaffolds. Three-dimensional (3D) bioprinting is a rapidly growing technique in tissue engineering because of its ability to create complex scaffold structures, encapsulate cells, and perform these tasks with precision. More recently, 3D bioprinting has made its debut in cardiac tissue engineering, and scientists are investigating this technique for development of new strategies for cardiac tissue regeneration. In this review, the fundamentals of cardiac tissue biology, available 3D bioprinting techniques and bioinks, and cells implemented for cardiac regeneration are briefly summarized and presented. Afterwards, the pioneering and state-of-the-art works that have utilized 3D bioprinting for cardiac tissue engineering are thoroughly reviewed. Finally, regulatory pathways and their contemporary limitations and challenges for clinical translation are discussed.

With a limited supply of organ donors and available organs for transplantation, the aim of tissue engineering with three-dimensional (3D) bioprinting technology is to construct fully functional and viable tissue and organ replacements for various clinical applications. 3D bioprinting allows for the customization of complex tissue architecture with numerous combinations of materials and printing methods to build different tissue types, and eventually fully functional replacement organs. The main challenge of maintaining 3D printed tissue viability is the inclusion of complex vascular networks for nutrient transport and waste disposal. Rapid development and discoveries in recent years have taken huge strides toward perfecting the incorporation of vascular networks in 3D printed tissue and organs. In this review, we will discuss the latest advancements in fabricating vascularized tissue and organs including novel strategies and materials, and their applications. Our discussion will begin with the exploration of printing vasculature, progress through the current statuses of bioprinting tissue/organoids from bone to muscles to organs, and conclude with relevant applications for in vitro models and drug testing. We will also explore and discuss the current limitations of vascularized tissue engineering and some of the promising future directions this technology may bring.

Organ or cell transplantation is medically evaluated for end-stage failure saving or extending the lives of thousands of patients who are suffering from organ failure disorders. The unavailability of adequate organs for transplantation to meet the existing demand is a major challenge in the medical field. This led to day-day-increase in the number of patients on transplant waiting lists as well as in the number of patients dying while on the queue. Recently, technological advancements in the field of biogenerative engineering have the potential to regenerate tissues and, in some cases, create new tissues and organs. In this context, major advances and innovations are being made in the fields of tissue engineering and regenerative medicine which have a huge impact on the scientific community is three-dimensional bioprinting (3D bioprinting) of tissues and organs. Besides this, the decellularization of organs and using this as a scaffold for generating new organs through the recellularization process shows promising results. This review discussed about current approaches for tissue and organ engineering including methods of scaffold designing, recent advances in 3D bioprinting, organs regenerated successfully using 3D printing, and extended application of 3D bioprinting technique in the field of medicine. Besides this, information about commercially available 3D printers has also been included in this article.Lay SummaryToday’s need for organs for the transplantation process in order to save a patient’s life or to enhance the survival rate of diseased one is the prime concern among the scientific community. Recent, advances in the field of biogenerative engineering have the potential to regenerate tissues and create organs compatible with the patient’s body. In this context, major advances and innovations are being made in the fields of tissue engineering and regenerative medicine which have a huge impact on the scientific community is three-dimensional bioprinting (3D bioprinting) of tissues and organs. Besides this, the decellularization of organs and using this as a scaffold for generating new organs through the recellularization process shows promising results. This review dealt with the current approaches for tissue and organ engineering including methods of scaffold designing, recent advances in 3D bioprinting, organs regenerated successfully using 3D printing, and extended application of 3D bioprinting technique in the field of medicine. Furthermore, information about commercially available 3D printers has also been included in this article.

Organ reconstruction and manufacturing is a field that aims to create functional organs for transplantation or therapeutic purposes. The development of this field has been driven by rapid advances in various technologies, including three-dimensional (3D) bioprinting, organs-on-chips, organoids, stem cell reprogramming, genome editing and artificial intelligence (AI). Take, for example, the development of organoids and organs-on-chips, which has completely revolutionized the way scientists study organ development, disease progression and drug effects in vitro. 3D bioprinting, which can produce tissues and organs with customized shapes, sizes and functions, has also made it possible to create complex structures with high precision and accuracy, including livers, kidneys, hearts, ears and skin grafts. Bioprinted tissues and organs may soon be used for transplantation on demand in the clinic. Furthermore, manipulation of cell fates and genomes with the latest techniques in reprogramming, genome editing and AI-based computational modelling has allowed us to unlock the hidden potential within human cells and produce new human cell types with new capabilities. Genome editing of patient-derived cells to correct any underlying defects could also ensure that synthetic organs are created with improved functionality and compatibility with the recipient's body. Advancements like these have paved the way for new biomedical applications such as personalized medicine and regenerative therapies. In this special issue on Organ Reconstruction and Manufacturing, we have assembled a corpus of the latest studies that shed light on the cutting-edge progress and challenges in this field. Our special issue highlights the most significant new findings, technologies and therapies that are emerging in this burgeoning field, providing a platform for experts in the field to share their thoughts and predict future trends. The topics covered in this special issue include leading-edge technologies like 3D bioprinting, organs-on-chips and organoids, as well as genetically engineered cells and animals—all of which are critical pieces in the quest for regenerative medicine. If this dream is realized, scientists may well be able to use patient-derived cells to complete drug testing at warp speed, and make it possible to create synthetic organs for transplantation, potentially addressing the shortage of donor organs on a global scale. As we rapidly make technological progress towards this dream, a final piece in the puzzle is the development of ethical guidelines and manufacturing standards to ensure that the production and applications of synthetic organs remain safe, ethical and properly regulated. The creation of synthetic organs raises many ethical questions, including issues related to patient privacy, informed consent and accessibility to healthcare. Therefore it is crucial for us to establish ethical guidelines and manufacturing standards in a collaborative manner, based on multinational and global consensus, to regulate the proper development and use of synthetic organs. We believe our efforts in building such frameworks will help ensure that the benefits of technological breakthroughs in organ reconstruction and manufacturing are maximized, while minimizing potential risks and negative consequences for all of humanity. In conclusion, synthetic organ reconstruction and manufacturing is a rapidly evolving field that has the potential to revolutionize the healthcare industry. I believe recent advancements in biotechnology, computational methods, therapeutic applications, ethics and standards will pave the way for a quantum leap in innovation for the field in the near future.

Chapter 8 - Bioprinting of hydrogels for tissue engineering and drug screening applications

Although liver transplantation is the gold-standard therapy for end-stage liver disease, the shortage of suitable organs results in only 25% of waitlisted patients undergoing transplants. Three-dimensional (3D) bioprinting is an emerging technology and a potential solution for personalized medicine applications. This review highlights existing 3D bioprinting technologies of liver tissues, current anatomical and physiological limitations to 3D bioprinting of a whole liver, and recent progress bringing this innovation closer to clinical use. We reviewed updated literature across multiple facets in 3D bioprinting, comparing laser, inkjet, and extrusion-based printing modalities, scaffolded versus scaffold-free systems, development of an oxygenated bioreactor, and challenges in establishing long-term viability of hepatic parenchyma and incorporating structurally and functionally robust vasculature and biliary systems. Advancements in liver organoid models have also increased their complexity and utility for liver disease modeling, pharmacologic testing, and regenerative medicine. Recent developments in 3D bioprinting techniques have improved the speed, anatomical, and physiological accuracy, and viability of 3D-bioprinted liver tissues. Optimization focusing on 3D bioprinting of the vascular system and bile duct has improved both the structural and functional accuracy of these models, which will be critical in the successful expansion of 3D-bioprinted liver tissues toward transplantable organs. With further dedicated research, patients with end-stage liver disease may soon be recipients of customized 3D-bioprinted livers, reducing or eliminating the need for immunosuppressive regimens.

Bone defects are due to trauma, infections, tumors, or aging, including bone fractures, bone metastases, osteoporosis, or osteoarthritis. The global burden of these demands research into innovative strategies that overcome the limitations of conventional autografts. In this sense, the development of three-dimensional (3D) bioprinting has emerged as a promising approach in the field of tissue engineering and regenerative medicine (TERM) for the on-demand generation and transplantation of tissues and organs, including bone. It combines biological materials and living cells, which are precisely positioned layer by layer. Despite obtaining some promising results, 3D bioprinting of bone tissue still faces several challenges, such as generating an effective vascular network to increase tissue viability. In this review, we aim to collect the main knowledge on methods and techniques of 3D bioprinting. Then, we will review the main biomaterials, their composition, and the rationale for their application in 3D bioprinting for the TERM of bone.

Cardiovascular diseases remain one of the leading causes of death worldwide. Given the limited self-repair capacity of cardiac tissue, cardiac tissue engineering (CTE) aims to develop strategies and materials for repairing or replacing damaged cardiac tissue by combining biology, medicine, and engineering. Indeed, CTE has made significant strides since the discovery of induced pluripotent stem cells (iPSCs) in 2006, including creating cardiac patches, organoids, and chip models derived from iPSCs, thus offering new strategies for treating cardiac diseases. A systematic search for relevant literature published between 2003 and 2024 was conducted in the PubMed and Web of Science databases using "Cardiac Tissue Engineering", "3D Bioprinting", "Scaffold in Tissue Engineering", "Induced Pluripotent Stem Cells", and "iPSCs" as keywords. This systematic search using the abovementioned keywords identified relevant articles for inclusion in this review. The resulting literature indicated that CTE can offer innovative solutions for treating cardiac diseases when integrated with three-dimensional (3D) bioprinting and iPSC technology. Despite notable advances in the field of CTE, multiple challenges remain relating to 3D-bioprinted cardiac tissues. These include maintaining long-term cell viability, achieving precise cell distribution, tissue vascularization, material selection, and cost-effectiveness. Therefore, further research is needed to optimize printing techniques, develop more advanced bio-inks, explore larger-scale tissue constructs, and ensure the biosafety and functional fidelity of engineered cardiac tissues. Subsequently, future research efforts should focus on these areas to facilitate the clinical translation of CTE. Moreover, additional long-term animal models and preclinical studies should be conducted to ensure the biosafety and functionality of engineered cardiac tissues, thereby creating novel possibilities for treating patients with heart diseases.

A significant challenge facing tissue engineering is the fabrication of vasculature constructs which contains vascularized tissue constructs to recapitulate viable, complex and functional organs or tissues, and free-standing vascular structures potentially providing clinical applications in the future. Three-dimensional (3D) bioprinting has emerged as a promising technology, possessing a number of merits that other conventional biofabrication methods do not have. Over the last decade, 3D bioprinting has contributed a variety of techniques and strategies to generate both vascularized tissue constructs and free-standing vascular structures. This review focuses on different strategies to print two kinds of vasculature constructs, namely vascularized tissue constructs and vessel-like tubular structures, highlighting the feasibility and shortcoming of the current methods for vasculature constructs fabrication. Generally, both direct printing and indirect printing can be employed in vascularized tissue engineering. Direct printing allows for structural fabrication with synchronous cell seeding, while indirect printing is more effective in generating complex architecture. During the fabrication process, 3D bioprinting techniques including extrusion bioprinting, inkjet bioprinting and light-assisted bioprinting should be selectively implemented to exert advantages and obtain the desirable tissue structure. Also, appropriate cells and biomaterials matter a lot to match various bioprinting techniques and thus achieve successful fabrication of specific vasculature constructs. The 3D bioprinting has been developed to help provide various fabrication techniques, devoting to producing structurally stable, physiologically relevant, and biologically appealing constructs. However, although the optimization of biomaterials and innovation of printing strategies may improve the fabricated vessel-like structures, 3D bioprinting is still in the infant period and has a great gap between in vitro trials and in vivo applications. The article reviews the present achievement of 3D bioprinting in generating vasculature constructs and also provides perspectives on future directions of advanced vasculature constructs fabrication.