For the damage and loss of tissues and organs caused by urinary system diseases, the current clinical treatment methods have limitations. Tissue engineering provides a therapeutic method that can replace or regenerate damaged tissues and organs through the research of cells, biological scaffolds and biologically related molecules. As an emerging manufacturing technology, three-dimensional (3D) bioprinting technology can accurately control the biological materials carrying cells, which further promotes the development of tissue engineering. This article reviews the research progress and application of 3D bioprinting technology in tissue engineering of kidney, ureter, bladder, and urethra. Finally, the main current challenges and future prospects are discussed.
Bioprinting ; Regeneration ; Technology ; Tissue Engineering/methods*

As a cutting-edge technology of tissue engineering, three-dimensional bioprinting can accurately fabricate biomimetic tissue, which has made great progress in the field of hard tissue printing such as bones and teeth. Meanwhile, the research on soft tissue bioprinting is also developing rapidly. This article mainly discussed the development progress in various bioprinting technologies and supporting equipment including printing software, printing hardware, supporting consumables, and bioreactors for soft tissue three-dimensional bioprinting, and made a prospect for the future research and development direction of soft tissue three-dimensional bioprinting.
Bioprinting/methods* ; Biocompatible Materials ; Printing, Three-Dimensional ; Tissue Engineering ; Research

3D bioprinting technology is a rapidly developing technique that employs bioinks containing biological materials and living cells to construct biomedical products. However, 3D-printed tissues are static, while human tissues are in real-time dynamic states that can change in morphology and performance. To improve the compatibility between in vitro and in vivo environments, an in vitro tissue engineering technique that simulates this dynamic process is required. The concept of 4D printing, which combines "3D printing + time" provides a new approach to achieving this complex technique. 4D printing involves applying one or more smart materials that respond to stimuli, enabling them to change their shape, performance, and function under the corresponding stimulus to meet various needs. This article focuses on the latest research progress and potential application areas of 4D printing technology in the cardiovascular system, providing a theoretical and practical reference for the development of this technology.
Humans ; Tissue Engineering/methods* ; Bioprinting/methods* ; Printing, Three-Dimensional ; Cardiovascular System ; Tissue Scaffolds

The scar brings a huge economic burden and creates a serious psychological shadow for patients. Although the current methods for scar treatment tend to be diversified, the treatment method that can truly achieve the goal of "perfect healing" or "scarless healing" after human skin injury is quite scarce. With the wide application of tissue engineering technologies in medicine research, technologies such as three-dimensional bioprinting, organoid culture, and organ chip technologies are constantly emerging. Disease models in vitro based on these innovative technologies showed more advantages than traditional animal disease models. The article introduces the current hotspot technologies in skin tissue engineering such as organoid culture, three-dimensional bioprinting, and organ chip technologies, focuses on summarizing the three key elements to be mastered for constructing an ideal scar model in vitro, and puts forward the future prospect of constructing an ideal scar model in vitro based on our research team's long-term experience in skin tissue repair and regeneration research.
Animals ; Humans ; Tissue Engineering ; Cicatrix ; Bioprinting/methods* ; Wound Healing ; Technology ; Printing, Three-Dimensional

The need for organ and tissue regeneration in patients continues to increase because of a scarcity of donors, as well as biocompatibility issues in transplant immune rejection. To address this, scientists have investigated artificial tissues as an alternative to transplantation. Three-dimensional (3D) bioprinting technology is an additive manufacturing method that can be used for the fabrication of 3D functional tissues or organs. This technology promises to replicate the complex architecture of structures in natural tissue. To date, 3D bioprinting strategies have confirmed their potential practice in regenerative medicine to fabricate the transplantable hard tissues, including cartilage and bone. However, 3D bioprinting approaches still have unsolved challenges to realize 3D hard tissues. In this manuscript, the current technical development, challenges, and future prospects of 3D bioprinting for engineering hard tissues are reviewed.
Bioprinting* ; Cartilage ; Humans ; Methods ; Regeneration ; Regenerative Medicine ; Tissue Donors ; Tissue Engineering*

Three-dimensional (3D) printing technology is characterized by "inside-out" stack manufacturing. Compared with conventional technologies, 3D printing has the advantage of personalization and precision. Therefore, the shape and internal structure of the scaffolds made by 3D printing technology are highly biomimetic. Besides, 3D bioprinting can precisely deposit the biomaterials, seeding cells and cytokines at the same time, which is a breakthrough in printing technique and material science. With the development of 3D printing, it will make great contributions to the reconstruction of vertebrae and intervertebral disc in the future.
Biocompatible Materials ; Bioprinting ; Humans ; Intervertebral Disc ; growth & development ; Printing, Three-Dimensional ; Tissue Engineering ; methods ; Tissue Scaffolds

OBJECTIVETo fabricate organic-inorganic composite tissue engineering scaffolds for reconstructing calcified cartilage layer based on three-dimensional (3D) printing technique.

METHODSThe scaffolds were developed by 3D-printing technique with highly bioactive calcium-magnesium silicate ultrafine particles of 1%, 3% and 5% of mass fraction, in which the organic phases were composed of type I collagen and sodium hyaluronate. The 3D-printed scaffolds were then crosslinked and solidified by alginate and CaCl₂ aerosol. The pore size and distribution of inorganic phase were observed with scanning electron microscope (SEM); the mechanical properties were tested with universal material testing machine, and the porosity of scaffolds was also measured.

RESULTSPore size was approximately (212.3 ± 34.2) μm with a porosity of (48.3 ± 5.9)%, the compressive modulus of the scaffolds was (7.2 ± 1.2) MPa, which was irrelevant to the percentage changes of calcium-magnesium silicate, the compressive modulus was between that of cartilage and subchondral bone.

CONCLUSIONThe porous scaffolds for calcified cartilage layer have been successfully fabricated, which would be used for multi-layered composite scaffolds in osteochondral injury.

Bioprinting ; Cartilage ; growth & development ; Materials Testing ; Porosity ; Printing, Three-Dimensional ; Tissue Engineering ; methods ; Tissue Scaffolds ; chemistry

BACKGROUND: The shortage of donor corneas is a severe global issue, and hence the development of corneal alternatives is imperative and urgent. Although attempts to produce artificial cornea substitutes by tissue engineering have made some positive progress, many problems remain that hamper their clinical application worldwide. For example, the curvature of tissue-engineered cornea substitutes cannot be designed to fit the bulbus oculi of patients. OBJECTIVE: To overcome these limitations, in this paper, we present a novel integrated three-dimensional (3D) bioprinting-based cornea substitute fabrication strategy to realize design, customized fabrication, and evaluation of multi-layer hollow structures with complicated surfaces. METHODS: The key rationale for this method is to combine digital light processing (DLP) and extrusion bioprinting into an integrated 3D cornea bioprinting system. A designable and personalized corneal substitute was designed based on mathematical modelling and a computer tomography scan of a natural cornea. The printed corneal substitute was evaluated based on biomechanical analysis, weight, structural integrity, and fit. RESULTS: The results revealed that the fabrication of high water content and highly transparent curved films with geometric features designed according to the natural human cornea can be achieved using a rapid, simple, and low-cost manufacturing process with a high repetition rate and quality. CONCLUSIONS This study demonstrated the feasibility of customized design, analysis, and fabrication of a corneal substitute. The programmability of this method opens up the possibility of producing substitutes for other cornea-like shell structures with different scale and geometry features, such as the glomerulus, atrium, and oophoron.
Artificial Organs ; Bioprinting ; Cornea/cytology* ; Humans ; Models, Theoretical ; Printing, Three-Dimensional ; Tensile Strength ; Tissue Engineering/methods* ; Tissue Scaffolds

BACKGROUND/AIMS: Chronic liver disease is a major widespread cause of death, and whole liver transplantation is the only definitive treatment for patients with end-stage liver diseases. However, many problems, including donor shortage, surgical complications and cost, hinder their usage. Recently, tissue-engineering technology provided a potential breakthrough for solving these problems. Three-dimensional (3D) printing technology has been used to mimic tissues and organs suitable for transplantation, but applications for the liver have been rare. METHODS: A 3D bioprinting system was used to construct 3D printed hepatic structures using alginate. HepG2 cells were cultured on these 3D structures for 3 weeks and examined by fluorescence microscopy, histology and immunohistochemistry. The expression of liver-specific markers was quantified on days 1, 7, 14, and 21. RESULTS: The cells grew well on the alginate scaffold, and liver-specific gene expression increased. The cells grew more extensively in 3D culture than two-dimensional culture and exhibited better structural aspects of the liver, indicating that the 3D bioprinting method recapitulates the liver architecture. CONCLUSIONS: The 3D bioprinting of hepatic structures appears feasible. This technology may become a major tool and provide a bridge between basic science and the clinical challenges for regenerative medicine of the liver.
Bioprinting ; Cause of Death ; Gene Expression ; Hep G2 Cells* ; Humans ; Immunohistochemistry ; Liver ; Liver Diseases ; Liver Transplantation ; Methods ; Microscopy, Fluorescence ; Printing, Three-Dimensional ; Regenerative Medicine ; Tissue Donors