Over the last decades, the fabrication of 3D tissues has become commonplace in tissue engineering and regenerative medicine. However, conventional 3D biofabrication techniques such as scaffolding, microengineering, and fiber and cell sheet engineering are limited in their capacity to fabricate complex tissue constructs with the required precision and controllability that is needed to replicate biologically relevant tissues. To this end, 3D bioprinting offers great versatility to fabricate biomimetic, volumetric tissues that are structurally and functionally relevant. It enables precise control of the composition, spatial distribution, and architecture of resulting constructs facilitating the recapitulation of the delicate shapes and structures of targeted organs and tissues. This Review systematically covers the history of bioprinting and the most recent advances in instrumentation and methods. It then focuses on the requirements for bioinks and cells to achieve optimal fabrication of biomimetic constructs. Next, emerging evolutions and future directions of bioprinting are discussed, such as freeform, high-resolution, multimaterial, and 4D bioprinting. Finally, the translational potential of bioprinting and bioprinted tissues of various categories are presented and the Review is concluded by exemplifying commercially available bioprinting platforms.

/pdf/3d-bioprinting-from-benches-to-translational-applications-46mowdfimd.pdf

3D Bioprinting: from Benches to Translational Applications.

Recent advances have allowed for three-dimensional (3D) printing technologies to be applied to biocompatible materials, cells and supporting components, creating a field of 3D bioprinting that holds great promise for artificial organ printing and regenerative medicine. At the same time, stem cells, such as human induced pluripotent stem cells, have driven a paradigm shift in tissue regeneration and the modeling of human disease, and represent an unlimited cell source for tissue regeneration and the study of human disease. The ability to reprogram patient-specific cells holds the promise of an enhanced understanding of disease mechanisms and phenotypic variability. 3D bioprinting has been successfully performed using multiple stem cell types of different lineages and potency. The type of 3D bioprinting employed ranged from microextrusion bioprinting, inkjet bioprinting, laser-assisted bioprinting, to newer technologies such as scaffold-free spheroid-based bioprinting. This review discusses the current advances, applications, limitations and future of 3D bioprinting using stem cells, by organ systems.

/pdf/3d-bioprinting-using-stem-cells-2sxsug5e05.pdf

3D bioprinting using stem cells

Photo-crosslinkable, injectable sericin hydrogel as 3D biomimetic extracellular matrix for minimally invasive repairing cartilage

Poly(glycolic acid) (PGA): a versatile building block expanding high performance and sustainable bioplastic applications

Soft tissue reconstructs require materials that form three-dimensional (3-D) structures supportive to cell proliferation and regenerative processes. Polysaccharides, due to their hydrophilicity, biocompatibility, biodegradability, abundance, and presence of derivatizable functional groups, are distinctive scaffold materials. Superior mechanical properties, physiological signaling, and tunable tissue response have been achieved through chemical modification of polysaccharides. Moreover, an appropriate formulation strategy enables spatial placement of the scaffold to a targeted site. With the advent of newer technologies, these preparations can be tailor-made for responding to alterations in temperature, pH, or other physiological stimuli. In this review, we discuss the developmental and biological aspects of scaffolds prepared from four polysaccharides, viz. alginic acid (ALG), chitosan (CHI), hyaluronic acid (HA), and dextran (DEX). Clinical studies on these scaffolds are also discussed.

/pdf/polysaccharide-based-scaffolds-for-soft-tissue-engineering-5acxtvd7oo.pdf

Polysaccharide Based Scaffolds for Soft Tissue Engineering Applications.

Stem cells play essential roles in tissue regeneration in vivo via specific lineage differentiation induced by environmental factors. In the past, biochemical signals were the focus of induced stem cell differentiation. As reported by Engler et al (2006 Cell 126 677-89), biophysical signal mediated stem cell differentiation could also serve as an important inducer. With the advancement of material science, it becomes a possible strategy to generate active biophysical signals for directing stem cell fate through specially designed material microstructures. In the past five years, significant progress has been made in this field, and these designed biophysical signals include material elasticity/rigidity, micropatterned structure, extracellular matrix (ECM) coated materials, material transmitted extracellular mechanical force etc. A large number of investigations involved material directed differentiation of mesenchymal stem cells, neural stem/progenitor cells, adipose derived stem cells, hematopoietic stem/progenitor cells, embryonic stem cells and other cells. Hydrogel based materials were commonly used to create varied mechanical properties via modifying the ratio of different components, crosslinking levels, matrix concentration and conjugation with other components. Among them, polyacrylamide (PAM) and polydimethylsiloxane (PDMS) hydrogels remained the major types of material. Specially designed micropatterning was not only able to create a unique topographical surface to control cell shape, alignment, cell-cell and cell-matrix contact for basic stem cell biology study, but also could be integrated with 3D bioprinting to generate micropattered 3D structure and thus to induce stem cell based tissue regeneration. ECM coating on a specific topographical structure was capable of inducing even more specific and potent stem cell differentiation along with soluble factors and mechanical force. The article overviews the progress of the past five years in this particular field.

https://iopscience.iop.org/article/10.1088/1748-6041/11/1/014109/pdf

Recent progress in stem cell differentiation directed by material and mechanical cues.

Synthetic polymers such as polyglycolic acid (PGA) fibers are the traditional tissue engineering scaffolds that are widely used for engineering a variety of soft tissues. However, the major disadvantage of this polymer material is its released acidic degradation products that trigger inflammatory response and fibrotic process, which affects the biocompatibility and the quality of the engineered tissues. In this study, the effect of hyaluronic acid (HA) coating on improving PGA biocompatibility was explored. The results showed that 1% HA solution could better coat PGA fibers than other tested concentrations of HA, and coated PGA exhibited less inflammatory reaction upon in vivo subcutaneous implantation. In vitro characterization demonstrated that HA coating could enhance cell adhesion to the scaffold and reduce gene expression of IL-1, IL-6, IL-8, and α-SMA. It also decreased the acidity of degradation products in vitro. Furthermore, coated PGA could engineer better cartilages in vitro with higher content of total collagen and glycosaminoglycan, as well as higher gene expression levels of collagen II, aggrecan, and Sox9. Collectively, the data indicate that HA coating can significantly enhance the biocompatibility of this traditional scaffold material, which also enhances the quality of engineered tissues.

Hyaluronic Acid Coating Enhances Biocompatibility of Nonwoven PGA Scaffold and Cartilage Formation.

Tissue engineering and regenerative medicine (TERM) remains to be one of the fastest growing fields, which covers a wide scope of topics of both basic and applied biological researches. This overview article summarized the advancements in basic researches of TERM area, including stem cell biology, cell engineering, somatic nuclear transfer, genomic editing, discovery of new tissue progenitor/stem cells, and immunomodulation of stem cells and tissue regeneration. It reflects the cutting-edge achievements in basic researches, which will lay solid scientific foundation for future TERM translational researches.

Tissue engineering and regenerative medicine in applied research: a year in review of 2014.

In the current study, a novel filler material was developed to improve the healing activity of an electrospun cellulose acetate neural guidance channel. Tenocyclidine was loaded into chitosan nanoparticles, dispersed in a calcium alginate hydrogel, and their effect on Schwann cells’
 viability was assessed using MTT assay. Study showed that chitosan nanoparticles loaded with 0.5% Tenocyclidine had the optimal effects on cells viability. In vivo study on a rat model of peripheral nerve injury showed that the neural guidance channels containing Schwann cells and Tenocyclidine-loaded
 chitosan nanoparticles had the highest rate of nerve repair as evidenced by functional analysis assays and histopathological examinations.

Alginate-Based Hydrogels Composited with Tenocyclidine-Loaded Chitosan Nanoparticles, a Sophisticated Delivery System for Transplantation of Allogenic Schwan Cells Through Cellulose Acetate Neural Guidance Channels: A Preclinical Study

Xunxun Lin

Papers

Recent progress in stem cell differentiation directed by material and mechanical cues.

Hyaluronic Acid Coating Enhances Biocompatibility of Nonwoven PGA Scaffold and Cartilage Formation.

Tissue engineering and regenerative medicine in applied research: a year in review of 2014.

Alginate-Based Hydrogels Composited with Tenocyclidine-Loaded Chitosan Nanoparticles, a Sophisticated Delivery System for Transplantation of Allogenic Schwan Cells Through Cellulose Acetate Neural Guidance Channels: A Preclinical Study