Three-Dimensional Bioprinting of Cartilage by the Use of Stem Cells: A Strategy to Improve Regeneration

Abstract

Cartilage lesions fail to heal spontaneously, leading to the development of chronic conditions which worsen the life quality of patients. Three-dimensional scaffold-based bioprinting holds the potential of tissue regeneration through the creation of organized, living constructs via a "layer-by-layer" deposition of small units of biomaterials and cells. This technique displays important advantages to mimic natural cartilage over traditional methods by allowing a fine control of cell distribution, and the modulation of mechanical and chemical properties. This opens up a number of new perspectives including personalized medicine through the development of complex structures (the osteochondral compartment), different types of cartilage (hyaline, fibrous), and constructs according to a specific patient's needs. However, the choice of the ideal combination of biomaterials and cells for cartilage bioprinting is still a challenge. Stem cells may improve material mimicry ability thanks to their unique properties: the immune-privileged status and the paracrine activity. Here, we review the recent advances in cartilage three-dimensional, scaffold-based bioprinting using stem cells and identify future developments for clinical translation. Database search terms used to write this review were: "articular cartilage", "menisci", "3D bioprinting", "bioinks", "stem cells", and "cartilage tissue engineering".

Keywords: 3D bioprinting; 4D printing; bioink; biomaterials; cartilage; meniscus; organ-on-a-chip; osteoarthritis; stem cells.

Figure 1

Comparison between tissue engineering conventional and three-dimensional (3D) bioprinting approaches. (a) In the conventional method, cells can be seeded in vitro in a static and/or dynamic mode onto a previously fabricated scaffold. The static seeding allows a non-homogenous cell distribution into the scaffold. The dynamic seeding can be carried out with different types of bioreactors to favor a more homogenous cell distribution. Here, there is an example of a perfusion bioreactor performing 3D cell seeding. Both types of “conventional” tissue-like constructs need to be subsequently shaped by the surgeon to match the defect site; (b) Representation of the main three bioprinting techniques: extrusion-based bioprinting; jetting-based bioprinting, and laser-based bioprinting. Such options allow cell encapsulation, spatial control, and the match between implant and defect size in the clinical setting.

Figure 2

(a) Custom-made printed meniscal model. The construct is realized in a poly(ethylene glycol) methacrylate (PEGMA)-based hydrogel (Bioink, RegenHU, CH) that requires UV light cross-linking (365 nm wavelength) to improve structural and mechanical properties; (b) Post-printing evaluations: mesenchymal stem cell (MSC) distribution by microscopy and cell viability by the Live and Dead test (green: live cells (FITC channel); red: dead cells (TRITC channel); scale bar: 100 µm).

Figure 3

Regenerative ability of agarose-, alginate-, GelMA- and PEGMA-based hydrogels seeded with MSCs and cultured in a chondrogenic medium for four weeks. (A) Immunohistochemical and histological analyses showed that agarose and alginate both stained for collagen type II and glycosaminoglycans (GAG). In contrast, GelMA and PEGMA were more positive collagen type I; (B) DNA content (ng) quantification for each construct; (C) GAGs per DNA ratio; (D) Weight/weight GAG percent (%WW). Biochemical analyses showed that GelMA had the lowest GAG levels. Significance p < 0.05, (a) versus alginate at the same time point, (b) versus agarose, (c) versus PEGMA, (d) versus GelMA, (d*) versus GelMA at day 0 [88]. Reproduced with permission from IOP SCIENCE.

Figure 4

Schematic representation of four possible future perspectives for cartilage bioprinting approaches of MSCs. Upper left part: 3D biomimetic tissue platforms for the development of micro-organs/-tissues as new models for mimicking diseased anatomical sites and studying possible therapies (i.e., organ-on-chip); upper right part: advanced biomaterials that can modify their properties according to biological cues: 4D bioprinting; lower left part: combination of multiple cell types to mimic the tissue complexity; lower right part: innovative bioprinting tools to improve scalability, manufacturing time, and surgical approach (i.e., Biopen).