Direct Human Cartilage Repair Using Three-Dimensional Bioprinting Technology

Abstract

Current cartilage tissue engineering strategies cannot as yet fabricate new tissue that is indistinguishable from native cartilage with respect to zonal organization, extracellular matrix composition, and mechanical properties. Integration of implants with surrounding native tissues is crucial for long-term stability and enhanced functionality. In this study, we developed a bioprinting system with simultaneous photopolymerization capable for three-dimensional (3D) cartilage tissue engineering. Poly(ethylene glycol) dimethacrylate (PEGDMA) with human chondrocytes were printed to repair defects in osteochondral plugs (3D biopaper) in layer-by-layer assembly. Compressive modulus of printed PEGDMA was 395.73±80.40 kPa, which was close to the range of the properties of native human articular cartilage. Printed human chondrocytes maintained the initially deposited positions due to simultaneous photopolymerization of surrounded biomaterial scaffold, which is ideal in precise cell distribution for anatomic cartilage engineering. Viability of printed human chondrocytes increased 26% in simultaneous polymerization than polymerized after printing. Printed cartilage implant attached firmly with surrounding tissue and greater proteoglycan deposition was observed at the interface of implant and native cartilage in Safranin-O staining. This is consistent with the enhanced interface failure strength during the culture assessed by push-out testing. Printed cartilage in 3D biopaper had elevated glycosaminoglycan (GAG) content comparing to that without biopaper when normalized to DNA. These observations were consistent with gene expression results. This study indicates the importance of direct cartilage repair and promising anatomic cartilage engineering using 3D bioprinting technology.

3D bioprinting for cell culture and tissue fabrication

“…In the past few years, researchers adopted joint replacement surgery to treat arthritis, but the difficulties and costs of this method were too high [56]. Nowadays, although tissue engineering emerges and aims at cartilage regeneration by fabricating cell-laden structures [57], it cannot fabricate a cartilage tissue as the same as the native one due to its complicated structures and specific characters.…”

Current progresses of 3D bioprinting based tissue engineering

“…After 2 weeks of in vitro culture and 8 weeks of in vivo culture, the fabricated cartilage showed fine deposition of collagen and glycosaminoglycan, resembling the organization and mechanical properties of natural cartilages. Xiaofeng Cui [27] and colleagues had applied a different strategy by using a natural osteochodral plug (extracted from bovine femoral condyles) as scaffold instead of synthesized polymers, then printed human chondrocytes mixed with modified PEG (polyethylene glycol dimethacrylate) onto the plug using thermal inkjet printer ( Figure 2C), and were able to generate integrated and stabilized new cartilage tissue after 6 weeks of culture. In another trial, Chang H. Lee and colleagues replaced the sheep native meniscus with a PCL-printed scaffold carrying connective tissue growth factor (CTGF) and transforming Smooth muscle cell [40] Epithelial cell [24] growth factor-β3 (TGF-β).…”

3D bioprinting for tissue engineering: Stem cells in hydrogels

“…However, once these issues are addressed, inkjet methods offer fast, cheap and high resolution bioprinting with the ability to change drop size and density, thereby the ability to create gradients. When this is coupled with multiple nozzles, it is clear why inkjet printing techniques are so attractive to tissue engineers [21,22] .…”

“…The ability to encapsulate cells within the material as it is being printed allows researchers to create a more tissue-like environment compared with creating a 2D construct first onto which cells are then seeded [89] . With hydrogels this has been attempted with some success [90] , creating cell-laden constructs that contain microvascular networks [91] and are able to integrate well with native tissue [22] . Combining cells with hydrogels is a delicate balance of maintaining high cell viability whilst ensuring that there are not too many cells in the gel to cause hyperplasia or apoptosis, either by optimising the number of cells added at the loading stage of the process or by controlling the rate of cell proliferation post-printing [13] .…”

“…Furthermore, as knowledge on technologies and materials advances, it is entirely plausible that in the future in situ bioprinting systems could be developed to both scan the patient's wound site and print the cell-laden scaffold directly into the wound, all without leaving the operating theatre. Significant progress in this area has already been made towards skin [21] and cartilage repair [22] .…”