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International Journal of Bioprinting                                Progress in bioprinted ear reconstruction






 Study  Aim of study  Study   Animal   Study focus  3D printing   Components  Printed  Printed  Cell nature/type  Notable post-  Assessment   Findings  Limitations and suggested
 setting  model (if   technique  shape  material  printing   of success/                      improvements
 any)                             modifications  integration
 Dong et al.   To determine the   In vivo   Rat  Direct printing  Extrusion (FDM)  Scaffold only  Other shape  PLA  Bone marrow  Cells were cultured,  Histopathology;  •  A combination of MSCs and chondrocytes   The implantation of the
 (2022)  [48]  minimum fraction   animal  ‐derived   passaged, and then   micro-CT scan  was used to create cartilage that demonstrated  constructs in nude rats,
 of human auricular   mesenchymal stem  slowly injected into   consistent mechanical function, even when   which manifest different
 chondrocyte required   cells     the scaffolds and            the ratio of MSCs to chondrocytes was high.  skin characteristics from
 to form healthy elastic          gelled at 37°C for 1       •  When chondrocytes made up only 10% of   humans (e.g. looseness
 cartilage when co‐cultured       h. Cell‐loaded               the initial cell population, the resulting tissue   of rodent skin does
 with human MSCs.                 constructs were              had characteristics similar to native elastic   not simulate the high
                                  then cultured                cartilage in terms of both biomechanics and   pressure caused by
                                  overnight                    biochemistry.                  implantation under the
                                  before                     •  Co-implantation of a small number of   tight scalp), as well as
                                  implantation.                chondrocytes with MSCs in a type I collagen   significant differences in
                                                               matrix resulted in the production of cartilage   immunocompetency.
                                                               that was indistinguishable from native
                                                               auricular cartilage after 6 months in vivo.
                                                             •  It is not yet clear if the more efficient cartilage
                                                               formation observed in this study is due
                                                               to the differentiation of MSCs toward a
                                                               chondrogenic lineage, a trophic effect of the
                                                               MSCs, or a combination of both, but this is
                                                               the subject of ongoing research.
                                                             •  The use of a small number of chondrocytes
                                                               could be an important step toward the clinical
                                                               translation of auricular tissue engineering due
                                                               to the limited availability of auricular cartilage
                                                               donor tissue.
 Park et al.    To apply 3D cell printing   In vivo   Rabbit  Direct printing  Multi-head tissue/  Cells in bioink +   Other shape  PCL  Primary   Incubated at 37℃   Histopathology;  •  A multi-head tissue/organ building system   Small sample
 (2017)  [49]  to fabricate a tissue-  animal  organ building   scaffold printed   chondrocytes from  for 1 h. Fabricated   mechanical   can successfully be used to 3D-print a
 engineered graft, and   system (extrusion)  together; scaffold   the New Zealand   CSHS was   testing; electron   cell-printed structure (CPS) using layers of
 evaluate its effects on   printed first and   white rabbit  crosslinked using   microscopy  alginate bio-ink encapsulating chondrocytes
 cartilage reconstruction.  then seeded with   CaCl . Washed   and PCL.
                                      2
 cells                            with PBS thrice.           •  The CPS was found to have a higher efficiency
                                  Then chondrocytes            of cellular settlement, improved survival and
                                  were seeded onto             function of chondrocytes in vitro compared to
                                  the CSHS with the            a cell-seeded scaffold (CSS).
                                  same cell density          •  When implanted in a rabbit ear with a
                                  with CSS.                    cartilage defect, the CPS led to complete
                                                               cartilage regeneration after 3 months, while
                                                               the CSS and autologous cartilage only led to
                                                               incomplete healing.
                                                             •  These results suggest that 3D printing
                                                               synthetic polymer scaffolds with hydrogel
                                                               materials and cells can be a viable alternative
                                                               to using autologous cartilage for auricular
                                                               reconstruction.
 Jia et al.    To create and test a proper   In vitro;  Mice  Indirect   Cast-molding   Scaffold printed   Resembling   Other:   Goat chondrocyte   A cell suspension   Histopathology;  •  The scaffold showed excellent   Important unknowns
 (2020)  [25]  scaffold created with ACM   in vivo   printing  and freeze-drying   first and then   pinna; other   ACM/  seeding  was seeded into   electron   biocompatibility and successfully regenerated   remain, including how
 with precise human-  animal  mixture  seeded with cells  shape  gelatin-PCL   each scaffold. This   microscopy  human-ear-shaped cartilage that retained a   best to optimize scaffold
 ear-shape and necessary   scaffold  was followed by 24        satisfactory shape, good elasticity, abundant   preparation, evaluation
 mechanical strength              h of incubation              lacuna structure, and cartilage-specific ECM   of scaffold biosafety, and
 that will elicit a low                                        deposition.                    the feasibility of human-
 inflammatory reaction.                                      •  Cell seeding efficiency in both ACM/gelatin   ear-shaped cartilage
                                                               and gelatin scaffolds was more than 90%,   regeneration in large
                                                               which was significantly superior than that of   animals.
                                                               PGA/PLA scaffolds.

                                                                                                         (Continued)



            Volume 9 Issue 6 (2023)                        297                        https://doi.org/10.36922/ijb.0898
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