Page 270 - IJB-9-5

International Journal of Bioprinting 3D-printed scaffolds for TMJ fibrocartilage regeneration

controlled laser completes the bioink solidification on fibrocartilage tissue engineering, such as fibrochondrocytes
the surface layer, the vat is lowered. The next layer is and articular chondrocytes . The limited availability
[48]
crosslinked at the top of the previous section, and layer- of tissue and dedifferentiation tendency during in vitro
by-layer solidification eventually forms a 3D model . In culture are assumed to be the main challenges of mature
[32]
contrast to stereolithography, in the course of digital light chondrocytes as seed cells in application .
[12]
processing, UV light projects a 2D pattern onto the surface Mesenchymal stem cells (MSCs) have been widely used
of the liquid resin material through a digital micromirror as seed cells in TMJ fibrocartilage tissue engineering due
device . With the vertical movement of the substrate, to their great ability of differentiation, proliferation, and
[38]
the liquid resin material is solidified layer by layer until ECM secretion. Extensive research has demonstrated the
a designed structure is constructed . VPP prevents cells potential of MSCs from bone marrow, adipose tissue, and
[39]
from physical stress, thus maintaining high cell viability synovial fluid for TMJ fibrocartilage tissue engineering .
[49]
and supporting high printing resolution . However, Continuous attempts have been made to explore more seed
[40]
VPP is only applicable to liquid photosensitive materials, cells suitable for TMJ fibrocartilage tissue engineering.
which limits its application scope . In the past decade, It has been reported that dental pulp stem cells (DPSCs)
[30]
several strategies of VPP have been developed to fabricate seeded on the scaffold were cultured in chondrogenic
multi-material constructs, including multi-vat, sequential media for 8 weeks, resulting in increased gene expression
injection, sequential deposition, and multi-wavelength, of fibrocartilaginous markers . In addition, umbilical
[50]
thus increasing the potential of VPP for tissue-engineering cord MSCs , induced pluripotent stem cells (iPSCs) ,
[51]
[52]
applications . periodontal ligament stem cells (PDLSCs) , and deciduous
[41]
[53]
teeth stem cells (DTSCs) have been demonstrated as
[54]
3. Scaffold components potential seed cells in TMJ regenerative medicine.
3.1. Seed cell The effect of cell density on cell behavior and scaffold
Due to the lack of blood vessels and nerves, articular cartilage properties should not be ignored. Excessive cell density
tissue has insufficient self-repair capacity. Therefore, seed may lead to a decrease in the ability of individual cells to
cells are required to have the ideal ability to proliferate and secrete ECM and prolong the expansion cycle of cell culture
secrete extracellular matrix (ECM). Seeding techniques in vitro, while low cell density may not be conducive to cell
such as static seeding, negative pressure seeding, centrifugal differentiation and secretion of ECM . The density of
[55]
seeding, spinner flask, orbital shaker, and perfused bioreactor articular chondrocytes is distributed in a density gradient,
can be used to seed cells onto the scaffolds to promote gradually decreasing from superficial to deep . To mimic
[56]
articular cartilage regeneration [42-44] . The commonly used natural articular cartilage, cell density gradient scaffolds
seed cells in cartilage tissue engineering and the effects of were fabricated and it was demonstrated that ECM
cell density in the scaffolds will be discussed below. production was positively correlated with cell density [57,58] .
Mature chondrocytes as part of cartilage tissue can Furthermore, the comparison of the scaffolds seeded with
be cultured in vitro, then inoculated onto 3D-printed different initial cell densities showed that the compressive
artificial scaffolds, and ultimately transplanted into the stiffness, modulus, thickness, and wet weight as well as
defect site to promote articular cartilage regeneration. GAG and collagen content of the cartilaginous constructs
The feasibility of this regimen has been verified on mature increased with increasing cell density . A recent review
[59]
chondrocytes from various sources, including humans, summarized that the cell density in the majority of bioinks
bovine, rabbits, etc. Specifically, compared with tissue- for articular cartilage repair ranged from 5 to 20 × 10 cells/
[12]
6
[12]
engineered constructs with articular chondrocytes, tissue- mL . Under the specific conditions, desirable results can
engineered constructs with costal chondrocytes showed also be achieved by the scaffolds with the cell densities of
[60]
6
[61]
greater glycosaminoglycan (GAG)/wet weight and tensile 25 × 10 cells/mL , 50 × 10 cells/mL , 60 × 10 cells/
6
6
strength, suggesting a better tissue-engineering potential of mL , and so on. So far, there is no gold standard for
[62]
costal chondrocytes in TMJ fibrocartilage regeneration . optimal cell density because it depends on cell type, scaffold
[45]
Furthermore, the passaged costal chondrocytes were biomaterial, BFs, and culture conditions. Therefore, it is
demonstrated to have potential superiority over primary suggested to compare the effects of the combination of the
costal chondrocytes in TMJ fibrocartilage tissue specific scaffold and multiple cell densities to determine
engineering, as the former produced more GAG than the the appropriate cell density for the specific scaffold.
latter in vitro . An in vivo study further confirmed the
[46]
ability of the passaged costal chondrocytes in TMJ disc 3.2. Scaffold biomaterial
[47]
repair . Chondrocytes co-cultured with other types of Artificial scaffolds with biocompatibility and biodegradability
cells have been demonstrated to be a feasible strategy in TMJ are required to have mechanical properties similar to
Volume 9 Issue 5 (2023) 262 https://doi.org/10.18063/ijb.761