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International Journal of Bioprinting Bioprinted cell-laden hydrogel for tracheal application

bacterial activity and enhanced therapeutic effect after recipient tissue, which provided the necessary nutrients for
orthotopic tracheal transplantation in a rabbit model. In the regeneration of the tracheal cartilage. 31
summary, these findings suggest that the ICA/CS/GelMA The inflammatory response of TETC is a significant
hydrogel is a suitable platform for 3D bioprinting with cells concern in vivo, as it can be induced by various factors
and exhibits both anti-inflammatory and anti-bacterial such as surgical trauma, biomaterials, and their
activities that can promote tracheal cartilage regeneration degradation products, and it can considerably affect
and restoration. the stability of the cartilaginous phenotype. 32,33 Several

Recent research has emphasized the importance of studies have shown that this inflammatory reaction can
achieving satisfactory tracheal cartilage regeneration lead to necrosis of engineered cartilage tissue, fibrosis,
for successful functional reconstruction of the trachea. granulation hyperplasia, and, ultimately, failure of TETC
However, several challenges, such as uneven chondrocyte after orthotopic tracheal transplantation. 9,19,20 Moreover,
distribution in the scaffold, difficult shape control, pro-inflammatory cytokines such as IL-6 and TNF-α
inevitable inflammatory reactions, and bacterial infections, can activate the NF-κB signaling pathway, causing local
have compromised the structure and functionality of inflammation and apoptosis of tracheal tissues, particularly
TETC in vivo. In this study, we developed an ICA/CS/ the cartilage. In our current study, we observed high
9,34
GelMA hydrogel that could be 3D bioprinted with expression of inflammatory-related factors (TNF-α and
chondrocytes to fabricate C-shaped rings with uniform IL-6), as well as apoptosis of chondrocytes (TUNEL),
chondrocyte distribution, thereby addressing the issues of confirming that the inflammatory response was a crucial
chondrocyte distribution and shape control. The inclusion factor causing cartilage deterioration.
of ICA endowed the ICA/CS/GelMA hydrogel with anti- The airway mucosa plays a vital role in preventing
inflammatory properties, significantly enhancing TETC infections and performing key physiological functions, such
formation in vivo. Furthermore, the addition of CS as the clearance of secretions via the mucociliary escalator.
imparted the ICA/CS/GelMA hydrogel with anti-bacterial Minor injuries involving limited surface areas can be self-
properties, reducing bacterial infection and increasing repaired through epithelial migration from the wound
the survival rate of experimental rabbits after orthotopic edge. However, the epithelialization of TETC through
tracheal transplantation. Our findings suggest that this self-migration of adjacent epithelium is time-consuming
approach is a promising strategy for clinical translation in and unreliable. Studies have shown that inflammation
35
tracheal tissue engineering.
caused by bacterial infections can severely compromise
3D bioprinting is an innovative technology that offers TETC due to a lack of airway mucosa. This can lead
1-6
high reproducibility and precise control over the fabrication to airway obstruction and excess mucus, supporting the
of constructs in an automated manner. This technology colonization of potential pathogens such as Pseudomonas
has been employed to develop functional constructs for aeruginosa, and increasing mortality in experimental
replacing damaged or injured tissues. In previous studies, animals. However, few studies have investigated the impact
two strategies were adopted to reconstruct tracheal of anti-bacterial effects on TETC. It is well-established
cartilage: (i) seeding chondrocytes onto scaffolds and (2) that the upper respiratory tract of healthy individuals is
using a molding method. However, these strategies failed continuously colonized by microbes. Researchers have
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1-6
to overcome uneven cell distribution and chondrocyte suggested that defects in mucociliary clearance, as well
wastage. To address these concerns, we have previously as airway macrophage and neutrophil dysfunction, may
developed a new strategy for 3D bioprinting of a cartilage- contribute to inflammation progression and exacerbation.
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vascularized fibrous tissue-integrated trachea. Although In this study, we discovered that anti-bacterial effects may
this approach enabled even distribution of chondrocytes contribute to maintaining the cartilaginous phenotype and
in hydrogel and reduced chondrocyte wastage, the time- promoting tracheal cartilage formation. It is worth noting
consuming 3D bioprinting process was detrimental to the that despite the demonstrated superior anti-bacterial
survival of chondrocytes. To overcome this challenge, we efficacy of the ICA/CS/GelMA group at the third week,
18
adopted a two-step strategy: (i) we separately 3D-bioprinted there was a significant mortality rate of 30% observed
C-shaped chondrocyte-loaded hydrogel rings, which among rabbits in this group during the 1st to 3rd weeks
facilitated even distribution of chondrocytes in the following transplantation. This observation led us to
hydrogel and required less total printing time compared speculate that the released CS from the ICA/CS/GelMA
to 3D printing a trachea-mimetic cellular construct, and group might not adequately fulfill the essential functions
(2) we reconstructed the tracheal cartilage using an in vivo of the tracheal epithelium, such as mucus-based trapping
bioreactor. Using an in vivo bioreactor allowed tissue fluid of toxic particles and their subsequent clearance from the
infiltration and vessel in-growth from the surrounding respiratory tract via cilia movement; therefore, further
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Volume 10 Issue 1 (2024) 172 https://doi.org/10.36922/ijb.0146