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International Journal of Bioprinting DEX-Loaded PLGA microspheres enhance cartilage regeneration

distribution, forming more consistent rectangular shapes. cells. In contrast, the PLGA-dex30 MPs@GelMA group
Therefore, we conclude that bioinks containing PLGA- showed only a small number of inflammatory cells
dex0 MPs and PLGA-dex30 MPs demonstrate superior surrounding the hydrogel and within the capsule on day
printing performance when employed in extrusion-based 7. By day 14, the number of inflammatory cells decreased
3D bioprinting. (Figure 10B). In Figure 10C, Alcian blue dye stained the
chondrocytes and the surrounding extracellular matrix
3.3.2. Viability staining of 3D-bioprinted constructs in blue. On day 14, the PLGA-dex30 MPs@GelMA group
Following an overnight culture of the 3D-bioprinted exhibited more chondrocytes, with the largest and most
tissue-engineered constructs, live/dead cell staining was intense staining area surrounding the cartilage matrix,
performed. As depicted in Figure 9B, a considerable indicating that the PLGA-dex30 MPs@GelMA group
population of viable cells were evident within the constructs possesses higher chondrogenic capacity and drives more
in PLGA-dex0 MPs and PLGA-dex30 MPs groups, with rapid chondrocyte maturation compared to the PLGA-
only a minimal presence of dead cells exhibiting red dex0 MPs@GelMA group. The presence of medication
fluorescence. Further details regarding live/dead cell in the PLGA-dex30 MPs@GelMA bioink resulted in
staining following in vitro culture for the bioprinting of improved chondrocyte activity and the formation of
the two groups of bioinks are provided in Figure S2 (in more abundant neo-cartilage, albeit with a weaker
Supplementary File). vascularization capability. Additionally, the capsule of
Statistical analysis of the AOD values, which represent group PLGA-dex0 MPs@GelMA tissue assumed a more
the amount of live cells in the two groups (Figure 9C), orderly arrangement, coupled with a thicker fibrous
revealed no significant difference between the groups. No structure and an apparent inflammatory response. These
statistically significant differences in fluorescence intensity findings confirm the excellent biocompatibility of PLGA-
were observed (p > 0.05). dex30 MPs@GelMA.

3.3.3. Macroscopic examination of Immunohistochemical staining was conducted to
regenerated cartilage compare the depth of CD86 antibody staining in the
Specimens were examined and photographed at 7 and 14 capsules of PLGA-dex30 MPs@GelMAand PLGA-dex0
days post-implantation for macroscopic assessment. As MPs@GelMAgroups (Figure 10D). The results indicated
illustrated in Figure 10A, at day 7, both groups displayed that PLGA-dex30 MPs@GelMA significantly reduced
evident capsule formation on the surface of the constructs, staining depth for M1-type macrophages compared to
with minimal volume shrinkage. By day 14, both groups PLGA-dex0 MPs@GelMA, suggesting that sustained DEX
were completely surrounded by capsules, albeit with a release inhibits M1 cell polarization. In terms of capsule
noticeable inter-group difference in volume. The PLGA- tissue arrangement, PLGA-dex30 MPs@GelMA exhibited
dex0 MPs@GelMA group exhibited more pronounced a more orderly structure with a dense fibrous matrix, while
shrinkage compared to its initial size, while the PLGA- PLGA-dex0 MPs@GelMA showed thick but disorganized
dex30 MPs@GelMA group maintained a relatively larger and loose capsules. Quantitative analysis revealed a gradual
volume (Figure 10A). increase in CD86-positive staining area over time in both
groups, with lower intensity observed in PLGA-dex30
The macroscopic observation indicates that tissue- MPs@GelMA compared to PLGA-dex0 MPs@GelMA
engineered cartilage constructs underwent more rapid (Figure 10E).
degradation in the rabbit body compared to in C57 mice.
By day 7, significant capsule formation became apparent, Immunohistochemical staining was conducted
and by day 14, the PLGA-dex30 MPs@GelMA constructs to further assess vascularization in the two groups of
exhibited a larger volume compared to the control. This cartilage tissue engineering constructs (Figure 10F).
indicates that the sustained release of DEX from PLGA- CD31-positive staining was observed at sites indicated by
dex30 MPs slowed down the absorption of capsules by the red arrowheads, exhibiting weaker expression in PLGA-
rabbit body that was in inflammatory condition. dex30 MPs@GelMA and the strongest expression in the
capsule of the PLGA-dex30 MPs@GelMA group. This
3.3.4. Histological observations suggests a significant contribution of DEX to chondrocyte
H&E staining consistently revealed pronounced survival and proliferation during tissue regeneration
inflammation and necrotic cells surrounding the post-implantation of the constructs. To summarize,
hydrogel and within the capsule of the PLGA-dex0 MPs@ compared to traditional PLGA MPs carriers, PLGA-dex30
GelMA group starting from day 7. By day 14, there was MPs demonstrate superior cellular affinity and confer
a noticeable increase in the number of inflammatory cell protection, and hold promise for functional tissue

Volume 10 Issue 5 (2024) 399 doi: 10.36922/ijb.3396