Page 343 - IJB-10-5

International Journal of Bioprinting Immunomodulatory bone repair by MBG/PCL

to the immunomodulation of osteogenesis. In the presence to expression of M2 phenotype genes (CD206, ARG).
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of an MP-conditioned medium, the 10MBG/PCL group However, MPs polarization to M2 phenotype was more
scaffolds upregulated M2 phenotypic genes, such as CD206 pronounced in F300 than in F800, possibly due to the fact
and Arg, and formed an immune microenvironment that with the same area, F300 has more fiber crossings,
conducive to osteogenesis, stimulating the upregulation of which facilitate MPs stretching and promote M2
osteogenic gene expression in BMSCs, and demonstrating polarization. P200 and P800 were comparatively weaker
excellent immune-coordinated osteogenic properties. in promoting MPs polarization than P500, possibly
Fiber diameter and pore size have a critical impact on because the scaffold performance and cell permeation
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the performance of the scaffolds. In terms of compressive were not optimally balanced. This may also be due to the
strength, coarser fibers increased the force area of the lack of optimal balance between scaffold performance and
scaffolds, and thus the overall performance of the scaffolds cell permeation. Meanwhile, the pore size of the scaffolds
had a greater effect on MPs polarization compared to
showed that the compressive capacity of the scaffolds fiber thickness, which is consistent with previous studies
increased with the coarsening of the fibers. The overall 61,62
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compressive capacity of the scaffolds increased with the on micro-sized scaffolds. The present study verified
coarsening of the fibers. Similarly, the widening of the that MPs polarization regulates osteogenesis and that
pore size reduces the force area of the scaffolds, which in the microenvironment enriched with M2-type cytokines
turn leads to the weakening of the compressive capacity. promotes bone regeneration. In the presence of an MP-
In terms of the porosity of the scaffolds, the amount of conditioned medium, F500 and P500 still possessed
optimal immune-coordinated osteogenic properties.
the same material filled in the unit volume determines In particular, the scaffold’s pore size that contributed
the porosity of the scaffolds, specifically reflecting the
associations among several parameters: (i) the coarser the to optimal osteogenic and immunomodulatory
fiber of the scaffolds, the lower the porosity; and (ii) the potential in this study was similar to that described in
63,64
larger the pore diameter, the higher the porosity. However, previous studies.
the difference in the hydrophilicity of the scaffolds could In summary, highly active MBG conferred higher
be due to the slight gap in MBG deposition during 3D compressive strength and more potent osteogenic activity
printing. In terms of promoting the proliferation of to the scaffolds. MBG significantly inhibited the expression
BMSCs, the finer the fiber, the higher the number of of pro-inflammatory genes (Tnfa and Il1b) and promoted
filament diameters per unit area, which can provide more the polarization of MPs to the M2 phenotype, creating
adhesion sites for cells. However, due to the relatively an optimal microenvironment for immune-coordinated
larger arc of F300, it is instead most unfavorable for early osteogenesis. Meanwhile, fiber diameter and pore size had
cell adhesion. Differences in cell proliferation were also a significant effect on the performance of the scaffolds,
reflected in osteogenic properties. In a comparison of pore and the scaffolds with both fiber diameter and pore size
sizes, the more filling material per unit area, the larger the of 500 μm had the best performance in regulating MPs
area to which cells could adhere. Nonetheless, the relatively and osteogenesis. These findings offer an insight on the
small pore size of P200 has a much lower porosity than size of the scaffolds when conducting subsequent studies.
that of P800, which is unfavorable for material exchange, In addition, the high specific surface area and pore size of
and therefore, BMSCs showed the lowest proliferative MBG prepared in this study as drug delivery systems are
activity. 57,58 In addition, in a study comparing the effects also aspects worthy of future research.
of scaffold pore size on osteogenesis, Swanson et al.
found that smaller pore sizes were detrimental to the 5. Conclusion
functional differentiation of osteogenic tissue phenotypes, In this study, we synthesized highly active MBG
and sufficiently large (>250 μm) pore sizes favored bone to enhance the overall compressive properties and
mineralization. In contrast, we found that F500 and P500 bioactivity of PCL scaffolds. Among them, 10MBG/
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possessed the most significant osteogenic potential. A PCL possessed the highest compressive strength (about
plausible reason for this disparity is that scaffolds with a twofold of pure PCL scaffolds) and the most excellent
fiber diameter of 500 μm and a pore size of 500 μm are in in vitro induced osteogenic activity. 10MBG/PCL
the optimal balance between physicochemical properties, scaffolds significantly inhibited the MPs M1 phenotypic
cell adhesion, and nutrient exchange. 60 polarization process and upregulated the M2 anti-
Upon the expression of inflammatory genes, thicker inflammatory phenotypic genes. Further exploration
fibers and larger pore sizes appear to be more favorable revealed that the physicochemical properties and
for extracellular matrix secretion and deposition, tending osteogenic activity of the scaffolds were affected by both

Volume 10 Issue 5 (2024) 335 doi: 10.36922/ijb.3551