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3D Printing Osteochondral Scaffold
A

B

C

D

Figure 7. The bilayered constructs facilitated the regeneration of osteochondral tissues in vivo (n = 6). The grafts were sampled 3 months
after operation. (A) Gross observations of defect repair at 3 months for the control group, pristine-bilayered construct group, and GF-
bilayered construct group (scale bar: 4 mm). (B) Hematoxylin and eosin (H & E) staining of repaired cartilage at 3 months (N, normal
cartilage; R, repair cartilage; blue arrows, typical cartilage lacunae structures; black arrows, the repair boundary of the cartilage surface;
scale bar: 200 μm). (C) Masson staining of repaired cartilage at 3 months (scale bar: 200 μm). (D) Safranin-O/fast green staining of repaired
cartilage at 3 months (scale bar: 200 μm).

Coll II immunohistochemical staining demonstrated significant differences (P < 0.05). The collagen content
more intense staining in the GB group compared to other of neocartilage was 72.95 ± 5.82 μg/mg in control
two groups (Figure 8A). A high expression of Coll II group, 106.50 ± 7.84 μg/mg in PB group, and 115.50 ±
surrounding the chondrocytes could be observed in the 11.28 μg/mg in GB group. The collagen content of GB
neocartilage of GB group. Neovascularization, trabecula group and PB group was significantly higher than that
structure (Figure 8B and C), and higher intensity of of control group. There was no significant difference
staining of OCN (Figure 8D) could be observed in between collagen content in the GB group and PB
the neo-bone of GB group. While in the control group, group.
incompletely calcified cancellous bone could be found in In the current study, we demonstrated that a 3D
the bone layer. Furthermore, we performed a histologic bioprinted bilayered scaffolds can be used as a controlled
score according to the ICRS Visual Histological released system, which leads to the reconstruction of
Assessment Scale (Figure S2C). The histologic score osteochondral tissue. Each layer of bilayered scaffolds
was significantly higher in the GB group than in the PB had a suitable mechanical strength and degradation rate.
and control groups. Furthermore, the scaffolds encapsulating TGF-β1 and
Regenerated cartilage was further investigated by BMP-2 can act as a controlled release system and promote
quantifying sGAG and collagen contents. The sGAG osteochondral regeneration. Although the mechanical
content of neocartilage was 9.36 ± 1.279 μg/mg in strength of the bilayered scaffolds needs to be further
control group, 16.03 ± 0.784 μg/mg in PB group, and enhanced, this method does provide a novel strategy for
24.83 ± 1.866μg/mg in GB group, with statistically osteochondral regeneration.

94 International Journal of Bioprinting (2021)–Volume 7, Issue 4