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International Journal of Bioprinting 3D-printed skin substitute accelerates wound healing in vivo

Fourteen days after operation, Masson staining results disadvantages, especially when skin defect involves a large
showed that blue-stained collagen fibers were observed in area, it is very difficult to obtain autologous skin tissue
all four groups, indicating that collagen fibers proliferated for repair . Tissue-engineered skin substitutes, first
[11]
to fill dermal defects. The collagen fibers in Groups A started with biodegradable matrix materials that mimic
and C were irregular in shape, with coarse, deep-stained the dermis as scaffold and then constructed with live cells,
collagen fibers and fine, light-stained collagen fibers has shown great potential in wound healing. dECM from
scattered and disordered in arrangement. In Group D, the different tissue or organ has been a promising biomaterial
layer of collagen was thin, and the collagen fibers were fine, for repairing tissue defect due to its biomimetic properties
small and arranged sparsely. In Group B, the thickness of that promote cell-cell and cell-matrix interactions and
the layer of collagen was moderate, the collagen deposition tissue regeneration . Acellular dermal matrix, usually
[12]
was dense, and the arrangement was orderly and uniform. used to cover skin defect and promote wound healing,
The area percentage of collagen in Group B was higher is accompanied by many shortcomings, such as limited
than that of the other three groups, and it was statistically sources, immune response due to xenogeneic or allogeneic
significant compared to that of Groups C and D, which origin, small pore size and low porosity, and additional cell
showed that 3D-bioprinted skin substitute could improve seeding and culture process, resulting in prolonged healing
the production and arrangement of dermal collagen time and inaccurate control of cell distribution and density
(Figure 5B and C). within scaffold. 3D bioprinting, emerging from the course
of tissue engineering technology development, is a new
3.4.3. 3D-bioprinted skin substitute promotes type of additive manufacturing technology. Computer-
angiogenesis of wound aided layered printing of cells, biological materials and
We performed CD31 immunohistochemistry staining to bioactive factors can form biologically active 3D tissue
assess the angiogenesis of wound. On days 7 (Figure 6A) constructs with precise size and shape, high resolution and
and 14 (Figure 6B), observation of capillaries in Group B uniform cell distribution, which has great research value
revealed that the 3D-bioprinted skin substitute promoted and application prospects in skin tissue engineering. It is
angiogenesis. Quantification of capillary number was crucial to select the ideal combination of biomaterials and
performed, and capillary number was significantly higher seed cells for skin tissue bioprinting. The cells commonly
in Group B than that in Groups A, C, and D on day used in skin tissue engineering are keratinocytes and
7 (Figure 6C), and capillary number in Group B was still fibroblasts. Mesenchymal stem cells exhibit good
significantly higher than that in Groups A and D on day proliferation and differentiation potential, representing a
14 (Figure 6D), but no statistical difference was observed new cell type for bioprinting cell-loaded scaffolds.
between Groups B and C on day 14. As liposuction is getting more common, adipose tissue
3.4.4. 3D-bioprinted skin substitute promotes blood is becoming readily available in clinical practice. Adipose
perfusion of the wound tissue dECM, rich in multiple protein components
and various bioactive factors, could facilitate hADSCs
The blood flow of the wound was assessed using a laser accumulation, proliferation, differentiation and paracrine
Doppler perfusion imaging. On day 7, the blood flow function, and in turn stimulate angiogenesis and tissue
of wound in the regions of interest (refers to the white repair [3,4] . It has shown tremendous potential as a biomaterial
circle) in Group B was higher than that in the other three in tissue engineering and regeneration medicine, such
groups and was significantly higher than that in Group A. as adipose or cartilage tissue engineering. DAPI staining
No statistical difference was observed among Groups B, and DNA quantitative analysis proved that the cellular
C, and D (Figure 7A). On day 14, the blood flow of the component (primarily DNA) had been removed, and the
wound in Group B was higher than that in the other three ECM components were preserved so that dECM would
groups and was significantly higher than that in Group D. not induce immune and inflammatory response. A series
No statistical difference was observed among Groups A, B, of solubilization, neutralization and ion concentration
and C (Figure 7B). adjustment helped dECM pre-gel simulate the

4. Discussion physiological environment. Due to increased hydrophobic
interactions between chains, dECM pre-gel transformed
Skin is most vulnerable to various injuries, such as burns from sol to gel with temperature increasing [13,14] . Adipose
or trauma. Wound healing after skin defect has always tissue dECM provides a favorable microenvironment for
been a big challenge for healthcare workers and it has hADSCs, allows cell adhesion, survival and proliferation,
become a growing burden for patients worldwide. The and enhances paracrine activity and regenerative potential
current methods in clinical practice are limited by many of hADSCs to accelerate wound healing. Although dECM

Volume 9 Issue 2 (2023) 401 https://doi.org/10.18063/ijb.v9i2.674