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Zheng, et al.
response will be triggered . It has been shown that if properties of 3D-bioprinted structures do not match with
[21]
the DNA content in the ECM is less than 50 ng/mg the natural tissue (PCL is stiffer than adipose tissue),
[22]
it does not trigger an immune response, but promotes this can lead to complication. Therefore, using a lower
tissue remodeling . Our results meet this criterion stiffness material or an appropriate strategy to match, the
[23]
and indicate the suitability for implantation. Another mechanical properties seem to be more suitable than using
challenge in decellularization is to retain as much of the PCL in the 3D-bioprinted structural design. Therefore,
ECM components as possible while effectively removing we mixed the dECM solution with the seaweed gelatin
the cells. Collagen fibers and proteoglycans are the major blend solution to match the mechanical properties of
components of the basement membrane , and their natural tissues. The hardness of the bioink is increased
[24]
presence, further, demonstrates that the decellularization by chemical cross-linking of the seaweed with divalent
process preserves the major components of the ECM. An cations such as Ca or Sr . Gelatin has high viscosity
2+
2+
intact basement membrane is important for tissue growth and easy freezing properties, and it is homologous to
and differentiation . Several studies have identified collagen . The dECM-based bioink conformed to the
[25]
[34]
more than 200 unique protein molecules present in typical collagen triple helix conformation and remained
the decellularized human vocal fold scaffolds . Our stable at physiological temperature. After printing, the
[26]
study also confirmed the presence of proteins in the mechanical properties of the 3D scaffolds were enhanced
decellularized ovarian tissue, which would guarantee by calcium ion cross-linking and maintained an open
the advantages of bioink 3D scaffolds based on dECMs. porous 3D structure, allowing nutrients transfer for tissue
Indeed, decellularized ovarian tissue has been shown remodeling.
to preserve 3D follicular structures and support follicle The biocompatibility of the dECM-based bioink
development in vivo [9-12] . must first be evaluated before assessing the role of 3D
However, the dECMs often lack tailored bioprinting structures in vivo, which is one of the great
microgeometry , resulting in cell distribution confined concerns in regenerative medicine . We observed that
[35]
[27]
to the surface of the material, with only a fraction of the inflammation elicited by the injected bioink gradually
cells infiltrating the internal regions . Furthermore, decreased with the passage of time. It shows the bioink
[28]
once implant the dECMs, the cells infiltrated, or seeded with an ability that performs an appropriate host response
on the dECMs are mainly sustained by the diffusion in the specific application. Meanwhile, the live/dead
of oxygen and nutrients before forming a vascular assay also shows that the bioink is non-cytotoxic. From
network . The above problems can be resolved by 3D these, we can conclude that the dECM-based bioink has
[29]
bioprinting technology. The 3D-bioprinted cell-loaded good biocompatibility.
scaffolds have an ideal spatial distribution. Thus, the In vivo testing of 3D scaffolds, 3D scaffolds
deposition of bioink can be precisely controlled (down encapsulating POCs, and hydrogels encapsulating POCs
to the micron) to form tissue ultrastructure . The 3D in the female castrated mouse model yielded some
[30]
scaffold retains its 3D ultrastructure before degradation. interesting results. Bioink in a normal subcutaneous
Besides provides the location of the substrate, it also mice induced a strong angiogenic response at 1 week
determines the spatial distribution of the loaded cells , after implantation and promoted the migration of
[31]
and then creates a suitable living environment for the inflammatory cells at 2 weeks, possibly due to proteolytic
cells. After the 3D-printed scaffold loses its physical stimulation of cell migration by the bioink or increased
support, the cells in the scaffold can build their own ECM availability of major angiogenic growth factors during
locally by secreting matrix proteins, enabling finer tissue bioink degradation . Neovascularization of implanted
[36]
remodeling. Furthermore, several studies have shown structures is an important indicator for in vivo studies.
that 3D scaffolds with 50–200 µm pores could not only There is considerable synergistic effect of POCs
promote cell proliferation, migration, and infiltration, and decellularized ovarian tissue on angiogenesis of
but also promote tissue regeneration and repair through implanted structures. As reported elsewhere, stromal
loading more cells [16,32] . The higher survival rate of POCs cells in POCs can promote angiogenesis [3,10,37] . However,
within the 3D scaffolds during first 2 weeks of in vitro neovascularization was also observed in the 3D scaffold
culture suggests that the use of porous 3D scaffolds with group. It has been reported that dECM has the potential
dECM-based bioink allows sufficient nutrient and oxygen capacity for angiogenesis . Thus, decellularized ovarian
[38]
delivery to the cells within the grafts, making long-term tissues may induce angiogenesis from the peri-host tissue
in vitro culture become possible. to the grafts. Macroscopically, in the 4-week study, the
As we all known, dECM has poor mechanical volume of the hydrogels encapsulating POCs decreased
properties. The previous studies have used more rapidly than those of the 3D scaffolds and the 3D
polycaprolactone (PCL) to assist adipose tissue in dECM scaffolds encapsulating POCs in the 4-week study. This
to print 3D scaffolds . However, if the mechanical suggests that the 3D-printed scaffolds have a relatively
[33]
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