Page 148 - IJB-9-3

International Journal of Bioprinting Bioprinting tissue-engineered bone-periosteum biphasic complex.

gradually from group (I) to group (V) (Figure 5C). To sum Bone healing depends on osteogenesis, osteoinduction,
up, the µCT results showed that using bone-periosteum and osteoconduction indispensably and simultaneously [27,28] .
biphasic complex to repair bone defects was better than In the process of bone healing, mesenchymal stem cells,
other control groups. including those in bone marrow and periosteum, provide
We also applied H&E, Masson’s trichrome and IHC bone progenitor cells that differentiate into osteoblasts;
staining of OCN to evaluate the maturity of the newly moreover, osteoinductive factors can accelerate this
[29]
formed bone. H&E staining showed that there was new process . In our study, we used rabBMSCs and rabPDSCs to
bone in the skull defects. With the increasing complexity simulate the cell components of bone phase and periosteum
of the scaffold, the fibrous tissue decreased relatively, phase within the complex structure. As shown in Figure 2,
while the mature bone tissue increased gradually rabBMSCs and rabPDSCs had the ability to differentiate
(Figure 5D). Masson’s trichrome staining showed that the into osteoblasts, adipocytes, and chondrocytes. In addition,
newly formed osteoid tissue was blue, and the boundaries co-culture of these two cells could significantly promote the
between the new bone and the edge of skull defect became osteogenic differentiation. In fact, the successful application
blurred in the composite repair groups (Figure 5E). of BMSCs in bone tissue engineering also lies in its ability
IHC staining of OCN could also be used to evaluate to secrete inductive factors, including vascular endothelial
[30]
osteogenesis. As shown in Figure 5F, both original cortical growth factor (VEGF) . Other studies have reported that
bone and newly formed bone expressed OCN. Based on the osteogenic and angiogenic factors of PDSCs increased
[31,32]
the quantitative results of collagen volume fraction and under mechanical stimulation . Furthermore, bone
mean density of OCN (%), the content of collagen and healing process also depends on a sufficient of blood
the expression of OCN from group I to group V were vessels. Studies have shown that avascularity is the main
[33]
increasing, respectively, indicating the improved quality factor in the pathogenesis of critical-sized bone defects .
of bone formation as evidenced by the formation of new Osteoinductive factors, including pro-inflammatory
bone, which was more mature (Figure S3). Taken together, cytokines, growth factors, and angiogenic factors, are
bone-periosteum biphasic complex is advantageous to transmitted to the fracture site through the vascular
[4]
bone repair and regeneration. system . Chen et al. reported that neovascularization
was also found after the co-culturing of bone marrow and
[15]
4. Discussion periosteal mesenchymal stem cells . Therefore, in this
study, we planned to evaluate the angiogenic factors within
To date, tissue-engineered bone has been used in the the complex, and even improved the construction of the
treatment of bone defects and other bone diseases, but there complex by introducing the vascular structural system in
[25]
were relatively few clinical reports . In order to improve the future. Due to the complexity of bone tissue structure,
the repair of bone defects, especially of the critical-sized the macro and micro structures of the composite need to
bone defects, studies on periosteum tissue engineering be further optimized, and the angiogenesis mechanism also
have been conducted. Various bionic artificial periosteum, needs to be further clarified to improve the performance of
including cell-sheet artificial periosteum, acellular scaffold tissue-engineered complex.
artificial periosteum and synthetic scaffold artificial
periosteum, have been developed. As a direct substitute Bone conductive scaffold is necessary to allow bone
of natural periosteum, the tissue-engineered periosteum to grow onto its surfaces . Combining the advantages
[34]
could significantly improve the efficiency of bone of synthetic polymers and ceramic materials, we mixed
[26]
transplantation and scaffold engineering . However, most PLLA and HA in a certain proportion and found an
studies separated the structure of bone and periosteum interesting phenomenon that the mechanical strength
and only constructed the tissue-engineered periosteum of different scaffolds did not increase with the increasing
structure. The highlight of our study is to treat the bone of the mixing proportion of materials (Figure 3A and
and periosteum structure as a whole, and attempt to B). During the printing process, when the molecular
improve bone regeneration in morphology and function at weight of PLLA and the mass fraction of HA in the mixed
the same time. On the one hand, we promoted osteogenic materials gradually increased, higher melting temperature
differentiation of stem cells through co-culture strategy, was required to make them printable. Polymer–ceramic
and then used bioprinting technology to build complex materials are printed by fused deposition modeling, and
structure. The results of our study showed that the 3D different melting temperatures often affect the mechanical
[35]
bioprinting tissue-engineered bone-periosteum biphasic properties of the composites . Therefore, we should not
complex had good mechanical strength and cell activity, only consider the biocompatibility of materials, but also
and also achieved good repair effect after being implanted think about the impact of printing mode on the properties
into the skull defect area of rabbit. of materials in the process of bioprinting, which would

Volume 9 Issue 3 (2023) 140 https://doi.org/10.18063/ijb.698