1. Introduction
Long tracheal injury or stenosis have always been a difficult problem to
be solved in surgical reconstruction.[1, 2] When
the resections of the diseased tissue or stenosis and end-to-end
anastomosis can not achieve the clinical curative effects,
tissue-engineered trachea provides a new inspiration for tracheal
replacement therapy.[3] Scaffolds, seed cells and
growth factors are the three elements of tissue engineering. Scaffolds
provide the guarantee for the adhesion and growth of cells and the role
play of cytokines.[4] Therefore, appropriate
tracheal scaffolds are the key to the successful implementation of
tissue-engineered trachea, and the selection of scaffold materials has
become the important part.[5] Autologous tissue
has good vascularization and does not need immunosuppressive treatment,
but its long-term application is restricted by large surgical trauma,
limited scope of use and lack of epithelialization. After allogeneic
transplantation, there are serious immunological rejection and lack of
biological function.[6, 7] With the deepening of
the interdisciplinary concept, synthetic polymer materials have been
continuously developed and applied. Among them, PCL occupies a place in
the field of scaffold materials for its slow rate of biodegradation and
perfect biomechanical properties.[8] In previous
study, we have successfully manufactured tracheal graft using PCL as the
material by 3D printing technology. Biomechanical and biocompatible test
proved that 3D printed tracheal graft was equipped with favorable
cellular biocompatibility and biomechanical
properties.[9] However, the surface hydrophobicity
of PCL greatly affects cell adhesion. Therefore, we performed
nano-silicon dioxide surface modification to make the surface smoother
and significantly improve the cytotropism. In addition, the porous
structure of 200 μm made it more conducive to cell adhesion and
proliferation.[10] Even so, PCL scaffolds are
still difficult to load seed cells and cytokines, and thus cannot
achieve subsequent cartilaginification, vascularization and
epithelization.
In recent years, hydrogels have been widely used as carriers of cells
and growth factors, and their 3D network structure is conducive to the
transport of seed cells, growth factors, nutrients and the discharge of
metabolic wastes.[11] Silk fibroin (SF) is a
natural biomaterial with good biocompatibility, excellent mechanical
properties, and tunable degradability.[12, 13]Silk Fibroin Methacryloyl is the
product of SF, which was modified by methylacrylylation. Its rapid
solubilization in water allows SilMA to be photocurable as a hydrogel.
KGN is a kind of small-molecule drug, which was discovered in 2012 for
the first time.[14] It could selectively stimulate
chondrogenic differentiation of endogenous bone marrow mesenchymal stem
cells.[15]
Here, the purpose of this study was to prepare 3D printed hybrid
tracheal graft fabricated by PCL coated with SilMA, in which BMSCs, KGN
and epithelia were co-cultured, and to select the appropriate
concentration. So that, the effect on cell behavior can be explored.
BMSCs were isolated from tibial plateau and
epithelia
were cultured from autologous tracheal mucosal epithelium, which
was
extracted by biopsy forceps in endoscope. Biocompatibility and
mechanical properties were evaluated by in vitro experiments. What’s
more, the role of epithelization and cartilaginization of this hybrid
tracheal graft were evaluated via in vivo window-shape defect repair(Figure 1) .
This
study provides the theoretic and experimental basis for further research
and practice in tracheal reconstruction.