A novel automated cell-seeding device for tissue engineering of tubular scaffolds: design and functional validation

Differentiation of Adipose-Derived Stem Cells into Vascular Smooth Muscle Cells for Tissue Engineering Applications

Synthetic grafts have been developed for vascular bypass surgery, however, the risks of thrombosis and neointimal hyperplasia still limit their use. Tissue engineering with the use of adipose-derived stem cells (ASCs) has shown promise in addressing these limitations. Here we further characterized and optimized the ASC differentiation into smooth muscle cells (VSMCs) induced by TGF-β and BMP-4. TGF-β and BMP-4 induced a time-dependent expression of SMC markers in ASC. Shortening the differentiation period from 7 to 4 days did not impair the functional property of contraction in these cells. Stability of the process was demonstrated by switching cells to regular growth media for up to 14 days. The role of IGFBP7, a downstream effector of TGF-β, was also examined. Finally, topographic and surface patterning of a substrate is recognized as a powerful tool for regulating cell differentiation. Here we provide evidence that a non-woven PET structure does not affect the differentiation of ASC. Taken together, our results indicate that VSMCs differentiated from ASCs are a suitable candidate to populate a PET-based vascular scaffolds. By employing an autologous source of cells we provide a novel alternative to address major issues that reduces long-term patency of currently vascular grafts.

The preparation of cell-containing microbubble scaffolds to mimic alveoli structure as a 3D drug-screening system for lung cancer

Cancer is the leading cause of mortality worldwide, and lung cancer is the most malignant. However, the high failure rate in oncology drug development from in vitro studies to in vivo preclinical models indicates that the modern methods of evaluating drug efficacies in vitro are not reliable. Traditional 2D cell culture has proved inadequate to mimic real physiological conditions. Current 3D cell culture methods do not represent the delicate structure of lung alveoli. To mimic lung alveoli structure, a cell-containing enzyme-crosslinked gelatin microbubble scaffold was produced by mixing surfactant-containing gelatin solution with microbial transglutaminase (mTGase)-mixed A549 cell suspension in a four-channel flow-focusing microfluidic device. With uniform pore size of about 100 μm in diameter, this gelatin microbubble scaffold resembled the lung alveoli in structure and in mechanical properties with good biocompatibility. Effective gemcitabine concentration required to induce cell death in microbubble scaffolds was significantly higher than in 2D culture together with a longer treatment time. Cell death mechanisms were confirmed to be gemcitabine-induced cell apoptosis through Western blotting and real-time polymerase chain reaction. H&E staining and TUNEL assay showed rounded cells with DNA damage in drug-treated scaffolds. Taken together, the cell-containing microbubble scaffolds successfully mimicked lung alveoli in structure and cellular responses after gemcitabine treatment were similar to clinical regimen of treating lung carcinoma. The microbubble scaffold is promising to facilitate anticancer drug discovery by providing more accurate preclinical predictions.

Fabrication and Characterization of Electrospun Bi-Hybrid PU/PET Scaffolds for Small-Diameter Vascular Grafts Applications

In spite of advances have been made during the past decades, the problems associated with small-diameter vascular grafts, including low patency and compliance mismatch and in consequence of that thrombosis, aneurysm and intimal hyperplasia are still challenges. To address these problems, net polyurethane (PU) and poly (ethylene terephthalate) (PET) polymers and hybrid PU/PET were electrospun to create three different types of small-diameter vascular scaffolds due to their unique physicochemical characteristics: PU, PET, and novel hybrid PU/PET scaffolds. The results show that the PU and PET composite can improve the mechanical properties of the tissue-engineered vascular scaffolds in the range of the native vessels where the non-cytotoxicity characteristic of these well-known polymers is still immutable. The compliance and stiffness factor of the fabricated hybrid scaffolds were 4.468 ± 0.177 and 22.718 ± 0.896%/0.01 mmHg, respectively, which were significantly different with that of the net PU and PET electrospun scaffolds. Other properties such as ultimate tensile stress (UTS) (3.56 ± 1.21 MPa) were also in good accordance with the native vessels. Furthermore, FT-IR analysis testified the presence of both PU and PET in the hybrid scaffolds. Overall, we were able to fabricate a hybrid scaffold as a small-diameter vascular graft that mechanically matched the gold standard of blood vessel substitution.

Engineering bone regeneration with novel cell-laden hydrogel microfiber-injectable calcium phosphate scaffold

Cell-based tissue engineering is promising to create living functional tissues for bone regeneration. The implanted cells should be evenly distributed in the scaffold, be fast-released to the defect and maintain high viability in order to actively participate in the regenerative process. Herein, we report an injectable calcium phosphate cement (CPC) scaffold containing cell-encapsulating hydrogel microfibers with desirable degradability that could deliver cells in a timely manner and maintain cell viability. Microfibers were synthesized using partially-oxidized alginate with various concentrations (0-0.8%) of fibrinogen to optimize the degradation rate of the alginate-fibrin microfibers (Alg-Fb MF). A fibrin concentration of 0.4% in Alg-Fb MF resulted in the greatest enhancement of cell migration, release and proliferation. Interestingly, a significant amount of cell-cell contact along the long-axis of the microfibers was established in Alg-0.4%Fb MF as early as day 2. The injectable tissue engineered construct for bone reconstruct was fabricated by mixing the fast-degradable Alg-0.4%Fb MF with CPC paste at 1:1 volume ratio. In vitro study showed that cells re-collected from the construct maintained good viability and osteogenic potentials. In vivo study demonstrated that the hBMSC-encapsulated CPC-MF tissue engineered construct displayed a robust capacity for bone regeneration. At 12weeks after implantation, osseous bridge in the rat mandibular defect was observed in CPC-MF-hBMSCs group with a new bone area fraction of (42.1±7.8) % in the defects, which was >3-fold that of the control group. The novel tissue-engineered construct presents an excellent prospect for a wide range of dental, craniofacial and orthopedic applications.