Dong-Heon Ha

Biomimetic 3D tissue printing for soft tissue regeneration

Engineered adipose tissue constructs that are capable of reconstructing soft tissue with adequate volume would be worthwhile in plastic and reconstructive surgery. Tissue printing offers the possibility of fabricating anatomically relevant tissue constructs by delivering suitable matrix materials and living cells. Here, we devise a biomimetic approach for printing adipose tissue constructs employing decellularized adipose tissue (DAT) matrix bioink encapsulating human adipose tissue-derived mesenchymal stem cells (hASCs). We designed and printed precisely-defined and flexible dome-shaped structures with engineered porosity using DAT bioink that facilitated high cell viability over 2 weeks and induced expression of standard adipogenic genes without any supplemented adipogenic factors. The printed DAT constructs expressed adipogenic genes more intensely than did non-printed DAT gel. To evaluate the efficacy of our printed tissue constructs for adipose tissue regeneration, we implanted them subcutaneously in mice. The constructs did not induce chronic inflammation or cytotoxicity postimplantation, but supported positive tissue infiltration, constructive tissue remodeling, and adipose tissue formation. This study demonstrates that direct printing of spatially on-demand customized tissue analogs is a promising approach to soft tissue regeneration.

Development of Liver Decellularized Extracellular Matrix Bioink for Three-Dimensional Cell Printing-Based Liver Tissue Engineering

The liver is an important organ and plays major roles in the human body. Because of the lack of liver donors after liver failure and drug-induced liver injury, much research has focused on developing liver alternatives and liver in vitro models for transplantation and drug screening. Although numerous studies have been conducted, these systems cannot faithfully mimic the complexity of the liver. Recently, three-dimensional (3D) cell printing technology has emerged as one of a number of innovative technologies that may help to overcome this limitation. However, a great deal of work in developing biomaterials optimized for 3D cell printing-based liver tissue engineering remains. Therefore, in this work, we developed a liver decellularized extracellular matrix (dECM) bioink for 3D cell printing applications and evaluated its characteristics. The liver dECM bioink retained the major ECM components of the liver while cellular components were effectively removed and further exhibited suitable and adjustable properties for 3D cell printing. We further studied printing parameters with the liver dECM bioink to verify the versatility and fidelity of the printing process. Stem cell differentiation and HepG2 cell functions in the liver dECM bioink in comparison to those of commercial collagen bioink were also evaluated, and the liver dECM bioink was found to induce stem cell differentiation and enhance HepG2 cell function. Consequently, the results demonstrate that the proposed liver dECM bioink is a promising bioink candidate for 3D cell printing-based liver tissue engineering.

Effects of micro-patterns in three-dimensional scaffolds for tissue engineering applications

Micro-patterns, typically fabricated by microelectromechanical systems technologies, have been applied to two-dimensional (2D) environments for tissue engineering applications. Nano-stereolithography, a unique solid freeform technology, is now available to apply micron-sized patterns to three-dimensional (3D) scaffolds in a direct process. Many studies have reported that the micro-patterns, which are smaller than cell sizes, have effects on cell behavior. Thus, we considered that a scaffold incorporating micro-patterns might be more appropriate for tissue engineering applications than non-patterned scaffolds. In this study, we fabricated 3D scaffolds with micro-patterns (micro-pillar and micro-ridge types) on each layer using an NSTL system. In an in vitro study using pre-osteoblast cells, we observed the effects of micro-patterns on cellular behaviors, such as proliferation, adhesion and osteogenic differentiation. The scaffolds with micro-patterns showed significantly improved cell adhesion ability versus a scaffold with no patterning. We also observed that the expression of osteogenic markers, such as ALP and Runx2, increased significantly in scaffolds with micro-pillar and micro-ridge patterns compared with non-patterned scaffolds. Thus, it could be a promising strategy for effective tissue engineering applications to add such micro-patterns on 3D scaffolds.

Robust tissue growth and angiogenesis in large-sized scaffold by reducing H2O2-mediated oxidative stress

The implantation of cell-seeded large-sized scaffold often results in insufficient tissue regeneration, which is still a challenge for successful grafting. Excess hydrogen peroxide (H2O2) released by cells propagates oxidative stress, which is the primary cause of tissue injury leading to failure in tissue regeneration. Hence, preventing tissue from oxidative damage becomes imperative. For the first time, we entrapped catalase, an antioxidant in a scaffold as a novel approach in bioengineering to prevent tissue from H2O2-induced damage. The gel prepared from the mixture of decellularized adipose tissue and high viscous sodium alginate was used to entrap the catalase, and was coated to 3D polycaprolactone porous scaffolds. This study showed that our 3D design would regulate the release of catalase in a sustained and efficient manner protecting human turbinate mesenchymal stem cells cultured in 2D/3D in vitro oxidative microenvironment provided by H2O2, and supporting their robust growth. Interestingly, in vivo study revealed that our design was successful in tissue engineering by both an increase in tissue growth (≥45%) throughout the large-sized scaffold with substantial reduction in inflammation (≥40%), and an increase in the induction of angiogenesis (≥40%). This novel design, therefore, would be highly applicable for successful grafting to replace a damaged tissue in future.

Redefining the Septal L-Strut to Prevent Collapse.

During septorhinoplasty, septal cartilage is frequently resected for various purposes but the L-strut is preserved. Numerous materials are inserted into the nasal dorsum during dorsal augmenation rhinoplasty without considering nasal structural safety. This study used a finite element method (FEM) to redefine the septal L-strut, to prevent collapse as pressure moved from the rhinion to the supratip breakpoint on the nasal dorsum and as the contact percentage between the caudal L-strut and the maxillary crest changed. We designed a 1-cm-wide L-strut model based on computed tomography data. At least 45% of the width of the L-strut in the inferior portion of the caudal strut must be preserved during septoplasty to stabilize the septum. In augmentation rhinoplasty, the caudal L-strut must either be preserved perfectly or reinforced to prevent collapse or distortion of the L-strut. The dorsal augmentation material must be fixed in an augmentation pocket to prevent movement of graft material toward the supratip breakpoint, which can disrupt the L-strut. We conducted a numerical analysis using a FEM to predict tissue/organ behavior and to help clinicians understand the reasons for target tissue/organ collapse and deformation.

Smart Microbubble Eluting Theranostic Stent for Noninvasive Ultrasound Imaging and Prevention of Restenosis

A pH-responsive microbubble-eluting theranostic stent is developed for real-time ultrasound imaging of stent implanted blood vessels and dissolution of fat-rich plaques to prevent the blocking of blood vessels in rats. This smart theranostic stent can be effectively applied to facilitate noninvasive monitoring and prevent restenosis after stent implantation.

Correction: Redefining the Septal L-Strut in Septal Surgery

The third author’s name is incorrect. The correct name is: Dong-Heon Ha. The correct citation is: Lee J-S, Lee DC, Ha D-H, Kim SW, Cho D-W (2015) Redefining the Septal L-Strut in Septal Surgery. PLoS ONE 10(3): e0119996. doi:10.1371/journal.pone.0119996

Nasal Reconstruction Using a Customized Three-Dimensional-Printed Stent for Congenital Arhinia: Three-Year Follow-up: Nasal Reconstruction Using a 3D-Printed Stent

A male Mongolian child with a complete congenital absence of both nose and nasal passage had a poor survival prognosis due to respiratory distress. To enable his survival, a new nose capable of conferring respiratory function was constructed. Following reconstructive surgery, an absence of mucoepithelium in the nasal passage can lead to rhinostenosis. To avoid this complication, a custom‐made nasal silicone stent was created using three‐dimensional (3D) printing technology in conjunction with the patients computed tomography data. The stent was implanted for 2 months to maintain the shape and size of the nasal passage. At 2 months after stent implantation, the mucoepithelium tissue in the passage had successfully regenerated with no immune reaction. Three years after stent removal, respiratory function, nasal passage structure, and external nose shape were maintained without additional medical care. These results indicate the successful nasal reconstruction in an arhinia patient using a customized, 3D‐printed nasal stent. Laryngoscope, 129:582–585, 2019

Development of a functional airway-on-a-chip by 3D cell printing

We used 3D cell printing to emulate an airway coupled with a naturally-derived blood vessel network in vitro. Decellularized extracellular matrix bioink derived from porcine tracheal mucosa (tmdECM) was used to encapsulate and print endothelial cells and fibroblasts within a designated polycarprolactone (PCL) frame. Providing a niche that emulates conditions in vivo, tmdECM gradually drives endothelial re-orientation, which leads to the formation of a lumen and blood vessel network. A fully-differentiated in vitro airway model was assembled with the printed vascular platform, and collectively reproduced a functional interface between the airway epithelium and the vascular network. The model presented respiratory symptoms including asthmatic airway inflammation and allergen-induced asthma exacerbation in physiological context. Because of the adaptable and automated nature of direct 3D cell printing, we expect that this will have relevance in vivo and high reproducibility for production of high-content platforms for preclinical trials in biomedical research.

Amnion-Analogous Medical Device for Fetal Membrane Healing: A Preclinical Long-Term Study

Although recent invasive fetal surgeries have improved fetal outcomes, fetal membrane rupture remains a major complication, leading to premature delivery, thus undermining the complete benefits of such procedures. A biocompatible amnion-analogous medical device (AMED) consisting of polycaprolactone framework and decellularized amniotic membrane (dAM)-derived hydrogel for restoration of amniotic membrane defect is developed using 3D printing technology. Its efficacy on healing iatrogenic fetal membrane defects in vitro is evaluated, showing that the dAM gel contains migratory and proliferative properties. The fetoscope feasibility of the developed AMED is assessed using a pregnant swine model. All animals had successfully recovered from anesthesia and the fetoscopic procedure and maintained a healthy condition until the end of the pregnancy. AMED exhibits superior surgical handling characteristics and is easy to manufacture, nonimmunogenic, biocompatible, and suitable for storage and transport for off-the-shelf use; hence, it can be used in successfully sealing defect sites, thus improving the preservation of the amniotic fluid, which in turn improves fetal survival and development.