Cellular channelopathy mediated by hypergravity: IL-6-mediated Nkcc1 activation and enhanced Trpm2 expression in rat atrium.

Although cardiac tissue is considered a target of gravitational force (g-force), the mechanism of hypergravity on the ion modulation or identification of ion transporters is still unknown. Thus, we determine the effect of hypergravity on a physical force-sensitive cytokine, IL-6 and its related channel activity to investigate rat cardiac function changes in response to accelerated g-force. Serum IL-6 levels and intracellular calcium levels of the right atrium were moderately increased under hypergravity stimulation (4g). IL-6 was involved in the modulation of sodium-potassium-chloride cotransporter (Nkcc) activity. Surprisingly, the right atrium under 4g revealed significantly enhanced Nkcc1 activity. The use of IL-6 on the NKCC1-overexpressed or native NKCC-expressing cells also showed enhanced NKCC1 activity. Hypergravity conditions were also involved in the oxidative stress activated Trpm2 channel and revealed an enhanced expression of the Trpm2 channel under 4g in the rat right atrium. In conclusion, hypergravity revealed that moderate increases in serum IL-6 and enhanced Nkcc1 activity was modulated by IL-6. In addition, enhanced Trpm2 channel expression could be involved in the increased intracellular calcium levels of the right atrium under hypergravitational force. We therefore address that enhanced physical force-sensitive cytokine and oxidative stress by the gravitational force mediate activation of the cotransporter involved in possibilities of edema and calcium loading in cardiac tissue.

Heart monitoring using left ventricle impedance and ventricular electrocardiography in left ventricular assist device patients.

BACKGROUND: Patients who develop critical arrhythmia during left ventricular assist device (LVAD) perfusion have a low survival rate. For diagnosis of unexpected heart abnormalities, new heart-monitoring methods are required for patients supported by LVAD perfusion. Ventricular electrocardiography using electrodes implanted in the ventricle to detect heart contractions is unsuitable if the heart is abnormal. Left ventricular impedance (LVI) is useful for monitoring heart movement but does not show abnormal action potential in the heart muscle. OBJECTIVES: To detect detailed abnormal heart conditions, we obtained ventricular electrocardiograms (v-ECGs) and LVI simultaneously in porcine models connected to LVADs. METHODS: In the porcine models, electrodes were set on the heart apex and ascending aorta for real-time measurements of v-ECGs and LVI. As the carrier current frequency of the LVI was adjusted to 30 kHz, it was easily derived from the original v-ECG signal by using a high-pass filter (cutoff: 10 kHz). In addition, v-ECGs with a frequency band of 0.1 - 120 Hz were easily derived using a low-pass filter. Simultaneous v-ECG and LVI data were compared to detect heart volume changes during the Q-T period when the heart contracted. A new real-time algorithm for comparison of v-ECGs and LVI determined whether the porcine heartbeats were normal or abnormal. Several abnormal heartbeats were detected using the LVADs operating in asynchronous mode, most of which were premature ventricle contractions (PVCs). To evaluate the accuracy of the new method, the results obtained were compared to normal ECG data and cardiac output measured simultaneously using commercial devices. RESULTS: The new method provided more accurate detection of abnormal heart movements. This method can be used for various heart diseases, even those in which the cardiac output is heavily affected by LVAD operation.

Evaluation of the Performance and Safety of a Newly Developed Intravenous Fluid Warmer.

To evaluate the performance and safety of a newly developed blood warmer (ThermoSens), we tested its heating capability under various conditions using isotonic saline and hemolysis analysis with swine blood. The following two in vitro tests were performed: (i) To investigate the performance of the device, the inflow and outflow temperatures were measured at various flow rates (30, 50, and 100 mL/min) using cold (5°C) and room temperature (20°C) isotonic saline (0.9%). Several parameters were measured including the highest temperature of the outlet, the time required to reach the highest temperature, and the temperature of the intravenous line. (ii) To investigate the safety of the device, a hemolysis test was performed using swine blood. We obtained 320 mL of whole blood from swine and refrigerated the blood for 35 days at 3°C. In order to replicate the clinical situation, blood flow by gravity and pressure (300 mm Hg) was used. Before and after the heating test, blood samples were obtained and a comparison was made between these samples. Hemoglobin, hematocrit, lactate dehydrogenase, and plasma hemoglobin were used for red blood cell (RBC) damage analysis. The highest outlet temperatures obtained using flow rates of 30, 50, and 100 mL/min were 39.10 ± 0.59, 39.25 ± 0.69, and 37.63 ± 1.03°C, respectively, with cold saline, and 39.40 ± 0.40, 39.66 ± 0.36, and 39.49 ± 0.49°C, respectively, with room temperature saline. Hemolysis tests showed no significant changes in hemoglobin, hematocrit, lactate dehydrogenase, or plasma hemoglobin (P > 0.05) between before and after heating for both gravity and pressure blood flow. The ThermoSens blood warmer warms isotonic saline effectively, reaching temperatures up to 36°C under various conditions. Hemolysis tests showed no RBC damage. Therefore, the newly developed ThermoSens has good heating performance and is safe for RBC products.

Trends in recurrence of primary spontaneous pneumothorax in young population after treatment for first episode based on a nationwide population data.

The aim of this study is to identifying post treatment recurrence rates in pneumothorax patients under 35 and without any comorbidities according to the treatment types, gender, and age categories based on nationwide population data. Clinical information of pneumothorax patients was extracted from the Korean National Health Insurance Service (NHIS) database between January 2002 and December 2020. Enrolled patients were categorized into two groups; (1) Group I, those who underwent conservative management including pain relief, oxygen therapy, and closed thoracostomy, and (2) Group II, surgical intervention. Recurrence rates were compared according to age, gender, and type of treatment. Surgical intervention was performed in 25.6% patients as first treatment. The overall recurrence rate was 20.3%. Male patients showed a higher 5-year recurrence rate than female (20.8% vs. 10.9%, p < 0.001). Those with conservative management showed lower 5-year recurrence rates than those with surgical treatment (7.9% vs. 23.7%, p < 0.001). The 5-year recurrence rates of patients aged 14≤, and < 20 was higher than other age groups (29.2% vs. 4.5 and 11.9%, p < 0.001). Surgical intervention, male gender and aged under 20 showed association with higher recurrence rates.

Analysis of pulsatile and nonpulsatile blood flow effects in different degrees of stenotic vasculature.

Vessel lumens that have been chronically narrowed by atherosclerosis should be increased in flow velocity and intrastenotic area pressure to maintain an equal flow. This might be followed by a decrease in hemodynamic energy, leading to a reduction of tissue perfusion. In this study, we compared hemodynamic energies according to degrees of stenotic vasculature between pulsatile flow and nonpulsatile flow. Cannuale with 25, 50, and 75% diameter stenosis (DS) were located at the outlet cannula. Using the Korea Hybrid ventricular assist device (KH-VAD) (pulsatile pump: group A) and Biopump (nonpulsatile pump: group B), constant flow of 2 L/min was maintained then real-time flow and velocity in the proximal and distal part of the stenotic cannula were measured. The hemodynamic energies of two groups were compared. At 75% DS, proximal energy equivalent pressure (EEP) delivered to the distal end was only 41.9% (group A) and 42.5% (group B). As the percent EEP fell below 10%, pulsatility disappeared from the 50% stenosis in group A. The surplus hemodynamic energy (SHE) of group B at all degrees of stenosis must have been 0, which was also the case of group A at 75% stenosis. This research evaluated the hemodynamic energy on various degrees of DS in both pulsatile and nonpulsatile flow with mock system. Using a pulsatile pump, pulsatility disappeared above 50% DS while hemodynamic energy was maintained. Therefore, our results suggest that pulsatile flow has a better effect than nonpulsatile flow in reserving hemodynamic energy after stenotic lesion.

Development of magnetic bearing system for a new third-generation blood pump.

A magnetic bearing system is a crucial component in a third-generation blood pump, particularly when we consider aspects such as system durability and blood compatibility. Many factors such as efficiency, occupying volume, hemodynamic stability in the flow path, mechanical stability, and stiffness need to be considered for the use of a magnetic bearing system in a third-generation blood pump, and a number of studies have been conducted to develop novel magnetic bearing design for better handling of these factors. In this study, we developed and evaluated a new magnetic bearing system having a motor for a new third-generation blood pump. This magnetic bearing system consists of a magnetic levitation compartment and a brushless direct current (BLDC) motor compartment. The active-control degree of freedom is one; this control is used for controlling the levitation in the axial direction. The levitation in the radial direction has a passive magnetic levitation structure. In order to improve the system efficiency, we separated the magnetic circuit for axial levitation by using a magnetic circuit for motor drive. Each magnetic circuit in the bearing system was designed to have a minimum gap by placing mechanical parts, such as the impeller blades, outside the circuit. A custom-designed noncontact gap sensor was used for minimizing the system volume. We fabricated an experimental prototype of the proposed magnetic bearing system and evaluated its performance by a control system using the Matlab xPC Target system. The noncontact gap sensor was an eddy current gap sensor with an outer diameter of 2.38 mm, thickness of 0.88 mm, and resolution of 5 µm. The BLDC motor compartment was designed to have an outer diameter of 20 mm, length of 28.75 mm, and power of 4.5 W. It exhibited a torque of 8.6 mNm at 5000 rpm. The entire bearing system, including the motor and the sensor, had an outer diameter of 22 mm and a length of 97 mm. The prototype exhibited sufficient levitation performance in the stop state and the rotation state with a gap of 0.2 mm between the rotor and the stator. The system had a steady position error of 0.01 µm in the stop state and a position error of 0.02 µm at a rotational speed of 5000 rpm; the current consumption rates were 0.15 A and 0.17 A in the stop state and the rotation state, respectively. In summary, we developed and evaluated a unique magnetic bearing system with an integrated motor. We believe that our design will be an important basis for the further development of the design of an entire third-generation blood pump system.

Sodium alginate hydrogel-based bioprinting using a novel multinozzle bioprinting system.

Bioprinting is a technology for constructing bioartificial tissue or organs of complex three-dimensional (3-D) structure with high-precision spatial shape forming ability in larger scale than conventional tissue engineering methods and simultaneous multiple components composition ability. It utilizes computer-controlled 3-D printer mechanism or solid free-form fabrication technologies. In this study, sodium alginate hydrogel that can be utilized for large-dimension tissue fabrication with its fast gelation property was studied regarding material-specific printing technique and printing parameters using a multinozzle bioprinting system developed by the authors. A sodium alginate solution was prepared with a concentration of 1% (wt/vol), and 1% CaCl(2) solution was used as cross-linker for the gelation. The two materials were loaded in each of two nozzles in the multinozzle bioprinting system that has a total of four nozzles of which the injection speed can be independently controlled. A 3-D alginate structure was fabricated through layer-by-layer printing. Each layer was formed through two phases of printing, the first phase with the sodium alginate solution and the second phase with the calcium chloride solution, in identical printing pattern and speed condition. The target patterns were lattice shaped with 2-mm spacing and two different line widths. The nozzle moving speed was 6.67 mm/s, and the injection head speed was 10 µm/s. For the two different line widths, two injection needles with inner diameters of 260 and 410 µm were used. The number of layers accumulated was five in this experiment. By varying the nozzle moving speed and the injection speed, various pattern widths could be achieved. The feasibility of sodium alginate hydrogel free-form formation by alternate printing of alginate solution and sodium chloride solution was confirmed in the developed multinozzle bioprinting system.

The effect of fluid viscosity on the hemodynamic energy changes during operation of the pulsatile ventricular assist device.

Blood viscosity during operation of ventricular assist device (VAD) can be changed by various conditions such as anemia. It is known generally that the blood viscosity can affect vascular resistance and lead to change of blood flow. In this study, the effect of fluid viscosity variation on hemodynamic energy was evaluated with a pulsatile blood pump in a mock system. Six solutions were used for experiments, which were composed of water and glycerin and had different viscosities of 2, 2.5, 3, 3.5, 4, and 4.5 cP. The hemodynamic energy at the outlet cannula was measured. Experimental results showed that mean pressure was increased in accordance with the viscosity increase. When the viscosity increased, the mean pressure was also increased. However, the flow was decreased according to the viscosity increase. Energy equivalent pressure value was increased according to the viscosity-induced pressure rise; however, surplus hemodynamic energy value did not show any apparent changing trend. The hemodynamic energy made by the pulsatile VAD was affected by the viscosity of the circulating fluid.

A durability study of a paracorporeal pulsatile electro-mechanical pneumatic biventricular assist device.

In 2002, the paracorporeal pulsatile electro-mechanical pneumatic ventricular assist device (VAD) began to be developed by the Korea Artificial Organ Center at Korea University under a Health & Medical Technology Research and Development program which finished in 2008. In vitro durability testing was conducted on the paracorporeal pulsatile pneumatic VAD to determine device durability and to evaluate device failures. The 1- and 2-year reliability of the paracorporeal pulsatile pneumatic VAD was shown to be 91.2% and 54.9%, respectively, with an 80% confidence level. Failure modes were analyzed using fault tree analysis, with customized software continuously acquiring data during the test period. After this period, 21 in vivo animal tests were done, with 14 cases of left atrium to left ventricle (LV) inflow cannulation (36Fr)/outflow grafting to descending aorta, and seven cases of apex cannulation of LV to descending aorta (12 mm). The longest postoperative day (182 days) in Korea was recently recorded in in vivo animal testing (bovine, 90 kg, male, 3.5-4.0 L/min flow rate, and 55 bpm).

Motility Improvement of Biomimetic Trachea Scaffold via Hybrid 3D-Bioprinting Technology.

A trachea has a structure capable of responding to various movements such as rotation of the neck and relaxation/contraction of the conduit due to the mucous membrane and cartilage tissue. However, current reported tubular implanting structures are difficult to impelement as replacements for original trachea movements. Therefore, in this study, we developed a new trachea implant with similar anatomical structure and mechanical properties to native tissue using 3D printing technology and evaluated its performance. A 250 µm-thick layer composed of polycaprolactone (PCL) nanofibers was fabricated on a rotating beam using electrospinning technology, and a scaffold with C-shaped cartilage grooves that mimics the human airway structure was printed to enable reconstruction of cartilage outside the airway. A cartilage type scaffold had a highest rotational angle (254°) among them and it showed up to 2.8 times compared to human average neck rotation angle. The cartilage type showed a maximum elongation of 8 times higher than that of the bellows type and it showed the elongation of 3 times higher than that of cylinder type. In cartilage type scaffold, gelatin hydrogel printed on the outside of the scaffold was remain 22.2% under the condition where no hydrogel was left in other type scaffolds. In addition, after 2 days of breathing test, the amount of gelatin remaining inside the scaffold was more than twice that of other scaffolds. This novel trachea scaffold with hydrogel inside and outside of the structure was well-preserved under external flow and is expected to be advantageous for soft tissue reconstruction of the trachea.

Development of a Multi-Layer Skin Substitute Using Human Hair Keratinic Extract-Based Hybrid 3D Printing.

Large-sized or deep skin wounds require skin substitutes for proper healing without scar formation. Therefore, multi-layered skin substitutes that mimic the genuine skin anatomy of multiple layers have attracted attention as suitable skin substitutes. In this study, a novel skin substitute was developed by combining the multi-layer skin tissue reconstruction method with the combination of a human-derived keratinic extract-loaded nano- and micro-fiber using electrospinning and a support structure using 3D printing. A polycaprolactone PCL/keratin electrospun scaffold showed better cell adhesion and proliferation than the keratin-free PCL scaffold, and keratinocytes and fibroblasts showed better survival, adhesion, and proliferation in the PCL/keratin electrospun nanofiber scaffold and microfiber scaffold, respectively. In a co-culture of keratinocytes and fibroblasts using a multi-layered scaffold, the two cells formed the epidermis and dermal layer on the PCL/keratin scaffold without territorial invasion. In the animal study, the PCL/keratin scaffold caused a faster regeneration of new skin without scar formation compared to the PCL scaffold. Our study showed that PCL/keratin scaffolds co-cultured with keratinocytes and fibroblasts promoted the regeneration of the epidermal and dermal layers in deep skin defects. Such finding suggests a new possibility for artificial skin production using multiple cells.

Comparison of Hemodynamic Energy between Expanded Polytetrafluoroethylene and Dacron Artificial Vessels.

BACKGROUND: Artificial grafts such as polyethylene terephthalate (Dacron) and expanded polytetrafluoroethylene (ePTFE) are used for various cardiovascular surgical procedures. The compliance properties of prosthetic grafts could affect hemodynamic energy, which can be measured using the energy-equivalent pressure (EEP) and surplus hemodynamic energy (SHE). We investigated changes in the hemodynamic energy of prosthetic grafts. METHODS: In a simulation test, the changes in EEP for these grafts were estimated using COMSOL MULTIPHYSICS. The Young modulus, Poisson ratio, and density were used to analyze the grafts' material properties, and pre- and post-graft EEP values were obtained by computing the product of the pressure and velocity. In an in vivo study, Dacron and ePTFE grafts were anastomosed in an end-to-side fashion on the descending thoracic aorta of swine. The pulsatile pump flow was fixed at 2 L/min. Real-time flow and pressure were measured at the distal part of each graft, while clamping the other graft and the descending thoracic aorta. EEP and SHE were calculated and compared. RESULTS: In the simulation test, the mean arterial pressure decreased by 39% for all simulations. EEP decreased by 42% for both grafts, and by around 55% for the native blood vessels after grafting. The in vivo test showed no significant difference between both grafts in terms of EEP and SHE. CONCLUSION: The post-graft hemodynamic energy was not different between the Dacron and ePTFE grafts. Artificial grafts are less compliant than native blood vessels; however, they can deliver pulsatile blood flow and hemodynamic energy without any significant energy loss.

Quantitative proteomic analysis of bile in extrahepatic cholangiocarcinoma patients.

Background and Aims: Extrahepatic cholangiocarcinoma (CCA) without liver-fluke is increasing. Multifactorial carcinogenesis makes it hard to find biomarkers related to CCA. Although there are a few studies of bile proteomics, these showed different protein profiles because of having heterogeneous groups of patients and different sampling methods. Our aim was to identify the specific bile proteins of extrahepatic CCA patients. Methods: We collected bile from 23 patients undergoing endoscopic nasobiliary drainage in Korea University Guro Hospital from May 2018 to January 2019. The CCA group included 18 patients diagnosed with extrahepatic CCA, and the control group included 5 patients with benign biliary conditions. We analyzed bile proteome using liquid chromatography mass spectrometry. We compared the relative abundance of various proteins in the CCA and control groups. Results: In all, we identified a total of 245 proteins in the bile of CCA and control patients. Increased top 14 proteins in CCA patients were immunoglobulin kappa light chain, apolipoprotein B, inter-alpha-trypsin inhibitor heavy chain H4, apolipoprotein E, Mucin 5B, inter-alpha-trypsin inhibitor heavy chain H1, apolipoprotein A-IV, intercellular adhesion molecule 1, complement C7, complement C5, apolipoprotein C-III, albumin, antithrombin-III, and apolipoprotein A-II. However, the significantly increased proteins in bile of CCA patients comparing with control patients were immunoglobulin kappa light chain, apolipoprotein E, albumin, apolipoprotein A-I, antithrombin-III, α1-antitrypsin, serotransferrin, immunoglobulin heavy constant mu, immunoglobulin J chain, complement C4-A, and complement C3 (p<0.05). Conclusions: In this study, we identified several proteins that were significantly increased in the bile of extrahepatic CCA. Further study is needed to validate them as potential tumor-associated proteins that may be potential biomarkers for CCA.

Development of a heat labile antibiotic eluting 3D printed scaffold for the treatment of osteomyelitis.

In general, osteomyelitis is treated with antibiotics, and in severe cases, the inflammatory bone tissue is removed and substituted with poly (methyl methacrylate) (PMMA) beads containing antibiotics. However, this treatment necessitates re-surgery to remove the inserted PMMA beads. Moreover, rifampicin, a primary heat-sensitive antibiotic used for osteomyelitis, is deemed unsuitable in this strategy. Three-dimensional (3D) printing technology has gained popularity, as it facilitates the production of a patient-customized implantable structure using various biodegradable biomaterials as well as controlling printing temperature. Therefore, in this study, we developed a rifampicin-loaded 3D scaffold for the treatment of osteomyelitis using 3D printing and polycaprolactone (PCL), a biodegradable polymer that can be printed at low temperatures. We successfully fabricated rifampicin-loaded PCL 3D scaffolds connected with all pores using computer-aided design and manufacturing (CAD/CAM) and printed them at a temperature of 60 °C to prevent the loss of the antibacterial activity of rifampicin. The growth inhibitory activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), the representative causative organisms of osteomyelitis, was confirmed. In addition, we optimized the rifampicin-loading capacity that causes no damage to the normal bone tissues in 3D scaffold with toxicity evaluation using human osteoblasts. The rifampicin-releasing 3D scaffold developed herein opens new possibilities of the patient-customized treatment of osteomyelitis.

Optimal pressure regulation of the pneumatic ventricular assist device with bellows-type driver.

The bellows-type pneumatic ventricular assist device (VAD) generates pneumatic pressure with compression of bellows instead of using an air compressor. This VAD driver has a small volume that is suitable for portable devices. However, improper pneumatic pressure setup can not only cause a lack of adequate flow generation, but also cause durability problems. In this study, a pneumatic pressure regulation system for optimal operation of the bellows-type VAD has been developed. The optimal pneumatic pressure conditions according to various afterload conditions aiming for optimal flow rates were investigated, and an afterload estimation algorithm was developed. The developed regulation system, which consists of a pressure sensor and a two-way solenoid valve, estimates the current afterload and regulates the pneumatic pressure to the optimal point for the current afterload condition. Experiments were performed in a mock circulation system. The afterload estimation algorithm showed sufficient performance with the standard deviation of error, 8.8 mm Hg. The flow rate could be stably regulated with a developed system under various afterload conditions. The shortcoming of a bellows-type VAD could be handled with this simple pressure regulation system.

Development of a closed air loop electropneumatic actuator for driving a pneumatic blood pump.

In this study, we developed a small pneumatic actuator that can be used as an extracorporeal biventricular assist device. It incorporated a bellows-transforming mechanism to generate blood-pumping pressure. The cylindrical unit is 88 +/- 0.1 mm high, has a diameter of 150 +/- 0.1 mm, and weighs 2.4 +/- 0.01 kg. In vitro, maximal outflow at the highest pumping rate (PR) exceeded 8 L/min when two 55 mL blood sacs were used under an afterload pressure of 100 mm Hg. At a pumping rate of 100 beats per minute (bpm), maximal hydraulic efficiency was 9.34% when the unit supported a single ventricle and 13.8% when it supported both ventricles. Moreover, pneumatic efficiencies of the actuator were 17.3% and 33.1% for LVAD and BVAD applications, respectively. The energy equivalent pressure was 62.78 approximately 208.10 mm Hg at a PR of 60 approximately 100 bpm, and the maximal value of dP/dt during systole was 1269 mm Hg/s at a PR of 60 bpm and 979 mm Hg/s at a PR of 100 bpm. When the unit was applied to 15 calves, it stably pumped 3 approximately 4 L/min of blood at 60 bpm, and no mechanical malfunction was experienced over 125 days of operation. We conclude that the presently developed pneumatic actuator can be utilized as an extracorporeal biventricular assist device.

Development of a 3D-Printed Drug-Eluting Stent for Treating Obstructive Salivary Gland Disease.

Most studies of obstructive salivary gland disease have reported only statistical aspects, surgical operations, and prescriptions and have simulated the phenomena occurring in the salivary glands and ductal tissues. However, no direct lesion treatments involving drug-eluting stents have been used to reduce salivary pooling induced by inflammation. In this study, a biodegradable polymer polycaprolactone (PCL)-based antibiotic-eluting stent was developed to treat recurrent obstructive salivary gland disease. The structure's diameter was designed after consideration of the human anatomical structure, and the data were processed in a form suitable for three-dimensional (3D) printing via computer-aided design and manufacturing. After the proper mixing conditions of the antibiotics and PCL were ensured, the optimized printing conditions were secured and the stent was successfully printed with the original lumen size diameter maintained. Amoxicillin and cefotaxime, the antibiotics loaded in this study, did not lose their original antimicrobial activity under the 3D printing process and were effectively released from the constructs for verification of the antimicrobial activity against the causative bacteria according to their concentrations. In addition, antibiotic-eluting stents fabricated in a mesh-like network form were proven stable and capable of sustained release, thereby demonstrating the possibility of treating recurrent obstruction salivary gland disease.

Simulated microgravity inhibits C2C12 myogenesis via phospholipase D2-induced Akt/FOXO1 regulation.

The skeletal muscle system has evolved to maintain body posture against a constant gravitational load. Mammalian target of rapamycin (mTOR) regulates the mechanically induced increase in the skeletal muscle mass. In the present study, we investigated mTOR pathway in C2C12 myoblasts in a model of mechanical unloading by creating a simulated microgravity (SM) using 3 D clinorotation. SM decreased the phosphorylation of Akt at Ser 473, which was mediated by mTOR complex 2 (mTORC2), in C2C12 myoblasts, leading to a decrease in the cell growth rate. Subsequently, SM inhibited C2C12 myogenesis in an Akt-dependent manner. In addition, SM increased the phospholipase D (PLD) activity by enhancing PLD2 expression, resulting in the dissociation of mSIN1 from the mTORC2, followed by decrease in the phosphorylation of Akt at Ser 473, and FOXO1 at Ser 256 in C2C12 myoblasts. Exposure to SM decreased the autophagic flux of C2C12 myoblasts by regulation of mRNA level of autophagic genes in a PLD2 and FOXO1-dependent manner, subsequently, resulting in a decrease in the C2C12 myogenesis. In conclusion, by analyzing the molecular signature of C2C12 myogenesis using SM, we suggest that the regulatory axis of the PLD2 induced Akt/FOXO1, is critical for C2C12 myogenesis.

Development of a flexible 3D printed scaffold with a cell-adhesive surface for artificial trachea.

Trachea stents are widely used to treat stenosis arising from various trachea injuries. However, they are associated with inflammation, re-stenosis, and tracheal obstruction. Seeking to overcome these problems, the development of an artificial trachea using tissue engineering has been explored. However, the artificial trachea did not mimic the natural rigidity and flexibility of the trachea and provide the micro-environment necessary for re-epithelialization. In this study, we developed a thermoplastic polyurethane (TPU) trachea scaffold that possesses a restoration characteristic, using flexible 3D printed patterns, and an improved cell attachment performance, utilizing electrospun fibers. With the aim of enhancing flexibility, we compared two geometric tubes, one with a straight pattern (SP) and the other with a wave pattern (WP). Simulation results showed that the WP scaffold was more flexible than the SP scaffold. A tensile expansion and torsion experiment demonstrated lower tensile strength and elastic modulus, and higher elongation ratio and rotation angle of the WP scaffold. Addition of the electrospun layers increased the tensile strength and elastic modulus and decreased the elongation ratio and rotation angle of both the SP and WP scaffolds. The same trend was observed regardless of electrospinning. However, polycaprolactone (PCL)-based scaffolds displayed lower elongation ratio and rotation angle in simulations and experiments. Although the cell attachment capacity of TPU-based electrospun WP scaffolds was less than 10% that of PCL-based scaffolds, the former showed good initial cell attachment performance and their cell numbers increased by more than three times within a week. The improved biomechanical performance and cell affinity of the TPU trachea scaffold could be exploited in patient-customized grafts for trachea reconstruction.

Simulated microgravity with floating environment promotes migration of non-small cell lung cancers.

A migration of cancer is one of the most important factors affecting cancer therapy. Particularly, a cancer migration study in a microgravity environment has gained attention as a tool for developing cancer therapy. In this study, we evaluated the proliferation and migration of two types (adenocarcinoma A549, squamous cell carcinoma H1703) of non-small cell lung cancers (NSCLC) in a floating environment with microgravity. When we measured proliferation of two NSCLCs in the microgravity (MG) and ground-gravity (CONT), although initial cell adhesion in MG was low, a normalized proliferation rate of A549 in MG was higher than that in CONT. Wound healing results of A549 and H1703 showed rapid recovery in MG; particularly, the migration rate of A549 was faster than that of H1703 both the normal and low proliferating conditions. Gene expression results showed that the microgravity accelerated the migration of NSCLC. Both A549 and H1703 in MG highly expressed the migration-related genes MMP-2, MMP-9, TIMP-1, and TIMP-2 compared to CONT at 24 h. Furthermore, analysis of MMP-2 protein synthesis revealed weaker metastatic performance of H1703 than that of A549. Therefore, the simulated microgravity based cancer culture environment will be a potential for migration and metastasis studies of lung cancers.