Dense Text-to-Image Generation with Attention Modulation

Existing text-to-image diffusion models struggle to synthesize realistic images given dense captions, where each text prompt provides a detailed description for a specific image region. To address this, we propose DenseDiffusion, a training-free method that adapts a pre-trained text-to-image model to handle such dense captions while offering control over the scene layout. We first analyze the relationship between generated images' layouts and the pre-trained model's intermediate attention maps. Next, we develop an attention modulation method that guides objects to appear in specific regions according to layout guidance. Without requiring additional fine-tuning or datasets, we improve image generation performance given dense captions regarding both automatic and human evaluation scores. In addition, we achieve similar-quality visual results with models specifically trained with layout conditions.Comment: Accepted by ICCV2023. Code and data are available at https://github.com/naver-ai/DenseDiffusio

Association between Body Mass Index and Gastric Cancer Risk According to Effect Modification by Helicobacter pylori Infection

Purpose Few studies investigated roles of body mass index (BMI) on gastric cancer (GC) risk according to Helicobacter pylori infection status. This study was conducted to evaluate associations between BMI and GC risk with consideration of H. pylori infection information. Materials and Methods We performed a case-cohort study (n=2,458) that consists of a subcohort (n=2,193 including 67 GC incident cases) randomly selected from the Korean Multicenter Cancer Cohort (KMCC) and 265 incident GC cases outside of the subcohort. H. pylori infection was assessed using an immunoblot assay. GC risk according to BMI was evaluated by calculating hazard ratios (HRs) and their 95% confidence intervals (95% CIs) using weighted Cox hazard regression model. Results Increased GC risk in lower BMI group (= 25 kg/m(2)) showed non-significantly increased GC risk (HR, 10.82; 95% CI, 1.25 to 93.60 and HR, 11.33; 95% CI, 1.13 to 113.66, respectively). However, these U-shaped associations between BMI and GC risk were not observed in the group who had ever been infected by H. pylori. Conclusion This study suggests the U-shaped associations between BMI and GC risk, especially in subjects who had never been infected by H. pylori.Peer reviewe

Diacetyl odor shortens longevity conferred by food deprivation in C. elegans via downregulation of DAF-16/FOXO

Dietary restriction extends lifespan in various organisms by reducing the levels of both nutrients and non-nutritional food-derived cues. However, the identity of specific food-derived chemical cues that alter lifespan remains unclear. Here, we identified several volatile attractants that decreased the longevity on food deprivation, a dietary restriction regimen in Caenorhabditis elegans. In particular, we found that the odor of diacetyl decreased the activity of DAF-16/FOXO, a life-extending transcription factor acting downstream of insulin/IGF-1 signaling. We then demonstrated that the odor of lactic acid bacteria, which produce diacetyl, reduced the nuclear accumulation of DAF-16/FOXO. Unexpectedly, we showed that the odor of diacetyl decreased longevity independently of two established diacetyl receptors, ODR-10 and SRI-14, in sensory neurons. Thus, diacetyl, a food-derived odorant, may shorten food deprivation-induced longevity via decreasing the activity of DAF-16/FOXO through binding to unidentified receptors. © 2020 The Authors. Aging Cell published by the Anatomical Society and John Wiley & Sons Ltd.1

Cell Culture Insert-Mountable Lung-on-a-chip for the Inkjet Bioprinted Alveolar Model

Organ-on-a-chip is an emerging technology that can biomimic the dynamic microenvironment and key functions of organ units. Although various organ-on-chips have been developed through the efforts of numerous researchers, most of them have closed structures with a porous membrane in the middle. Injection of cell suspension is generally used to seed cells inside a closed structured chip, but controlling the number of cells or distributing cells uniformly is challenging. As a way to overcome these limitations, we constructed an open-structured chip in a form that can integrate with commercial cell culture inserts. The fabricated open-structured organ-on-a-chip was used for culturing the previously developed inkjet bioprinted alveolar barrier model for biomimetic blood flow at the epithelial-blood barrier interface. The results show that the 3D structured model maintained distinct three thin layers and the tight junction of the epithelial layer, which are the key properties of alveoli, in the process of being cultured in the chip. Additionally, the upregulation of genes involved in alveolar respiratory function was confirmed. Our open-structured organ-on-a-chip is an innovative platform that can be applied to various types of organ models by simply mounting and interchanging cell culture inserts. In particular, it will be advantageous for mass production and the development of customized models through convergence with bioprinting technology.2

Inkjet printing of high-concentration Gelatin methacryloyl (GelMA) ink for biofabrication

Inkjet printing can precisely arrange biomaterials at high resolution by jetting picoliter-sized droplets and create complicated 3D structures by stacking a thin layer of hydrogel. So inkjet bioprinting has a great potential to fabricate highly-complex tissue constructs for use in drug screening, cancer research, and transplantation. However, the high-concentration inks that provide appropriate mechanical support and slow degradation rates after gelation generally have too high viscoelasticity to be ejected from inkjet nozzle. Gelatin methacryloyl(GelMA), which is an attractive biomaterial due to its printability, biocompatibility, mechanical tunability, and instant crosslinkability, can be utilized in inkjet printing only at low concentrations. Therefore, it is difficult to produce GelMA hydrogels with a wide range of physical properties by inkjet printing. In this study, we apply sonication for the first time to control the viscoelasticity of high-concentration GelMA ink for inkjet bioprinting. It is found that the viscoelasticity of GelMA ink decreases after sonication, so printing becomes possible. To validate the impact of sonication on polymers, the molecular weight and functional groups of GelMA are analyzed after different sonication times. We then compare the physical hydrogel properties of the 3% (w/v) pristine GelMA ink, 10 h sonicated 6% GelMA ink, and 20 h sonicated 10% GelMA ink which are all printable in the inkjet printer. After the cell-laden GelMA ink is inkjet-printed and gelated, we also quantify cell viability to demonstrate the biocompatibility of inkjet printing and sonicated ink in biofabrication. Finally, 3D hydrogel structures which consist of thin multilayer cells are fabricated by inkjet printing with sonicated ink. The significance of our work is to apply highly viscoelastic biomaterials to inkjet printing by using simple sonication to lower molecular weight and characterize the physical properties of inks and hydrogels. Sonication will deliver a new path to inkjet printing to build microarchitectures with various physical properties by expanding the range of applicable bioinks.1

Development of Printable Lung-on-a-chip by using Mountable Cell Culture Insert

Through an inkjet bio-printing, we have previously developed a novel 3D-structured lung model. Despite the advantages of its structural property and functions, it is necessary to combine the model with lung-on-a-chip to mimic the blood flow at the epithelial-blood barrier interface. However, printing inside the chip was a challenging issue because it is difficult to print a bioink directly into the inner chip module. Thus, we constructed an open-structured chip in a form that can be integrated with a mountable cell culture insert that is known as suitable for inkjet printing. The chip consists of lower and upper PDMS layers for microfluid circulation and the cell culture insert, respectively. This chip utilizes the elasticity of PDMS to hold the cell culture insert firmly to prevent leakage during media supplying. It also contains a pressure regulating system to prevent a high internal pressure which may cause the penetration of the membrane in cell culture insert by media overflow. The cultured tissue on a cell culture insert after the layer-by-layer inkjet printing was mounted to the upper layer, and media was infused into the microchannel of the lower layer to induce the model to be cultured under flowing conditions. To verify this system, a 3D-structured lung model fabricated by inkjet printing was mounted on the chip. After cultured for 7 days, the tissue was evaluated with TEER measurement and identified with H&E staining. The TEER values show that the lung model cultured through this system has robust tight junctions similar to that cultured under non-flow conditions. Through the H&E staining, the histological structure of the tissue was also confirmed that the printed lung tissue was not damaged during the process of being cultured in the chip. Furthermore, by comparing lung models under various flow rate conditions with tissues cultured in conventional well plates, the effect of shear stress on inkjet-printed lung models was analyzed. Considering that this system can be easily integrated with various tissues fabricated by inkjet printing, we expect that it may contribute to a reliable measurement and analysis tools in organ-on-a-chip researches.1

Control of viscosity of gelatin methacryloyl bioink by ultrasound sonication for inkjet bioprinting

Drop-on-demand inkjet printing, one of the most effective tools for tissue fabrication, allows high resolution printing by positioning very small droplets of liquid in a picolitre (10-12 L) level. However, a limited range of polymer concentration is printable as this technique cannot print an ink with viscosity of above 20 mPa·s. Here, we report a simple method to control the viscosity of high-concentration gelatin mathacryloyl(GelMA) bioinks by exposing ultrasound sonication to print with an inkjet-print nozzle. We prepared GelMA inks with varying concentration from 5 to 10 and 15 % (w/v). Those inks were exposed to ultrasound sonication with different duration from 0 to 48 min to lower their viscosity which were measured with a rotational rheometer. By increasing the sonication time, the viscosity of GelMA inks decreased with the shortened chain length of peptide polymer. The 10% GelMA which was initially unjettable with an 80 μm-sized inkjet nozzle turns out to be jettable owing to the reduction of viscosity by ultrasound sonication. The 5% GelMA inks were jettable and 15% GelMA inks were not jettable regardless ultrasound exposure. We believe that this method enables us to expand inkjet-ink range and control ink physical properties easily.2

Development of Optimal Gelatin Methacryloyl Bioink for 3D Inkjet Bioprinting

Gelatin methacryloyl (GelMA) is receiving significant attention in the field of biofabrication due to its biocompatibility, mechanical tunability, and printability. However, it is difficult to print the hydrogel with high-resolution inkjet bioprinting because of the high viscoelasticity involved during the printing process. In this study, we suggest a simple ultrasound sonication method to control the viscoelasticity of the bioink without sacrificing its biocompatibility and mechanical properties. After the 20 hours of sonication, the viscosity of 10%(w/v) GelMA ink decreased from 81 mPa·s to 21 mPa·s at the 10,000 s-1, making unprintable GelMA bioink be printed possible. Multi-Angle Light Scattering measurement showed that the molecular weight of GelMA was reduced, which led to a decrease in viscoelasticity. In addition, Nuclear Magnetic Resonance spectroscopy confirmed that the sonication did not destroy the methacryloyl group that determines the degree of crosslinking. We compared the physical hydrogel properties of the 3% (w/v) pristine GelMA ink, 10 hours sonicated 6% GelMA ink, and 20 hours sonicated 10% GelMA ink which were all printable in inkjet printer. SEM image analysis was conducted to observe the microstructure of each lyophilized hydrogel. Higher wall thickness was observed with the high concentration of GelMA hydrogel. Due to dense microstructure, 10% GelMA hydrogel with 20 hours sonication showed about 7 times higher compressive modulus than pristine 3% GelMA hydrogel. Also, the higher concentration of GelMA hydrogel showed a slower enzyme degradation rate. Finally, we fabricated the three-dimensional cylindrical hydrogel constructs with different physical properties by using inkjet printing. Since the characteristics of ink can be easily controlled through the ultrasound sonication, this method will be widely used for biofabrication by expanding the range of inkjet bioinks.1

Sonochemical Degradation of Gelatin Methacryloyl to Control Viscoelasticity for Inkjet Bioprinting

Inkjet printing enables the mimicry of the microenvironment of natural complex tissues by patterning cells and hydrogels at a high resolution. However, the polymer content of an inkjet-printable bioink is limited as it leads to strong viscoelasticity in the inkjet nozzle. Here it is demonstrated that sonochemical treatment controls the viscoelasticity of a gelatin methacryloyl (GelMA) based bioink by shortening the length of polymer chains without causing chemical destruction of the methacryloyl groups. The rheological properties of treated GelMA inks are evaluated by a piezo-axial vibrator over a wide range of frequencies between 10 and 10 000 Hz. This approach enables to effectively increase the maximum printable polymer concentration from 3% to 10%. Then it is studied how the sonochemical treatment effectively controls the microstructure and mechanical properties of GelMA hydrogel constructs after crosslinking while maintaining its fluid properties within the printable range. The control of mechanical properties of GelMA hydrogels can lead fibroblasts more spreading on the hydrogels. A 3D cell-laden multilayered hydrogel constructs containing layers with different physical properties is fabrictated by using high-resolution inkjet printing. The sonochemical treatment delivers a new path to inkjet bioprinting to build microarchitectures with various physical properties by expanding the range of applicable bioinks.11Nsciescopu