Sarcomere function activates a p53-dependent DNA damage response that promotes polyploidization and limits in vivo cell engraftment.

Human cardiac regeneration is limited by low cardiomyocyte replicative rates and progressive polyploidization by unclear mechanisms. To study this process, we engineer a human cardiomyocyte model to track replication and polyploidization using fluorescently tagged cyclin B1 and cardiac troponin T. Using time-lapse imaging, in vitro cardiomyocyte replication patterns recapitulate the progressive mononuclear polyploidization and replicative arrest observed in vivo. Single-cell transcriptomics and chromatin state analyses reveal that polyploidization is preceded by sarcomere assembly, enhanced oxidative metabolism, a DNA damage response, and p53 activation. CRISPR knockout screening reveals p53 as a driver of cell-cycle arrest and polyploidization. Inhibiting sarcomere function, or scavenging ROS, inhibits cell-cycle arrest and polyploidization. Finally, we show that cardiomyocyte engraftment in infarcted rat hearts is enhanced 4-fold by the increased proliferation of troponin-knockout cardiomyocytes. Thus, the sarcomere inhibits cell division through a DNA damage response that can be targeted to improve cardiomyocyte replacement strategies

Studying the Role of Mechanical Contraction in Cardiac Muscle Development Using Genetically Engineered Non-Contractile Human Stem Cell-Derived Cardiomyocytes

Thesis (Ph.D.)--University of Washington, 2021Mechanical contraction is an inherent function of cardiomyocytes but much of the effect of contraction on multiple cellular functions and therapeutic potential remains unknown. Due to the complete lethality of mechanical quiescence in cardiomyocytes, many researchers have used antagonists to mimic and study the effect of mechanical inactivity in vitro. However, this poses a great barrier as the antagonists are toxic and transient and cannot be used for long-term studies. With the emergence of human induced pluripotent stem cells (hiPSCs), we are now able to circumvent this shortcoming by creating in vitro models to induce stable and long-term mechanical quiescence in human cardiomyocytes. The following dissertation reports on the effects of mechanical contraction in human cardiomyocytes on regenerative stem cell therapeutics after myocardial infarction (MI), proliferation, and early development cardiac biology. To evaluate if mechanical contraction from the cardiac grafts after MI contribute to the overall functional improvement, we transplanted non-contractile and contractile hiPSC-cardiomyocytes (hiPSC-CMs) into the infarcted rat hearts. At 3 months post transplantation, non-contractile cardiomyocytes were equipotent with contractile cardiomyocytes in preventing the decline of systolic function after MI. These results suggest that force production by cardiac grafts is not necessary to prevent decline in cardiac function post MI in rodents. However, during this study, we observed significantly larger graft sizes from non-contractile cardiomyocytes compared to contractile cardiomyocytes. To understand this difference in graft sizes, we investigated the effect of mechanical contraction on cardiomyocytes proliferation by studying the relationship between cyclin B1 and p53. We found that mechanical contraction, one of the most demanding metabolic activities, increases p53 activity that degrades cyclin B1 due to increased oxidative stress from contracting sarcomeres. This results in decreased cardiomyocyte proliferation that inhibits cardiac regeneration upon injury. Additionally, we further investigated if cardiomyocytes can form sarcomeres, the fundamental contractile units, in the absence of contraction to understand if mechanical activity is needed for structural development. By investigating the effect of contraction in areas ranging from therapeutic mechanism to developmental biology, these findings provide new understanding of how contraction affects cellular mechanisms and development

A First Study on Distribution Characteristics of Common Dolphin in Korean Waters: A Study Using Data Collected during the Past 20 Years

The common dolphin (Delphinus delphis) is the second-most bycaught species in Korean waters. To provide key information about their habitat boundaries and hotspots for spatial conservation and management, the spatial use of this species was examined using data obtained from sighting and bycatch surveys of cetaceans in the past 20 years. The 95% minimum convex polygon and 95% density contour of fixed-kernel analysis suggested that the boundary of the home range of common dolphins is limited to the coastal region (Busan–Sokcho) of the East Sea/Sea of Japan. From 50% density contours drawn by kernel density estimation, it was suggested that their hotspots are around the coast of Ulsan–Pohang, Doghae, and Sokcho within the home range. Common dolphins were not observed in the Yellow Sea. Hence, shallow waters in the geographic area of the coastal region of the Yellow Sea are likely not a suitable habitat for common dolphins in this region

Individual Differences and Impacts of Psychopathological Symptoms in Observational Reward Learning

When making repeated decisions, individuals can learn about associations between actions and outcomes through obtained feedbacks. Such a learning process can occur based on individuals' direct experiences in the past, or simply on observed social others' actions and outcomes. Previous computational and neuroimaging studies have shown that one's learning performance is dependent on her sensitivity to reward (or punishment) and reward prediction error, the differences between experienced and expected rewards (or punishments). However, it remains unknown whether individuals' experience-based and observational learning have common or differential cognitive characteristics (e.g., value sensitivity) that affect the learning performances. Here, we use a probabilistic reward learning task, a choice task with different types of uncertainty, and computational modeling approach to quantify individuals' value sensitivity and learning performances. We further examine associations between performances in observational- and experience-based learnings with individuals' psychopathological symptoms. Particularly, depression, a most prevalent symptom in modern society and known factor that affects reward sensitivity, is used as a psychopathological measure of interest. The current study contributes to understanding how individuals' psychopathological symptoms affect their experience-based and observational reward learning

Deep Learning-Based Segmentation of Intertwined Fruit Trees for Agricultural Tasks

Fruit trees in orchards are typically placed at equal distances in rows; therefore, their branches are intertwined. The precise segmentation of a target tree in this situation is very important for many agricultural tasks, such as yield estimation, phenotyping, spraying, and pruning. However, our survey on tree segmentation revealed that no study has explicitly addressed this intertwining situation. This paper presents a novel dataset in which a precise tree region is labeled carefully by a human annotator by delineating the branches and trunk of a target apple tree. Because traditional rule-based image segmentation methods neglect semantic considerations, we employed cutting-edge deep learning models. Five recently pre-trained deep learning models for segmentation were modified to suit tree segmentation and were fine-tuned using our dataset. The experimental results show that YOLOv8 produces the best average precision (AP), 93.7 box [email protected]:0.95 and 84.2 mask [email protected]:0.95. We believe that our model can be successfully applied to various agricultural tasks

Post-synthetic ligand cyclization in metal-organic frameworks through functional group connection with regioisomerism

A covalent connection between two orthogonal functional groups (-NH2 and -OH) in metal-organic frameworks (MOFs) has been developed. This post-synthetic ligand cyclization (PSLC) was successfully demonstrated to synthesize a benzoxazole-functionalized MOF from a Zr-based UiO-66-2,3-(NH2)(OH) under microwave irradiation. In contrast, the regioisomeric UiO-66-2,5-(NH2)(OH) only produces a non-cyclized formamide-functionalized MOF

Post-synthetic ligand cyclization in metal-organic frameworks through functional group connection with regioisomerism

A covalent connection between two orthogonal functional groups (-NH2 and -OH) in metal-organic frameworks (MOFs) has been developed. This post-synthetic ligand cyclization (PSLC) was successfully demonstrated to synthesize a benzoxazole-functionalized MOF from a Zr-based UiO-66-2,3-(NH2)(OH) under microwave irradiation. In contrast, the regioisomeric UiO-66-2,5-(NH2)(OH) only produces a non-cyclized formamide-functionalized MOF.N

Thermal Ablation and High-Resolution Imaging Using a Back-to-Back (BTB) Dual-Mode Ultrasonic Transducer: In Vivo Results

We present a back-to-back (BTB) structured, dual-mode ultrasonic device that incorporates a single-element 5.3 MHz transducer for high-intensity focused ultrasound (HIFU) treatment and a single-element 20.0 MHz transducer for high-resolution ultrasound imaging. Ultrasound image-guided surgical systems have been developed for lesion monitoring to ensure that ultrasonic treatment is correctly administered at the right locations. In this study, we developed a dual-element transducer composed of two elements that share the same housing but work independently with a BTB structure, enabling a mode change between therapy and imaging via 180-degree mechanical rotation. The optic fibers were embedded in the HIFU focal region of ex vivo chicken breasts and the temperature change was measured. Images were obtained in vivo mice before and after treatment and compared to identify the treated region. We successfully acquired B-mode and C-scan images that display the hyperechoic region indicating coagulation necrosis in the HIFU-treated volume up to a depth of 10 mm. The compact BTB dual-mode ultrasonic transducer may be used for subcutaneous thermal ablation and monitoring, minimally invasive surgery, and other clinical applications, all with ultrasound only.11Nsciescopu

Core-Cross-Linked Nanoparticles Reduce Neuroinflammation and Improve Outcome in a Mouse Model of Traumatic Brain Injury

Traumatic brain injury (TBI) is the leading cause of death and disability in children and young adults, yet there are currently no treatments available that prevent the secondary spread of damage beyond the initial insult. The chronic progression of this secondary injury is in part caused by the release of reactive oxygen species (ROS) into surrounding normal brain. Thus, treatments that can enter the brain and reduce the spread of ROS should improve outcome from TBI. Here a highly versatile, reproducible, and scalable method to synthesize core-cross-linked nanoparticles (NPs) from polysorbate 80 (PS80) using a combination of thiol–ene and thiol–Michael chemistry is described. The resultant NPs consist of a ROS-reactive thioether cross-linked core stabilized in aqueous solution by hydroxy-functional oligoethylene oxide segments. These NPs show narrow molecular weight distributions and have a high proportion of thioether units that reduce local levels of ROS. In a controlled cortical impact mouse model of TBI, the NPs are able to rapidly accumulate and be retained in damaged brain as visualized through fluorescence imaging, reduce neuroinflammation and the secondary spread of injury as determined through magnetic resonance imaging and histopathology, and improve functional outcome as determined through behavioral analyses. Our findings provide strong evidence that these NPs may, upon further development and testing, provide a useful strategy to help improve the outcome of patients following a TBI