Antibiotic-Induced Primary Biles Inhibit SARS-CoV-2 Endoribonuclease Nsp15 Activity in Mouse Gut

The gut microbiome profile of COVID-19 patients was found to correlate with a viral load of SARS-CoV-2, COVID-19 severity, and dysfunctional immune responses, suggesting that gut microbiota may be involved in anti-infection. In order to investigate the role of gut microbiota in anti-infection against SARS-CoV-2, we established a high-throughput in vitro screening system for COVID-19 therapeutics by targeting the endoribonuclease (Nsp15). We also evaluated the activity inhibition of the target by substances of intestinal origin, using a mouse model in an attempt to explore the interactions between gut microbiota and SARS-CoV-2. The results unexpectedly revealed that antibiotic treatment induced the appearance of substances with Nsp15 activity inhibition in the intestine of mice. Comprehensive analysis based on functional profiling of the fecal metagenomes and endoribonuclease assay of antibiotic-enriched bacteria and metabolites demonstrated that the Nsp15 inhibitors were the primary bile acids that accumulated in the gut as a result of antibiotic-induced deficiency of bile acid metabolizing microbes. This study provides a new perspective on the development of COVID-19 therapeutics using primary bile acids

Efficient generation of human primordial germ cell-like cells from pluripotent stem cells in a methylcellulose-based 3D system at large scale

Background The mechanisms underlying human germ cell development and infertility remain largely unknown due to bioethical issues and the shortage of experimental materials. Therefore, an effective in vitro induction system of human primordial germ-like cells (hPGCLCs) from human pluripotent stem cells (hPSC) is in high demand. The current strategies used for the generation of hPGCLCs are not only costly but also difficult to perform at a large scale, thereby posing barriers to further research. In this study, we attempted to solve these problems by providing a new 3D culture system for hPGCLC differentiation. Methods The efficiency and relative yield of a methylcellulose (MC)-based 3D hPGCLC induction system were first compared with that of a conventional U96 system. Then, we examined the gene expression of germ cell marker genes and the key epigenetic modifications of the EpCAM-/INTEGRINα6-high cells from the 3D MC induction system and the U96 system via quantitative PCR and immunofluorescence. Finally, the reliability of the MC-based 3D hPGCLC induction system was evaluated via the generation of induced pluripotent stem cells (iPSCs) from the testicular cells of one patient with obstructive azoospermia (OA) and followed by the subsequent differentiation of iPSCs into the germ cell lineage. Results In the present study, we demonstrated that the 3D MC induction system combined with low-cell attachment plates facilitated the generation of hPGCLCs at a large scale. We found that the hPGCLCs generated via the MC system shared similar characteristics to that via the U96 system in terms of the gene expression profiles, germ cell-specific markers, epigenetic modification states and cellular states. In addition, hPGCLCs from iPSCs derived from one OA patient were generated with high efficiency via the present 3D MC induction system. Discussion The in vitro induction of hPGCLCs from human embryonic stem cells (hESCs)/human induced pluripotent stem cells (hiPSCs) has significant implications in exploring the underlying mechanisms of the origin and specification of hPGCs and the epigenetic programming of the human germ line as well as treating male infertility. Here, we developed a simple and efficient 3D induction system to generate hPGCLCs from hESCs/hiPSCs at a large scale, which facilitated the study of human germ cell development and stem cell-based reproductive medicine

Topography of calcium phosphate ceramics regulates primary cilia length and TGF receptor recruitment associated with osteogenesis

The surface topography of synthetic biomaterials is known to play a role in material-driven osteogenesis. Recent studies show that TGFβ signalling also initiates osteogenic differentiation. TGFβ signalling requires the recruitment of TGFβ receptors (TGFβR) to the primary cilia. In this study, we hypothesize that the surface topography of calcium phosphate ceramics regulates stem cell morphology, primary cilia structure and TGFβR recruitment to the cilium associated with osteogenic differentiation. We developed a 2D system using two types of tricalcium phosphate (TCP) ceramic discs with identical chemistry. One sample had a surface topography at micron-scale (TCP-B, with a bigger surface structure dimension) whilst the other had a surface topography at submicron scale (TCP-S, with a smaller surface structure dimension). In the absence of osteogenic differentiation factors, human bone marrow stromal cells (hBMSCs) were more spread on TCP-S than on TCP-B with alterations in actin organization and increased primary cilia prevalence and length. The cilia elongation on TCP-S was similar to that observed on glass in the presence of osteogenic media and was followed by recruitment of transforming growth factor-β RII (p-TGFβ RII) to the cilia axoneme. This was associated with enhanced osteogenic differentiation of hBMSCs on TCP-S, as shown by alkaline phosphatase activity and gene expression for key osteogenic markers in the absence of additional osteogenic growth factors. Similarly, in vivo after a 12-week intramuscular implantation in dogs, TCP-S induced bone formation while TCP-B did not. It is most likely that the surface topography of calcium phosphate ceramics regulates primary cilia length and ciliary recruitment of p-TGFβ RII associated with osteogenesis and bone formation. This bioengineering control of osteogenesis via primary cilia modulation may represent a new type of biomaterial-based ciliotherapy for orthopedic, dental and maxillofacial surgery applications. Statement of Significance The surface topography of synthetic biomaterials plays important roles in material-driven osteogenesis. The data presented herein have shown that the surface topography of calcium phosphate ceramics regulates mesenchymal stromal cells (e.g., human bone marrow mesenchymal stromal cells, hBMSCs) with respect to morphology, primary cilia structure and TGFβR recruitment to the cilium associated with osteogenic differentiation in vitro. Together with bone formation in vivo, our results suggested a new type of biomaterial-based ciliotherapy for orthopedic, dental and maxillofacial surgery by the bioengineering control of osteogenesis via primary cilia modulation

Effect Decomposition and Heterogeneity in Development Economics and Policy Evaluation

This dissertation covers various topics ranging from migration to wealth measures in developing countries and to policy analysis in general. In Chapter 1, I study the internal migration in China and aim to understand its effect on the human capital accumulation of the later generations. In Chapter 2, I investigate novel wealth measures and look for ways to understand the low-cost wealth metrics. In Chapter 3, I discuss a doubly-robust method to estimate causal effects for panel data in the presence of effect heterogeneity.In Chapter 1, I investigate the mechanisms through which parental migration affects the schooling outcomes of children left behind in rural China. This issue affects 61 million children. Previous literature on this topic focuses on estimating the net effect of migration, whereas this paper disentangles the net effect into different mechanisms of policy interests. I establish a theoretical framework to incorporate three essential and widely-studied mechanisms that migration could affect left-behind children’s school performance: parental accompaniment, child’s study time, and investment in children. Motivated by the theoretical model’s solution, I apply the structural equation model to estimate the influence through different mechanisms. I propose an identification strategy based on instrumental variables and the Heckman selection model. Using the model on rural household survey data from nine provinces, I find that the effects through parental absence and investment are both significantly negative with large sizes. In contrast, the impact through the child’s study time is insignificant with a negligible size. The surprising negative effect through investment is mainly driven by reduced nutrition investment by the de facto custodians, who may not have compatible incentives to allocate the remittances to the child. Through a refined subgroup analysis, I find that girls are suffering ten times more from the underinvestment than boys, revealing a shocking gender inequality in rural China. In Chapter 2 (co-authored with Professor Ashish Shenoy), I aim to understand novel poverty measures. For under-developed countries, wealth measures are essential for measuring economic growth, policy design, and setting development goals. In particular, I focus on the use of nighttime light data. Unlike standard wealth measures based on national accounts or expenditure surveys, nighttime light data has the advantages of high frequency, low cost, and precision over small geographic units. These advantages make it an ideal substitute for in-person surveys. Nighttime light data has been a popular wealth measure in recent years, and previous papers mainly argue that nighttime light intensity and gross domestic production levels are highly correlated globally. However, we analyze the relationship between night light growth and economic growth for 179 countries or regions and find heterogeneity in the correlation. To deal with the heterogeneity, we propose a weighted least squares estimator for the average correlation coefficient by properly re-weighting each country. We find a significant and positive average correlation among middle-income countries. Moving beyond the average association, we apply the LASSO regression to identify and estimate non-zero individual correlation coefficients. This is inspired by the sparsity of country-level associations observed in the preliminary analysis. We further apply the ”knockoff” method to control the false discovery rate among the selected countries. In Chapter 3 (co-authored with Professor Dmitry Arkhangelsky, Professor Guido W. Imbens, and Lihua Lei), we develop a novel method for causal inference with observational panel data, which overcomes the limitations of existing methods. Cross-sectional models account for treatment assignment using methods such as inverse probability weighting. We extend this approach to panel data. Taking the case of staggered adoption as an example, we model the adoption time with duration models such as the Cox hazards model. As long as the information about the assignment mechanism is accurate, our method works under substantially weaker assumptions than the traditional methods. As a byproduct, we characterize the class of experimental designs under which the conventional methods are guaranteed to produce consistent estimates of the causal effects. The method from our paper can be widely applied to empirical analysis, such as program evaluation

Controlling surface microstructure of calcium phosphate ceramic from random to custom-design

Calcium phosphate ceramics have long been studied as bone graft substitutes due to their similarity with the mineral constitute of bone and teeth, excellent biocompatibility and bioactivity. Chemical composition, macrostructure and surface microstructure are believed to be important for the bone formation within calcium phosphate ceramics. Surface microstructure has shown its crucial role in the osteogenic response of calcium phosphate ceramics; however the presence of surface irregularities and random distribution of surface microstructure in traditional calcium phosphate ceramics make it difficult to explain how surface microstructure play its role in bone formation. In the present study, we evaluated the influence of various starting apatites and sintering temperatures on the surface microstructure of the resulting hydroxyapatite ceramics. In order to minimize the randomness of the surface microstructure, laser ablation was used to generate custom-designed surface microstructures. The resulting hydroxyapatite ceramics with controlled surface microstructures would be helpful to study the role of surface microstructure on bone formation and may provide useful information for further optimization of calcium phosphate ceramics for bone regeneratio

Restructuring for Growth in Development Zones, China: A Systematic Literature and Policy Review (1984–2022)

China’s development zones have been enjoying a process of dramatic growth and restructuring since the start of the new millennium, which has been extensively documented in the literature. The growth stems from the increased scope and expansion in demand created by China’s economic growth, as well as gradual global economic reconfiguration, which has, in itself, become a factor in advancing the country’s spiraling economic growth. This article examines the trajectory of the growth and restructuring of China’s development zones since 1984, by reviewing critical policies and their measures and effects, as well as academic research in this field, focusing on transitional stages, features and mechanisms. Based on different academic viewpoints, the work sets out a three-pronged conceptual framework composed of institutional transition, industrial evolution and land use transformation to systematize the growth process. In recent years, the restructuring of development zones has come to be considered as a comprehensive and complex issue, and its main challenges arise from factors such as overcoming outdated institutional arrangements, strengthening market participation, promoting high-end industrial agglomeration and breaking the bottleneck of inefficient land use. This article uses a multi-dimensional, logical approach to address the growth of development zones, and examines relevant practices and studies so as to explore the deeply rooted correlations between different dimensions in more depth and to examine the innate and unchanged logic involved in the restructuring of development zones

Restructuring for Growth in Development Zones, China: A Systematic Literature and Policy Review (1984–2022)

China’s development zones have been enjoying a process of dramatic growth and restructuring since the start of the new millennium, which has been extensively documented in the literature. The growth stems from the increased scope and expansion in demand created by China’s economic growth, as well as gradual global economic reconfiguration, which has, in itself, become a factor in advancing the country’s spiraling economic growth. This article examines the trajectory of the growth and restructuring of China’s development zones since 1984, by reviewing critical policies and their measures and effects, as well as academic research in this field, focusing on transitional stages, features and mechanisms. Based on different academic viewpoints, the work sets out a three-pronged conceptual framework composed of institutional transition, industrial evolution and land use transformation to systematize the growth process. In recent years, the restructuring of development zones has come to be considered as a comprehensive and complex issue, and its main challenges arise from factors such as overcoming outdated institutional arrangements, strengthening market participation, promoting high-end industrial agglomeration and breaking the bottleneck of inefficient land use. This article uses a multi-dimensional, logical approach to address the growth of development zones, and examines relevant practices and studies so as to explore the deeply rooted correlations between different dimensions in more depth and to examine the innate and unchanged logic involved in the restructuring of development zones