The Role of Mesenchymal Stromal Cells and Classical Dendritic Cells in the Maintenance and Regulation of the Bone Marrow Niche

The bone marrow niche is an important microenvironment for the regulation of normal and malignant hematopoiesis. The first discovered niche component is mesenchymal stromal cells, which are the major source for the production and secretion of multiple niche factors. Mesenchymal stromal cells are heterogeneous and various transgenes have been used to target non-identical but overlapping subpopulations. To further characterize the heterogeneity of mesenchymal stromal cells, we tested the targeting specificity of three tissue-specific Cre-recombinase transgenes. We show that in addition to osteoblasts, Ocn-Cre targets a majority of Cxcl12-abundant reticular (CAR) cells and arteriolar pericytes. Surprisingly, Dmp1-Cre also targets a subset of CAR cells, in which expression of osteoblast-lineage genes is enriched. Moreover, a new tissue-specific Cre-recombinase, Tagln-Cre efficiently targets osteoblasts, a majority of CAR cells, and both venous sinusoidal and arteriolar pericytes. These observations highlight the heterogeneity of mesenchymal stromal cells in the bone marrow and provide tools to interrogate this heterogeneity. To further analyze the functional heterogeneity of mesenchymal stromal cells, we assessed the function of CXCL12 from different subsets of mesenchymal stromal cells on B lymphopoiesis. We show that CXCL12 from Ocn-Cre targeted stromal cells is particularly important for the regulation of mature naive B cells and memory B cells, potentially through the regulation of their homing and/or retention. This suggests that B cell development requires distinct niches at different stages and Ocn-Cre targeted stromal cells may represent a specific niche for late-stage B cell development. Besides mesenchymal stromal cells, this thesis also assesses the function of a recently identified resident population of murine bone marrow classical dendritic cells (BM cDCs). We show that BM cDC ablation results in a secondary, non-cell autonomous loss of BM macrophages. And more importantly, BM cDCs regulate hematopoietic progenitor and stem cell (HSPC) trafficking through a macrophage independent pathway, at least in part, through its regulation of sinusoidal CXCR2 signaling and vascular permeability. These findings suggest BM cDCs may serve as a novel bone marrow niche component regulating HSPCs. Collectively, this thesis improves on the overall understanding of the bone marrow niche and provides insights with significant relevance to both basic and clinical research

Frameshift coding sequence variants in the LPL gene: identification of two novel events and exploration of the genotype–phenotype relationship for variants reported to date

Background: Lipoprotein lipase (LPL) is the rate-limiting enzyme for triglyceride hydrolysis. Homozygous or compound heterozygous LPL variants cause autosomal recessive familial chylomicronemia syndrome (FCS), whereas simple heterozygous LPL variants are associated with hypertriglyceridemia (HTG) and HTG-related disorders. LPL frameshift coding sequence variants usually cause complete functional loss of the affected allele, thereby allowing exploration of the impact of different levels of LPL function in human disease. Methods: All exons and flanking intronic regions of LPL were Sanger sequenced in patients with HTG-related acute pancreatitis (HTG-AP) or HTG-AP in pregnancy. Previously reported LPL frameshift coding sequence variants were collated from the Human Gene Mutation Database and through PubMed keyword searching. Original reports were manually evaluated for the following information: zygosity status of the variant, plasma LPL activity of the variant carrier, disease referred for genetic analysis, patient’s age at genetic analysis, and patient’s disease history. SpliceAI was employed to predict the potential impact of collated variants on splicing. Results: Two novel rare variants were identified, and 53 known LPL frameshift coding sequence variants were collated. Of the 51 variants informative for zygosity, 30 were simple heterozygotes, 12 were homozygotes, and 9 were compound heterozygotes. Careful evaluation of the 55 variants with respect to their clinical and genetic data generated several interesting findings. First, we conclude that 6–7% residual LPL function could significantly delay the age of onset of FCS and reduce the prevalence of FCS-associated syndromes. Second, whereas a large majority of LPL frameshift coding sequence variants completely disrupt gene function through their "frameshift" nature, a small fraction of these variants may act wholly or partly as "in-frame" variants, leading to the generation of protein products with some residual LPL function. Third, we identified two candidate LPL frameshift coding sequence variants that may retain residual function based on genotype–phenotype correlation or SpliceAI-predicted data. Conclusions: This study reported two novel LPL variants and yielded new insights into the genotype–phenotype relationship as it pertains to LPL frameshift coding sequence variants

Effects and mechanisms of auricular electroacupuncture on gastric hypersensitivity in a rodent model of functional dyspepsia

Background Functional dyspepsia (FD) is a common functional gastrointestinal disease, and abdominal pain is one of the main symptoms. The aim of this study was to explore the effects and mechanisms of auricular electro-acupuncture (AEA) on gastric hypersensitivity in a rodent model of FD. Methods Ten-day-old pups were gavaged with 0.2 ml of 0.1% iodoacetamide daily for 6 days. AEA at the “stomach” point with different parameters or sham-EA was performed on 8-week-old animals. Gastric sensitivity to gastric distention was measured under different conditions. Autonomic functions were assessed from the spectral analysis of heart rate variability (HRV) derived from the electrocardiogram. Naloxone was injected intraperitoneally before AEA to explore the opioid mechanism. Gastric emptying was measured at the end of the study. Results 1) Gastric sensitivity to gastric distention was higher in the FD rats. AEA with parameters of 0.1s on, 0.4s off, 100Hz, 0.3ms and 0.4–0.5mA, but not other parameters or sham-EA, decreased gastric hypersensitivity in the FD rats. Naloxone did not block the effect of AEA. 2) Lower vagal activity and higher sympathovagal ratio were noted in the FD rats, compared with the controls. AEA increased vagal activity and improved sympathovagal imbalance. Conclusions AEA ameliorates gastric hypersensitivity in FD rats and this effect may be attributed to the improvement of sympathovagal balance.Yeshttp://www.plosone.org/static/editorial#pee

How Green Are the Streets Within the Sixth Ring Road of Beijing? An Analysis Based on Tencent Street View Pictures and the Green View Index

Street greenery, an important urban landscape component, is closely related to people’s physical and mental health. This study employs the green view index (GVI) as a quantitative indicator to evaluate visual greenery from a pedestrian’s perspective and uses an image segmentation method to calculate the quantity of visual greenery from Tencent street view pictures. This article aims to quantify street greenery in the area within the sixth ring road in Beijing, analyse the relations between road parameters and the GVI, and compare the visual greenery of different road types. The authors find that (1) the average GVI value in the study area is low, with low-value clusters inside the third ring road and high-value clusters outside; (2) wider minor roads tend to have higher GVI values than motorways, major roads and provincial roads; and (3) longer roads, except expressways, tend to have higher GVI values. This case study demonstrates that the GVI can effectively represent the quantity of visual greenery along roads. The authors’ methods can be employed to compare street-level visual greenery among different areas or road types and to support urban green space planning and management

Additional file 1 of Underreporting of non-study cigarette use by study participants confounds the interpretation of results from ambulatory clinical trial of reduced nicotine cigarettes

Additional file 1: Wilcoxon matched-pairs signed-rank test output