The use of human iPSC-derived alveolar organoids to explore SARS-CoV-2 variant infections and host responses.

Severe acute respiratory syndrome-related coronavirus 2 (SARS-CoV-2) primarily targets the respiratory system. Physiologically relevant human lung models are indispensable to investigate virus-induced host response and disease pathogenesis. In this study, we generated human induced pluripotent stem cell (iPSC)-derived alveolar organoids (AOs) using an established protocol that recapitulates the sequential steps of in vivo lung development. AOs express alveolar epithelial type II cell protein markers including pro-surfactant protein C and ATP binding cassette subfamily A member 3. Compared to primary human alveolar type II cells, AOs expressed higher mRNA levels of SARS-CoV-2 entry factors, angiotensin-converting enzyme 2 (ACE2), asialoglycoprotein receptor 1 (ASGR1) and basigin (CD147). Considering the localization of ACE2 on the apical side in AOs, we used three AO models, apical-in, sheared and apical-out for SARS-CoV-2 infection. All three models of AOs were robustly infected with the SARS-CoV-2 irrespective of ACE2 accessibility. Antibody blocking experiment revealed that ASGR1 was the main receptor for SARS-CoV2 entry from the basolateral in apical-in AOs. AOs supported the replication of SARS-CoV-2 variants WA1, Alpha, Beta, Delta, and Zeta and Omicron to a variable degree with WA1 being the highest and Omicron being the least. Transcriptomic profiling of infected AOs revealed the induction of inflammatory and interferon-related pathways with NF-κB signaling being the predominant host response. In summary, iPSC-derived AOs can serve as excellent human lung models to investigate infection of SARS-CoV-2 variants and host responses from both apical and basolateral sides.

Obesity-induced dysregulation of skin-resident PPARγ+ Treg cells promotes IL-17A-mediated psoriatic inflammation.

Obesity is a major risk factor for psoriasis, but how obesity disrupts the regulatory mechanisms that keep skin inflammation in check is unclear. Here, we found that skin was enriched with a unique population of CD4+Foxp3+ regulatory T (Treg) cells expressing the nuclear receptor peroxisome proliferation-activated receptor gamma (PPARγ). PPARγ drove a distinctive transcriptional program and functional suppression of IL-17A+ γδ T cell-mediated psoriatic inflammation. Diet-induced obesity, however, resulted in a reduction of PPARγ+ skin Treg cells and a corresponding loss of control over IL-17A+ γδ T cell-mediated inflammation. Mechanistically, PPARγ+ skin Treg cells preferentially took up elevated levels of long-chain free fatty acids in obese mice, which led to cellular lipotoxicity, oxidative stress, and mitochondrial dysfunction. Harnessing the anti-inflammatory properties of these PPARγ+ skin Treg cells could have therapeutic potential for obesity-associated inflammatory skin diseases.

Long Noncoding RNA FENDRR Inhibits Lung Fibroblast Proliferation via a Reduction of ß-Catenin.

Idiopathic Pulmonary Fibrosis (IPF) is a chronic, progressive, and usually lethal lung disease and it has been widely accepted that fibroblast proliferation is one of the key characteristics of IPF. Long noncoding RNAs (lncRNAs) play vital roles in the pathogenesis of many diseases. In this study, we investigated the role of lncRNA FENDRR on fibroblast proliferation. Human lung fibroblasts stably overexpressing FENDRR showed a reduced cell proliferation compared to those expressing the control vector. On the other hand, FENDRR silencing increased fibroblast proliferation. FENDRR bound serine-arginine rich splicing factor 9 (SRSF9) and inhibited the phosphorylation of p70 ribosomal S6 kinase 1 (PS6K), a downstream protein of the mammalian target of rapamycin (mTOR) signaling. Silencing SRSF9 reduced fibroblast proliferation. FENDRR reduced ß-catenin protein, but not mRNA levels. The reduction of ß-catenin protein levels in lung fibroblasts by gene silencing or chemical inhibitor decreased fibroblast proliferation. Adenovirus-mediated FENDRR transfer to the lungs of mice reduced asbestos-induced fibrotic lesions and collagen deposition. RNA sequencing of lung tissues identified 7 cell proliferation-related genes that were up-regulated by asbestos but reversed by FENDRR. In conclusion, FENDRR inhibits fibroblast proliferation and functions as an anti-fibrotic lncRNA.

Interferon-α-producing plasmacytoid dendritic cells drive the loss of adipose tissue regulatory T cells during obesity.

The visceral adipose tissue (VAT) of lean mice hosts a unique population of regulatory T cells (Tregs) that have a distinct transcriptome and T cell receptor (TCR) repertoire and regulate local and systemic inflammation and metabolism. Perplexingly, this population disappears in obese mice, limiting the promise of Treg-based therapies for metabolic disorders. We exploited the power of a VAT-Treg TCR-transgenic mouse model to follow the dynamics of, and phenotypic changes in, the VAT-Treg population throughout the development of diet-induced obesity. Our results show that VAT-Tregs are lost under obesogenic conditions due to downregulation of their defining transcription factor, PPARγ, coupled with their strikingly enhanced responses to pro-inflammatory cytokines. In particular, the VAT from obese mice (and reportedly humans) was strongly enriched in plasmacytoid dendritic cells that actively express interferon-alpha. These cells were directly toxic to PPARγ+ VAT-Tregs. Blocking this pathway in obese mice by multiple approaches substantially restored the VAT-Treg population and enhanced insulin sensitivity.

Derivation and Differentiation of Adipose-Tissue Regulatory T Cells: A Stepwise, Multi-Site Process.

CD4+ Foxp3+ regulatory T cells (Tregs) not only enforce peripheral tolerance and restrain self-reactive immune responses, but also maintain organismal homeostasis and safeguard the function of parenchymal tissues. A paradigmatic tissue-Treg population resides in the visceral adipose tissue (VAT) and regulates organismal metabolism by interacting with adipocytes and local immunocytes. Compared with their lymphoid-tissue counterparts, VAT-Tregs have a distinct T cell receptor (TCR) repertoire and transcriptional profile, allowing them to maintain and function in the unique tissue microenvironment. However, when, where, and how VAT-Tregs acquire their distinct features and what signals drive their phenotypic diversification have just started to be unraveled. Here we summarize the recent advances in our understanding on the mechanisms of VAT-Treg derivation and differentiation. We discuss the origin and life history of VAT-Tregs, review the identification and characterization of a VAT-Treg precursor population in the secondary lymphoid organs, and highlight a stepwise reprogramming model of VAT-Treg differentiation that involves multiple stages at distinct locations. Lastly, we discuss whether a similar process may also be involved in the differentiation of Tregs from other non-lymphoid tissues and the imperative questions that remain to be addressed.

Xylosyltransferase 2 deficiency and organ homeostasis.

In this paper we characterize the function of Xylosyltransferase 2 (XylT2) in different tissues to investigate the role XylT2 has in the proteoglycan (PG) biochemistry of multiple organs. The results show that in all organs examined there is a widespread and significant decrease in total XylT activity in Xylt2 knock out mice (Xylt2-/-). This decrease results in increased organ weight differences in lung, heart, and spleen. These findings, in addition to our previous findings of increased liver and kidney weight with loss of serum XylT activity, suggest systemic changes in organ function due to loss of XylT2 activity. The Xylt2-/- mice have splenomegaly due to enlargement of the red pulp area and enhanced pulmonary response to bacterial liposaccharide. Tissue glycosaminoglycan composition changes are also found. These results demonstrate a role of XylT2 activity in multiple organs and their PG content. Because the residual XylT activity in the Xylt2-/- is due to xylosyltransferase 1 (XylT1), these studies indicate that both XylT1 and XylT2 have important roles in PG biosynthesis and organ homeostasis.

Adipose tissue loss and lipodystrophy in xylosyltransferase II deficient mice.

BACKGROUND/OBJECTIVES: The cellular and extracellular matrix (ECM) interactions that regulate adipose tissue homeostasis are incompletely understood. Proteoglycans (PGs) and their sulfated glycosaminoglycans (GAGs) provide spatial and temporal signals for ECM organization and interactions with resident cells by impacting growth factor and cytokine activity. Therefore, PGs and their GAGs could be significant to adipose tissue homeostasis. The purpose of this study was to determine the role of ECM sulfated GAGs in adipose tissue homeostasis. METHODS: Adipose tissue and metabolic homeostasis in mice deficient in xylosyltransferase 2 (Xylt2-/-) were examined by histologic analyses, gene expression analyses, whole body fat composition measurements, and glucose tolerance test. Adipose tissue inflammation and adipocyte precursors were characterized by flow cytometry and in vitro culture of mesenchymal stem cells. RESULTS: Xylt2-/- mice have low body weight due to overall reductions in abdominal fat deposition. Histologically, the adipocytes are reduced in size and number in both gonadal and mesenteric fat depots of Xylt2-/- mice. In addition, these mice are glucose intolerant, insulin resistant, and have increased serum triglycerides as compared to Xylt2 + / + control mice. Furthermore, the adipose tissue niche has increased inflammatory cells and enrichment of proinflammatory factors IL6 and IL1ß, and these mice also have a loss of adipose tissue vascular endothelial cells. Lastly, xylosyltransferease-2 (XylT2) deficient mesenchymal stem cells from gonadal adipose tissue and bone marrow exhibit impaired adipogenic differentiation in vitro. CONCLUSIONS: Decreased GAGs due to the loss of the key GAG assembly enzyme XylT2 causes reduced steady state adipose tissue stores leading to a unique lipodystrophic model. Accumulation of an adipocytic precursor pool of cells is discovered indicating an interruption in differentiation. Therefore, adipose tissue GAGs are important in the homeostasis of adipose tissue by mediating control of adipose precursor development, tissue inflammation, and vascular development.

Augmentation of therapeutic potential of curcumin using nanotechnology: current perspectives.

Curcumin, an active principle of Curcuma longa, is extracted from the rhizome. Its therapeutic efficiency has been proved using various in vitro and in vivo models. Inflammatory, neoplastic and preneoplastic diseases are the major targets using curcumin as therapeutic agent. Feasible clinical formulations could not be obtained because of its lack of solubility, stability and higher degradation rate. Recently, many techniques have been evolved to improve the physicochemical properties of pharmacological compounds, thereby increasing their biological activity. Curcumin has been developed using various techniques, particularly micro and nanotechnology to improve its stability and bioavailability. This review focuses on the studies pertaining to the delivery of curcumin in the form of micro and nanosize formulations for the treatment of a variety of diseases.