Sine oculis homeobox homolog 1 plays a critical role in pulmonary fibrosis

Deletion of adipocyte Sine Oculis Homeobox Homolog 1 prevents lipolysis and attenuates skin fibrosis

Dermal fibrosis is a cardinal feature of systemic sclerosis (SSc) for which there are limited treatment strategies. This is in part due to our fragmented understanding of how dermal white adipose tissue (DWAT) contributes to skin fibrosis. We identified elevated sine oculis homeobox homolog 1 (SIX1) expression in SSc skin samples from the GENISOS and PRESS cohorts, the expression of which correlated with adipose-associated genes and molecular pathways. SIX1 localization studies identified increased signals in the DWAT area in SSc and in experimental models of skin fibrosis. Global and adipocyte specific Six1 deletion abrogated end-stage fibrotic gene expression and dermal adipocyte shrinkage induced by SQ bleomycin treatment. Further studies revealed a link between elevated SIX1 and increased expression of SERPINE1 and its protein PAI-1 which are known pro-fibrotic mediators. However, SIX1 deletion did not appear to affect cellular trans differentiation. Taken together these results point at SIX1 as a potential target for dermal fibrosis in SSc.

Novel AT2 Cell Subpopulations and Diagnostic Biomarkers in IPF: Integrating Machine Learning with Single-Cell Analysis

Idiopathic pulmonary fibrosis (IPF) is a long-term condition with an unidentified cause, and currently there are no specific treatment options available. Alveolar epithelial type II cells (AT2) constitute a heterogeneous population crucial for secreting and regenerative functions in the alveolus, essential for maintaining lung homeostasis. However, a comprehensive investigation into their cellular diversity, molecular features, and clinical implications is currently lacking. In this study, we conducted a comprehensive examination of single-cell RNA sequencing data from both normal and fibrotic lung tissues. We analyzed alterations in cellular composition between IPF and normal tissue and investigated differentially expressed genes across each cell population. This analysis revealed the presence of two distinct subpopulations of IPF-related alveolar epithelial type II cells (IR_AT2). Subsequently, three unique gene co-expression modules associated with the IR_AT2 subtype were identified through the use of hdWGCNA. Furthermore, we refined and identified IPF-related AT2-related gene (IARG) signatures using various machine learning algorithms. Our analysis demonstrated a significant association between high IARG scores in IPF patients and shorter survival times (p-value < 0.01). Additionally, we observed a negative correlation between the percent predicted diffusing capacity for lung carbon monoxide (% DLCO) and increased IARG scores (cor = -0.44, p-value < 0.05). The cross-validation findings demonstrated a high level of accuracy (AUC > 0.85, p-value < 0.01) in the prognostication of patients with IPF utilizing the identified IARG signatures. Our study has identified distinct molecular and biological features among AT2 subpopulations, specifically highlighting the unique characteristics of IPF-related AT2 cells. Importantly, our findings underscore the prognostic relevance of specific genes associated with IPF-related AT2 cells, offering valuable insights into the advancement of IPF.

Mutual Regulation of Transcriptomes between Murine Pneumocytes and Fibroblasts Mediates Alveolar Regeneration in Air-Liquid Interface Cultures

Alveolar type 2 and club cells are part of the stem cell niche of the lung and their differentiation is required for pulmonary homeostasis and tissue regeneration. A disturbed crosstalk between fibroblasts and epithelial cells contributes to the loss of lung structure in chronic lung diseases. Therefore, it is important to understand how fibroblasts and lung epithelial cells interact during regeneration. Here, we analyzed the interaction of fibroblasts and the alveolar epithelium modeled in air-liquid interface cultures. Single-cell transcriptomics showed that cocultivation with fibroblasts leads to increased expression of type 2 markers in pneumocytes, activation of regulons associated with the maintenance of alveolar type 2 cells (e.g., Etv5), and transdifferentiation of club cells toward pneumocytes. This was accompanied by an intensified transepithelial barrier. Vice versa, the activation of NF-κB pathways and the CEBPB regulon and the expression of IL-6 and other differentiation factors (e.g., fibroblast growth factors) were increased in fibroblasts cocultured with epithelial cells. Recombinant IL-6 enhanced epithelial barrier formation. Therefore, in our coculture model, regulatory loops were identified by which lung epithelial cells mediate regeneration and differentiation of the alveolar epithelium in a cooperative manner with the mesenchymal compartment.

MIF inhibition alleviates vitiligo progression by suppressing CD8+ T cell activation and proliferation

In vitiligo, autoreactive CD8⁺ T cells have been established as the main culprit considering its pathogenic role in mediating epidermal melanocyte-specific destruction. Macrophage migration inhibitory factor (MIF) is a pleiotropic molecule that plays a central role in various immune processes including the activation and proliferation of T cells; but whether MIF is intertwined in vitiligo development and progression and its involvement in aberrantly activated CD8⁺ T cells remains ill-defined. In this study, we found that MIF was overabundant in vitiligo patients and a mouse model for human vitiligo. Additionally, inhibiting MIF ameliorated the disease progression in vitiligo mice, which manifested as less infiltration of CD8⁺ T cells and more retention of epidermal melanocytes in the tail skin. More importantly, in vitro experiments indicated that MIF-inhibition suppressed the activation and proliferation of CD8⁺ T cells from the lymph nodes of vitiligo mice, and the effect extended to CD8⁺ T cells in peripheral blood mononuclear cells of vitiligo patients. Finally, CD8⁺ T cells derived from MIF-inhibited vitiligo mice also exhibited an impaired capacity for activation and proliferation. Taken together, our results show that MIF might be clinically targetable in vitiligo treatment, and its inhibition might ameliorate vitiligo progression by suppressing autoreactive CD8⁺ T cell activation and proliferation. © 2023 The Pathological Society of Great Britain and Ireland.

Retinal determination gene networks: from biological functions to therapeutic strategies

The retinal determinant gene network (RDGN), originally discovered as a critical determinator in Drosophila eye specification, has become an important regulatory network in tumorigenesis and progression, as well as organogenesis. This network is not only associated with malignant biological behaviors of tumors, such as proliferation, and invasion, but also regulates the development of multiple mammalian organs. Three members of this conservative network have been extensively investigated, including DACH, SIX, and EYA. Dysregulated RDGN signaling is associated with the initiation and progression of tumors. In recent years, it has been found that the members of this network can be used as prognostic markers for cancer patients. Moreover, they are considered to be potential therapeutic targets for cancer. Here, we summarize the research progress of RDGN members from biological functions to signaling transduction, especially emphasizing their effects on tumors. Additionally, we discuss the roles of RDGN members in the development of organs and tissue as well as their correlations with the pathogenesis of chronic kidney disease and coronary heart disease. By summarizing the roles of RDGN members in human diseases, we hope to promote future investigations into RDGN and provide potential therapeutic strategies for patients.

Alveolar Epithelial Type 2 Cell Dysfunction in Idiopathic Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive and irreversible pulmonary interstitial disease that seriously affects the patient's quality of life and lifespan. The pathogenesis of IPF has not been clarified, and its treatment is limited to pirfenidone and nintedanib, which only delays the decline of lung function. Alveolar epithelial type 2 (AT2) cells are indispensable in the regeneration and lung surfactant secretion of alveolar epithelial cells. Studies have shown that AT2 cell dysfunction initiates the occurrence and progression of IPF. This review expounds on the AT2 cell dysfunction in IPF, involving senescence, apoptosis, endoplasmic reticulum stress, mitochondrial damage, metabolic reprogramming, and the transitional state of AT2 cells. This article also briefly summarizes potential treatments targeting AT2 cell dysfunction.