Abstract
Chronic lung allograft dysfunction (CLAD) is the leading cause of mortality after lung transplantation, yet its molecular mechanisms remain poorly understood. To elucidate the pathogenesis of CLAD, we conducted a comprehensive single-cell transcriptomic analysis of CLAD lungs, integrating our generated datasets with approximately 1.6 million cells from 15 published studies of other fibrotic lung diseases. By applying pseudo-bulk approaches to mitigate batch effects, we identified molecular signatures specific to CLAD and those shared with idiopathic pulmonary fibrosis, COVID-19, and other fibrotic conditions. Our analysis revealed CLAD-specific cellular subsets including Fibro.AT2 cells, exhausted CD8+ T cells, and superactivated macrophages while suggesting that pathogenic keratin 17–positive, keratin 5–negative (KRT17+KRT5−) cells represent a common fibrotic mechanism across fibrotic lung diseases. Additionally, we performed donor-recipient cell deconvolution in lung allografts, uncovering distinct transcriptional programs and intercellular crosstalk between donor- and recipient-derived cells that drive allograft fibrosis. Recipient-derived stromal and immune cells showed enhanced pro-fibrotic and allograft rejection pathways compared with their donor counterparts. By leveraging insights from other fibrotic diseases to elucidate CLAD-specific mechanisms, our study provides a molecular framework for understanding CLAD pathogenesis and identifies potential therapeutic targets for this treatment-refractory condition.
Authors
Yuanqing Yan, Taisuke Kaihou, Emilia Lecuona, Xin Wu, Masahiko Shigemura, Haiying Sun, Chitaru Kurihara, Ruli Gao, Felix L. Nunez-Santana, G.R. Scott Budinger, Ankit Bharat
Abstract
The mechanisms underlying cyst growth and progression in Autosomal Dominant Polycystic Kidney Disease (ADPKD) remain unresolved. Since cyst expansion requires epithelial salt and water secretion likely involving basolateral membrane K+ recycling, we investigated the role of KCNN4-encoded K+ channel KCa3.1, inhibited by the potent, pharmacospecific, well-tolerated antagonist, senicapoc. We hypothesized that genetic and/or pharmacological inactivation of KCNN4/KCa3.1 would slow PKD progression. KCNN4 was upregulated in kidneys of patients with ADPKD and of mechanistically distinct PKD mouse models. Cyst expansion in Pkd1–/– murine metanephroi was stimulated by KCa3.1 agonist and was prevented/reversed by senicapoc. In rapidly and/or slowly progressive mouse Pkd1 models, Kcnn4 inactivation slowed renal cyst growth; attenuated PKD-stimulated cAMP and ERK/Myc signaling pathways; reduced PKD-associated ciliary elongation, cell proliferation, and fibrosis; improved renal function; and prolonged survival. Importantly, senicapoc treatment of Pkd1 mouse models phenocopied most effects of Kcnn4 inactivation. This first study on the efficacy of KCa3.1 inhibition in PKD progression recommends senicapoc as a clinical trial candidate for ADPKD.
Authors
Guanhan Yao, Almira Kurbegovic, Camila Parrot, William Foley, William Roman, Seth L. Alper, Marie Trudel
Abstract
The cellular etiology of seizures in CLN2 disease, a childhood-onset neurodegenerative lysosomal storage disorder caused by a deficiency of tripeptidyl peptidase 1 (TPP1), remains elusive. Given that Cln2R207X/R207X mice display fatal spontaneous seizures and an early loss of several cortical GABAergic interneuron populations, we hypothesized that these 2 events might be causally related. To study the cell-autonomous effects of interneuron-specific TPP1 deficiency, we first generated transgenic mice expressing loxP-flanked lysosomal membrane–tethered TPP1 (TPP1LAMP1 mice) on the Cln2R207X/R207X genetic background, and then crossed TPP1LAMP1 mice with Vgat-Cre mice. These Vgat-Cre; TPP1LAMP1 mice accumulated storage material in cortical and striatal interneurons. Vgat-Cre; TPP1LAMP1 mice also died more readily after pentylenetetrazole-induced seizures, indicating that interneuron-specific TPP1 deficiency renders these mice more susceptible to seizure-induced mortality. We also selectively activated interneurons using designer receptors exclusively activated by designer drugs (DREADDs) in Vgat-Cre; Cln2R207X/R207X mice. Electroencephalogram monitoring revealed that DREADD-mediated activation of interneurons markedly accelerated the onset of spontaneous seizures and seizure-associated death in Vgat-Cre; Cln2R207X/R207X mice, suggesting that modulating interneuron activity can exacerbate epileptiform abnormalities. Taken together, these results provide mechanistic insights into the underlying etiology of seizures and premature death that characterize CLN2 disease.
Authors
Keigo Takahashi, Nicholas R. Rensing, Elizabeth M. Eultgen, Letitia L. Williams, Sophie H. Wang, Hemanth R. Nelvagal, Steven Q. Le, Marie S. Roberts, Balraj Doray, Edward B. Han, Patricia I. Dickson, Michael Wong, Mark S. Sands, Jonathan D. Cooper
Abstract
Adipose inflammation plays a key role in obesity-induced metabolic abnormalities. Epigenetic regulation, including DNA methylation, is a molecular link between environmental factors and complex diseases. Here we found that high-fat diet (HFD) feeding induced a dynamic change of DNA methylome in mouse white adipose tissue (WAT) analyzed by reduced representative bisulfite sequencing. Interestingly, DNA methylation at the promoter of estrogen receptor α (Esr1) was significantly increased by HFD, concomitant with a downregulation of Esr1 expression. HFD feeding in mice increased the expression of DNA methyltransferase 1 (Dnmt1) and Dnmt3a and binding of DNMT1 and DNMT3a to Esr1 promoter in WAT. Mice with adipocyte-specific Dnmt1 deficiency displayed increased Esr1 expression, decreased adipose inflammation, and improved insulin sensitivity upon HFD challenge; mice with adipocyte-specific Dnmt3a deficiency showed a mild metabolic phenotype. Using a modified CRISPR/RNA-guided system to specifically target DNA methylation at the Esr1 promoter in WAT, we found that reducing DNA methylation at Esr1 promoter increased Esr1 expression, decreased adipose inflammation, and improved insulin sensitivity in HFD-challenged mice. Our study demonstrated that DNA methylation at Esr1 promoter played an important role in regulating adipose inflammation, which may contribute to obesity-induced insulin resistance.
Authors
Rui Wu, Fenfen Li, Shirong Wang, Jia Jing, Xin Cui, Yifei Huang, Xucheng Zhang, Jose A. Carrillo, Zufeng Ding, Jiuzhou Song, Liqing Yu, Huidong Shi, Bingzhong Xue, Hang Shi
Abstract
Pulmonary veno-occlusive disease (PVOD) is a rare and severe subtype of pulmonary arterial hypertension, characterized by progressive remodeling of small pulmonary arteries and veins with no therapies. Using a mitomycin C–induced (MMC-induced) rat model, we previously demonstrated that protein kinase R–mediated (PKR-mediated) integrated stress response (ISR) drives endothelial dysfunction and vascular remodeling. To determine whether PKR is the primary mediator of ISR and the pathogenesis, we treated control (Ctrl) and PKR-knockout (KO) mice with the same dose of MMC. Consistent with rat data, Ctrl mice displayed ISR activation, vascular remodeling, and pulmonary hypertension after MMC treatment, while KO mice showed none of these phenotypes. Proteomic analysis revealed that MMC-mediated ISR activation attenuated protein synthesis in Ctrl but not in KO mice. These findings underscore the critical role of PKR-dependent ISR activation and subsequent perturbation of proteostasis as central mechanisms driving PVOD pathogenesis and identify PKR as a promising therapeutic target.
Authors
Amit Prabhakar, Rahul Kumar, Meetu Wadhwa, Abhilash Barpanda, Joseph Lyons, Asavari Gowda, Simren Gupta, Ananyaa Arvind, Prajakta Ghatpande, Arun P. Wiita, Brian B. Graham, Giorgio Lagna, Akiko Hata
Abstract
Mutations in the transcription factor TFAP2A are linked to congenital anomalies of the kidney and urinary tract in humans. While Tfap2a knockout (KO) in mouse collecting ducts leads to tubular epithelial abnormalities, its precise molecular functions in kidney tubules remain unclear. To investigate Tfap2a-dependent gene regulatory networks in the mouse kidney collecting ducts, we employed conditional KO (Hoxb7-Cre; Tfap2afl/fl) models combined with transcriptomics. Histomorphological and physiological assessments of Tfap2a-KO mice revealed progressive postnatal dilation of the outer medullary collecting ducts. Integrating bulk and single-nucleus RNA sequencing with in silico motif mapping in ATAC-seq datasets demonstrated that Tfap2a is highly expressed and active in normal collecting duct principal cells. Comparative transcriptomics between 3-month-old Tfap2a-KO and control mice identified dysregulated genes associated with cell adhesion and WNT signaling, including Alcam and Wnt9b. These changes were confirmed by in situ hybridization. Our findings reveal that Tfap2a regulates medullary collecting duct diameter by orchestrating a transcriptional network involving Wnt9b and Alcam, providing insights into its role in kidney structural integrity.
Authors
Janna Leiz, Karen I. López-Cayuqueo, Shuang Cao, Louisa M.S. Gerhardt, Christian Hinze, Kai M. Schmidt-Ott
Abstract
BK virus nephropathy is a severe, graft-threatening complication of kidney transplantation that requires an effective T cell response. It typically emerges in the kidney medulla. Elevated osmolyte concentrations that dynamically respond to loop diuretic therapy characterize this environment. Here, BK viremia development in kidney graft recipients negatively correlated with loop diuretic therapy. The association remained significant in multivariable and propensity score–matched analyses. Kidney function was better preserved and CD8+ T cell abundance higher in loop diuretic–exposed allografts. CD8+ T cell densities in healthy human and murine kidney medulla were lower than in cortex and increased upon loop diuretic therapy in mice. As a potential underlying mechanism, kidney medullary NaCl and urea concentrations decreased primary human CD8+ T cell numbers in vitro by induction of cell death and limitation of proliferation, respectively. Both osmolytes downregulated interferon-related gene expression. NaCl induced p53-dependent apoptosis and upregulated Na+-transporter SLC38A2, which promoted caspase-3 activation. Both decreased T cell response and cytokine secretion in response to viral peptide and allogeneic tubular epithelial cell killing, components of anti-BK virus response in the kidney allograft. Our results propose osmolyte-mediated mitigation of CD8+ T cell function as a what we believe to be novel mechanism that impairs immune response to BK virus, the therapeutic potential of which is testable.
Authors
Peyman Falahat, Adrian Goldspink, Lucia Oehler, Jessica Schmitz, Julia Miranda, Islem Gammoudi, Jan Hinrich Bräsen, Niklas Klümper, Olena Babyak, Christian Kurts, Herrmann Haller, Marieta Toma, Sibylle von Vietinghoff
Abstract
Talc pleurodesis is highly effective for preventing recurrence of pneumothorax and pleural effusion, but it can be complicated by dissemination, acute lung injury, lead exposure, and foreign body–induced chronic inflammation and pain. Our objective is to develop a safe, biodegradable, contaminant-free particle for pleurodesis. We used mouse models of pneumothorax and malignant pleural effusion to compare the efficacy and safety of pleurodesis with talc and hydroxyapatite microspheres (HAM). Intrapleural instillation of microspheres induced pleural adhesions, fibrosis, and symphysis as effectively as talc and resulted in more durable protection from experimental pneumothorax. HAM and talc both induced an osteoclastogenic, inflammatory, and fibrotic response in pleural lavage cells. Intrapleural HAM was resorbed by osteoclast action over 3 months, whereas talc was not cleared. Deletion of the osteoclast effector, CTSK, diminished pleural adhesion formation and fibrosis by HAM, and inhibition of osteoclastogenesis with anti-RANKL antibody delayed HAM clearance. We found no difference in activity level, feeding behavior, or lung compliance between particles, but talc induced more persistent pleural inflammation. We conclude that HAM resulted in an osteoclastogenic and fibrogenic pleural response that induced pleurodesis that was more durable than talc with a superior safety profile due in part to osteoclast-mediated particle clearance.
Authors
Yusuke Tanaka, Yuki Takahashi, Yuma Shindo, Lori B. Pitstick, Steven L. Teitelbaum, Wei Zou, Xiangning Wang, Jason C. Woods, Kathryn A. Wikenheiser-Brokamp, Francis X. McCormack
Abstract
Inflammation plays important roles in the pathogenesis of vascular diseases. We here show the involvement of perivascular inflammation in aortic dilatation of Marfan syndrome (MFS). In the aorta of patients with MFS and Fbn1C1041G/+ mice, macrophages markedly accumulated in periaortic tissues with increased inflammatory cytokine expression. Metabolic inflammatory stress induced by a high-fat diet (HFD) enhanced vascular inflammation predominantly in periaortic tissues and accelerated aortic dilatation in Fbn1C1041G/+ mice, both of which were inhibited by low-dose pitavastatin. HFD feeding also intensifies structural disorganization of the tunica media in Fbn1C1041G/+ mice, including elastic fiber fragmentation, fibrosis, and proteoglycan accumulation, along with increased activation of TGF-β downstream targets. Pitavastatin treatment mitigated these alterations. For noninvasive assessment of perivascular adipose tissues (PVAT) inflammation in a clinical setting, we developed an automated analysis program for CT images using machine learning techniques to calculate the perivascular fat attenuation index of the ascending aorta (AA-FAI), correlating with periaortic fat inflammation. The AA-FAI was significantly higher in patients with MFS compared with patients without hereditary connective tissue disorders. These results suggest that perivascular inflammation contributes to aneurysm formation in MFS and might be a target for preventing and treating vascular events in MFS.
Authors
Hiroyuki Sowa, Hiroki Yagi, Kazutaka Ueda, Masaki Hashimoto, Kohei Karasaki, Qing Liu, Atsumasa Kurozumi, Yusuke Adachi, Tomonobu Yanase, Shun Okamura, Bowen Zhai, Norifumi Takeda, Masahiko Ando, Haruo Yamauchi, Nobuhiko Ito, Minoru Ono, Hiroshi Akazawa, Issei Komuro
Abstract
Maternal low thyroxine (T4) serum levels during the first trimester of pregnancy correlate with cerebral cortex volume and mental development of the progeny, but why neural cells during early fetal brain development are vulnerable to maternal T4 levels remains unknown. In this study, using iPSCs obtained from a boy with a loss-of-function mutation in MCT8 — a transporter previously identified as critical for thyroid hormone uptake and action in neural cells — we demonstrate that thyroid hormone induces transcriptional changes that promote the progression of human neural precursor cells along the dorsal projection trajectory. Consistent with these findings, single-cell, spatial, and bulk transcriptomics from MCT8-deficient cerebral organoids and cultures of human neural precursor cells underscored the necessity for optimal thyroid hormone levels for these cells to differentiate into neurons. The controlled intracellular activation of T4 signaling occurs through the transient expression of the enzyme type 2 deiodinase, which converts T4 into its active form, T3, alongside the coordinated expression of thyroid hormone nuclear receptors. The intracellular activation of T4 in neural precursor cells results in transcriptional changes important for their division mode and cell cycle progression. Thus, T4 is essential for fetal neurogenesis, highlighting the importance of adequate treatment for mothers with hypothyroidism.
Authors
Federico Salas-Lucia, Sergio Escamilla, Amanda Charest, Hanzi Jiang, Randy Stout, Antonio C. Bianco
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