Biology subjects

Tomer, Y.

Publications and source records attributed to Tomer, Y..

6 recordsLinked to original sources

bioRxiv2026

Inflammatory Fibroblasts Promote Repair After Injury Through Epithelial Proliferation

Fibroblast heterogeneity after lung injury is a well observed phenomenon made highly relevant by the widespread application of single cell RNA-sequencing. The characterization of homeostatic and injury associated states has led to the identification of a population of fibroblasts that emerge during inflammation and express cytokines that may potentially amplify the inflammatory circuit. However, whether these cells actively contribute to inflammation or serve an alternative function within the broader injury-repair cascade remains unclear. By integrating several robust murine lung injury data sets we establish the persistence of the inflammatory fibroblast across multiple injury models and identify a role for these cells in lung repair after injury through effects on alveolar epithelial proliferation. We validate this observation in-vivo using a genetic model of spontaneous lung fibrosis and in-vitro with mixed alveolar organoid cultures of various homeostatic and injury associated fibroblasts wherein we identify a mesenchymal-epithelial BMP signaling axis as a key driver of the AT2 cell injury repair response. Finally, we present supporting evidence from human disease, reinforcing the relevance of this fibroblast subset in pathological settings. These findings extend critical observations made prior to the single-cell era and contribute to our evolving understanding of fibroblast heterogeneity as a key feature of lung repair.

molecular biology↗

bioRxiv2025

Divergent Pathways of Surfactant Protein C Maturation for Disease-Associated Isoforms

Surfactant Protein C (SP-C), a hydrophobic protein exclusively synthesized and secreted by alveolar type II (AT2) cells, is important for reducing alveolar surface tension in the distal lung. Chronic interstitial pulmonary diseases have been associated with SFTPC mutations. However, a detailed understanding of SP-C maturation in the secretory pathway and disruptions caused by mutations has remained incomplete. The goal of this study was to comprehensively ascertain differences in trafficking and post-translational processing between wild-type and disease-associated SP-C mutants using doxycycline-inducible mouse lung epithelial (MLE-12) cell lines expressing either wildtype SP-C or the common clinical variant SP-CI73T, validated using primary AT2 cells isolated from a murine SP-CI73T pulmonary fibrosis model and induced pluripotent stem cell (iPSC)-derived human alveolar type 2 cells (iAT2s) expressing the same mutant. In all 3 models SP-CWT was highly concentrated in acidic LROs while SP-CI73T accumulated on the plasma membrane, which was corroborated by inhibition of clathrin-mediated endocytosis, surface biotinylation, immunogold EM, immunofluorescent staining in non-permeabilized cells, and proteinase K protection assays supporting divergence of SP-CI73T trafficking from SP-CWT. The exclusion of SP-CI73T from normal routing occurred early in the biosynthetic pathway as Brefeldin A blocked processing of both SP-C proproteins, while a 20{degrees}C temperature shift caused selective accumulation of a processed proSP-CWT intermediate, suggesting initial C-terminal cleavage of proSP-CWT occurs in late-Golgi/ trans-Golgi network (TGN). This cleavage event was sensitive to DC1, an inhibitor of furin-related subtilisin-like proprotein convertase (PPC) family members. Site-directed mutagenesis of canonical residues K160, R167 within a predicted PPC recognition site in the proSP-C BRICHOS domain blocked its processing. Expression constructs encoding inhibitory pre-proprotein (pp) peptide fragments of Furin and ppPC7 each inhibited cleavage of proSP-CWT by MLE-12 cells. Collectively, our data demonstrate that trafficking pathways for maturation of WT and mutant I73T SP-C diverge prior to the TGN where initial cleavage of the COOH-terminal SP-C propeptide occurs via a Furin-like proprotein convertase.

cell biology↗

bioRxiv2025

REGULATORY T CELLS PROTECT AGAINST ABERRANT REMODELING IN A MOUSE MODEL OF PULMONARY FIBROSIS

Regulatory T (Treg) cells are well recognized for their role in immune regulation; however, their role in tissue regeneration is not fully understood. This study demonstrates such a role of Tregs in a published preclinical murine model of spontaneous pulmonary fibrosis (PF) expressing a human PF related mutation in the Surfactant Protein-C (SP-C) gene (SFTPCI73T). Genetic crosses of SP-CI73T mice with Foxp3GFP and Foxp3DTR lines were utilized to study Treg behavior during PF development. We found that FoxP3+Tregs accumulate during the transition from inflammation to fibrogenesis, peaking at 21-28 days after mutant SftpcI73T induction localizing to both perivascular and distal fibrotic lung regions. Diphtheria toxin mediated ablation of Tregs at 17 days worsened fibrosis and increased levels of TGF{beta} and inflammatory cytokines. Tregs expressed Th2 markers (Gata3+) and elaborated factors including amphiregulin (Areg) and Osteopontin (Spp1). Reductionist experiments showed that lung Tregs enhanced organoid formation when co-cultured with alveolar epithelial cells and adventitial fibroblasts, an effect size mimicked using Areg and Spp1 in combination. Our findings demonstrate that immune-mesenchymal-epithelial signaling crosstalk is present in the distal lung wherein Tregs play a protective role by limiting fibrosis and promoting tissue repair, highlighting their broader function beyond immune modulation in lung injury. HIGHLIGHTSO_LIIn a preclinical model of spontaneous pulmonary fibrosis, regulatory T cells (Tregs) were found to infiltrate the lung coincident with the resolution of early injury and transition to fibrogenesis. C_LIO_LIDepletion of Tregs at this transition worsened lung injury and enhanced fibrogenesis. C_LIO_LITregs recovered from the fibrotic lung are Type 2 skewed - GATA3+ and produce growth factors (e.g. Amphiregulin, Osteopontin) that promote lung tissue repair in ex vivo organoid models. C_LI

molecular biology↗

bioRxiv2024

Aberrant Transitional Alveolar Epithelial Cells Promote Pathogenic Activation of Lung Fibroblasts in Preclinical Fibrosis Modeling

Pulmonary fibrosis (PF) is a chronic progressive lung disease histopathologically characterized by fibrotic remodeling and the presence of pathological epithelial and mesenchymal cell populations in the distal lung parenchyma. Within the epithelial compartment, a subset of alveolar type 2 cells (AT2s) enter and persist in an aberrant transitional state. Whether and how these aberrant transitional cells participate in lung fibrosis is not known. To address this, we exploited the SftpcC121G mouse model, where we previously demonstrated that chronic expression of a PF-associated point mutation (C121G) in the AT2-specific surfactant protein C (Sftpc) gene results in spontaneous and progressive fibrosis driven by intrinsic AT2 dysfunction. We utilized single cell RNA sequencing to demonstrate the emergence of pathologic epithelial and mesenchymal cells in the SftpcC121G murine lung fibrosis model, including aberrant transitional alveolar epithelial cells as well as transitional and fibrotic fibroblasts. Aberrant transitional alveolar epithelial cells share similar transcriptional profiles to human aberrant basaloid cells, including the upregulation of profibrotic gene markers (Fn1, Ctgf, Tgfb2, Pdgfb, Spp1), and develop a unique interactome with pathogenic lung fibroblasts. We developed a method to reliably flow sort aberrant transitional alveolar epithelial cells, and we highlight their ability to cause fibrotic activation of fibroblasts in ex vivo organoid assays and using conditioned supernatant, suggesting a profibrotic secretome. We conclude that aberrant transitional alveolar epithelial cells actively contribute to fibrotic lung remodeling through pathogenic activation of alveolar fibroblasts.

cell biology↗

bioRxiv2024

Impaired AMPK Control of Alveolar Epithelial Cell Metabolism Promotes Pulmonary Fibrosis

Alveolar epithelial type II (AT2) cell dysfunction is implicated in the pathogenesis of familial and sporadic idiopathic pulmonary fibrosis (IPF). We previously described that expression of an AT2 cell exclusive disease-associated protein isoform (SP-CI73T) in murine and patient-specific induced pluripotent stem cell (iPSC)-derived AT2 cells leads to a block in late macroautophagy and promotes time-dependent mitochondrial impairments; however, how a metabolically dysfunctional AT2 cell results in fibrosis remains elusive. Here using murine and human iPSC-derived AT2 cell models expressing SP-CI73T, we characterize the molecular mechanisms governing alterations in AT2 cell metabolism that lead to increased glycolysis, decreased mitochondrial biogenesis, disrupted fatty acid oxidation, accumulation of impaired mitochondria, and diminished AT2 cell progenitor capacity manifesting as reduced AT2 self-renewal and accumulation of transitional epithelial cells. We identify deficient AMP-kinase signaling as a key upstream signaling hub driving disease in these dysfunctional AT2 cells and augment this pathway to restore alveolar epithelial metabolic function, thus successfully alleviating lung fibrosis in vivo.

molecular biology↗

bioRxiv2023

Disruption of Prostaglandin F2α Receptor Signaling Attenuates Fibrotic Remodeling and Alters Fibroblast Population Dynamics in A Preclinical Murine Model of Idiopathic Pulmonary Fibrosis

Idiopathic Pulmonary Fibrosis (IPF) is a chronic parenchymal lung disease characterized by repetitive alveolar cell injury, myofibroblast proliferation, and excessive extracellular matrix deposition for which unmet need persists for effective therapeutics. The bioactive eicosanoid, prostaglandin F2, and its cognate receptor FPr (Ptfgr) are implicated as a TGF{beta}1 independent signaling hub for IPF. To assess this, we leveraged our published murine PF model (IER -SftpcI73T) expressing a disease-associated missense mutation in the surfactant protein C (Sftpc) gene. Tamoxifen treated IER -Sftpc I73T mice develop an early multiphasic alveolitis and transition to spontaneous fibrotic remodeling by 28 days. IER -Sftpc I73T mice crossed to a Ptgfr null (FPr-/-) line showed attenuated weight loss and gene dosage dependent rescue of mortality compared to FPr+/+ cohorts. IER -Sftpc I73T /FPr-/- mice also showed reductions in multiple fibrotic endpoints for which administration of nintedanib was not additive. Single cell RNA sequencing, pseudotime analysis, and in vitro assays demonstrated Ptgfr expression predominantly within adventitial fibroblasts which were reprogrammed to an "inflammatory/transitional" cell state in a PGF2/ FPr dependent manner. Collectively, the findings provide evidence for a role for PGF2 signaling in IPF, mechanistically identify a susceptible fibroblast subpopulation, and establish a benchmark effect size for disruption of this pathway in mitigating fibrotic lung remodeling.

molecular biology↗