Biology subjects

Zepp, J. A.

Publications and source records attributed to Zepp, J. A..

5 recordsLinked to original sources

bioRxiv2026

Dysplastic Epithelial Repair Propagates Chronic Pathology Through the Paracrine Transformation of Pulmonary Fibroblasts

Severe lung injury promotes the ectopic accumulation of basal cells in the alveoli and the presence of these dysplastic epithelial cells are strongly associated with regions of pulmonary fibrosis (PF) in diseased lungs. Recent studies have identified a unique subset of "inflammatory" fibroblasts expressing pro-inflammatory genes, especially cytokines involved in monocyte recruitment, that are also enriched in disease and thought to contribute to the onset and progression of PF. Here we show that these two injury-induced cell types are intricately connected, in that dysplastic basal cells generate diffusible signals to robustly induce the inflammatory phenotype in pulmonary fibroblasts. Capitalizing on transcriptomic analysis, we identify the enriched inflammatory signaling pathways in treated fibroblasts and specifically demonstrate that IL-1 secreted by dysplastic basal cells is responsible for this fibroblastic transformation. IL-1 neutralization in vivo is sufficient to significantly reduce the inflammatory fibroblast burden in regions of alveolar bronchiolization, and the resolution of inflammatory fibroblasts in turn reduces CCR2+ immune cell recruitment to these areas. These results suggest dysplastic basal cells play an indirect role in chronic inflammation and fibrotic remodeling through the induction of a proinflammatory fibroblast phenotype and subsequent recruitment of immune cells, establishing a chronic wound healing microenvironment that prolongs localized pathologic remodeling.

cell biology↗

bioRxiv2025

Stc1-expressing myofibroblasts are a developmentally distinct lineage cleared through intrinsic apoptosis in the neonatal lung

Lung myofibroblasts are necessary for early postnatal alveolar growth and develop again during pathological fibrosis. Determining the unique contributions of multiple myofibroblast lineages to development and disease is hampered by a lack of genetic tools to distinguish between them. In this study, we generated a Stc1CreERT2 mouse line that faithfully labels the developmentally transient secondary crest myofibroblasts (SCMF) and distinguishes SCMFs from alveolar duct myofibroblasts (DMF) and smooth muscle. SCMF populations expand by clonal proliferation of Stc1-expressing progenitors and contract by apoptosis. We deleted the intrinsic apoptosis effectors Bax and Bak1 in the Stc1-lineage, which prevented SCMF clearance during alveologenesis. Single-cell RNA-seq revealed that residual Stc1-lineage cells lacking Bax and Bak1 lose myofibroblast identity but express a combination of SCMF and DMF marker genes. Embryonic lineage tracing identified that SCMFs and DMFs have distinct progenitor populations with unique niches, and genetic activation of developmentally important signaling pathways could not interconvert these lineages. These findings establish Stc1-lineage SCMFs as a discrete population, developmentally divergent from DMFs, and define their life cycle in isolation from other myofibroblast lineages.

developmental biology↗

bioRxiv2023

Dynamic Hippo pathway activity underlies mesenchymal differentiation during lung alveolar morphogenesis

Alveologenesis, the final stage in lung development, substantially remodels the distal lung, expanding the alveolar surface area for efficient gas exchange. Secondary crest myofibroblasts (SCMF) exist transiently in the neonatal distal lung and are critical for alveologenesis. However, the pathways that regulate SCMF function, proliferation, and temporal identity remain poorly understood. To address this, we purified SCMFs from reporter mice, performed bulk RNA-sequencing, and found dynamic changes in Hippo-signaling components during alveologenesis. We deleted Hippo effectors, Yap/Taz, from Acta2-expressing SCMFs at the onset of alveologenesis, causing a significant arrest in alveolar development. Using scRNA-seq, we identified a distinct cluster of cells in mutant lungs with altered expression of marker genes associated with proximal mesenchymal cell types, airway smooth muscle (ASM), and alveolar duct myofibroblasts (DMF). Using lineage tracing, we show that neonatal Acta2-expressing SCMFs give rise to adult DMFs and that Yap/Taz mutants have an increase of persisting DMF-like cells in the alveolar ducts. Our findings identify plasticity in neonatal lung myofibroblasts and demonstrate that Yap/Taz are critical for maintaining lineage commitment along the proximal-distal axis.

developmental biology↗

bioRxiv2023

Dysregulated alveolar epithelial maintenance in Hermansky-Pudlak syndrome pulmonary fibrosis

Hermansky-Pudlak syndrome (HPS) is a genetic disorder of endosomal protein trafficking associated with pulmonary fibrosis in specific subtypes, including HPS-1 and HPS-2. Single mutant HPS1 and HPS2 mice display increased fibrotic sensitivity while double mutant HPS1/2 mice exhibit spontaneous fibrosis with aging, which has been attributed to HPS mutations in alveolar epithelial type II (AT2) cells. We utilized HPS mouse models and human lung tissue to investigate mechanisms of AT2 cell dysfunction driving fibrotic remodeling in HPS. Starting at 8 weeks of age, HPS mice exhibited progressive loss of AT2 cell numbers. HPS AT2 cell function was impaired ex vivo and in vivo. Incorporating AT2 cell lineage tracing in HPS mice, we observed aberrant differentiation with increased AT2-derived alveolar epithelial type I cells. Transcriptomic analysis of HPS AT2 cells revealed elevated expression of genes associated with aberrant differentiation and p53 activation. Lineage tracing and organoid modeling studies demonstrated that HPS AT2 cells were primed to persist in a Krt8+ reprogrammed transitional state, mediated by p53 activity. Intrinsic AT2 progenitor cell dysfunction and p53 pathway dysregulation are novel mechanisms of disease in HPS-related pulmonary fibrosis, with the potential for early targeted intervention before the onset of fibrotic lung disease.

cell biology↗

bioRxiv2022

A CXCL12 morphogen gradient uncovers lung endothelial heterogeneity and promotes distal vascular growth

In adults, there is a growing amount of data uncovering the cellular diversity of the pulmonary circulation and mechanisms governing vascular repair after injury, however, molecular and cellular mechanisms contributing to the morphogenesis and growth of the pulmonary vasculature during embryonic development are less clear. Importantly, deficits in vascular development lead to a large number of lung diseases in children, indicating a need to uncover fetal programs that promote pulmonary vascular growth. To address this, we used a transgenic mouse reporter for expression of Cxcl12, an arterial hallmark gene, and performed single-cell RNA sequencing on isolated Cxcl12-DsRed+ endothelium to assess cellular heterogeneity within pulmonary endothelium. Combining cell annotation, gene ontology analysis, and spatial transcriptomics allowed us to segregate the developing artery into spatially and functionally distinct novel subpopulations. In addition, expression of Cxcl12 suggests a morphogen gradient from arteries to capillaries, suggesting directed cell migration for pulmonary vascular development. Disruption of this gradient led to abnormal branching and pulmonary vascular hypoplasia. These data provide evidence for arterial endothelial functional heterogeneity and reveal conserved signaling mechanisms essential for pulmonary vascular development.

developmental biology↗