Gelbard, A. | Search bioRxiv

bioRxiv2026

Lymphangiogenesis is Critical for Healing and Survival in a Murine Model of Laryngotracheal Injury

Objective: Lymphatic dysfunction has been implicated in exacerbating fibrosis in numerous diseases, yet the role of the lymphatic system in laryngotracheal injury has not previously been explored. This study aims to evaluate lymphatic vascular remodeling in a murine model of laryngotracheal stenosis (LTS) and determine how pharmacologic blockade of lymphangiogenesis impacts airway healing after mucosal injury. Methods: LTS was induced in C57BL6 mice using an established chemomechanical injury model. Lymphatic density was quantified using LYVE-1 immunohistochemistry. Mice were treated with the VEGFR-3-selective tyrosine kinase inhibitor SAR131675 to block lymphangiogenesis after injury. Outcomes assessed included survival, histopathology, immunohistochemistry, and Evans blue dye vascular leakage. Results: Laryngotracheal injury induced a substantial increase in subepithelial lymphatic vessel density concomitant with fibrotic remodeling. Pharmacologic inhibition of VEGFR-3 signaling with SAR131675 abrogated this lymphangiogenic response and resulted in markedly increased mortality, impaired epithelial repair with obstructive sloughing, increased edema, and persistent histopathologic evidence of tissue injury. A qualitative increase in pathologic fibrocellular remodeling was also observed, though with no measurable difference in lamina propria thickness. Conclusion: These findings establish lymphatic remodeling as an essential component of successful airway repair following mucosal injury. Lymphatic dysfunction is a common feature of known risk factors for LTS including diabetes, obesity, and prematurity, and can be exacerbated by positive pressure ventilation. Disruption of the lymphangiogenic response to airway injury may lead to stasis of pro-inflammatory factors that result in chronic inflammation, maladaptive remodeling, and pathologic tissue changes. The lymphatic vasculature is a viable target for future mechanistic study and potential therapeutic intervention following airway injury.

physiology↗

bioRxiv2023

Low Gut Microbial Diversity Augments Estrogen-driven Pulmonary Fibrosis in Female-Predominant Interstitial Lung Disease

Although profibrotic cytokines such as IL-17A and TGF-{beta}1 have been implicated in interstitial lung disease (ILD) pathogenesis, interactions between gut dysbiosis, gonadotrophic hormones and molecular mediators of profibrotic cytokine expression, such as phosphorylation of STAT3, have not been defined. Here we show by chromatin immunoprecipitation sequencing (ChIP-seq) analysis of primary human CD4+ T cells that regions within the STAT3 locus are significantly enriched for binding by the transcription factor estrogen receptor alpha (ERa). Using the murine model of bleomycin-induced pulmonary fibrosis, we found significantly increased regulatory T cells compared to Th17 cells in the female lung. Genetic absence of ESR1 or ovariectomy in mice significantly increased pSTAT3 and IL-17A expression in pulmonary CD4+ T cells, which was reduced after repletion of female hormones. Remarkably, there was no significant reduction in lung fibrosis under either condition, suggesting that factors outside of ovarian hormones also contribute. Assessment of lung fibrosis among menstruating females in different rearing environments revealed that environments favoring gut dysbiosis augment fibrosis. Furthermore, hormone repletion following ovariectomy further augmented lung fibrosis, suggesting pathologic interactions between gonadal hormones and gut microbiota on lung fibrosis severity. Analysis in female sarcoidosis patients revealed a significant reduction in pSTAT3 and IL-17A levels and a concomitant increase in TGF-{beta}1 levels in CD4+ T cells, compared to male sarcoidosis patients. These studies reveal that estrogen is profibrotic in females and that gut dysbiosis in menstruating females augments lung fibrosis severity, supporting a critical interaction between gonadal hormones and gut flora in lung fibrosis pathogenesis.

immunology↗