A109-13 STING-HIF-1α Coupling in Myeloid Cells Drives Fibroblast Activation in Progressive Sarcoidosis-Associated Pulmonary Fibrosis

Rationale Sarcoidosis is a granulomatous disease that often remits, yet a subset develops a progressive fibrosing phenotype with meaningful matrix deposition and loss of lung function. Mechanisms linking granulomatous inflammation to fibrosis remain unclear. We hypothesized that cGAS-STING activation in sarcoidosis myeloid cells licenses HIF-1α, establishing a hypoxia-programmed, macrophage-dominated niche that instructs fibroblasts to deposit collagen at lesion fronts, and disrupting this axis attenuates fibrosis. Methods Human studies included (i) multiplex immunofluorescence (IF) on sarcoidosis lung tissue for IL-6, CD68, HIF-1α, mapped to fibrotic fronts; (ii) PBMC flow cytometry quantifying intracellular HIF-1α across T cells, B cells, and monocytes; (iii) monocyte phospho-TBK1 (Ser172) as a STING readout. To anchor mechanism, we analyzed serial sections of fibrotic lungs to map hypoxia, CD68+ macrophages, αSMA+ myofibroblasts, and collagen; and tested causality in murine lungs using myeloid Hif1a-deletion and HIF-1α inhibition. Primary endpoints were spatial co-localization and staging metrics; secondary endpoints included temporal order of macrophage/fibroblast activation and antifibrotic efficacy. Results In sarcoidosis lung, IF showed IL-6 co-localization with CD68+ macrophages and juxtaposition with HIF-1α+ cells, implicating hypoxia-licensed signaling in macrophage-rich niches. PBMCs had higher intracellular HIF-1α in monocytes than in T or B cells. Phospho-TBK1 was elevated in sarcoidosis monocytes vs control monocytes, consistent with cGAS-STING activation upstream of HIF-1α. Serial sections of fibrotic lungs revealed hypoxic rims encircling nascent αSMA+ islands with a CD68+ macrophage cuff at the advancing front; mature collagen-dense cores were macrophage-poor. Across staged human lesions, macrophage density declined as fibrotic area increased, indicating overall front-focused myeloid activity. In mice, macrophages rose first (day 3) and fibroblast subsets later (days 5-14); HIF-1α appeared in CD68+ cells by day 3 and in PDGFRα+ fibroblasts thereafter, placing HIF-1α at the macrophage-fibroblast interface in hypoxic niches. Functionally, myeloid Hif1a-deletion reduced macrophage accumulation and fibrosis (histology, Ashcroft, collagen). Liposomal echinomycin and shHIF-1α lipid nanoparticles similarly decreased macrophage burden and fibrosis in vivo, indicating HIF-1α is necessary and targetable. Conclusions Human sarcoidosis samples show STING activation and HIF-1α bias in myeloid cells, aligning with a hypoxic, macrophage-front architecture driving fibroblast activation and collagen production. In the subset with progressive sarcoidosis-associated pulmonary fibrosis, a myeloid STING→HIF-1α pathway emerges as a mechanistic bridge and therapeutic node, motivating steroid-sparing, mechanism-anchored interventions targeting STING or HIF-1α. This abstract is funded by: University pilot funding