(WHS-K2.01) Circulating Mechanoresponsive Myeloid Cells Contribute to Fibrosis Across Disease States and Organ Systems
Thursday, May 16, 2024
9:15 AM – 10:15 AM East Coast USA Time
Background Tissue injury activates signaling pathways to recruit different cell types to orchestrate the healing response. Excessive cell activation and recruitment leads to prolonged inflammation and fibrosis with overproduction and accumulation of extracellular matrix (ECM) proteins, leading to dysfunctional scar. In this study, we identify and modulate mechanoresponsive myeloid cells that contribute to fibrosis during both cutaneous hypertrophic scar (HTS) and biomedical implant foreign body response (FBR) formation in humans, mice, and pigs. Methods We performed single cell RNA sequencing and/or Visium spatial transcriptomics on human and mouse scar and healthy skin tissue, as well as severe and mild FBR tissue. We collected human tissue with approved IRBs. We utilized murine HTS (Arabi 2007, Chen 2024 unpublished), pig wound (Chen 2021, Chen 2022), and murine FBR (Padmanabhan, Chen 2023) models. In each of these, we physically modulated the mechanical signaling environment to increase fibrosis and used genetic knockout (KO) and/or pharmacological disruption of mechanotransduction to reduce fibrosis. Results In humans, we observed that mechanical signaling pathways were distinctly upregulated in severe HTS (unpublished) and FBR (Padmanabhan, Chen 2023), compared to unwounded/benign HTS/FBR. Mechanoresponsive myeloid cells upregulated pathways related to the Rac/Rho and FAK pathways to drive downstream fibrotic pathways. In murine HTS, mechanical strain significantly increased scar formation and inflammatory recruitment (p < 0.01), while both KO and pharmacological disruption of myeloid mechanical signaling mitigated scar and restored regenerative Thbs-/Egr1+ myeloid subpopulations. In murine FBR, increasing mechanical forces significantly increased pathological FBR to human levels (p < 0.01), while immune-cell specific KO and pharmacological inhibition both significantly reduced FBR (p < 0.05) and promoted myeloid subpopulations seen in humans. In porcine models of wound healing and fibrosis, myeloid cells demonstrated the largest differential gene expression changes at early time points (d7), which led to eventual skin fibrosis at d90. Pharmacological disruption of mechanical signaling restored Thbs-/Egr1+ myeloid subpopulations, leading to skin tissue regeneration (p < 0.01), with restoration of collagen architecture and skin mechanical properties (p < 0.001) (Chen 2021, Chen 2022). Conclusions In these studies, we observe that in both humans and animals, mechanosensitive myeloid cells predominantly push the development of pathological fibrosis, which then stimulates fibroblasts to produce excessive amounts of collagen. This previously unappreciated link and reciprocal relationship between mechanosensitive myeloid cells and fibroblasts could be exploited therapeutically in humans, such as using a combined mechano-inhibitor to prevent pathological FBR or severe HTS.