Distinct fibroblast and perivascular senotypes define spatial niches that regulate fibrosis

Area of Science:

• Cellular Biology
• Tissue Engineering
• Immunology

Background:

• Fibrotic conditions are a major cause of global morbidity and mortality.
• The complex cellular and spatial interactions regulating fibrosis are poorly understood.
• Senescent cells (SnCs) have proposed roles in fibrosis, but their functions are debated.

Purpose of the Study:

• To investigate the functional and spatial heterogeneity of senescent cells in fibrosis.
• To identify distinct senescent cell subpopulations (senotypes) and their microenvironments.
• To elucidate the role of specific senotypes in fibrotic disease progression and vascular remodeling.

Main Methods:

• Integrated single-cell and spatial transcriptomics analyses in a murine fibrosis model.
• Hierarchical factorization to identify senotype gene signatures.
• Functional validation through depletion of pericyte-lineage SnCs.
• Web-based infrastructure for querying senotype conservation in public datasets.

Main Results:

• Fibrosis-associated SnCs comprise functionally divergent senotypes organized in distinct spatial niches.
• Identified fibroblast and perivascular SnC subpopulations with unique gene expression profiles.
• Fibroblast senotypes localized to niches associated with ECM production, immune signaling, and cartilage development.
• Perivascular SnCs were found at the interface of fibrotic and immune niches, upregulating vascular and fibrotic remodeling pathways.
• Depletion of pericyte-lineage SnCs enhanced vascular maturation and fibrotic ECM deposition.
• Identified senotypes are conserved across murine and human fibrotic conditions.

Conclusions:

• Senescence acts as a spatially organized regulator of fibrosis.
• Perivascular SnCs play a beneficial role in vascular remodeling and fibrosis modulation.
• These findings highlight perivascular senescence as a critical link between vascular remodeling and fibrotic outcomes.
• The identified senotypes and their spatial organization provide novel insights into fibrotic disease mechanisms.