Author ORCID Identifier
https://orcid.org/0000-0002-7017-1409
Date of Award
Winter 2-20-2026
Document Type
Thesis (Ph.D.)
Department or Program
Molecular and Systems Biology
First Advisor
Michael L. Whitfield, Ph.D.
Second Advisor
Yina Huang, Ph.D.
Third Advisor
Sladjana Skopelja-Gardner, Ph.D.
Abstract
Systemic sclerosis (SSc) is a rare autoimmune disease hallmarked by fibrosis, vascular damage, loss of dermal adipose tissue, and internal organ dysfunction. The pathogenesis of SSc is incompletely understood. There is a critical need to better characterize the intercellular and molecular alterations that contribute to SSc skin fibrosis. This dissertation investigates signaling pathways between macrophages and fibroblasts, immune-cell alterations, and the fibrotic remodeling of dermal white adipose tissue.
Chapter 2 is focused on characterizing the signaling dynamics, activation, and spatial localization of SSc-specific fibroblasts and macrophages. Using snMultiome analyses, I identified significant PDGF signaling in IL6/Oxidative Phosphorylation-high macrophages that activated fibroblasts, which were enriched for the PI3K-AKT-MTOR pathway. Analysis of bulk in vitro experiments validated PDGF’s activation of SSc fibroblasts and showed how inhibiting PDGFR or PI3K can reduce fibroblast profibrotic activation. PDGF signaling and the PI3K pathway were enriched in fibroblasts and regions located near the vasculature. Ex vivo staining and multiple spatial transcriptomic technologies validated the near proximity of immunomodulatory fibroblasts and macrophages to endothelial cells. These studies revealed a previously understudied model of interaction in SSc skin fibrosis.
In Chapter 3, I compiled all appropriately matched scRNA-seq datasets from SSc skin and integrated them to perform a meta-analysis of cellular alterations. This included an easily accessible web application for users to access these datasets. Using an integrated dataset, I consolidated fibroblast subtypes into a functional, spatially relevant nomenclature and identified enrichment for SSc in an under-characterized subset. These studies also identified aberrantly activated immune cells, including macrophages, CD4+ T cells, and Tregs.
Chapter 4 demonstrates that TGFβ induces adipocyte-derived stem cell-to-fibroblast activation. I generated an adipose-derived fibroblast (ADF) gene signature to identify evidence of this transition in human single-cell fibroblasts. This ADF signature was enriched in the same immunomodulatory (C3highAPOEhigh, F2/3: Perivascular) fibroblast population observed in Chapters 2 and 3.
The work described in this thesis uses a wide range of transcriptomic and molecular approaches to elucidate the mechanisms underlying SSc skin fibrosis. Together, they highlight the consistent activity of immunomodulatory fibroblasts, profibrotic macrophage activation, and aberrant alterations in other immune populations.
Recommended Citation
Jarnagin, Helen C., "A Multiomic Investigation of the Cellular and Molecular Landscapes in Early Systemic Sclerosis Skin" (2026). Dartmouth College Ph.D Dissertations. 460.
https://digitalcommons.dartmouth.edu/dissertations/460
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