Author ORCID Identifier:

https://orcid.org/0000-000-7237-6002

Date of Graduation

8-2025

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Engineering (PhD)

Degree Level

Graduate

Department

Biomedical Engineering

Advisor/Mentor

Erf, Gisela

Committee Member

Goswami, Aranyak

Second Committee Member

Nelson, Christopher

Third Committee Member

Orlowski-Workman, Sara

Keywords

Autoimmunity; Immunology; Systemic Sclerosis; UCD-SSc

Abstract

Scleroderma/Systemic Sclerosis (SSc) is a multifaceted autoimmune disorder affecting approximately 300,000 people in the United States. Main features include vasculitis, immune dysfunction (innate and adaptive), autoantibody production, perivascular leukocyte infiltration, and extensive tissue fibrosis. The University of California, Davis (UCD) SSc chicken line was shown to exhibit all clinical and biological manifestations of human SSc. One early and distinctive clinical sign in both humans and UCD-SSc chickens is Raynaud’s phenomenon (RP), characterized by decreased blood flow in extremities and skin lesions. RP-like lesions develop in combs of UCD-SSc chickens within one- to two-weeks post-hatch, progressing from erythema and edema to necrosis and fibrosis, resulting in partial or complete comb-loss by six to eight weeks of age. This dissertation presents several longitudinal studies that explore cellular and molecular changes in the RP-like comb lesions of UCD-SSc chickens compared to healthy controls from 0 (hatch) to 47 days of age. In Chapter 1, immunohistochemistry was used to track the presence and quantity of immune cells in UCD-SSc combs as RP-like lesions developed. Macrophages were the first to infiltrate, accumulating in large numbers at 11 days when comb inflammation was first visible. By day 15 and 21, macrophages, T cell subsets (CD4+, CD8+, γδ T cells), and B cells reached maximum infiltration. Lymphocyte levels returned to baseline by day 35, but macrophages remained elevated. The coordinated activity of these immune cells appears crucial for comb regression and mirrors the immune activity observed in human SSc-affected skin. In Chapter 2, comb samples collected from UCD-SSc and control chickens based on RP-phenotype were assigned to age groups: 0 and 3 days (no RP), 8 days (early lesions), 21 days (active lesions), and 47 days (various stages of inflammation and regression). These samples were analyzed with next-generation RNA-sequencing to identify gene pathways altered in UCD-SSc. Early on (0 and 3 days), upregulated genes pointed to differences in comb growth. By 8 days, genes involved in immune responses and inflammation were significantly upregulated, while at 21 days, signatures of cell dysfunction, necrosis, and cell death emerged. At 47 days, immune-related pathways were upregulated again, likely reflecting ongoing inflammation and fibrosis. These findings highlight strong parallels between the SSc progression in UCD-SSc chickens and humans. Chapter 3 delved into the role of transforming growth factors (TGF)-β and their receptors. Using RNA-sequencing data, the study found higher TGF-β1 and TGF-β3 expression at 8 and 47 days, respectively, but lower TGF-β2 at 47 days in SSc combs compared to controls. TGFβ-receptor expression analysis revealed TGFBR1, TGFBR2, and TGFBR3 increasing from 0 to 47 days in UCD-SSc combs, with constitutively higher expression of TGFBR-2 and -3 throughout. Elevated plasma TGF-β1 levels, especially at 4, 7, and 28 days, suggest a role of TGF-β1 in promoting vascular changes and fibrosis. The altered expression patterns of TGF-β and its receptors likely contribute to SSc susceptibility and disease progression. Together, these studies strengthen the link between the UCD-SSc chicken model and human SSc, providing valuable insights into disease mechanisms and potential therapeutic targets.

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