Thesis Research Summary:
Systemic sclerosis (SSc) is an inflammatory autoimmune disease affecting connective tissue, characterized by excessive collagen deposition in the skin and other organs. SSc ranges from a less severe yet disabling disease with primarily skin involvement to a more severe and often fatal diffuse disease involving internal organs. The Tight Skin 2 (Tsk2/+) mouse is a model of this disease, and these mice have many features of the human disease including tight skin, excessive collagen deposition, and occurrence of antinuclear antibodies (ANA) with age. Because current treatments only ameliorate disease symptoms, studies of the Tsk2/+ mouse are important for understanding of disease pathology and progression, and the potential unmasking of new therapeutic targets. Throughout our studies, this model was used to develop a novel timeline of disease progression and to evaluate ECM changes essential for fibrosis and disease development that are difficult to study in human individuals with SSc.
Skin samples from Tsk2/+ and WT littermates in our colony of B6.Tsk2/+ congenic mice (N4-N8) (2 – 24 weeks old) were examined for ECM alterations and cellular infiltrates with age. Neonatal fibroblasts were obtained from Tsk2/+ and WT mice and evaluated for collagen and elastin protein production in vitro. Blood samples were collected serially from individual mice and examined by indirect immunofluorescence for the presence of antinuclear antibodies.
In vivo, studies using histological and total protein analysis have shown that collagen accumulation increases with age in Tsk2/+ mice, with significant increases as compared to WT littermates not occurring until 10 weeks of age. This age is fully 8 weeks after the development of the “tight” phenotype. In contrast, histological examination of the ECM of the dermis revealed a significant 2-fold increase of elastin fibers at 2 weeks of age that continued throughout adulthood. Skin from 2 week old Tsk2/+ males have a 2.5-fold increase in production of elastin transcripts compared to WT males as well as increased production of collagens, TGF-B1 signatures, and other ECM protein transcripts. The first occurrence of antinuclear antibody production in Tsk2/+ mice was at 17 weeks of age and the presence of antinuclear antibody overall was not different between Tsk2/+ and WT littermates, suggesting that the disease is not antibody driven.
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