Increased accumulation of extracellular thrombospondin-2 due to low degradation activity stimulates type I collagen...

Area of Science:

• Connective tissue diseases
• Molecular biology
• Biochemistry

Background:

• Systemic sclerosis (SSc) is a complex autoimmune disease characterized by fibrosis and vascular damage.
• Thrombospondin-2 (TSP-2) is a matricellular protein implicated in various biological processes, including tissue remodeling and fibrosis.

Purpose of the Study:

• To investigate the expression and functional role of TSP-2 in systemic sclerosis (SSc).
• To explore the relationship between TSP-2, collagen production, and microRNA-7 (miR-7) in SSc fibroblasts.

Main Methods:

• Quantitative analysis of TSP-2 mRNA and protein levels in cultured SSc and normal fibroblasts.
• Measurement of serum TSP-2 levels in SSc patients and healthy controls.
• In vitro knockdown of TSP-2 in SSc fibroblasts to assess collagen and miR-7 expression.
• Analysis of miR-7 expression in SSc dermal fibroblasts in vivo and in vitro.

Main Results:

• Cultured SSc fibroblasts showed lower intracellular TSP-2 synthesis but increased extracellular TSP-2 accumulation due to longer protein half-life.
• Serum TSP-2 levels were elevated in SSc patients, correlating with pitting scars and ulcers.
• TSP-2 knockdown reduced type I collagen expression and increased miR-7 levels in SSc fibroblasts.
• miR-7 expression was upregulated in SSc dermal fibroblasts both in vivo and in vitro.

Conclusions:

• Increased extracellular TSP-2 deposition in SSc fibroblasts may promote tissue fibrosis by upregulating collagen expression.
• Downregulation of intracellular TSP-2 synthesis and subsequent miR-7 upregulation in SSc fibroblasts might be a feedback mechanism to limit fibrosis.
• TSP-2 is implicated in maintaining fibrosis and angiopathy in systemic sclerosis.