Fibroblasts
Cytokines and Growth Factors
Activated FBs release cytokines and growth factors, such as IL-1, IL-6, prostaglandin E, TGFβ, CTGF, and PDGF. Both TGFβ and CTGF may exercise self-activation via an autocrine loop.[67,68] In this way ICAM-1 is expressed on FBs, which augments adhesion and retention of immune cells within the tissue.[69,70]
Several cytokines and growth factors, such as IL-1, IL-2, IL-4, IL-6, IL-8, IL-10, IL-13, IL-17, TGFβ, PDGF, tumor necrosis factor-alpha (TNF-α), interferon (IFN)-γ, and particularly the high-affinity IL-2 rec, can also be found elevated in the serum of SSc patients.[71,72] To some extent they are correlated with the degree of organ involvement and disease activity. Transforming growth factor beta clearly activates FBs to produce increased amounts of ECM components such as collagen I, III, V, and VII, and fibronectin. .[67] The presence of TGFβ1 prior to the onset of fibrosis indicates an early involvement of this factor in the pathogenesis of SSc. .[73] The TFGβ1 increases the promoter activity and type I collagen mRNA and protein synthesis in FBs.[74] via SMAD transcription factor pathway. Connective tissue growth factor exhibits a permanent over-expression of mRNA in fibrotic lesions of SSc skin and in isolated FBs.[75]
Lab Med. 2011;42(9):562-572. © 2011 American Society for Clinical Pathology
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