Matrix Protein Metabolism
In SSc, abundant deposits of collagen type I are found in the perivascular region of the dermis and at the border between deep dermis and subcutis, as demonstrated by immunohistochemistry and in situ hybridization. In addition, collagen types III, V, VI, VII, as well as fibronectin and tenascin are also overexpressed in the skin.[76] Recently, an increased formation of bone-type cross-links due to activation of lysyl hydroxylase 2 has been reported in SSc skin as well as bone-type degradation products in the serum (collagen telopeptides may be used as a surrogate marker of disease activity). Hypoxia may contribute in the process of transdifferentiation of FBs to an altered bone-like phenotype.[77,78]
Increased collagen synthesis and decreased collagenase expression may result in excessive accumulation of collagen, indicating that the balance between these synthesizing and degrading processes (MMPs) is crucial and may be modulated
by TIMP-1 expression.[79] On the other hand, increase in the proteolytic activity (cathepsin K) could indicate major remodeling as a counter-regulatory mechanism.[80]
Lab Med. 2011;42(9):562-572. © 2011 American Society for Clinical Pathology
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