Title: Fibronectin Matrix Assembly by Transglutaminase in Cultured Satellite Cells and its Possible Role in Muscle Regeneration
Abstract: We demonstrate the effect of activated plasma transglutaminase (Factor XIIIa) on the assembly of fibronectin into extracellular matrix of cultured satellite cells and its possible role in muscle regeneration. The binding of 125I-fibronectin and 125I-28 kDa fragment to cell layers decreased significantly following the cell fusion. In the absence of Factor XIIIa, 125I-fibronectin was assembled into extracellular matrix (pool II) of cultured satellite cells as reducible disulfide cross-linked multimers, whereas in the presence of Factor XIIIa, 125I-fibronectin was assembled into extracellular matrix mostly as nonreducible disulfide cross-linked multimers. Furthermore, the assembly of fibronectin into extracellular matrix was stimulated by Factor XIIIa to a greater extent than by Factor XIII. Under these conditions, the proliferation of satellite cells was significantly promoted as revealed by the increase in cell number and thymidine incorporation rate. Therefore, we propose that Factor XIIIa enhances the assembly of fibronectin into extracellular matrix of cultured satellite cells and that the fibronectin matrix assembled by Factor XIIIa stimulates the proliferation of satellite cells, which in turn contributes to muscle regeneration.