Structural and functional changes in heparan sulfate proteoglycan expression associated with the myofibroblastic phenotype.
The principal cells implicated as the source of the extracellular matrix in areas of progressive fibrosis are fibroblasts with the phenotypic appearance of myofibroblasts. This report describes differences in heparan sulfate proteoglycan expression between myofibroblasts and normal fibroblasts, associated with impaired responses to fibroblast growth factor-2 (FGF-2). Although both cell types responded to platelet-derived growth factor, myofibroblasts, unlike fibroblasts, did not proliferate to FGF-2. A response was acquired, however, when myofibroblasts were incubated with FGF-2 in the presence of heparan sulfate (HS) and heparin. Selective digestion with pronase, NaOH/NaBH(4), heparinase I, or low pH nitrous acid showed that each HS-glycosaminoglycan region comprised a pronase-resistant peptide separating two HS chains. The HS-glycosaminoglycan chains from myofibroblasts were larger (K(av), 0.32; molecular weight, 50 kd) than those from fibroblasts (K(av), 0.4; molecular weight, 33 kd), although their disaccharide composition was identical. The chains from myofibroblasts, however, contained three, compared to two, heparinase 1-resistant sequences separated by larger contiguous areas of low sulfation. Furthermore, although there was no difference in FGF-2-binding affinity between the two cell types, the chains secreted by myofibroblasts had twice the binding capacity of those from fibroblasts. Thus, it is likely that the difference in response to FGF-2 is because of a difference in FGF-2 sequestration and receptor interaction with FGF-2-HS complexes. A comparative investigation into HS fine structure is being undertaken to examine these findings in more detail.
Thomas
Gareth
G
Institute of Nephrology, University of Wales College of Medicine, Heath Park, Cardiff, Wales, UK.
Clayton
Aled
A
Thomas
Janet
J
Davies
Malcolm
M
Steadman
Robert
R
D000818:Animals; D002455:Cell Division; D002460:Cell Line; D004187:Disaccharides / Q000737:chemistry / Q000302:isolation & purification; D016222:Fibroblast Growth Factor 2 / Q000494:pharmacology; D005347:Fibroblasts / Q000187:drug effects / Q000502:physiology; D005434:Flow Cytometry; D006133:Growth Substances / Q000494:pharmacology; D019812:Heparan Sulfate Proteoglycans / Q000096:biosynthesis* / Q000737:chemistry / Q000302:isolation & purification; D007700:Kinetics; D018482:Muscle, Skeletal / Q000187:drug effects / Q000502:physiology*; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology; D011865:Radioisotope Dilution Technique; D051381:Rats; D017468:Receptors, Fibroblast Growth Factor / Q000502:physiology; D013431:Sulfates / Q000378:metabolism; D013462:Sulfur Radioisotopes
D004187:Disaccharides; D006133:Growth Substances; D019812:Heparan Sulfate Proteoglycans; D010982:Platelet-Derived Growth Factor; D017468:Receptors, Fibroblast Growth Factor; D013431:Sulfates; D013462:Sulfur Radioisotopes; D016222:Fibroblast Growth Factor 2