Differences in binding to the solid substratum and extracellular matrix may explain isoform-specific paracrine effects of platelet-derived growth factor.
We have studied the paracrine response of fibroblasts to the two homodimeric isoforms of platelet-derived growth factor (PDGF-AA and -BB). CHO-cells stably transfected with a B-chain cDNA expression vector (CHO-PDGF-B cells), were found to elicit a marked paracrine response when seeded at clonal density on preformed monolayers of human or murine fibroblasts; no such response was elicited by CHO-PDGF-A cells. Immunofluorescence microscopy of CHO-PDGF-B cell cultures showed the presence of a pericellular deposit of material reacting with antibodies against PDGF-BB; no corresponding PDGF-AA immunoreactive material was found in the CHO-PDGF-A cultures. The pericellular material, deposited by CHO-PDGF-B cells, was shown to have a growth promoting effect on target cells. Furthermore, we could show that 125I-PDGF-BB binds more efficiently than 125I-PDGF-AA to extracellular matrix prepared from foreskin fibroblast cultures, as well as to defined extracellular matrix components (fibronectin, laminin and collagen III). The results reveal a marked difference in the paracrine activity of PDGF-AA and PDGF-BB; the latter has a strong local growth enhancing effect, that is mostly likely to be ascribed to its association with components of the extracellular matrix.
Pekny
M
M
Department of Pathology, University Hospital, Uppsala, Sweden.
Ostman
A
A
Hermansson
A
A
Nistér
M
M
Heldin
C H
CH
Westermark
B
B
D016475:3T3 Cells; D000818:Animals; D016466:CHO Cells; D002452:Cell Count; D002460:Cell Line; D003094:Collagen / Q000378:metabolism; D006224:Cricetinae; D005109:Extracellular Matrix / Q000378:metabolism*; D005347:Fibroblasts / Q000378:metabolism; D005353:Fibronectins / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D006801:Humans; D007457:Iodine Radioisotopes; D007797:Laminin / Q000378:metabolism; D046911:Macromolecular Substances; D008297:Male; D051379:Mice; D016685:Mitomycin / Q000494:pharmacology; D010982:Platelet-Derived Growth Factor / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology*; D011994:Recombinant Proteins / Q000378:metabolism; D014162:Transfection
D005353:Fibronectins; D007457:Iodine Radioisotopes; D007797:Laminin; D046911:Macromolecular Substances; D010982:Platelet-Derived Growth Factor; D011994:Recombinant Proteins; D016685:Mitomycin; D003094:Collagen