Thrombospondin-1 is a potent mitogen and chemoattractant for human vascular smooth muscle cells.
Thrombospondin-1 (TSP-1) is a matricellular protein that is present in negligible amounts in normal human vasculature but occurs in significant amounts in diseased vessels. In this study, we examined the effect of TSP-1 on DNA synthesis, proliferation, and migration in human vascular smooth muscle cells grown from saphenous vein. TSP-1 (0.1 to 30 micrograms/mL) elicited a concentration-dependent increase in DNA synthesis under serum-free conditions. In combination with platelet-derived growth factor, TSP-1 induced a synergistic effect on DNA synthesis that was significantly higher than the additive effect of both agents. In proliferation assays, TSP-1 increased cell numbers by 50% relative to the serum-free controls over 14 days. In migration assays, conducted using modified Boyden chambers, TSP-1 (> or = 10 micrograms/mL) elicited marked chemotaxis to a degree equivalent to platelet-derived growth factor. The chemotactic response to TSP-1 (10 micrograms/mL) was abolished by the GRGDSP peptide but unaffected by the control GRGESP peptide, whereas neither peptide inhibited DNA synthesis stimulated by TSP-1. Inhibition of tyrosine kinase activity with genistein or tyrphostin A23 abolished DNA synthesis induced by TSP-1, and a neutralizing antibody to platelet-derived growth factor had no effect on DNA synthesis. Similarly, migration in response to TSP-1 was largely inhibited by these tyrosine kinase inhibitors. TSP-1 is a strong mitogen and chemoattractant for human vascular smooth muscle cells under serum-free conditions. The novel finding that TSP-1 is mitogenic for human cells contrasts with previous studies that have not shown any significant effect of TSP-1 itself on the growth of animal-derived smooth muscle cells. TSP-1 may play an important modulatory role in the local regulation of vascular smooth muscle function in vascular pathologies in humans.
Patel
M K
MK
Department of Clinical Pharmacology, Imperial College School of Medicine at St Mary's, London, UK. m.k.patel@ic.ac.uk
Lymn
J S
JS
Clunn
G F
GF
Hughes
A D
AD
D002455:Cell Division; D002465:Cell Movement / Q000187:drug effects; D002478:Cells, Cultured; D002630:Chemotactic Factors / Q000494:pharmacology*; D004247:DNA / Q000096:biosynthesis; D006801:Humans; D008934:Mitogens / Q000494:pharmacology*; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects*; D010982:Platelet-Derived Growth Factor / Q000502:physiology; D019699:Thrombospondins / Q000494:pharmacology*; D016212:Transforming Growth Factor beta / Q000494:pharmacology
D002630:Chemotactic Factors; D008934:Mitogens; D010982:Platelet-Derived Growth Factor; D019699:Thrombospondins; D016212:Transforming Growth Factor beta; D004247:DNA