Growth regulatory activities of endothelial extracellular matrix: mediation by transforming growth factor-beta.
The potential of transforming growth factor-beta (TGF-beta) to modulate the growth of endothelial cells via alterations in the cell's extracellular matrix (ECM) was examined. Rat brain endothelial cells were cultured in the presence or absence of TGF-beta, and subsequently ECM was prepared from the cell cultures by hypotonic lysis of the cells. Untreated endothelial cells were then cultured on the various matrices. Cells grown on TGF-beta-treated ECM showed a significant decrease in cell number (41 +/- 6% mean growth inhibition at 6 days, P less than 0.005 by paired T-test) compared with cells grown on untreated ECM. The growth inhibitory activity of the ECM was depleted by 9 days of culture, and resumption of exponential cell growth was observed. A similar phenomenon was observed if anti-TGF-beta neutralizing antibodies were incubated with the ECM. When the TGF-beta-treated matrix was exposed to a brief dithiothreitol treatment in order to inactivate residual TGF-beta, an approximately equal degree of growth inhibition was observed initially, but the reversal of inhibition occurred at an earlier time point than that with unreduced TGF-beta-treated matrix. Analyses of the composition of matrices synthesized in the presence or absence of TGF-beta revealed about a twofold increase in the accumulation of various radioactive metabolic precursors in the TGF-beta-treated matrices. However, no qualitative alterations in the matrix or cellular-associated proteins or glycoproteins were observed, as analyzed by polyacrylamide gel electrophoresis in sodium dodecyl sulfate. An increase in cell-associated heparan sulfate, however, was observed in TGF-beta-treated cells. The results suggest that certain growth regulatory effects of TGF-beta may be mediated, at least in part, by alterations in the ECM.
Newton
L K
LK
Department of Neuro-oncology, University of Texas M.D. Anderson Cancer Center, Houston 77030.
Yung
W K
WK
Pettigrew
L C
LC
Steck
P A
PA
D000818:Animals; D001921:Brain / Q000166:cytology; D002455:Cell Division / Q000502:physiology; D004229:Dithiothreitol / Q000494:pharmacology; D004727:Endothelium / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D005109:Extracellular Matrix / Q000378:metabolism / Q000502:physiology*; D006025:Glycosaminoglycans / Q000378:metabolism; D066298:In Vitro Techniques; D013431:Sulfates / Q000378:metabolism; D015291:Transforming Growth Factors / Q000502:physiology*
D006025:Glycosaminoglycans; D013431:Sulfates; D015291:Transforming Growth Factors; D004229:Dithiothreitol