Transforming growth factor beta 1 modulates extracellular matrix organization and cell-cell junctional complex formation during in vitro angiogenesis.
Transforming growth factor-beta 1 (TGF-beta 1) is angiogenic in vivo. In two-dimensional (2-D) culture systems microvascular endothelial cell proliferation is inhibited up to 80% by TGF-beta 1; however, in three-dimensional (3-D) collagen gels TGF-beta 1 is found to have no effect on proliferation while eliciting the formation of calcium and magnesium dependent tube-like structures mimicking angiogenesis. DNA analyses performed on 3-D cell cultures reveal no significant difference in the amount of DNA or cell number in control versus TGF-beta 1 treated cultures. In 2-D cultures TGF-beta 1 is known to increase cellular fibronectin accumulation; however, in 3-D cultures no difference is seen between control and TGF-beta 1 treated cells as established by ELISA testing for type IV collagen, fibronectin, and laminin. In 3-D cultures there is increased synthesis and secretion of type V collagen in both control and TGF-beta 1 treated cultures over 2-D cultures. Even though an equal amount of type V collagen is seen in both 3-D conditions, there is a reorganization of the protein with concentration along an organizing basal lamina in TGF-beta 1 treated cultures. EM morphological analyses on 3-D cultures illustrate quiescent, control cells lacking cell contacts. In contrast, TGF-beta 1 treated cells show increased pseudopod formation, cell-cell contact, and organized basal lamina-like material closely apposed to the "abluminal" plasma membranes. TGF-beta 1 treated cells also appear to form junctional complexes between adjoining cells. Immunofluorescence using specific antibodies to the tight junction protein ZO-1 results in staining at apparent cell-cell junctions in the 3-D cultures. Northern blots of freshly isolated microvascular endothelium, 2-D and 3-D cultures, using cDNA and cRNA probes specific for the ZO-1 tight junction protein, reveal the presence of the 7.8 kb mRNA. Western blots of rat epididymal fat pad endothelial cells (RFC) monolayer lysates probed with anti-ZO-1 label a 220 kd band which co-migrates with the bonafide ZO-1 protein. These data confirm and support the hypothesis that TGF-beta 1 is angiogenic in vitro, eliciting microvascular endothelial cells to form tube-like structures with apparent tight junctions and abluminal basal lamina deposition in three-dimensional cultures.
Department of Pathology, Yale School of Medicine, New Haven, Connecticut 06510.
J R
JR
Merwin
J M
JM
Anderson
O
O
Kocher
C M
CM
Van Itallie
J A
JA
Madri
D000818:Animals; D002450:Cell Communication / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000166:cytology* / Q000187:drug effects / Q000648:ultrastructure; D005109:Extracellular Matrix / Q000187:drug effects* / Q000648:ultrastructure; D007365:Intercellular Junctions / Q000187:drug effects* / Q000648:ultrastructure; D008854:Microscopy, Electron; D009389:Neovascularization, Pathologic / Q000473:pathology*; D015388:Organelles / Q000648:ultrastructure; D051381:Rats; D011919:Rats, Inbred Strains; D015291:Transforming Growth Factors / Q000502:physiology*
D015291:Transforming Growth Factors