Biomedical Engineering Reference
In-Depth Information
down to a minimum of one repeating unit on the most hydrophilic poly-
mer [poly(ethylene-
alt
-maleic anhydride)], e.g. in Fig. 4. This again correlates
very well with the model of cellular sensing of the fibronectin anchorage
strength to the substrate and the corresponding intracellular feedback of
force and focal adhesion size regulation.
As already mentioned, downstream cellular processes like proliferation
and differentiation can be affected by extracellular signals, too. In order
to address this issue the behavior of endothelial cells was investigated not
only in respect to fibronectin fibrillogenesis on short-time scales. The pro-
liferation and differentiation of endothelial cells into vascular-like tubes was
analyzed in cell culture experiments over 5 days on substrates with a differ-
ent fibronectin anchorage strength. As described in detail elsewhere [103],
endothelial cells grew in a flat monolayer after 1 to 3 days of cell culture
on all substrates. However, after 5 days distinct morphological differences
were observed. On substrates with a high fibronectin anchorage strength en-
dothelial cells still exhibited monolayer characteristics. In contrast, an early
vascular-like network formation was observed on the substrate with a weaker
fibronectin anchorage strength. The cells also started to form tubular struc-
tures. As an underlying reason for the different morphology, the formation
of distinctively different extracellular matrix networks was found as shown
in Fig. 5. The cell-derived fibronectin network on substrates with a high fi-
bronectin anchorage strength showed a dense and fine structure and was
restrictedtothesubstratesurfacebelowthecells.Theformationofavascular-
like structure was accompanied by the formation of a coarse fibronectin net-
work which was distributed around the cellular structures also in the vertical
direction. The analysis by confocal laser scanning microscopy with imaging
in different horizontal planes allowed us to quantify the differential matrix
distribution (Fig. 5).
Fig. 4
Topography image of fibronectin nanofibrils after 50 min of reorganization by en-
dothelial cells on poly(ethylene-
alt
-maleic anhydride) substrates visualized by scanning
force microscopy at physiological conditions. The height of fibrils is 5 to 10 nm.
Scale bar
:
300 nm
