Biomedical Engineering Reference
In-Depth Information
fibroblast/keratinocyte system (Chiu et al. 2005). Pena et al. have investigated the effect of collagen
accumulation around fibroblasts as an effect of skin aging and observed a reduced effect when using
an inhibitor agent. Figure 18.3 presents results from their investigation and shows combined SHG
(green) and two-photon fluorescence (red) images of the collagen matrix and fibroblasts, respectively.
The images in Figure 18.3a-c were measured in a control sample without inhibitor added and an accu-
mulation of collagen around the cells can be observed. The images in Figure 18.3d-f were obtained in
a sample initially treated with the inhibitor agent and no collagen accumulation can be observed up to
24 h (Figure 18.3e). At this time, the inhibitor was removed and the image acquired after 48 h (Figure
18.3f) shows that collagen accumulation has been reinitiated.
To mimic the geometry of the intervertebral disc, Bowles et al. synthesized collagen gels seeded with
ovine annulus fibrosus cells (Bowles et al. 2010). SHG images measured on collagen gels of different
density were compared in terms of fiber alignment and material heterogeneity to identify a suitable
construct for a functional tissue-engineered intervertebral disc. In an investigation of tissue tumor
invasion, cell invasion has been monitored in synthetic as well as native collagen tissues by combined
two-photon fluorescence and SHG microscopy (Wolf et al. 2009). A similar combination of techniques
has been used to investigate cell-material invasion for endothelial cells grown on collagen scaffolds (Lee
et al. 2009). Their results showed an alignment of extruding cell processes along collagen fibers together
with degradation and displacement of the matrix during cell migration. Collagen has also been moni-
tored in a study of chondrocytes seeded on collagen type I/III membranes in order to optimize growth
for obtaining suitable implants for knee joints (Martini et al. 2006).
To develop a scaffold promoting spread of Schwann cells, constructs consisting of collagen treated
with Growth Factor Reduced Matrigel and seeded with cells have been investigated (Dewitt et al. 2009).
FIgurE 18.3
(
See color insert.
) Combined SHG (green) and two-photon fluorescence (red) images measured
on a collagen scaffold seeded with fibroblasts. Images (a)-(c) were obtained in a control sample and an increased
accumulation of collagen can be observed around the cells. For a sample where an inhibitor agent has been added
initially, images (d) and (e) show no collagen accumulation around the cells. However, after the inhibitor has been
removed at 24 h, collagen accumulation is initiated and clearly seen after 48 h in image (f). Scale bars 30 μm.
(Reprinted from Pena, A.-M. et al. 2010.
Journal of Biomedical Optics
15:056018, with the kind permission of the
authors.)
