Biomedical Engineering Reference
In-Depth Information
2.2 Effects of Compression
The effects of cell stretching on mesenchymal stem cell differentiation most cer-
tainly seem to inhibit adipogenesis while increasing osteogenesis. But what hap-
pens when MSCs are subjected to compression and shear stress? There are not
many studies on MSC adipogenesis in regard to compression and fluid shear
relative to mechanical stretch, and the results are not as clear and consistent as
those found for stretch. In this section, effects of cell compression on MSC fate
decision will be reviewed.
Relevant to the topic, as far as we know, there is no study that examined the
effect of compressive loading on MSC adipogenesis. One recent study utilized
preadipocytes, SGBS (Simpson-Golabi-Behmel syndrome) cells derived from
human adipose tissue, to test the effect of compression [
19
]. When SGBS cells
were subjected to a compressive force of 226 Pa for 12 h before the adipogenic
induction, their adipogenesis was inhibited (Fig.
4
). On the other hand, com-
pression applied immediately after adipogenic induction did not significantly
inhibit the adipogenesis. These data are comparable to the cell stretch inhibition of
MSC adipogenesis with stretches applied during the MSC commitment stage
(before the induction period) [
24
]. However, the observation that the compression
applied during the adipogenic induction did not affect the adipogenesis is different
from most of the cell stretch data, in which adipogenesis inhibition was achieved
by stretching cells while exposing them to the adipogenic media. Cell compression
was found to inhibit the expressions of PPARc and C/EBPa but not C/EBPb or
C/EBPd. As a mechanism, they proposed that compression blockage of adipo-
genesis may be accomplished through the upregulation of cyclooxygenase-2
(COX-2), which is known as a negative regulator of adipocytic transcription
through PPARc and C/EBPa. This was further confirmed by that a COX-2
inhibitor completely reversed the effect of adipogenesis inhibition once observed
under compression.
In the literature, compressive loading has been typically utilized for stimulating
stem cell fate toward osteogenesis and chondrogenesis. No research on the com-
pression has reported the relative MSC fate decision toward these lineages relative
to adipogenesis, which has been typically attempted in cell stretch studies. Recent
findings on compression-induced MSC osteogenesis and chondrogenesis will be
briefly reviewed.
It was shown that both adipose-derived and bone marrow-derived mesenchymal
stem cells have increased osteogenesis when subjected to dynamic hydraulic
compression [
35
]. However, effects of osteogenic induction by compression were
greater for bone marrow-derived MSCs relative to adipose-derived MSCs. In the
study by Haudenschild et al. [
18
], the effects of mechanical stretch and com-
pression on MSCs were compared. Morphologically, cell stretch caused cellular
distortion and cellular volume increase, which effects were not significant under
compression. In terms of differentiation, cell compression did enhance chondro-
genesis while not affecting osteogenesis, which was due to the upregulation of
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