Biomedical Engineering Reference
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cells via an ERK pathway (Gu et al. 2011). Further study suggested that more
pronounced proliferation and higher osteogenic gene expression for hPDLCs
cultured with akermanite extract were detected as compared to cells cul-
tured with β-TCP extract (Xia et al. 2011; Wu and Chang, forthcoming).
Akermanite could not only stimulate cell proliferation and osteogenic
differentiation of several stem cells cultured with their ionic extracts, but
also promote osteogenic differentiation of stem cells directly cultured with
their ceramic disks (Sun et al. 2006; Wu, Chang, Ni, et al. 2006; Wu and
Chang 2007; Gu et al. 2011; Xia et al. 2011). Therefore, it is suggested that sili-
cate bioceramics possess significant osteostimulation properties (Wu and
Chang, forthcoming).
To further investigate the potential mechanism of the osteostimulation
properties of silicate bioceramics, the effect of Si ions on the proliferation,
differentiation, bone-related gene expression, and cell signaling pathways
of bone marrow stromal cells was further studied by comparing BMSC
response to different concentrations of NaCl and Na
2
SiO
3
, taking into
account and excluding the effect of Na ions. Our study showed that Si ions
at a certain concentration significantly enhanced the proliferation, miner-
alization nodule formation, and bone-related gene expression (
OCN, OPN
,
and
ALP
) of BMSCs. Furthermore, Si ions at 0.625 mM could counteract the
effect of Wnt inhibitor on the osteogenic gene expression, (
OPN
,
OCN
, and
ALP
), Wnt and Shh signaling pathway-related genes in BMSCs. The results
suggest that Si ions by themselves play an important role in regulating the
proliferation and osetogenic differentiation of BMSCs with the involve-
ment of Wnt and Shh signaling pathways (unpublished data). Therefore, Si
ions released from silicate bioceramics can acquire enhanced bioactivity at
desired concentration.
2.5
In Vivo
Bone-Forming Ability of Silicate Bioceramics
Since some silicate bioceramics, such as wollastonite (CaSiO
3
), akermanite
(Ca
2
MgSi
2
O
7
), and baghdadite (Ca
3
ZrSi
2
O
9
), have shown excellent
in vitro
bio-
activity, we conducted further
in vivo
studies to investigate their osteogene-
sis and angiogenesis. The porous wollastonite scaffolds were implanted in
rabbit calvarial defects and after implanted for 4, 8, and 16 weeks, the micro-
CT and histomorphometric analysis showed that the resorption of wollas-
tonite scaffolds was much higher than that of β-TCP scaffolds. More bone
formation was observed with wollastonite scaffolds as compared with β-TCP
scaffolds (Xu et al. 2008). Our recent study demonstrated that the incorpora-
tion parts of wollastonite into β-TCP scaffolds could significantly promote
new bone formation after implanted in critical sized femur defects of rabbits
(Wang et al. 2012).
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