Orthopedics This Week - 2018 | July 17, 2018 | Page 20

ORTHOPEDICS THIS WEEK
VOLUME 14, ISSUE 23 | JULY 17, 2018
and repair existing bone, according to
a new study led by Kent Leach, Ph.D.,
a professor of Biomedical Engineering
and Orthopaedic Surgery at the Univer-
sity of California, Davis.
The periodical Stem Cells published the
study (“Hypoxic Preconditioning of
Mesenchymal Stem Cells with Subse-
quent Spheroid Formation Accelerates
Repair of Segmental Bone Defects”) and
is the source for the information in this
article.
“Cell-based approaches for muscu-
loskeletal tissue repair are limited by
poor cell survival and engraftment,”
Leach said. “Cells are initially deliv-
ered to harsh environments that lack
oxygen. We already knew that short-
term hypoxic (low oxygen levels) pre-
conditioning of mesenchymal stem
cells (MSCs) can prolong cell viability
in lab culture, while forming the MSCs
[mesenchymal stem cells] into spher-
oids increases cell survival, trophic
factor secretion and tissue formation
in vivo.
“So, we hypothesized that precondi-
tioning the MSCs in hypoxia culture
before being formed into spheroids
might boost the cells’ survival rate and
help them to perform better.”
He was right.
To test their theory, the researchers
exposed a single-layered culture of
human MSCs to 1% oxygen for three
days. A control group of cells was lim-
ited to ambient air only. Both groups
were then formed into spheroids in
an engineered hydrogel carrier. The
researchers found that the oxygen-
deprived cells had a better survival rate
than the control group—a factor that
increased with the amount of time the
20
cells were exposed to the hypoxic pre-
conditioning.
The next step was to test how the spher-
oids performed in treating bone defects
in rats. They tested spheroids of cells
deprived of oxygen against those that
were not deprived. They also exam-
ined how the spheroids of cells per-
formed compared to oxygen-restricted
single cells. “Once again, the oxygen-
deprived, spheroid-containing gels
induced significantly more bone heal-
ing than did gels containing either pre-
conditioned individual MSCs or acellu-
lar gels,” Leach said.
He added, “We believe these data
demonstrate that preconditioning the
cells with a low level of oxygen repre-
sents a simple approach for enhanc-
ing the therapeutic potential of MSC
spheroids when used for bone heal-
ing,” — BY
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