UCLA stem cell scientists purified a subset
of stem cells found in fat tissue and made from them bone that was formed
faster and was of higher quality than bone grown using traditional methods, a
finding that may one day eliminate the need for painful bone grafts that use
material taken from the patient during invasive procedures.
Adipose,
or fat, tissue is thought to be an ideal source of cells called mesenchymal
stem cells - capable of developing into bone, cartilage, muscle and other
tissues - because they are plentiful and easily attained through procedures
such as liposuction,
said Dr. Chia Soo, vice chair for research at UCLA Plastic and Reconstructive
Surgery. The co-senior authors on the project, Soo and Bruno Péault, are
members of the Eli and Edythe Broad Center of Regenerative Medicine and Stem
Cell Research at UCLA.
Traditionally,
cells taken from fat had to be cultured for weeks to isolate the stem cells
which could become bone, and their expansion increases risk of infection and
genetic instability. A fresh, non-cultured cell composition called stromal
vascular fraction (SVF) also is used to grow bone. However, SVF cells taken
from adipose tissue are a highly heterogeneous population that includes cells
that aren't capable of becoming bone.
Péault
and Soo's team used a cell sorting machine to isolate and purify human
perivascular stem cells (hPSC) from adipose tissue and showed that those cells
worked far better than SVF cells in creating bone. They also showed that a
growth factor called NELL-1, discovered by Dr. Kang Ting of the UCLA School of
Dentistry, enhanced the bone formation in their animal model.
"People
have shown that culture-derived cells could grow bone, but these are a fresh
cell population and we didn't have to go through the culture process, which can
take weeks," Soo said. "The best bone graft is still your own bone,
but that is in limited supply and sometimes not of good quality. What we show
here is a faster and better way to create bone that could have clinical
applications."
The
study appears June 11, 2012 in the early online edition of the peer-reviewed
journal Stem Cells Translational Medicine, a new journal that seeks
to bridge stem cell research and clinical trials.
In the
animal model, Soo and Péault's team put the hPSCs with NELL-1 in a muscle
pouch, a place where bone is not normally grown. They then used X-rays to
determine that the cells did indeed become bone.
"The
purified human hPSCs formed significantly more bone in comparison to the SVF by
all parameters," Soo said. "And these cells are plentiful enough that
patients with not much excess body fat can donate their own fat tissue."
Soo
said if everything goes well, patients may one day have rapid access to high
quality bone graft material by which doctors get their fat tissue, purify that
into hPSCs and replace their own stem cells with NELL-1 back into the area
where bone is required.
The
hPSC with NELL-1 could grow into bone inside the patient, eliminating the need
for painful bone graft harvestings.
The goal is for the process to isolate the hPSCs and add the NELL-1 with a
matrix or scaffold to aid cell adhesion to take less than an hour, Soo said.
"Excitingly,
recent studies have already demonstrated the utility of perivascular stem cells for
regeneration of disparate tissue types,
including skeletal muscle, lung and even myocardium," said Péault, a
professor of orthopedic surgery "Further studies will extend our findings
and apply the robust osteogenic potential of hPSCs to the healing of bone defects."
Provided
by University
of California, Los Angeles
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