Stem Cells From Liposuction Used to Make Blood Vessels

July 25, 2012

July 25, 2012 (New Orleans, Louisiana) — Researchers are attempting to develop small-diameter human blood vessels from autologous stem cells extracted from adipose tissue obtained via liposuction [1]. The vessels would be used for CABG; frequently, CABG surgery cannot go ahead because patients do not have any suitable vessels to use for grafts.

Dr Jaclyn A Brennan (University of Oklahoma, Norman) reported the work, conducted with her colleagues in the School of Chemical, Biological, and Materials Engineering, during a poster session here at the American Heart Association Basic Cardiovascular Sciences 2012 Scientific Sessions.

Senior author Dr Matthias U Nollert (University of Oklahoma) told heartwire : "The big picture is that there are over 100 000 CABG surgeries each year in the US alone, and in a substantial fraction of these--a third or so--the patient's own vessels are unsuitable to use as grafts, because the patient has undergone prior bypasses, for instance, or has peripheral artery disease."

Options do exist for vessels of larger diameter (>6 mm), in the form of inert synthetic grafts, says Nollert. But for the smaller-diameter vessels, "there is no alternative" that will function properly, and often surgery has to be abandoned and angioplasty performed instead in cases where the patient has no suitable small vessels.

Stem Cells From Liposuction Grown on Amniotic Tissue Beds

Nollert explains that while it's theoretically possible to grow blood vessels from stem cells extracted from people's bone marrow, most of the people awaiting CABG are too sick to undergo bone-marrow extraction. Instead, his team hit upon the idea of using adipose tissue, taken during a liposuction procedure, which is not as taxing. The idea is that the stem cells would be extracted from a patient, who would then need to wait three to four weeks for the blood vessels to grow before being able to undergo bypass surgery.

The Oklahoma team has been trying to grow the blood vessels in their lab. First, they differentiate the adipose-derived stem cells into smooth-muscle cells, and then "seed" them onto a flat sheet of amniotic membrane. The latter is obtained from discarded placentas, he says, and treated with detergent before being pulled into a flat sheet that is "very thin, around 50 µm, and very tough" and is already FDA approved for use in skin-grafting procedures and some forms of eye disease.

The researchers then roll the cell-seeded, biocompatible sheet of amniotic membrane into tubes of a few millimeters in diameter, and the stem cells multiply in three to four weeks into blood vessels. However, while this technique holds much potential for "off-the-shelf" replacement blood vessels, the resultant vessels are far from perfect right now, says Nollert.

This is something that has real potential to be clinically useful, but they are not great yet.

"This is something that has real potential to be clinically useful, but they are not great yet; they are not strong enough, and we don't have the data to show that they contract properly." For example, the current grown vessels have a "burst" pressure of around 200 mm Hg, he says, whereas native tissue has a burst pressure of 1000 mm Hg.

"Until we know our vessels are fully physiologically functioning, we won't do animal tests, because they will fail in the long term," Nollert says. "We need to be very close to physiologic values with these vessels, for burst pressure, vascular tone, thrombogenicity, and elastic modulus."

The authors report no conflicts of interest.

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