‘Leftover’ stem cells may aid recovery

“Thousands of heart patients' lives could be saved by a breakthrough in stem cell research,” the Daily Mirror reported. It said that researchers have extracted stem cells from leg veins, which were removed for heart bypass surgery, and grown them in the lab. These cells can then be “injected back into a patient's heart to stimulate growth of new blood vessel tissue”.

The news article is based on a study in which cells extracted from human blood vessels removed during operations were used to stimulate the growth of new arteries in mice.

This small animal study was successful and its findings are encouraging. Importantly, this is still early research and the technology has not yet been tested in humans. Several newspapers note that Bristol University has begun a study to assess the therapeutic potential of these cells in humans. The relevance of this discovery to human health will become clearer when the results of such research are available.

Where did the story come from?

The research was carried out by Dr Paola Campagnolo and colleagues from the University of Bristol and the University of Udine in Italy. The study was funded by the British Heart Foundation and the National Institute for Health Research. The paper was published in the peer-reviewed medical journal Circulation .

The media covered this story accurately, pointing out that the research is in its early stages and that the research team at the University of Bristol have launched a further study to determine how the technology can benefit humans.

What kind of research was this?

This laboratory study investigated the potential for using adult progenitor cells, harvested from the veins of patients undergoing coronary artery bypass surgery, to aid the recovery of vascular health. Progenitor cells are similar to stem cells, but are further in their differentiation (development) than stem cells. The researchers note that previous studies have had some success using progenitor bone marrow cells, but that “non-bone marrow progenitor cells” that can encourage the growth of blood cells have not been fully researched, due to their scarcity and the difficulty of accessing them and replicating them outside of living tissue. Through this study, they hoped to better understand these cells.

What did the research involve?

The researchers used portions of saphenous vein (from the leg), which are used for coronary and peripheral artery bypass operations. Surgeons usually take more of this vein than is required for the surgery, and there are often “leftovers” from these operations. The researchers wanted to establish whether there were progenitor cells that promoted angiogenesis (the stimulation of blood supply) in these leftovers.

Human progenitor cells have characteristics that distinguish them from other cells. These include particular compounds in their surfaces that are not found in other cells, such as CD34, and the absence of a molecule called CD31. These properties were used to isolate a pure sample of progenitor cells from the preparations of vein leftovers. From a small, nearly pure sample of these cells, 30 to 50 million viable cells were generated in culture. The researchers say that these “could be stored to create a bank of ready-to-use cells” for treatment.

The researchers then tested the capacity of these cultured cells to differentiate (develop) into precursors of bone cells, fat cells, cartilage cells, liver cells, muscle cells and brain cells. This was to prove their progenitor qualities, i.e. that they had not yet differentiated fully.

The progenitor cells were injected into mice with an ischemia-like disease (which causes a restriction in blood supply) in the muscles in one limb to test whether they aided recovery from disease. Progenitor cells or a placebo were injected into 14 mice (seven mice in each group) in three different points on the affected muscle. The recovery of blood flow was then assessed. The mice were dissected after 14 days to investigate what effect the progenitor cells or placebo had on vascularisation (blood flow) to the muscle. The researchers also determined exactly where in the vein the progenitor cells were located and how they interacted with cells that encourage the growth of blood vessels. Further experiments in mice demonstrated that injection of the progenitor cells improved the return of blood supply to the foot compared with placebo (recovery in seven days compared to 14 days with placebo).

What were the basic results?

The study found that a large number of viable cells could be recovered from a single 4–5cm leftover portion of saphenous vein. These cells demonstrated key properties of progenitor cells, namely their capacity to self-renew (clone) and to differentiate into a range of different cells.

The cells also interacted with cells involved in the stimulation of blood supply (angiogenesis) and, when injected into the ischaemic muscles of mice, encouraged the return of vascular health.

How did the researchers interpret the results?

The researchers concluded that saphenous vein-derived progenitor cells (SVPs), generated from cells isolated from human veins, “might represent a new therapeutic tool for angiogenic therapy in ischaemic patients”.

Conclusion

The researchers provided a good description of this laboratory study, which appears to have been well conducted using appropriate methods. They succeeded in extracting progenitor cells from sections of veins, left over from heart bypass operations. Detailed profiles of these cells were constructed, and the cells’ therapeutic potential was assessed in mouse models of disease.

Importantly, this is still early research and the technology has not yet been tested in humans. As the researchers note, further studies are needed to investigate the potential use of these cells in different types of ischaemia, including myocardial ischaemia (which can lead to heart attacks).

Several newspapers note that Bristol University has now begun a study to assess the therapeutic potential of these cells in humans. The relevance of this discovery to human health will become clearer when the results of such research are available.