New way to stimulate blood vessel growth shows promise in saving at-risk limbs

In the United States, approximately 2 million people live with an amputation, and another 185,000 amputations occur each year, according to the Amputee Coalition, a Washington, D.C.-based support group. Approximately 54% of these limb losses were caused by vascular disease, including diabetes and peripheral arterial disease (PAD).

And as more people are diagnosed with diabetes in the United States and around the world, the number of amputations continues to rise.

Now, Cincinnati children’s experts, working with colleagues at Kanazawa University in Japan, have discovered a new way to stimulate blood vessel growth that shows promise as a treatment to prevent amputations induced by ischemia. Their findings were based on a deeper understanding of why two patients participating in a clinical trial in Japan left with fully recovered limbs that appeared destined for amputation.

The study published in the journal Cell Reports Medicinewas led by first author Oto Inoue, MD, Ph.D., a Japanese cardiologist and researcher at Cincinnati Children’s, and Juan Sanchez-Gurmaches, Ph.D., Division of Endocrinology.

Their team reports that a specific subset of stem cells isolated from adipose (fat) tissue that also carry the cell surface marker CD271 outperformed all other similar cell types in inducing blood vessel formation. The study also details the main molecular mechanisms involved in the process.

The scientists confirmed these results by transplanting this population of human stem cells into mice with limb ischemia. In all cases, the treatment saved limbs that otherwise would have required amputation.

Next, the team analyzed data from a clinical trial to provide the first evidence that such a cell transplant might have already worked in humans. In this case, people with foot ulcers were treated with a generalized mixture of stem cells collected from the patient’s own tissues.

Among the small number of patients analyzed, the two patients whose limbs were completely recovered received high numbers of CD271-positive stem cells. These results, combined with the very consistent benefits seen in mouse tests, appear to warrant additional work to initiate a formal clinical trial, the co-authors say.

“Critical limb ischemia is one of the most serious consequences of PAD and undertreated diabetes. This research shows promising results that this new subset of progenitors may have positive therapeutic value,” Inoue said. “It was very inspiring to see that one of the patients recovered enough to return to work.”

A race to solve a widespread health problem

With increasing obesity rates in the United States, the incidence of diabetes has been increasing for years, causing a host of cardiovascular complications, including PAD, leading to critical limb ischemia.

Doctors treat PAD by using medications to slow the disease while performing bypass or catheter procedures to open blocked arteries in the limbs. However, many limb arteries requiring treatment are too small and difficult to access through surgery.

As a result, at least a third of people requiring revascularization treatment are not eligible for surgical procedures. Those who lose their limbs experience significant pain and disability, while their underlying cardiovascular disease makes them increasingly susceptible to heart attacks, strokes and other life-threatening problems.

Once considered a purely adult health problem, researchers at Cincinnati Children’s and other centers have found early signs of vascular disease in adolescents and even young children struggling with severe obesity and diabetes.

Emerging alternatives from international collaboration

Inoue, 40, has been studying PAD in Japan for more than a decade. He came to Cincinnati in 2021 to further study the emerging field of cell transplantation-induced angiogenesis as a member of the Sanchez-Gurmaches laboratory.

Many researchers have explored the idea of ​​transplanting progenitor cells to jumpstart the body’s tissue repair capabilities. However, the main limitation has been finding the right cells to use.

To solve this problem, the team used single-cell transcriptomics to sift through a haystack of different progenitor cell types to find the right population of cells. While many stem cells naturally reside in bone marrow, this study found that the most powerful trigger for blood vessel formation is hidden in fatty tissue. These cells carry the marker CD271, which has been shown in other studies to play an important role in tissue growth.

The team transplanted these CD271-positive human cells into mice to confirm their abilities. Human CD271 cells were 100% effective in causing sufficient blood vessel growth in mice to restore normal blood flow to diseased limbs.

Evidence demonstrating that this new cell population could be effective against human diseases has also been provided. The authors found that among people who received self-grafted progenitor cells from fat, those who recovered better and saved their limbs had higher numbers of CD271 progenitor cells.

“The positive correlation between healing and the number of CD271+ progenitors injected into the affected area of ​​these patients was striking,” says Sanchez-Gurmaches.

Challenges ahead

The co-authors emphasize that the results obtained so far are preliminary. The therapeutic value of CD271-positive adipose tissue cells should be evaluated in a larger number of patients in a formal clinical trial.

An important problem to solve is how to obtain enough CD271 progenitor cells to use as a treatment. The new paper reports that the number of CD271 progenitors found in the fat of insulin-resistant people may be up to 75% lower than those of non-insulin-resistant people. Additionally, the cells found tend to be less active in generating new vessels.

“Unfortunately, people living with insulin resistance who face a high risk of limb ischemia are the same ones who have low numbers of CD271-positive progenitor cells, which could make self-transplantation more difficult,” says Inoue.

Further research is needed to determine whether these cells can be expanded in the laboratory before transplantation.