Many patients with heart problems – such as heart disease or angina – may need to undergo cardiac surgery in order to restore or improve blood flow. But a new study suggests that the procedure may offer so much more; stem cells in fat discarded during cardiac surgery could be injected back into the patient’s heart to further improve its function.
A research team led by senior author Canadian cardiologist Dr. Ganghong Tian will present their findings at the Frontiers in Cardiovascular Biology meeting in Barcelona, Spain.
Previous work by this group has shown that subcutaneous fat (adipose tissue) contains stem cells that can reduce the severity of heart attacks, improve cardiac function, and augment blood vessel regeneration in laboratory animals with experimentally induced heart attacks. These fat-based stem cells can be easily obtained through liposuction. However, Tian noted, “But obtaining these from a patient undergoing cardiac surgery requires pre-surgery to collect adipose tissue from the subcutaneous region.”
Is there a better way? According to Tian, during cardiac surgery, the surgeon often removes fat tissue that resides around the heart (so-called mediastinal fat) in order to properly expose the heart. Tian wondered if this fat contain stem cells that could be re-introduced to the heart to improve its function after heart surgery
In order to test this hypothesis, Tian and others collected mediastinal fat tissue from 24 patients who had undergone cardiac surgery. Then Tian’s group injected rats with mediastinal fat stem cells. The rats injected with stem cells from mediastinal fat showed greater ventricular movement in their hearts and no reduction in left ventricular ejection fraction.
Closer examination of the stem cells from mediastinal fat showed that mediastinal fat housed a rather robust number of stem cells, and that these stem cells could differentiate into fat and bone cells. Also, these stem cells expressed genes that are often found in heart muscle cells.
With this pre-clinical information in hand, Tian and others examined the use of mediastinal fat-based stem cells in 13 rats with congestive heart failure. These stem cells were directly injected into the hearts of eight rats, and five were injected with a saline solution.
After 6 weeks, all the rats underwent magnetic resonance imaging (MRI). When the five control rats were compared with those who those rats that received injections of mediastinal fat-based stem cells, the stem cell-injected rats demonstrated greater ventricular movement in their hearts and no reduction in left ventricular ejection fraction (ejection fraction measures how much blood is being pumped out of the left ventricle of the heart).
Commenting on the team’s findings, Dr. Tian says: “This is the first evidence that stem cells collected from the mediastinal fat region are cardioprotective. They displayed the same cardioprotective capacity we found in our previous research on stem cells from subcutaneous fat tissue. This raises the exciting possibility of using a patient’s own stem cells, isolated from waste tissue during cardiac surgery, to improve their heart function.”
Tian noted that there are currently some issues with this procedure that need to be addressed with further research. Techniques must be developed to quickly isolate stem cells from mediastinal fat so they can be injected back into a patient’s heart during cardiac surgery. Tian said, “It currently takes several hours to purify the cells and we are looking for collaborators to help us devise a more efficient method.”
Tina and others would also like to examine the ability of these stem cells to improve cardiac function long-term, beyond the 6 weeks monitored in this study. Furthermore, Tian and his group would like to induce the stem cells into functional heart muscle cells that display electrical pulses and beating.