Are there stem cell therapies available for heart failure?
To our knowledge, no stem cell therapy has received U.S. Food and Drug Administration or Health Canada approval for treatment of heart failure at this time. Patients who are researching their options may come across companies with Web sites or materials that say otherwise and offer fee-based stem cell treatments for curing this disease. Many of these claims are not supported by sound scientific evidence and patients considering these therapies are encouraged to review some of the links below before making crucial decisions about their treatment plan.
For more about stem cell clinical trials for heart failure click here. (For printed version: http://goo.gl/gV0Dm)
How close are we? What do we know about heart failure?
- Heart failure is a chronic cardiovascular syndrome where damage to the heart muscle prevents it from filling or pumping blood normally.
- Blood returning to the heart through the veins backs up leading to congestion in the tissues and kidneys, swelling (most often in the legs and ankles), and shortness of breath.
- Major risk factors for congestive heart failure include coronary artery disease, high blood pressure, diabetes mellitus, abnormal heart valves, inflammation of the heart, and infection of the heart valves or muscle.
- Treating the underlying conditions can help to improve symptoms, stop heart failure from worsening, and prolong lifespan.
- Standard treatments for people with advanced symptoms of heart failure involve medications reducing fluid retention and/or slowing heart enlargement, surgeries repairing faulty valves or blocked arteries, and lifestyle changes focusing on rest, reducing dietary salt intake and modifying daily activities.
- Severely diseased or damaged hearts will eventually need to be replaced with a healthy heart, but donor hearts are in short supply and patients often face lengthy wait times for transplant surgery.
How can stem cells play a part?
Despite the myriad of treatments available that can slow the progression and alleviate the symptoms of heart failure, none are able to regenerate heart tissue. Novel treatments that can achieve enduring cures are in short supply and this is where stem cell based therapies offer some hope. Stem cells have an unparalleled regenerative capacity and the flexibility to grow into hundreds of different types of cells. This means that they might be coaxed into becoming a ready source of precursor cells that make heart cells, blood vessel cells, supporting cells and regulatory signals. The stem cell therapies being investigated aim to make the heart microenvironment healthier and restore some of the lost function of the heart by promoting the growth of new heart tissue and blood vessels.
Are there lots of groups working on developing a stem cell therapy?
There are many research teams around the globe working to develop stem cell therapies for heart failure. Their common goals are to identify which stem cells are best suited for the job, how to coax them into becoming the needed cells, how best to deliver them therapeutically, and the large scale lab methods required for ramping up the production for clinical use.
One of the major research accomplishments has been the identification of human cardiac stem cells in 2003. In the years following this exciting discovery researchers were able to show that cardiac stem cells do in fact slowly renew a fraction of heart cells over the course of one’s life. This news kindled great hope for the prospect of using stem cells to treat heart failure because it dispelled the long held notion that the heart was incapable of repairing itself after injury.
Stem cell research for heart failure is moving along a number of different routes and some of the successful stops along the way have yielded early Phase 1 and 2 clinical trials. The majority of these are testing the safety of adult stem cells and the outlook is promising, but it’s too early to tell if the stem cell therapies being tested can enhance heart function. Post-study follow-up in other trials is providing some hope, showing measurable improvement in cardiac function and decreases in the size of dying heart tissue up to one year after treatment.
A three-city study is examining the impact of using a patient’s own blood stem cells enhanced with a gene called endothelial nitric oxide synthase (eNOS) to repair damage after a heart attack.
What research is underway?
Some stem cell investigations are still at the animal model testing stage but research with adult stem cells, in particular muscle stem cells, bone marrow stem cells, cardiac stem cells and endothelial progenitors (cells that line blood vessels) has advanced rapidly to the point of early clinical trials. While knowledge gained from preclinical studies and clinical trials has yet to illuminate a cure for heart failure, it has helped set out the steps required for stem cells to become a contending therapy. High on the list is the need to develop new techniques for isolating and expanding large numbers of stem cells. It is vital to be able to transplant many stem cells to maximize the numbers that eventually reach the damaged heart. Delivery is also a challenge: not enough transplanted cells are retained in the heart and some become lodged in the lungs or travel to other organs in the body. To fix these problems, researchers are trying targeted delivery of cardiac stem cells loaded onto tissue-engineered biodegradable scaffolds or sheets. This approach is showing some promise. Getting stem cells to home specifically to sites of damage is also difficult but identifying cellular messengers that act like beacons may be the answer. Researchers are also using genetic markers to tag stem cells and track them to their preferred homes or niches in the body. These studies are important for identifying new stem cell sources and for better understanding basic stem cell biology.
The road to finding a stem cell therapy for heart failure is paved with many challenges that will take time to overcome. But the wealth of information generated from labs around the globe is converging to help with the transition from basic research to the clinic. The fact that clinical trials using stem cells for heart failure are being actively pursued speaks to the great achievements that have already been made in basic and clinical research. As these trials progress, their results should help to inform, refine and define future research questions, which may lead to new trials and bring the field ever closer to using stem cells as frontline treatments for heart failure.
Current research using muscle stem cells
The first stem cells to be used for cardiac therapy were myoblasts, a type of skeletal muscle stem cell isolated from muscle biopsies. The trial took place in 2008 and since then a number of other clinical studies using these stem cells have been initiated for patients who suffer from heart attack or congestive heart failure. Scientists are following the participants to gauge whether there is any sustained improvement in heart function and integration of skeletal muscle stem cells into the damaged hearts.
Current research using bone marrow stem cells
Pre-clinical studies have identified stem cells in the bone marrow as potential candidates for cardiovascular therapies. There are different types of stem cells residing in the bone marrow, and some are able to secrete factors that protect heart cells as well as modulate the immune system. This is important because it means these stem cells could be transplanted from one individual to another without the need for the immune suppressing drugs. Over 1,000 patients have been transplanted with various populations of bone marrow stem cells for heart disease and the procedure has shown to be safe and modestly beneficial. Although the transplanted bone marrow stem cells are not actually generating new heart cells, they appear to be providing some benefit by way of a mechanism yet to be understood. Future studies may focus on particular subsets of bone marrow stem cells in an effort to pinpoint the ones that work best.
Current research using cardiac stem cells
On the heels of discovering cardiac stem cells in 2003, researchers have toiled to amass enough pre-clinical proof to warrant moving ahead with clinical trials in humans. The majority of clinical trials are still at the small Phase 1 stage but early positive results endorse the plans for larger Phase 2 trials. These would specifically test for the ability of cardiac stem cells to regenerate heart tissue that has died following heart attack.
Current research using endothelial progenitor stem cells
Endothelial progenitor cells make the cells that line blood vessels throughout the body. The process of making new blood vessels is a critical step towards promoting the regeneration of damaged heart tissue. Scientists are still debating how precisely to characterize endothelial progenitor stem cells but they have found some important biomarkers that are helping to sort things out. A handful of clinical trials are exploring the potential of these cells to contribute to the formation of new blood vessels in regions of cardiac damage in patients with cardiovascular disease.