On average, injected stem cells improved the heart’s pumping ability by just 3-4%, and they didn’t prevent further heart attacks, produce new blood vessels, or actually save lives.Although the stem cells from bone marrow haven't proven very effective, stem cells from the heart itself might prove to be more useful. Yong notes of work by our grantee Eduardo Marban at Cedars-Sinai, who has found that by removing the heart's stem cells, growing them in the lab and reinjecting them into the patient can produce less scaring after the heart attack. Marban had a disease team award to develop that therapy, and a company he founded has another disease team award to take the therapy to clinical trials.
Yong also mentioned work by Deepak Srivastava at the Gladstone Institutes who has found a way of directly converting connective tissue in the heart into heart muscle. Yong writes:
The technique avoids all the problems and uncertainties of injecting stem cells since it works with what’s already in the heart. And as fibroblasts make up half of even healthy hearts, they represent a huge reservoir of potential cardiomyocytes-to-be. “Turning scar-forming cells into muscle itself at the region of injury is very attractive,” says Riley. “That’s the cutting edge of where we’re at.”The summary is a good cautionary tale for not getting too excited about potential "therapies" that haven't been tested in people. Bone marrow stem cells using current procedures don't seem like they passed the test, though some had hope based on animal studies.
There's more about stem cells for heart disease on our fact sheet. You can also see a complete list of all heart disease awards CIRM funds including descriptions of the different approaches.