stem cells

stem-cells-used-to-partially-repair-damaged-hearts

Stem cells used to partially repair damaged hearts

When we developed the ability to convert various cells into a stem cell, it held the promise of an entirely new type of therapy. Rather than getting the body to try to fix itself with its cells or deal with the complications of organ transplants, we could convert a few adult cells to stem cells and induce them to form any tissue in the body. We could potentially repair or replace tissues with an effectively infinite supply of a patient’s own cells.

However, the Nobel Prize for induced stem cells was handed out over a decade ago, and the therapies have been slow to follow. But a group of German researchers is now describing tests in primates of a method of repairing the heart using new muscle generated from stem cells. The results are promising, if not yet providing everything that we might hope for. But they’ve been enough to start clinical trials, and similar results are being seen in humans.

Heart problems

The heart contains a lot of specialized tissues, including those that form blood vessels or specialize in conducting electrical signals. But the key to the heart is a form of specialized muscle cell, called a cardiomyocyte. Once the heart matures, the cardiomyocytes stop dividing, meaning that you end up with a fixed population. Any damage to the heart due to injury or infection does not get repaired, meaning damage will be cumulative.

This is especially problematic in cases of blocked blood vessels, which can repeatedly starve large areas of the heart of oxygen and nutrients, killing the cardiomyocytes there. This leads to a reduction in cardiac function and can ultimately result in death.

It turns out, however, that it’s relatively easy to convert induced pluripotent stem cells (IPSC, with pluripotent meaning they can form any cell type). So researchers tried injecting these stem-cell-derived cardiomyocytes into damaged hearts in experimental animals, in the hope that they would be incorporated into the damaged tissue. But these experiments didn’t always provide clear benefits to the animals.

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De-extinction company manages to generate first elephant stem cells

Large collection of cells with a red outline and white nucleus.

Enlarge / Elephant stem cells turned out to be a hassle to generate. (credit: Colossal.)

A company called Colossal plans on pioneering the de-extinction business, taking species that have died within the past few thousand years and restoring them through the use of DNA editing and stem cells. It’s grabbed headlines recently by announcing some compelling targets: the tylacine, an extinct marsupial predator, and an icon of human carelessness, the dodo. But the company was formed to tackle an even more audacious target: the mammoth, which hasn’t roamed the northern hemisphere for thousands of years.

Obviously, there are a host of ethical and conservation issues that would need to be worked out before Colossal’s plans go forward. But there are some major practical hurdles as well, most of them the product of the distinct and extremely slow reproductive biology of the mammoth’s closest living relatives, the elephants. At least one of those has now been cleared, as the company is announcing the production of the first elephant stem cells. The process turned out to be extremely difficult, suggesting that the company still has a long road ahead of it.

Lots of hurdles

Colossal’s basic road map for de-extinction is pretty straightforward. We have already obtained the genomes of a number of species that have gone extinct recently, as well as those of their closest living relatives. By comparing the two, we can identify key genetic differences that make the extinct species distinct. We can then edit those differences into stem cells obtained from the living species and use that species as a surrogate for embryos produced from these stem cells. This will have to be done using stem cells from a number of individuals to ensure that the resulting population has sufficient genetic diversity to be stable.

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