Right now, most existing therapies are concerned with reducing symptoms in people with heart damage, but none have been successful at actually replacing tissue that was lost due to a heart attack or a similar condition.
This might soon change as researchers from Duke University in the US have recently published a paper detailing their success at growing a large strip of heart tissue using human pluripotent stem cells.
To date, most research in the area has been focused on injecting stem cells derived from the human body into the heart, and growing small amounts of tissue for use in pharmaceutical studies.
While there have been some promising results, the outlook is generally not very encouraging, which indicates the need for different approaches – such as growing ‘patches’ to make up for lost tissue.
In order to maintain smooth cardiac functioning and electrical conductivity, the patches must be of appropriate size and possess all the characteristics of the tissue chosen for replacement.
The new study is the first to scale up the production of artificial heart muscle, which, according to its authors, took a long time and “a lot of engineering ingenuity”.
Using stem cells extracted from embryos – and some that were artificially induced into a pluripotent state – the researchers placed them into a jelly-like substance where they self-organised and grew into functioning tissue.
Finding the right cocktail of cells, support structure, growth factors, nutrients, and culture conditions took several years of continuous work.
Somewhat unexpectedly, one of the key factors was rocking and swaying the samples to improve nutrient uptake.
“It turns out that rocking the samples to bathe and splash them to improve nutrient delivery is extremely important,” said Illia Shadrin, a doctoral student at Duke, and first author on the study. “We obtained five times better results with the rocking cultures compared to our static samples.”
The patches – as many as 16 square centimetres and five to eight cells thick – possess very similar properties to actual heart tissue, and were successfully tested in mouse and rat hearts.
Before they can be used in humans, however, the patches must grow significantly thicker. “We are actively working on that, as are others, but for now, we are thrilled to have the ‘size matters’ part figured out,” said Nenad Bursac, advisor to Shadrin at Duke.