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Scientists build human stem cells into a beating heart

Scientists at the University of Pittsburgh have used human stem cells to build a heart that beats.

(Heart frontally PDA image by Ekko, public domain)

Scientists at the University of Pittsburgh in Pennsylvania have used human stem cells to build a heart that beats.

Scientists at the University of Pittsburgh School of Medicine may have just moved us one step further away from relying on donor organs and towards growing replacements in the lab. Using human stem cells, a team led by senior investigator Dr Lei Yang has managed to create a beating heart.

The stem cells were created from fibroblast cells harvested from a human skin biopsy. These were reverse engineered into induced pluripotent stem cells (iPSC), which were treated with growth factors in order to stimulate their development into multipotent cardiovascular progenitor cells (MCPs) — that is, cells that can differentiate into the three kinds of cells that make up the heart.

The second stage was taking a mouse heart and stripping out all of its cells, leaving just a scaffolding — a process that takes about 10 hours. This scaffold was then seeded with the MCPs.

"Nobody has tried using these MCPs for heart regeneration before," said Dr Yang. "It turns out that the heart's extracellular matrix — the material that is the substrate of heart scaffold — can send signals to guide the MCPs into becoming the specialised cells that are needed for proper heart function."

A few weeks later, the mouse heart scaffolding had regrown into a new heart with human cells, and started beating again at a rate of 40 to 50 beats per minute. This is too slow and the beat too weak to pump blood. The heart's electrical conduction system also cannot effectively speed up or slow down the heart rate. More work is required in order to build a heart that can function properly.

"One of our next goals is to see if it's feasible to make a patch of human heart muscle," he added. "We could use patches to replace a region damaged by a heart attack. That might be easier to achieve because it won't require as many cells as a whole human-sized organ would."

Another benefit of the new technique is that it could potentially use a patient's own cells to build tissue, greatly reducing the chance of rejection.

The full study, "Repopulation of decellularised mouse heart with human induced pluripotent stem cell-derived cardiovascular progenitor cells", can be read in Nature Communications.