Heart formation filmed for the first time

The images show that cardiac cells in a mouse embryo begin to spontaneously organize themselves into a heart-like shape in the early stages of development.

Scientists say the technique could offer new insights into congenital heart defects, which affect almost one in 100 babies.

"This is the first time we have been able to observe heart cells so closely, for so long, during mammalian development," said the study's lead author, Dr. Kenzo Ivanovitch of the Great Ormond Street Institute of Child Health at University College London.

"First we had to grow the embryos reliably in a dish for long periods, from several hours to several days, and what we found was completely unexpected."

The images of developing embryos were captured using a technique called advanced light-sheet microscopy, the Telegraph reports.

This allowed scientists to track the embryos as they went through a developmental milestone known as gastrulation, when the embryo begins to form distinct cell lineages and begins to create the basic axes of the body.

Soon after, the heart muscle cells organize into a large tube that will continue to divide into sections that will eventually become the walls and chambers. In babies with heart defects, a hole may form during this process.

Using fluorescent markers, the team labeled heart muscle cells called cardiomyocytes, causing them to glow in distinct colors.

Snapshots were taken every two minutes for 40 hours, showing cells moving, dividing and forming a primitive organ. This allowed the team to see when and where the first cells that make up the heart appeared in the embryo.

The researchers found that early during gastrulation (about six days into mouse embryo development), cells that contribute only to the heart appeared rapidly and behaved in highly organized ways.

Instead of moving randomly, they began to follow distinct paths, either contributing to the ventricles (the pumping chambers of the heart) or to the atria (where blood enters the heart from the body and lungs).

"Our findings indicate that cardiac fate determination and directed cell movement may be regulated much earlier in the embryo than current models suggest," Ivanovitch said.

"This fundamentally changes our understanding of cardiac development by showing that what appears to be chaotic cell migration is actually guided by hidden patterns that ensure proper heart formation," he added.

The team said the knowledge could advance the understanding and treatment of congenital heart defects, and accelerate progress in growing heart tissue in the laboratory for use in regenerative medicine. /Telegraph/