The mechanics of embryonic eyes

Japanese scientists have created a “virtual precursor-eye” that models how stem cells in the human embryo form the real thing.

Understanding how cells move and bend in order to form three-dimensional tissue structures is a hot research topic in the fields of developmental biology and regenerative medicine.

To better understand the processes involved, scientists at Kyoto University’s Institute for Frontier Life and Medical Sciences used data gleaned from previous stem cell studies to demonstrate how cells respond to mechanical strain in order to form spherical shapes.

The researchers, led by Satoru Okuda, developed a simulation of the formation of a three-dimensional structure – known as an optic cup – that emerges during embryonic eye development.

“In the past, we succeeded in making the optic cup by culturing embryonic stem — ES – cells,” says Okuda.

“To form a sphere, the tissue needed to first protrude from primordial brain tissue and then invaginate inside, but how individual cells sensed and modulated themselves to form that shape had been unclear.”

The simulation revealed that an initial cell differentiation pattern causes cells in the proto-optic cup to spontaneously fold into the tissue. This “self-bending” generates a force that travels to the boundary region of the cell group, causing others to come under strain and repeat the process.

“The combination of the tissue deformation and the strain on the boundary of the optic cup generates a hinge that further pushes the bending cells, leading to the cup-like structure,” Okuda explains.

He and colleagues then successfully replicated the processes in the lab, using embryonic stem cells from mice.

The findings, the scientists say, reveal a new role for mechanical forces in the formation of three-dimensional tissue.

The research is published in the journal Science Advances.