Researchers turn human stem cells into retinal nerve cells

In a development that holds promise of restoring the eyesight of the blind, researchers at John Hopkins University have devised a method of turning human stem cells into retinal nerve cells that transmit visual signals from the eye to the brain.

Conditions like glaucoma and multiple sclerosis (MS) are caused by the death and dysfunction of these cells.

''Our work could lead… to a cell-based human model that could be used to discover drugs that stop or treat blinding conditions,'' said Donald Zack from Johns Hopkins' School of Medicine, the leader of the research group.

It could eventually lead to the development of cell transplant therapies for restoring vision in patients with glaucoma and MS.

Researchers used a genome editing laboratory tool, to introduce a fluorescent protein into the DNA of the stem cells. Using a technique called fluorescence-activated cell sorting they separated newly differentiated retinal ganglion (nerve) cells from a mixture of different cells into a highly purified cell population for the study.

''The cells showed biological and physical properties seen in retinal ganglion cells produced,'' Zack noted.

Further, they found that the addition of a naturally occurring plant chemical called forskolin on the first day of the process helped improve the efficiency with which the cells turned into retinal cells.

The researchers, however, sounded a precautionary note saying forskolin, was not scientifically proven to be safe.

The laboratory process entailed genetic modification of a line of human embryonic stem cells to become fluorescent upon their differentiation to retinal ganglion cells. The cell line was then used for development of new differentiation methods and characterisation of the resulting cells. Using a genome editing laboratory tool called CRISPR-Cas9, the researchers inserted a fluorescent protein gene into the stem cells' DNA.

The expression of red fluorescent protein POU4F2 would happen only with the expression of another gene named BRN3B. BRN3B is expressed by mature retinal ganglion cells, so with the differentiation of a cell into a retinal ganglion cell, it would appear red under a microscope.