The Growth and Transplant of Cone Photoreceptors

Light is captured in the eye by specialized nerve cells called photoreceptors. A damaged or destroyed photoreceptor cannot naturally be replaced or repaired by the body. Cone photoreceptors are specialized photoreceptors responsible for a person’s colour vision and their ability to see fine details. These cells can be permanently damaged by age-related macular degeneration and other retinal dystrophies. When a person’s cone photoreceptors are seriously damaged, they lose the ability to read or identify faces.

Valerie Wallace and her team at the Donald K Johnson Eye Institute are working to create new photoreceptors in the laboratory, in order to transplant these cells into the retinas of people whose eyes have been permanently damaged by age-related macular degeneration. They are working with experts on stem cell transplant including Dr. Derek van der Kooey and Dr. Molly Shiochet (University of Toronto), Dr. Carol Schuurmans (Sunnybrook Research Institute) and with other Donald K Johnson Eye Institute scientists including Dr. Phlippe Monnier and Dr. Martin Steinbach. 

              Research led by Valerie Wallace aims to improve 
                   the transplanted of cone cells (seen here)

Stem cells are immature cells that have the potential to become any type of human cell. To create new photoreceptors, Dr. Wallace and her colleagues are using knowledge adapted from the study of normal cell development to push stem cells to become photoreceptors. Stem cells can create any type of cell, so while many laboratories can now produce some photoreceptors, the challenge remains to create a large enough volume of pure photoreceptors to make transplants safe and practical. This is one of the key objectives of Dr. Wallace’s team.

In addition, Dr. Wallace and her colleagues are studying transplant techniques, working to determine the best ways to insert new photoreceptors into the eye, and to hold them in place until they can grow and make connections with other cells. To improve the successful growth and integration of transplanted cells, Dr. Shoichet has developed a biodegradable hydrogel that holds cells in place and nurtures them as they become established. The gel slowly dissolves, leaving the new cells in place. The research team is currently working to perfect this and other photoreceptor transplant techniques.

Eventually this team hopes to establish a photoreceptor transplant centre and begin human trials of photoreceptor transplants at the Donald K Johnson Eye Institute, in partnership with the Institute’s clinical scientists.  Clinicians at the Eye Centre already use stem cell transplants to treat people whose corneas have been damaged by injury or disease.

Dr. Wallace’s research is supported by grants from the Ontario Institute of Regenerative Medicine, the Foundation Fighting Blindness and the W. Garfield Weston Foundation - Brain Canada Multi Investigator Research Initiative.