A research team from the National Eye Institute (NEI), part of the National Institute of Health, have developed a technique to study degenerative retinal diseases, such as age-related macular degeneration (AMD) by using patient stem cells and 3D bioprinting.
Give me some background on this.
The outer blood-retina barrier consists of eye tissue supporting light-sensing receptors in the retina— and also where AMD might start to exert its pathophysiological insult. This barrier is made up of the retinal pigment epithelium (RPE) separated by Bruch’s membrane (which regulates nutrient and waste exchanges between the choriocapillaris and RPE) from blood-vessel choriocapillaris.
When AMD is present, lipoprotein deposits (drusen) develop outside Bruch’s membrane—causing damage and impeding function. This can lead to RPE breakdown over time with resultant photoreceptor degeneration and potential vision loss. (via)
Tell me about the study.
Scientists merged three types of immature choroidal cell types (pericytes, endothelial, and fibroblasts) derived from induced pluripotent stem cells in a hydrogel and then printed “bio-ink” gel formulation on a biodegradable scaffold.
The cells began to mature into a dense capillary network within days, with scientists seeding RPE cells on the opposite side of the scaffold on day 9. By day 42, the printed tissue reached full maturity.
Watch this short video for an overview.
What did they find?
Analyses and testing found that the printed tissue appeared and behaved similarly to the original outer blood-retina barrier. When under induced stress, the tissue presented signs associated with early AMD to late-stage dry AMD.
Any specific challenges?
A major hurdle to overcome was generating a suitable biodegradable scaffold and reaching a consistently regulated printing pattern by developing a temperature-sensitive hydrogel that reached distinct rows when cold, but dissolved when the gel was warmed.
How did they achieve this?
The team’s good row consistency allowed them to attain a more precise system of quantifying tissue structures as well as utilizing the ratio of cell combinations.
The take home.
This new technique provides a novel modeling template that could unlock the potential for a limitless supply of cell-derived tissue for studying regenerative retinal diseases, and has the potential to open the door to developing a human model for targeted drug testing and disease identification.