“We know that AMD starts in the outer blood-retina barrier,” said Kapil Bharti, Ph.D., who heads the NEI Section on Ocular and Stem Cell Translational Research. “However, mechanisms of AMD initiation and progression to advanced dry and wet stages remain poorly understood due to the lack of physiologically relevant human models.” 

How was the process?

Bharti and colleagues used a hydrogel to mix three immature choroidal cell types: pericytes and endothelial cells, which are important components of capillaries, and fibroblasts, which give tissues structure. The gel was then printed on a biodegradable scaffold by the scientists. The cells began to grow into a dense capillary network within days.

On the ninth day, the researchers implanted cells from the retinal pigment epithelium on the other side of the scaffold. On day 42, the printed tissue was fully developed. 

According to tissue investigations, genetic tests, and functional analysis, the printed tissue resembled the natural outer blood-retina barrier in appearance and behavior. Under conditions of generated stress, printed tissue displayed early AMD characteristics, such as drusen deposits beneath the RPE, and advanced to late dry-stage AMD, where tissue deterioration was seen.