is becoming more and more literal in eye research. Like a gardener
removes the dead roots of the soil's former dweller, tills and adds
fresh soil and fertilizer to make the ground replantable,
and finally adds new seeds, researchers have developed an implant that
clears out the scar tissue of diseased retinas and seeds new ones. This
quickly evolving procedure holds hope for millions of persons with retinitis pigmentosa (RP) and age-related macular degeneration (ARMD).
Image credit: Case Western Reserve University
Scientists from Harvard University, the University of California at Irvine, and Case Western Reserve University have been working on an implant to restore the function of photoreceptors in the eye so that the millions of persons blinded by RP and ARMD might regain their vision. RP and ARMD destroy the eye's photoreceptors, which convert light into electrical signals and carry them to the brain.
Recognizing that in order for retinal progenitor cells to grow, the scar tissue left by the degeneration of the photoreceptors must be replaced by "fertile soil," researchers created one implant that could disintegrate the scar tissue and plant the progenitor cells simultaneously.
The Case Western research team built a scaffold through a process called electrospinning, which uses electrical charges to spin and interweave biodegradable mesh fibers up to 1/1000th the width of a hair. Embedded in the fibers are special enzymes that migrate out and destroy the local scar tissue, while the progenitor cells, releasing from the surface of the scaffold, find "fertile ground" in which to seed.
The positive effects of the enzymes in clearing out the old scar tissue were witnessed by the survival rate of the retinal progenitor cells.
The implant structure that only contained progenitor cells was 16 times more effective at reaching the degraded retinal site, and the survival rate of the cells was 9 times more effective than simple injection of the progenitor cells. But when the scar tissue destroying enzymes were included in the scaffold, the number of progenitor cells that reached the site and survived reached 15 to 20-fold. In a mouse model that received the implant with the enzymes, progenitor cells were "taking on the form" of mature photoreceptors 14 days after implantation.
This study is published in the January issue of Biomaterials. But while scientific studies can take months to publish, researchers keep trying to perfect their outcomes, and this study is no exception. By the time it was published, the scientists had already reduced the size of the mesh implant, increased its flexibility, and made it more acceptable to the body so it would not cause irritation or inflammation.
ref. Biomaterials, Case Western Reserve University