Stem Cell Patch Shown to Repair Retinal Damage

(Public Domain Pictures, Pixabay)

29 Oct. 2021. Research with lab rats shows a transplanted tissue patch derived from stem cells repairs damaged retinas and helps restore visual functions. Results of the study conducted by researchers at biotechnology company Aivita Biomedical Inc. in Irvine, California, and two universities appear in the 26 October issue of the journal Frontiers in Neuroscience.

The study tested engineered tissue to repair damage to retinas that occurs from diseases such as age-related macular degeneration and retinitis pigmentosa, as well as trauma to the eye. The retina is a layer on the back of the eye with light-sensitive cells called photoreceptors that convert light into neural signals, carried into the brain by the optic nerve. Age-related macular degeneration is a common eye disorder, where damage to the macula, a small spot in the center of the retina, becomes damaged, resulting in progressive loss of vision. Retinitis pigmentosa is caused by genetic defects that damage cells in the retina affecting night vision, and sometimes peripheral and central vision, leading to blindness.

Aivita Biomedical is a six year-old company developing stem-cell based treatments for cancer, but more recently a vaccine protecting against Covid-19 infections. In addition, the company extends its work with stem cells to regenerative therapies for repairing retinas with damage previously considered irreversible. Aivita Bio’s technology adapts a patient’s own stem cells for transforming into mature functioning cells and tissue, for transplant back into the patient.

New photoreceptor cell growth

For this study, an academic-industry team led by Magdalene Seiler, professor of physical medicine and rehabilitation at University of California in Irvine, tested the Aivita Bio patch in lab rats induced with severe retinal damage. The two-part patch is made of a sheet of retinal photoreceptor progenitor cells plus healthy retinal pigment epithelium, or RPE cells that carry out vital functions supporting photoreceptors. The patch also contains retinal organoids, small pieces of retina tissue grown from Aivita Bio’s embryonic stem cell lines. The two parts of the patch are then held together with biocompatible gels and embedded in alginate, a naturally occurring polymer found in algae.

The tissue patches were surgically transplanted into the rats’ retinas in labs at University of Southern California. After 12 days, optical 3-D image scans of the retinas show the RPE-organoid implants started growing tissue, including new photoreceptor cells. After 2 months, the implants show integration with the animals’ host retinal tissue, and after 6.5 months new photoreceptor cells form into circular patterns called rosettes. The implants continued to survive and function after nearly 8 months.

The researchers also tested visual functioning of the rats. The team used a spinning cylinder with high-contrast black and white stripes displayed on a tablet screen to attract the animals’ attention. The researchers measured head movements for one-minute periods as indicators of visual attention. After 2 and 5.5 months, the implanted rats show more visual attention to the moving images than similar rats without surgery or with sham (no implant) surgery. In addition, tests of neurons in the rats’s brains show implanted rats responding to light stimuli, even at low levels.

The authors conclude the technology offers a new option for treating damaged retinas. “These findings,” says Aivita Bio’s CEO and study co-author Hans Keirstead in a company statement, “demonstrate the potential of this approach in treating common retinal degenerative conditions such as end-stage age-related macular degeneration, retinitis pigmentosa, and retinal damage due to injury.”

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