Source:
www.sandiegouniontribune.com/news/2016/mar/09/lens-regenerated-stem-cells-humans/
By Bradley J. Fikes
This boy had cataract surgery at 6 months. He is now 2 years old and has regained vision through a lens regenerated from stem cells in his eyes.
— Dr. Kang Zhang and Dr. Yizhi Liu
Infants with cataracts have regenerated functional lenses from stem cells naturally present in their eyes, according to UC San Diego and Chinese researchers.
Stem cells already present in the eyes of these infants regrew lenses, something never done before. The lenses are functional and appear to act normally in the infants, who are now toddlers.
The study was published Wednesday in the journal
Nature. It can be found online at j.mp/stemlens.
Zhang was a senior author of the paper, along with Yizhi Liu of Sun Yat-sen University in Guangzhou, China. The first author was Haotian Lin, also of Sun Yat-sen University.
Cataracts are normally removed and replaced with artificial implants. Lin et al. devised a minimally invasive method for lens removal, which left lens epithelial stem cells (LECs) intact. These LECs regenerated the lens in rabbits, macaques and children, eliminating the need for implants.
— Julie T. Daniels
Not only lenses, but other human tissues and organs might be regrown by tapping into the regenerative power of stem cells present throughout the body, said Dr. Kang Zhang, a study leader and UCSD's founding director of the Institute for Genomic Medicine.
This approach could prove to be less risky than other types of stem cell reparative research, which involve growing replacement parts outside the body and transplanting them, said Zhang, also chief of ophthalmic genetics at Shiley Eye Institute.
Such an advance would be a tremendous boon to an aging population that is increasingly vulnerable to degenerative ailments, including Parkinson’s disease, spinal disc degeneration, arthritis and heart disease. It could also save billions now spent on caring for those with such diseases who can’t live independently.
That goal is still far from reality. But in the nearer term, researchers say it may be possible to regenerate lenses in adults who have had cataract surgery. Lens stem cells lose power as people age, but this could be countered with drugs that increase the activity of these stem cells. This would provide better vision than now available with glasses or intraocular lens transplants.
Low risk
While the study treated only 12 infants (24 cataracts), the treatment was low-risk and produced uniformly favorable results, Zhang said. Doctors removed the cataracts using a newly developed surgical procedure that reduces damage to the surrounding lens capsule, preserving the lens stem cells. The infants regenerated new lenses within three months.
The procedure was first conducted in rabbits and in monkeys before it was performed on the infants.
All the regenerated lenses are clear and can focus on an object at varying distances, Zhang said. As far as can be determined at such a young age, the toddlers, appear to see normally. However, followup studies are needed to confirm if this remains the case as the children grow up. And studies are needed by other researchers to validate the results.
The treated infants exhibited fewer complications than a control group of 25 infants who received standard care, consisting of removal of the lens and replacement with glasses. The normal surgical procedure creates a wider cut into the capsule surrounding the lens, where the stem cells, called lens epithelial stem cells, are found.
These lens epithelial stem cells decline with age, and replace damaged lens tissue throughout life. However, complete lens regeneration hasn’t been shown before in people. Zhang said it might be possible to accomplish the same feat in adults with the use of drugs or chemicals called growth factors to promote regeneration.
Replacing tissue in the body with these stem cells represents the Holy Grail of regenerative medicine, said Dr. Martin Friedlander, a professor in the department of cell and molecular biology at The Scripps Research Institute in La Jolla. This avoids potential immune rejection of grafts grown from another person.
"Should the report of Lin, et al hold up, this could represent a highly significant step forward in treating ocular disorders as well as other diseases amendable to stem cell therapies," Friedlander said by email. "On a technical level, it will be interesting to see how well the reformed lens holds up over time and what its refractive capabilities are."
Superior results
Cataracts in adults are treated by removal of the lens and replacement with an artificial intraocular lens. But this isn't feasible with children, Friedlander said.
"In children, the eye continues to grow, making it problematic to implant an artificial lens into the eye after removing the cataract," Friedlander said. So if the research is confirmed, it would represent “a highly significant step towards successfully treating congenital cataracts."
Research funding sources included the National Basic Research Program of China, the National Natural Science Foundation of China; Zhongshan Ophthalmic Center, Sun Yat-sen University; Research to Prevent Blindness; and the Howard Hughes Medical Institute.
