STEM CELLS AND EYES IN THE FUTURE
In memories of all immobile dogs that were not given a second chance
A new study describes a pioneering new cataract treatment – tested in animals and in a small trial with human patients – where, after the cloudy lens is removed, the eye grows a new lens from its own stem cells.
The researchers – including teams from the University of California-San Diego (UCSD), Sun Yat-sen University in Guangzhou and Sichuan University, both in China – describe their new regenerative medicine approach in a paper published in the journal Nature.The treatment was tested in 12 babies born with cataracts. It resulted in significantly fewer surgical complications than current treatments, say the researchers. Sight was improved in all 12 patients.
“We believe that our new approach will result in a paradigm shift in cataract surgery and may offer patients a safer and better treatment option in the future.”
Kang Zhang, a professor of ophthalmology and chief of Ophthalmic Genetics at UCSD
Being born with a lens that is cloudy or shortly becomes so is rare, but it is a significant cause of blindness in children. Estimates suggest it affects around 3 out of 10,000 children, although this rate varies throughout the world.
The clouded lens stops light getting to the retina, resulting in significant loss of vision. Current treatments can be difficult and result in complications in very young patients. Most children need to wear glasses after cataract surgery.
Kang Zhang, M.D., Ph.D.
Professor of Ophthalmology Chief, Ophthalmic Genetics Founding Director, Institute for Genomic Medicine Co-Director, Biomaterials and Tissue Engineering, Institute for Engineering in Medicine
Haotian Lin, Hong Ouyang, Jie Zhu, Shan Huang, Zhenzhen Liu, Shuyi Chen, Guiqun Cao, Gen Li, Robert A. J. Signer, Yanxin Xu, Christopher Chung, Ying Zhang, Danni Lin, Sherrina Patel, Frances Wu, Huimin Cai, Jiayi Hou, Cindy Wen, Maryam Jafari, Xialin Liu, Lixia Luo, Jin Zhu, Austin Qiu, Rui Hou, Baoxin Chen, Jiangna Chen, David Granet, Christopher Heichel, Fu Shang, Xuri Li, Michal Krawczyk, Dorota Skowronska-Krawczyk, Yujuan Wang, William Shi, Daniel Chen, Zheng Zhong, Sheng Zhong, Liangfang Zhang, Shaochen Chen, Sean J. Morrison, Richard L. Maas, Kang Zhang
& Yizhi Liu
- Sichuan University, China;
- Sun Yat-sen University, China;
- University of California San Diego, United States;
- Brigham and Women Hospital and Harvard Medical School, United States;
- The First Affiliated Hospital of Sun Yat-sen University, China;
- University of California, United States
Method uses stem cells in the eyes to grow new lens
In the new study, the team used the ability of stem cells to grow new tissue. They did not use the more common approach – where stem cells are taken out of the patient, grown in the lab and then put back in the patient. This method can introduce disease and raise the risk of immune rejection.
Instead, the team coaxed stem cells in the patients’ eyes to regrow the lenses. So-called endogenous stem cells are stem cells that are naturally already in place, ready to regenerate new tissue in the case of injury or some other problem.
In the case of the human eye, the endogenous stem cells – known as lens epithelial stem cells (LECs) – generate replacement lens cells throughout a person’s life, although production wanes with age.
Current approaches to cataract surgery remove LECs along with the faulty lens – any few that are left can generate some lens cells, but the growth is random and disorganized in infants, resulting in no useful vision, note the researchers.
The approach the researchers describe in their paper has two important differences to conventional cataract surgery: it leaves the lens capsule intact, and it stimulates LECs to form a new lens. The lens capsule is a thin membrane that helps give the lens its required shape to function.
What are Stem Cells?
Stem cells are a class of undifferentiated cells that are able to differentiate into specialized cell types. Commonly, stem cells come from two main sources:
- Embryos formed during the blastocyst phase of embryological development (embryonic stem cells) and
- Adult tissue (adult stem cells).
Both types are generally characterized by their potency, or potential to differentiate into different cell types (such as skin, muscle, bone, etc.).
In early experiments, Zhang and his colleagues showed they could isolate LECs from mice, and that these cells could form transparent, lenslike structures. The scientists reasoned that minimally invasive surgeries, involving cuts of only 1 to 1.5 millimeters wide, could remove cataracts while also preserving LECs that could then go on to regenerate lenses, Zhang said. They achieved successful lens regeneration in rabbits and monkeys, before attempting the procedure in children.