23 July 2010
By Pushpa Narayan
Chennai, India
Stem cell transplant in eyes has remained a challenge for surgeons because of the infection risk of the ‘scaffold’ used to hold the cells. Now, a procedure tested in rabbits by Sankara Nethralaya and Nichi–in Bio Sciences holds new promise in scaffold–less transplant of stem cells with a higher success rate in humans.
The two institutions recently got a patent for the process and are now gearing up for human trials. The hospital is also looking for collaborations with research institutions for animal stem cell trials on other vital organs including the heart, liver, kidney and pancreas.
Stem cells have the potential to develop into many different types of tissues such as muscle, blood, nerve, heart, or even brain during early life and growth.
Stem cell therapy uses such cells to repair and regenerate damaged tissue. For those blinded due to ocular surface damage (caused by burns and chemical injuries) stem cell therapy is often the only option.
“We have been using scaffolds such as amniotic membrane (tissue discarded after child birth) because without them stem cells will be washed away by body fluids. These scaffolds were causing rejection and infection,” said Dr HN Madhavan, professor of microbiology and president, Vision Research Foundation, Sankara Nethralaya.
In 2003, a team of scientists identified a synthetic thermo–reversible gel, which liquifies when cooled. Mebiol gel, manufactured by a Japanese firm, was used as a scaffold to grow the rabbit’s corneal stem cells. The stem cells of the cornea, located in an area called the limbus, multiplied rapidly in the gel.
“Once the growth was satisfactory, we put the petri dish in the refrigerator. The gel liquified and the limbal stem cells settled down. We then separated the stem cells from the liquid,” he said. The stem cells were then loosely injected into the eyes of 12 rabbits blinded due to ocular surface damage.
The little amount of gel that remained with the stem cells kept it glued to the site. “It’s impossible to completely get rid of the liquid. Some liquid remains in the cell. Since the human body is warm enough, the liquid turns into gel. This is enough to help the cell stick to the surface and multiply. In nine months, we saw vision completely restored in seven of the rabbits and partially restored in three of them. The other two rabbits did not show significant response. But in all the rabbits the stem cells were multiplying,” he said.
The study was published in Tissue Engineering, an international journal. The two institutions filed for a patent on March 28, 2005. “We had to face more than seven challenges. Finally, we were given the patent for the process,” said Dr Madhavan.
The hospital sees 6,000 patients with such eye injuries. “Every year, we diagnose at least 125 patients with Stevens Johnson Syndrome, a common cause for ocular surface damage and more than 75 new patients with chemical injuries,” he said.
Infection–Free Transplants
- In 2003, scientists at Sankara Nethralaya with the help of their counterparts in Nichi–in BioSciences, identified a synthetic gel, which liquifies when cooled. The Mebiol gel was used to grow corneal stem cells in laboratories
- Once the growth was satisfactory, scientists cooled the petri dish. The gel liquified and the stem cells settled down. They then used special equipment to separate the stem cells from the liquid
- These stem cells were injected into the eyes of 12 rabbits blinded due to ocular surface damage. Nine months later they saw vision completely restored in seven rabbits, and partially restored in three others
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