Researchers here provide evidence in mice to suggest that stem cell treatments could be used to address some forms of glaucoma, usually caused by an increase in pressure in the eye that can damage the optic nerve and other structures. The types of glaucoma of interest here are those in which the drainage channels for aqueous humour deteriorate, as those channels might be induced to regenerate via the transplantation of stem cells produced from the patient's own tissues:
Researchers injected stem cells into the eyes of mice with glaucoma. The influx of cells regenerated the tiny, delicate patch of tissue known as the trabecular meshwork, which serves as a drain for the eyes to avoid fluid buildup. When fluid accumulates in the eye, the increase in pressure could lead to glaucoma. The disease damages the optic nerve and can result in blindness. "We believe that replacement of damaged or lost trabecular meshwork cells with healthy cells can lead to functional restoration following transplantation into glaucoma eyes."
One potential advantage of the approach is that the type of stem cells used - called induced pluripotent stem cells - could be created from cells harvested from a patient's own skin. That gets around the ethical quandary of using fetal stem cells, and it also lessens the chance of the patient's body rejecting the transplanted cells. The researchers were able to get the stem cells to grow into cells like those of the trabecular meshwork by culturing them in a solution that had previously been "conditioned" by actual human trabecular meshwork cells. The researchers were encouraged to see that the stem cell injection led to a proliferation of new endogenous cells within the trabecular meshwork. In other words, it appears the stem cells not only survived on their own, but coaxed the body into making more of its own cells within the eye, thus multiplying the therapeutic effect. The team measured the effects in the mice nine weeks after the transplant. Lab mice generally live only two or three years, and nine weeks is roughly equal to about five or six years for humans.
The researchers say they are confident that their findings hold promise for the most common form of glaucoma, known as primary open angle glaucoma. They aren't sure yet if their mouse model is as relevant for other forms of the disease. Another possible limitation of the research: It could be that new trabecular meshwork cells generated from the stem cell infusion eventually succumb to the same disease process that caused the breakdown in the first place. This would require retreatment. It's unclear, though, whether an approach requiring multiple treatments over time would be viable. The researchers plan to continue studying the approach.