Researchers in Boston, USA, have identified a way to find limbal stem cells that regrew human corneal tissue in mice, an early animal study that may one day support efforts to restore vision. The team was led by Dr Paraskevi Kolovou. The key to the new discovery was the ABCB5 molecule that acted like a marker to find limbal cells.
These limbal stem cells can be difficult to find and were previosuly only found in the limbus or “basal limbal epithelium.” Previously, the loss of human limbus is usually attributed to injuries or eye disease. Loss of limbus is currently one of the leading causes of blindness for humans. Previously, tissue regeneration using cell transplants has been done to allow the cornea to regenerate, but previously it was unknown if there were any limbal stem cells present during the grafting stage. Previously, Doctors were not able to count the volume of cells using flow cytometry leading to inconsistent results.
Scientists at the Harvard Stem Cell Institute finally overcame this limitation by using antibodies to detect the elusive ABCB5 molecule, enabling better targeting of limbal cells in human donor tissue. They then transplanted these cells into mice, where they regrew human corneal surface tissue.
Limbal cells are rare and difficult to isolate, and any chance of successful transplants depended heavily on these unique cells. This new finding may make it more feasible to restore the corneal surface in humans, although results from animal studies need to be confirmed in clinical studies. The ABCB5 molecule was originally discovered by Dr. Markus and Natasha Frank of the VA Boston Healthcare System. The doctors were able to produce the molecule in tissue precursor cells found in human intestinal and skin stromal cells.
They also recently found that ABCB5 is expressed in limbal stem cells, as this molecule is required for the survival, maintenance, and repair of the cornea. Studies have shown that the absence of properly functioning ABCB5 molecules in limbal stem cells and corneas prevents proper healing after injury. The ABCB5 gene enables limbal stem cells to survive by protecting them from programmed cell death, or apoptosis.
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