Why do stem cells on the cornea stop working in aniridia?

Research details

  • Type of funding: PhD Studentship
  • Grant Holder: Dr Sajjad Ahmad
  • Institute: University of Liverpool
  • Region: North West
  • Start date: October 2014
  • End Date: September 2017
  • Priority: Treatment
  • Eye Category: Corneal & external


Aniridia is a rare and severely blinding condition that affects 1 person in 100,000. Vision is affected from birth due to problems with eye development and this gets worse with age.

One of the affected areas is the cornea (the usually clear front surface of the eye). In aniridia, the cornea becomes painful and hazy because the cornea’s surface stem cells (called limbal stem cells) stop working normally. Limbal stem cell transplants can treat some other conditions but this doesn’t work in aniridia. So in this project the aim is to find what happens to the limbal stem cells that makes aniridia different.

The team is studying mice with a genetic fault in the gene PAX6. This gives them a mouse version of aniridia. Evidence from the mice suggests that nearby cells called fibroblasts and the tissue surrounding the limbal stem cells (called the extracellular matrix) are also affected, but they haven’t yet been studied.

In this project the team is finding out what happens to human limbal stem cells when you grow them on fibroblasts from aniridia mice. Fibroblasts and limbal stem cells can both make extracellular matrix, so the team is also looking at how it turns out when faulty PAX6 is involved. They also want to know what happens to fault limbal stem cells when they’re grown on normal fibroblasts and extracellular matrix, to see if they can be rescued. The results should shed light on how it might be possible to treat aniridia in future.

  • Scientific summary

    Investigation into the role of the extracellular microenvironment in the development of limbal stem cell failure in aniridia

    Aniridia is a rare but severe developmental and degenerative eye disease resulting from a PAX6 gene mutation. Limbal stem cell deficiency (LSCD) of the cornea is one of the progressive ocular manifestations of this disease that results in conjunctivalisation of the cornea surface. The result is not only a blinding disease but also a painful one with chronic ocular surface pain and glare.

    We still understand little about the pathogenesis of LSCD in aniridia and have few effective treatment strategies for the disease. Replacing the limbal stem cells (LSCs) alone is ineffective in the long-term. This proposal aims to understand the causes of this LSCD so that we can target our treatment options more effectively.

    Extracellular cues are important for adult stem cell survival. In this proposal, the role of PAX6+/- limbal fibroblasts and the extracellular matrix (ECM) in causing the LSC failure in aniridia is being investigated. Firstly, human limbal epithelial cells will be cultured on collagen I embedded murine PAX6+/- limbal fibroblasts to determine the effect of abnormal fibroblasts on human LSCs. Secondly, abnormalities in the ECM and its production resulting from the PAX6+/- fibroblasts will be determined. Thirdly, abnormalities in ECM production and re-modelling by human limbal epithelial cells cultured on PAX6+/- fibroblasts will also be determined. Fourthly, the effect of normalising the fibroblasts and ECM upon human limbal epithelial cells previously cultured on PAX6+/- fibroblasts will be determined. These investigations will determine whether LSCD in aniridia can be reversed or halted by normalising the LSC bed.