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We talk to prof. with dr hab. n. med. Eward Wylęgała.
Professor, what is severe and what is moderate limbal stem cell deficiency?
Prof. related dr hab. n. med. Edward Wylęgała: The epithelial cells of the human body are systematically replaced from the pool of stem cells. This happens in the skin, intestines and bronchi. Similarly, in the cornea, the epithelium, i.e. the superficial layer about 0.05 mm thick, is replaced with cells located in the so-called limbus. It is a 1 mm wide transitional border ring between the peripheral part of the clear cornea and the opaque sclera. The deficiency of limbal stem cells leads to a loss of transparency in the cornea, which is associated with loss of vision. Clinically, we divide limbal stem cell failure into light, moderate and severe. The division is based on the extent of the limbal damage. The cornea has the shape of a circle, so it can be hypothetically divided into the pattern of a clock face for hours. If the damage is less than six clock hours (two quadrants) then the damage is minor, if more than six hours it is moderate, and if more than 10 clock hours it is severe.
What are the effects of this condition?
EW: The disease is characterized by pain, redness, photophobia, and often tearing. In the cornea, areas not covered with epithelium form, which lead to ulceration. Blood vessels that are not present in the healthy cornea are formed, and the regularly arranged collagen fibers are converted into fibrous tissue. The cornea is covered with conjunctival epithelium. All these processes consequently lead to its dullness. Clinically, the patient is unable to see. The disease mainly affects young people who are therefore unable to work.
What is the disease data like?
EW: Limbal stem cell failure can be primary or secondary. It is primarily associated with syndromes of endocrine failure, lack of iris, keratitis, ichthyosis and deafness. Secondary, it is mainly associated with injuries, including burns. Failure may occur after eye surgery, inflammation of the cornea and conjunctiva, and wearing contact lenses. The prevalence is estimated between 0,33 and 1.0 per 10 inhabitants.
What treatment options for limbal stem cell deficiency are available to patients in Poland?
EW: We currently use limbal stem cell transplants transferred on the corneal scleral tissue. The source of these cells is the postmortem donor, the other healthy eye, or the family donor. These procedures are reimbursed by the National Health Fund. The effectiveness of these procedures is not high because we do not know what pool of cells we are transplanting. It is also problematic to extract large pieces of tissue from the healthy eye. Allografts (from donors) require the use of immunosuppressive drugs, such as after heart, liver or kidney transplants. I have been working with my team for 16 years of limbal stem cell failure, and during this time we have managed to conduct research on transplantation of cultured corneal epithelial cells. The obtained results were very promising, but unfortunately we were not able to introduce these studies into routine clinical use.
Is there a regenerative therapy on the market that can be treated as a breakthrough?
EW: Regenerative therapy using standardized epithelial cell transplantation is, in my opinion, a milestone in the treatment of limbal stem cell failure and is already approved as a drug. We have waited over a dozen years for this opportunity. We take the minimum size of tissue from a healthy eye (1-2 mm square). We send the biopsy to the laboratory, where epithelial cells are grown, along with the percentage of stem cells. The grown cells are covered with a thin fibrous membrane 2,2 cm in diameter. In this form, the medication is delivered to the operating room.
How does this therapy work?
EW: It contains up to 316 epithelial cells per square centimeter, and most importantly, the average stem cell content of this population is 000%. It is these cells after transplantation that nest in the limbus of the cornea and restore the surface of the cornea. Of course, the eye must be properly surgically prepared. The cornea should be cleaned of fibrovascular tissue. This is the only transplant procedure for limbal stem cell transplantation where we are sure that we are transplanting the correct pool of epithelial cells.
Is it safe and effective with regard to the clinical effects of the mentioned regenerative therapy?
EW: The therapy was assessed for safety and effectiveness. The drug is approved by the European Medicines Agency for use in the European Union. Clinical trials have shown that this therapy is very effective.
Has the professor already dealt with this therapy?
EW: At the Ophthalmology Clinic at the Regional Railway Hospital in Katowice, we conduct a clinical trial sponsored by Chiesi using this advanced tissue engineering therapy. A month ago, I performed my first limbal biopsy on a patient with severe limbal stem cell deficiency. It was the second biopsy in Europe. The first was done a week earlier by my friend, the co-creator of this procedure, Prof. Paulo Rama from Milan. We got a message from the laboratory that the biopsy was successful and that the first colonies of cells are already growing. After five months, we will perform a transplant. We already have five patients qualified for treatment.
Do patients in Poland have access to it?
EW: Currently, patients in Poland can be treated with this therapy only in a clinical trial. We have the option of including six patients and one additional child. Due to the very advanced technology of drug preparation, the cost of the procedure is very high. I hope there is a possibility of a refund for this procedure in the near future.