The technique employed by specialists from the Ophthalmology Department at the University of Navarra Hospital involves transplanting adult stem cells obtained from the limbus of a healthy eye from the patient him or herself or from a donor, in order to treat loss of vision due to limbal insufficiency. This limbal stem cell transplantation to the affected eye is carried out using amniotic membrane as a support medium. The rate of success for this technique is about 75%, according to international studies.
Outstanding amongst the cases already treated with this ophthalmological procedure is that of Mr Miguel Francés, a patient subjected to a transplant of this nature more than five years ago. Mr Francés had a total loss of vision in the right eye due to optic neuritis, and also with minimal vision in the left eye, due to a limbal insufficiency in its cornea. Thanks to the fact that the limbus of the sightless eye was intact, the ophthalmologists at the Hospital were able to transplant cultured limbal stem cells from this eye to the one with limbal insufficiency. After the transplant, the patient was able to recover 90% of his sight, a percentage that has been maintained after five years, and which today enables him to lead a perfectly normal life.
The limbus is the ocular region responsible for the cell regeneration of the corneal epithelium (the transparent and most superficial layer of the cornea). This regenerative task is that of the stem cells in the limbus. Thus, the cause of limbal insufficiency lies in the destruction of these limbal stem cells. The consequence of such deterioration is the vascularisation of the epithelium and its loss of transparency, the epithelial cells not being able to regenerate themselves, giving rise to an abnormal epithelium that impedes the passage of light towards the retina. “Limbal insufficiency may manifest itself at various levels, depending on the number of stem cells affected. In some cases, the patient can completely lose the sight of the affected eye”, explained Doctor Adriano Guarnieri, cornea specialist at the Ophthalmology Department at the University of Navarra Hospital
The transplant of adult stem cells of the limbus is a technique which the ophthalmologists at the University of Navarra Hospital have been applying for 8 years, the programme having started in 2003. It is one of the largest monitoring programmes for the transplant of cultured corneal cells in Spain.
The transplant technique starts with a small biopsy (the taking of a tissue sample) of about 2 mm2 from the healthy limbus. This sample is so small that the healthy eye remains unaffected.
Stem cells obtained from this extraction are then grown at the Hospital’s Cell Therapy GMP (Good Manufacturing Practice) Laboratory, directed by Doctor Felipe Prósper. Once suitable growth of this cell population has been obtained after several weeks, the stem cells obtained are transplanted to an amniotic membrane which acts as a support medium. “The employment of the amniotic membrane as a support medium for transplanting the limbal cells to the affected eye is because this medium is a surface that is resistant, transparent, thin and rich in collagen”, pointed out Dr Guarnieri.
These stem cells are grown again in the amniotic membrane and, when a sufficient cell population has been obtained, it is transplanted to the affected eye in this same membrane. “We thus manage to maintain the limbal cells transplanted to the surface of the eye, in such a way that these stem cells cover the ocular surface and lodge themselves in the affected limbus, until the damaged epithelium regenerates and recreates a transparent and homogeneous corneal surface. The end result is achieving enhancement in the vision of the patient and their symptoms”, stated the ophthalmologist.