A new cornea may be the only way to prevent a patient going blind – but there is a shortage of donated corneas and the queue for transplantation is long. Scientists at the Sahlgrenska Academy have for the first time successfully cultivated stem cells on human corneas, which may in the long term remove the need for donators.
Approximately 500 corneal transplantations are carried out each year in Sweden, and about 100,000 in the world. The damaged and cloudy cornea that is turning the patient blind is replaced with a healthy, transparent one. But the procedure requires a donated cornea, and there is a severe shortage of donated material. This is particularly the case throughout the world, where religious or political views often hinder the use of donated material.
Replacing donated corneas
Scientists Charles Hanson and Ulf Stenevi have used defective corneas obtained from the ophthalmology clinic at Sahlgrenska University Hospital in Mölndal. Their study is now published in the journal Acta Ophthalmologica, and shows how human stem cells can be caused to develop into what are known as “epithelial cells” after 16 days’ culture in the laboratory and a further 6 days’ culture on a cornea. It is the epithelial cells that maintain the transparency of the cornea.
First time ever on human corneas
“Similar experiments have been carried out on animals, but this is the first time that stem cells have been grown on damaged human corneas. It means that we have taken the first step towards being able to use stem cells to treat damaged corneas”, says Charles Hanson.
“If we can establish a routine method for this, the availability of material for patients who need a new cornea will be essentially unlimited. Both the surgical procedures and the aftercare will also become much more simple”, says Ulf Stenevi.
Few clinics conduct tranplants
Only a few clinics are currently able to transplant corneas. Many of the transplantations in Sweden are carried out at the ophthalmology clinic at Sahlgrenska University Hospital, Department of Ophthalmology, Mölndal.
The article “Transplantation of human embryonic stem cells onto a partially wounded human cornea in vitro” was published in Acta Ophthalmologica on 27 January.
Transplantation of human embryonic stem cells onto a partially wounded human cornea in vitro
Purpose: The aim of this study was to investigate whether cells originating from human embryonic stem cells (hESCs) could be successfully transplanted onto a partially wounded human cornea. A second aim was to study the ability of the transplanted cells to differentiate into corneal epithelial-like cells.
Methods: Spontaneously, differentiated hESCs were transplanted onto a human corneal button (without limbus) with the epithelial layer partially removed. The cells were cultured on Bowman’s membrane for up to 9 days, and the culture dynamics documented in a time-lapse system. As the transplanted cells originated from a genetically engineered hESC line, they all expressed green fluorescent protein, which facilitated their identification during the culture experiments, tissue preparation and analysis. To detect any differentiation into human corneal epithelial-like cells, we analysed the transplanted cells by immunohistochemistry using antibodies specific for CK3, CK15 and PAX6.
Results: The transplanted cells established and expanded on Bowman’s membrane, forming a 1–4 cell layer surrounded by host corneal epithelial cells. Expression of the corneal marker PAX6 appeared 3 days after transplantation, and after 6 days, the cells were expressing both PAX6 and CK3.
Conclusion: This shows that it is possible to transplant cells originating from hESCs onto Bowman’s membrane with the epithelial layer partially removed and to get these cells to establish, grow and differentiate into corneal epithelial-like cells in vitro.