The human eye makes use of two types of light-sensing cells, rods and cones. Of the two, the cones, which are active in daylight and which confer detailed (reading) vision, are by far the most important for day-to-day life. In conditions like cone dystrophy or Stargardt disease, the cone cells die over time, and as the human body is unable to replace these cells, this results in severe vision impairment. In this project we aim to create a source of transplantable cone cells and test whether the transplantation of these cells into the human eye can restore the vision that is lost in patients with advanced cone dystrophy.
In a previous project, we have shown that we can grow up human cones in the laboratory using methods that make them suitable for subsequent transplantation into patients. When we transplanted these cells into mice that lack all light-sensing cells, we could prove that the human cells survived and made connections with the nerve cells of the mouse. As a result, light-sensation was restored in the mouse eye and the animal's behaviour changed in response to light, indication that some vision was restored. The aim of this project is to (1) scale-up the cone production method to be able to make enough cells for treating the human eye, (2) produce a large batch of cones that passes the quality regulations for human use, and (3) transplant these cone cells into the eyes of up to 12 patients with advanced cone dystrophy. As this is the first time that we test these cells the primary objective of the patient study will be to establish whether the transplantation of cones is safe. The secondary objective is to determine whether the transplanted cone cells can survive and restore vision, using a range of vision tests. If the study is successful, we will develop the transplantation method further to be able to treat a increasing range of blinding diseases.