Deriving an in vitro source of canine corneal stromal cells for future studies of corneal disease and therapeutic applications

The cornea is the transparent tissue located at the front of the eye, that transmits and refracts light onto the retina. Despite great advances in corneal stem cell biology in human and laboratory animal research, no information is available in dogs. Corneal pathology, as corneal crystalline dystrophy has a prevalence of up to 15% and has been described in eight different canine breeds. Cholesterol and phospholipids are deposited in the stroma, similar to Schnyder’s dystrophy (SCD) in humans. Chronic corneal fibrosis is one of the leading causes of visual impairment in veterinary ophthalmology. Similar to the situation in human ophthalmology, there is a shortage of corneal donor tissue. Therefore, the overall aim was first to investigate whether corneal stromal stem cells exist in the canine cornea., The second aim was to determine the potential of deriving an in vitro source of corneal stroma cells from corneal stromal stem cells, adipose derived mesenchymal stromal cells (adMSC) and canine induced pluripotent stem cells (ciPSC), to provide a resource for studies investigating the pathogenesis of inherited stromal dystrophies, and for the development of novel cell-based therapies for dogs. First, a canine corneal stromal cell (CSC) population was characterised that demonstrated mesenchymal stromal cell properties, they differentiated into keratocyte-like cells (KDCs) in vitro and appeared to be immune privileged. Second, canine adMSC were differentiated into KDCs, but expressed high levels of a myofibroblastic marker, similar to those found in fibrotic tissue. Third, a modified protocol was established whereby ciPSCs were induced into neural crest (stem) cell lineages and then into KDCs. This led to the successful expression of some keratocyte associated markers in absence of a myofibroblastic expression. Taken together, a novel cell population was characterised in the canine corneal stroma. The differentiation protocols of adMSC and ciPSC led to preliminary results and built a basic foundation for future studies