Efficacy of Mesenchymal Stem Cells and Mesenchymal Stem Cell-Derived Extracellular Vesicles in Corneal Tissue Repair

Cornea, an avascular and immune-privileged structure, is the outermost transparent tissue of the eye, which enables transmission of light to the neurosensory retina. Due to its anatomical position, it is constantly amenable to injuries, and thus requires an inherent ability to repair tissue damage. A healthy corneal epithelium is of vital role for the maintenance of corneal integrity and transparency. It is renewed by a small population of self-renewing stem cells (SCs) primarily found at the densely innervated peripheral corneal area. Corneal nerves help to maintain the integrity of corneal surface by releasing epitheliotrophic substances. Damaged or dysfunctional corneal nerves result in poor wound-healing. Similarly to corneal nerves, human corneal endothelium has very low proliferative potential in vivo. Severe corneal damage can occur as a consequence of several clinical conditions. All these factors, along with inefficient tissue-repair processes trigger corneal scarring and neovascularization that can lead to complete loss of vision, with approximately 4.5 million individuals being visually impaired due to loss of corneal clarity. The diseased or damaged corneal layers can be replaced by healthy donated corneal tissue. However, despite significant advances in corneal surgery and tissue storage (eye banking), there are still major issues related to the availability, quality and storage limitations of donor corneal tissues with faster endothelial cell loss seen after transplantation than with normal aging. Therefore, as vision loss is a devastating condition, there is an urgent need to develop alternative treatment solutions. Although mesenchymal SCs (MSC) have been widely studied in several animal disease models that showed the therapeutic effects of MSCs rely not only on their innate differentiation capacity but also on their immune-modulatory and anti-inflammatory properties to repair damaged tissues, to date, only few research groups have reported first clinical results with allogeneic bone-marrow or adipose derived MSCs transplantation in restoring corneal epithelium in humans. Furthermore, the paracrine effects of MSCs could be mediated mainly by their extracellular vesicles (EV). However, none of these studies have focused on potential neurotrophic and neuroprotective potentials of transplanted MSCs or MSC-derived EVs to regenerate corneal nerves and thus enable better long-term stability of ocular surface. Even less is known about cytoprotective effects of MSC-derived EVs to be used in eye banking to prevent corneal endothelial cell death in storage medium. At the Eye Hospital of University Medical Centre of Ljubljana we have a well-established research collaboration with the Blood Transfusion Centre of Slovenia (BTC), with several publications in the field of corneal epithelial and MSC culture and the preparation of amniotic membrane for therapeutic and research purposes. In the last eight years, we developed and prepared the foundation for allogeneic ex vivo corneal SC culture. In addition, dr Lužnik Marzidovšek gained extensive knowledge and experience in the field of donor tissue storage (eye banking) and corneal immunobiology as a postdoctoral research fellow at Schepens Eye Research Institute, Massachusetts Eye and Ear, Harvard Medical School under mentorship of prof. dr. Reza Dana, giving her the expertise and skills to lead this project. As high quality donor corneal tissue is scarce and severe ocular surface disease is suboptimal managed with current treatment options, we want to further expand this field. In this project we wish to introduce new neuro- and epitheliotrophic MSC sources to be cultured on amniotic membrane, that will not only shed light into the biology of cultured MSC and their EV secretion, but will also enable new treatment option for ocular surface reconstruction in the near future. In addition, we will test if MSC-derived EV have cytoprotective properties.