Treating blindness by transplantation of cultured oral mucosal cells

Limbal stem cell deficiency (LSCD) is a potentially painful and blinding condition. Cell therapy has been increasingly favored in its treatment. For bilateral LSCD, more prevalent case compared to unilateral form, an appropriate cell type from patient is required for transplantation. Oral mucosal epithelial cells (OMECs) have experimentally and clinically shown to be a suitable source. Therefore, there have been attempts to improve transplantation success and expand access by investigating different transportation techniques and storage conditions. In light of such mission, this 3-year-project (2017-2020) was focused on optimization of a novel hyaluronic acid (HA) based hydrogel scaffold for culture of OMECs for potential application in LSCD therapy. In addition, the response of cultured OMECs to four different storage temperatures was studied structurally and transcriptionally. The results of this project indicated that coating HA with collagen IV and including a 3-day drying time in the absence of polyethylene glycol diacrylate (PEGDA) crosslinker, leads to a hydrogel that supports growth of a full sheet of OMECs after three weeks of culture. This optimized HA scaffold could maintain morphology, stemness markers, preventing differentiation and losing cells or retrieve them after 3 weeks of culture of OMECs. In another study, the structural and transcriptional effects of storage temperature (4°C, 12°C, 24°C and 37°C) on OMECs after two weeks suggested 4°C for optimal maintenance of structure, viability and function of cells. Blindness and marked visual impairment affect 160 million people worldwide. This imposes substantial costs on society, particularly to the patients and their families. Due to world demographic aging, the number of those with vision loss is likely to double over the next 20 years. Because many eye care interventions, including research, are cost-saving, even developing economies can afford to prevent or treat vision loss. The transparency of the cornea, the window of the eye, is dependent on well-functioning stem cells in the periphery of the cornea, known as limbus. Corneal diseases, which can be caused by limbal stem cell deficiency (LSCD), are the second leading cause of blindness. LSCD cannot be treated by conventional corneal transplantation, but the patients can be treated by transplanting tissue cultured in a laboratory from a small biopsy from a healthy cornea or a suitable alternative source such as oral mucosal epithelial cells (OMECs). The global need for treatment cannot be met as the procedure must be performed in highly specialized centers. The optimized HA scaffold in this project provides surgeons and patients with a suitable scaffold that supports the growth of a full sheet of OMECs, which maintains morphology, stemness markers, preventing differentiation and losing cells or retrieve them. These are considered influencing factors in treatment of LSCD and would improve transplantation success. The current project also studied optimal storage temperature as the prepared cell sheets may not be used immediately for transplantation due to patient readiness and the time required for transport from laboratory units to clinics. The findings showed that storing OMECs at 4˚C for two-week is the most appropriate temperature with optimal maintenance of structure, viability and function of cells. Therefore, it is most likely to be the best storage conditions for clinical transplantation that increases the success rate of regeneration in damaged tissue. The use of appropriate carrier scaffold and long-term storage of cultured cells in a sealed container prior to transplantation is advantageous for several reasons: • It allows quality control, including microbiological assessment of the cultured tissue. • It enables transportation of the cultured tissue from GMP approved laboratory to the clinics for transplantation, thereby increasing the availability of regenerative medicine. • Increased flexibility for both patient and surgeon with respect to the timing of the operation is provided. • Any delays during transportation and/or quality control become less problematic.