Introduction. In a number of pathological conditions accompanied by the basement membrane defects, such as chemical or thermal burns, mechanical trauma, Sjögren’s syndrome, neurotrophic keratopathy or some corneal dystrophies, in which conditions are created independent epithelialization is weakened or becomes impossible. This condition was named recurrent corneal erosion (RCE). For the experimental study of the regenerative processes and evaluation of the effectiveness of new treatments, a standardized and reproducible RCE model is needed. Several RCE models are known: chemical, bacterial. The disadvantages of such models are the labour intensity of their implementation and a relatively high cost. The proposed method makes it possible to create the necessary conditions for local inflammation and destruction of adhesive molecules using the energy of ultraviolet (UV) irradiation. In this study, an experimental RCE model in rabbits has been proposed.Purpose. To create a reproducible standardized experimental model of recurrent corneal erosion.Materials and methods. The studies were conducted in 8 chinchilla rabbits (16 eyes). After local instillation (0.5 % alkaine solution) and retrobulbar anesthesia (2 % lidocaine solution), superficial deepithelialization of the cornea was performed by mechanical removal of its epithelium with a blunt scraper; and the quality of deepithelialization was assessed by staining the surface with 2 % fluorescein solution. In the optical zone with a diameter of 4 mm, local UV irradiation of the cornea was performed with exposures of 30 and 45 minutes.Results. In case of 30-minute exposures, the epithelialization of the cornea subjected only to mechanical deepithelialization was observed since Day 3 in the form of concentric epithelial growth. On Day 14, a complete epithelialization of the cornea was observed, along with the formation of superficial newly formed vessels along the limbus. On Day 24, the vascular injection significantly decreased; and no erosion was observed. After 45-minute exposure without treatment, the regeneration occurred much slower; and a complete epithelialization had been achieved by Day 34 of the experiment, by the time the newly formed vessels grew to the epithelial defect zone. It was noted that since Day 86, the turbidity in the irradiation area persisted, as well as the inflammatory infiltrate.Conclusions. The proposed method makes it possible to reproduce RCE, in which there is an alternation of epithelialization and deepithelialization of the irradiated corneal area through 30 days of the experiment and is arrested only after the ingrowth of surface vessels into the affected area. At that, the non-irradiated cornea is epithelialized by Day 7 of the experiment.

Relevance. In a number of pathological conditions accompanied by defects of the basal membrane, such as chemical or thermal burn, mechanical trauma, Schegren’s syndrome, herpetic keratitis processes of corneal epithelization are slowed down, and sometimes epithelization does not occur at all. Slow epithelization or its complete absence creates conditions for infection, thinning, and sometimes perforation of the cornea. That is why the problem of chronic corneal erosions is very relevant. The most perspective method of treatment is the use of autologous platelet-riched plasma (PRP). Presence of platelet growth factors, adhesive molecules and cytokines in PRP allows to use it for acceleration of regeneration of corneal defects, and the presence of live platelets allows to refer this procedure to autologous cell transplantations.Objective: To evaluate the clinical and morphological features of corneal epithelium regeneration in response to the application of PRP in conditions of experimental chronic corneal erosion (ECCE).Materials and methods. Researches were carried out on 12 rabbits of Chinchilla breed (24 eyes). At first stage the model of ECCE was reproduced for all animals: local ultraviolet (UV) irradiation with the exposure time of 45 min. on the preliminary de-epithelized corneal surface. At the second stage all animals under study were divided into three groups (4 rabbits in each group). I-st main group (MG) was instillated with PRP at a rate of 1 drop / 1 min within 10 minutes (total of 10 drops) once, in the II MG treatment was carried out according to the above method, every day for 5 days. In the control group (CG) PRP treatment was not applied.Results. 45-min. UV irradiation causes persistent ECCE up to 30 days of the experiment and reverts only after surface vessels are ingrowed in the affected area. Single use of PRP has insufficient therapeutic effect. Instillation within 5 days accelerates the cornea reparative regeneration in ECCE conditions. The absence of epithelial defect, newly formed vessels and corneal clouding was registered on the 9th day. Histologically, on the 30th day a normal multilayer non-squamous epithelium was found, while the stroma had an organized structure with no signs of inflammation.Conclusions. Therapeutic effect of PRP in ECCE conditions is based on reforming of the normal «adhesion complex» between epithelium, olfactory membrane and multifactor stimulation of reparative regeneration due to growth factors located in it, adhesive molecules and cytokines, as a result of which the typical corneal epithelium is restored.

The review is focused on the modern view of the etiology and pathogenesis of limbal stem cells deficiency. The history of development of tissue and ex-vivo transplantation of limbal epithelial stem cells is presented. Certain promising directions of the treatment of patients with limbal stem cells deficiency are presented.