Biomechanical properties of keratoconus model – corneal fibrocytes cell culture in zinc depleted growth medium

Background . Etiology and pathogenesis research of such a corneal disease as keratoconus is rather difficult due to the impossibility to study the underlying ultrastructural and molecular cornea changes in vivo and in animal models. The aim . To evaluate zinc relevance in the biomechanical properties of the corneal stroma – by means of in vitro keratoconus cell model. Materials and methods . In this experimental study, normal and keratoconic cell models of the corneal stroma were exampled – three-dimensional tissue-engineered structures of corneal fibrocytes obtained from healthy donors keratocytes and grown on standard and zinc-depleted nutrient media, respectively. The biomechanical properties of tissue-engineered structures modeling the normal and keratoconic corneal stroma were evaluated by means of the atomic force microscope nanoindentation. Additionally, histological assessment of the obtained cell models and immunohistochemical analysis of type I collagen were performed. Results . According to the study of five samples of each of the corneal stroma models, a statistically significant difference in viscoplastic biomechanical properties was shown: the effective Young’s modulus of the normal and keratoconic models was 9.9 [5.4; 15.6] and 10.3 [6.1; 14.8] kPa, respectively. The in “healthy” group cell cultures thickness was 17.67 ± 1.32 and 18.10 ± 1.22 microns for two and four weeks of cultivation, respectively; in the “keratoconus” group, in a zinc depleted medium, the cell cultures thickness was 21.25 ± 8.39 and 25.55 ± 5.67 microns at the same time of cultivation, respectively. The extracellular component with an excess collagen fraction prevails in the structure of the latter. Conclusion . The data obtained confirms the modern keratoconus etiology and pathogenesis concept – the biomechanical function deterioration of the keratoconic cornea is a consequence of copper, iron and zinc mineral dysmetabolism in its stroma.