Effect of human corneal keratocytes and retinal pigment epithelial cells on the mechanical properties of micropatterned collagen films

Collagen-based micropatterned films were seeded with human corneal keratocyte and epithelial cells to study their mechanical properties as tissue engineering substrates. The patterns were in the form of parallel channels with slanted walls. Influence of cell presence, type and growth on the mechanical properties of the films was investigated. Unseeded films showed gradual strength reduction from an initial value of 0.046 N/mm, possibly due to degradation, down to 0.032±0.012 N/mm in 2 weeks. Keratocyte growth was found to significantly improve the mechanical behavior of the films upon 1 week of incubation (0.067±0.017 N/mm) and the improvement continued gradually over the next 2 weeks. Films seeded with D407 retinal pigment epithelial cells, on the other hand, experienced a decrease (0.023±0.011 N/mm), followed by a slight increase in mechanical properties in the 21-day period. A steady increase in the number of keratocytes along the channels, cytoskeleton alignment and extracellular matrix (ECM) secretion restricted to the channels was observed. Increase in strength observed with keratocytes and, to a lesser extent, with the epithelial cells can be attributed to directional ECM synthesis and the orientation of the cells and their cytoskeleton which contribute to the strength in the direction of the channels. This study showed that cell, especially keratocyte, presence compensates for the degradation of collagen films and improve the overall mechanical properties of the engineered tissue.