Tissue and cellular biomechanics during corneal wound injury and repair

Abstract

Corneal wound healing is an enormously complex process that requires the simultaneous cellular integration of multiple soluble biochemical cues, as well as cellular responses to the intrinsic chemistry and biophysical attributes associated with the matrix of the wound space. Here, we document how the biomechanics of the corneal stroma are altered through the course of wound repair following keratoablative procedures in rabbits. Further we documented the influence that substrate stiffness has on stromal cell mechanics. Following corneal epithelial debridement, New Zealand white rabbits underwent phototherapeutic keratectomy (PTK) on the right eye (OD). Wound healing was monitored using advanced imaging modalities. Rabbits were euthanized and corneas were harvested at various time points following PTK. Tissues were characterized for biomechanics with atomic force microscopy and with histology to assess inflammation and fibrosis. Factor analysis was performed to determine any discernable patterns in wound healing parameters. The matrix associated with the wound space was stiffest at 7 days post PTK. The greatest number of inflammatory cells were observed 3 days after wounding. The highest number of myofibroblasts and the greatest degree of fibrosis occurred 21 days after wounding. While all clinical parameters returned to normal values 400 days after wounding, the elastic modulus remained greater than pre-surgical values. Factor analysis demonstrated dynamic remodeling of stroma occurs between days 10 and 42 during corneal stromal wound repair. Elastic modulus of the anterior corneal stroma is dramatically altered following PTK and its changes coincide initially with the development of edema and inflammation, and later with formation of stromal haze and population of the wound space with myofibroblasts. Factor analysis demonstrates strongest correlation between elastic modulus, myofibroblasts, fibrosis and stromal haze thickness, and between edema and central corneal thickness.

Patterning of human epidermal stem cells on undulating elastomer substrates reflects differences in cell stiffness

“…While previous studies have focused on changes in the height of the undulations, our studies suggest that changes in the slope may also impact on the disruption of epidermal homeostasis that occurs in psoriatic lesions. In the case of corneal injury biomechanical changes in stromal cells are linked to accumulation of inflammatory cells [32] and it is therefore tempting to speculate that differences in the stiffness of epidermal cells and their junctions could lead to an altered immune infiltrate. It is also possible that materials that mimic the undulating topography of the epidermal-dermal junction, for example by casting topographies out of collagen gels, could enhance wound healing or reduce scarring.…”

Acetylcholine decreases formation of myofibroblasts and excessive extracellular matrix production in an in vitro human corneal fibrosis model

“…The physiological conditions differ greatly from the in vitro settings, and at least up to this date, it is hard to reproduce the physiological conditions. Issues such as substrate stiffness will affect the in vitro experiments, and isolation of the cells from their natural environment will, to a degree, change them too . We expected to see a significantly bigger decrease in α‐SMA expression, as contraction of the collagen gels, in which the corneal fibroblasts are embedded, was decreased greatly by the ACh‐treated cells.…”

The healing effect of the collagen-glycosaminoglycan copolymer on corneal thinning

“…These keep depositing multiple elements of extracellular matrix to increase the corneal thickness [ 32 ]. By remodeling the healing stroma, and replacing the disorganized repair matrix with regular corneal extracellular matrix, a better transparency can be achieved [ 33 , 34 ]. In addition, the number and the diameter of new vessels slowly decreases as the remodeling progresses [ 35 ].…”