Purpose:
Carboxymethylcellulose (CMC) is the active ingredient in numerous artificial tear formulations. CMC has previously been reported to reduce the signs and symptoms of dry eye, and to reduce symptoms of dry eye in post–surgical patients. This study investigated the interaction of CMC with cells of the ocular surface by utilizing a fluorescently–labeled form of CMC.
Methods:
Human corneal epithelial cells were either grown in cell culture or collected by irrigation from the corneas of volunteers. Corneal cells were incubated with fluorescein–labeled CMC (F–CMC) for up to 24 hr. Every 30 min cells were washed with fresh medium that did not contain CMC, and the bound CMC measured by photospectroscopy. To examine CMC's potential role in wound healing, cells were grown in the presence of fibronectin and collagen plus CMC, and compared to similar cultures with hyaluronic acid (HA) instead of CMC. Confluent cultures were "wounded" by scratching with a sterile pipet tip and the wound widths measured after 18 hr further incubation, along with a measure of cell proliferation.
Results:
CMC was found to bind to corneal cells with a primary residence time of 1 to 2.5 hr. A residual amount of CMC remained on the cells for 24 hr. Like HA, CMC bound to fibronectin and collagen, and such binding stimulated cell adhesion to these extracellular matrix components. CMC stimulated wound closure (photo) and cellular proliferation in comparison with untreated control cultures.
Conclusions:
CMC bound to the corneal epithelial cells and remained associated with them for a relatively long time. CMC also bound to extracellular matrix proteins, and the formation of the CMC–protein complex enhanced attachment of corneal cells. CMC's ability to promote wound closure in this in vitro model is consistent with clinical benefits reported with its use in post–surgical (e.g. LASIK) patients.
Keywords: cornea: epithelium • wound healing • extracellular matrix