Abstract
Purpose: :
To mimic the conditions of the wound healing process and to evaluate the re-epithelizing effect induced by xanthan gum formulations at 1% or 0.2% and by the hydrogel containing 1% xanthan gum plus 0.15% sodium hyaluronate, we used an experimental model of mechanical injury on multilayer HCE.
Methods: :
The model employs a commercially available 3D HCE multilayer (SkinEthic®) reconstituted from immortalized human corneal epithelial cells. Reproducible superficial incisions have been obtained by using a sterile thin glass edge and by making 4 cross sections on the middle of the HCE surface. Thirty minutes following mechanical injury, HCE samples were treated with 1% or 0.2% xanthan gum formulations, or with 1% xanthan gum plus 0.15% sodium hyaluronate gel and were monitored at different time points: 6,24,48 and 72 h. Sodium hyaluronate (0.15%) and 0.1% Desamethasone treatment were used as positive and negative control, respectively. The epithelium surface morphology and the evolution of the repair process were evaluated by histology and by scanning electron microscopy (SEM). The expression of the biomarker MMP-9 was evaluated by RT-PCR.
Results: :
Histological and SEM analyses showed that during the first 24h, the epithelium underwent a proliferation phase involving the basal cells. In the next 48-72h, it was observed an evident cellular migration and the repopulation of the injured area characterized by differentiation and remodelling of the multilayer. The proliferation and cellular migration took place earlier when the cells were treated with xanthan gum at both the concentrations used. In fact at 48h xanthan gum treated cells showed the typical landslide-like movement. Conversely, at the same time point cells treated with 0.15% sodium hyaluronate alone were shown to be in a preliminary phase of the sheetlike movement. The MMP-9, the primary MMP synthesized and secreted by basal corneal epithelial cells during the wound healing process, was shown to be upregulated in xanthan gum treatment groups.
Conclusions: :
Using this experimental in vitro model of mechanical injury on HCE multilayer, we investigated the effect of xanthan gum during the wound healing process. The results show that xanthan gum, probably by promoting MMP-9 expression, known to be released by HCE to remodel matrix behind the leading migratory front, improves and speeds up the healing process.
Keywords: wound healing • cornea: epithelium