Abstract
Purpose:
Vitamin A and its active forms (retinoic acids/RAs) are known to have pro-healing properties but their mechanism of action is still poorly understood. This work aimed to clarify by which molecular and cellular processes, atRA (all trans RA) improves wound healing using an in vitro (Human Corneal Epithelial cells) and in vivo (mouse) models. First, we showed that atRA promotes epithelium healing in both models principally by its effect on cell migration. Then, we studied the influence of atRA target genes known to be implied in the dynamic of the extra cellular matrix (ECM).
Methods:
Cells were treated (from 0 to 60 hours/h) with atRA or DMSO (vehicle control) after a scratch assay. Migration (migration chamber) and proliferation (BrdU labeling) of cells were determined after 48h of scratch assay. Our in-vivo protocol on mice was approved by the regional ethic committee (CEMEA Auvergne). For such tests, seven male CD1 mice with alkali burn on the right eye received a treatment (with DMSO or atRA) 6 times/day (d) during 7d. Wound healing was evaluated through slit lamp photographs at 0 and 7d. Areas of wounds were quantified from photographs using imageJ. Immunofluorescences, to characterize protein accumulation (coming from atRA target gene) were realized on treated, burned and intact corneas, using specific antibodies (negative control without primary antibody).
Results:
Scratch assay on HCE cells demonstrated that, from 12 to 60 h, the wound area of cells treated with atRA closes itself quickly (average 25%) than cells treated with DMSO. Same experiments demonstrate that cell migration increases by 72% (SEM=5,6) for atRA compared to DMSO condition whereas no difference were found for proliferation. On animals model, when burned corneas were treated with atRA, the % of remaining ulcer after 7d of treatment is 26% (SEM=7) compared to DMSO. Finally, immunofluorescence assays conducted on burned or intact eyes treated with atRA or DMSO revealed an induction of ECM protein production (statistically significant) for atRA treatment.
Conclusions:
We demonstrated that atRA promotes wound healing in HCE cells and animal models. Then, we showed that atRA preferentially acts on migration to exert its effect on epithelial wound healing. Finally, we discovered some genes induced in the cornea epithelium, that are implied in the mechanism of atRA dependent wound healing.