EBM regeneration and changes in EBM component mRNA expression in stromal cells after corneal injury

To investigate the production of the epithelial basement membrane (EBM) component mRNAs at time points before lamina lucida and lamina densa regeneration in anterior stromal cells after corneal injury that would heal with and without fibrosis.

Rabbit corneas were removed from 2 to 19 days after -4.5D or -9.0D photorefractive keratectomy (PRK) with the VISX S4 IR laser. Corneas were evaluated with transmission electron microscopy (TEM) for full regeneration of the lamina lucida and the lamina densa. Laser capture microdissection (LCM) based quantitative real-time (RT)-PCR was used to quantitate the expression of mRNAs for laminin α-3 (LAMA3), perlecan, nidogen-1, and nidogen-2 in the anterior stroma.

After -4.5D PRK, EBM was found to be fully regenerated at 8 to 10 days after surgery. At 4 days after PRK, the nidogen-2 and LAMA3 mRNAs levels were detected at statistically significantly lower levels in the anterior stroma of the -9.0D PRK corneas (where the EBM would not fully regenerate) compared to the -4.5D PRK corneas (where the EBM was destined to fully regenerate). At 7 days after PRK, nidogen-2 and LAMA3 mRNAs continued to be statistically significantly lower in the anterior stroma of the -9.0D PRK corneas compared to their expression in the anterior stroma of the -4.5D PRK corneas.

Key EBM components LAMA3 and nidogen-2 mRNAs are expressed at higher levels in the anterior stroma during EBM regeneration in the -4.5D PRK corneas where the EBM is destined to fully regenerate and no haze developed compared to the -9.0D PRK corneas where the EBM will not fully regenerate and myofibroblast-related stromal fibrosis (haze) will develop.