Previous studies have suggested that abnormal corneal wound healing in patients after
photorefractive keratectomy (PRK) is associated with the appearance of myofibroblasts in the stroma between two and four weeks after surgery. The purpose of this study was to examine potential myofibroblast progenitor cells that might express other filament markers prior to completion of the differentiation pathway that yields alpha-smooth muscle actin (SMA)-expressing myofibroblasts associated with haze localized beneath the epithelial basement membrane after PRK. Twenty-four female rabbits that had -9 diopter PRK were sacrificed at 1 week, 2 weeks, 3 weeks or 4 weeks after surgery. Corneal rims were collected, frozen at -80 degrees C, and analyzed by immunocytochemistry using anti-
vimentin, anti-
desmin, and anti-SMA
antibodies. Double immunostaining was performed for the co-localization of SMA with
vimentin or
desmin with SMA. An increase in
vimentin expression in stromal cells is noted as early as 1 week after PRK in the rabbit cornea. As the healing response continues at two or three weeks after surgery, many stromal cells expressing
vimentin also begin to express
desmin and SMA. By 4 weeks after the surgery most, if not all, myofibroblasts express
vimentin,
desmin and SMA. Generalized least squares regression analysis showed that there was strong evidence that each of the marker groups differed in expression over time compared to the other two (p<0.01). Intermediate filaments--
vimentin and
desmin co-exist in myofibroblasts along with SMA and may play an important role in corneal remodeling after
photorefractive keratectomy. The earliest precursors of myofibroblasts destined to express SMA and
desmin are detectable by staining for
vimentin at 1 week after surgery.