Corneal wound healing is modulated by topical application of amniotic fluid in an ex vivo organ culture model.

The purpose of this study was to evaluate the effects of topical human amniotic fluid (HAF) and equine amniotic fluid (EAF) on corneal reepithelialization and stromal wound healing. New Zealand white rabbit corneas (n=52) were placed in an ex vivo air-interface organ culture. An 8.5mm-diameter mark in the center of the cornea was produced with a hand trephine to select the area for epithelial scraping. A number 15 surgical blade was used to remove the epithelial layer within the demarcated area in a standardized fashion. The corneas were assigned to one of four treatment groups (n=8): fetal bovine serum (FBS), HAF, EAF, and a control group that was exposed to phosphate buffer solution (PBS). Corneal epithelial defects were imaged every 8 h for 72 h after the application of a 30 microl drop of 0.015% fluorescein. Five corneas of each treatment group were used for histology, proliferation, and apoptosis assay at 72 h after the epithelial defect was created. There was no significant difference in the mean rate of closure of the corneal epithelial defect between FBS treated corneas and controls (P>0.06). The mean epithelial defect area (MEDA) was significantly smaller in the EAF group as compared to control corneas at 24 h (P=0.016), 40 h (P=0.032), 64 h (P=0.008) and 72 h (P=0.007) following epithelial scrape. The MEDA in the HAF group was significantly smaller at 16 h (P=0.008), 64 h (P=0.0072), and 72 h (P=0.016) compared to the control group. The MEDA in the HAF and EAF groups was smaller at all time points as compared to the FBS group, but the difference was not significant. At histology, the mean keratocyte density was significantly higher in the anterior stroma in the HAF (P<0.001) and EAF groups (P=0.001) as compared to control group. The number of BrdU positive keratocytes was significantly higher in the superficial and deep stromal sub-areas in the HAF group as compared to control (P<0.001 and P=0.002, respectively). EAF and FBS treated corneas also showed a higher number of BrdU positive cells compared to control, but this difference was not significant. Finally, we did not observe any difference in the amount of TUNEL positive keratocytes among the different groups. Our data indicates that the topical application of HAF and EAF is associated with accelerated reepithelialization in this cornea organ culture model. Similarly, corneal keratocyte density appears to be less affected after epithelial injury using this treatment.

Castro-Combs J ，Noguera G ，Cano M ，Yew M ，Gehlbach PL ，Palmer J ，Behrens A ... -  《EXPERIMENTAL EYE RESEARCH》

Delay of corneal epithelial wound healing and induction of keratocyte apoptosis by platelet-activating factor.

To examine the role of the lipid mediator platelet-activating factor (PAF) in epithelial wound healing. A 7-mm central de-epithelializing wound was produced in rabbit corneas, and the tissue was incubated with 125 nM carbamyl PAF (cPAF), an analogue of PAF. Rabbit corneal epithelial and stromal cells were also cultured in the presence of cPAF. Cell adhesion, proliferation, and migration assays were conducted. Apoptosis was assayed by TUNEL staining on preparations of corneal tissue sections and in cells in culture. Twenty-four hours after injury, 50% of the wounded area was covered by new epithelium, whereas only 30% was covered in the presence of cPAF. At 48 hours, the epithelium completely closed the wound, but only 45% of the original wound was covered in corneas treated with cPAF. Similar inhibition of epithelial wound closure was found with human corneas incubated with PAF in organ culture. Moreover, addition of several growth factors involved in corneal wound healing, such as epidermal growth factor, hepatocyte growth factor, and keratinocyte growth factor, could not overcome the inhibitory action of PAF in wound closure. Three PAF antagonists, BN50727, BN50730, and BN50739, abolished the effect of PAF. A significant increase in TUNEL-positive staining occurred in corneal stromal cells (keratocytes), which was inhibited by preincubating the corneas with PAF antagonists. However, no TUNEL-positive staining was found in epithelial cells. TUNEL-staining results in cultured stromal cells (keratocytes) and epithelial cells in first-passage cell culture were similar to those in organ-cultured corneas. In addition, PAF caused 35% to 56% inhibition of adhesion of epithelial cells to proteins of the extracellular matrix: collagen I and IV, fibronectin, and laminin. There were no significant changes in proliferation or migration of epithelial cells induced by the lipid mediator. The results suggest PAF plays an important role in preventing corneal wound healing by affecting adhesion of epithelial cells and increasing apoptosis in stromal cells. PAF antagonists could be of therapeutic importance during prolonged ocular inflammation, helping to avoid loss of corneal transparency and visual acuity.

Chandrasekher G ，Ma X ，Lallier TE ，Bazan HE ... -  《INVESTIGATIVE OPHTHALMOLOGY & VISUAL SCIENCE》

[Proliferation of corneal epithelium and apoptosis of keratocytes in the rabbit cornea after treatment with 20% ethanol].

Sun LX ，Wang Z ，Yang B ，Liu J ，Qiu P ，Chen JQ ... -  《-》

Effects of the COOH-terminal tripeptide alpha-MSH(11-13) on corneal epithelial wound healing: role of nitric oxide.

Bonfiglio V ，Camillieri G ，Avitabile T ，Leggio GM ，Drago F ... -  《EXPERIMENTAL EYE RESEARCH》

Hepatocyte growth factor and keratinocyte growth factor regulation of epithelial and stromal corneal wound healing.

To investigate the effects of hepatocyte growth factor (HGF) and keratinocyte growth factor (KGF) on early wound healing in the corneal epithelium and stroma. Cell and Molecular Biology Unit, Department of Optometry and Vision Sciences, Cardiff University, and the Cardiff Institute of Tissue Engineering and Repair, Cardiff, United Kingdom. Corneal keratocyte cell cultures and wounded corneal organ cultures (both maintained in serum-free conditions) were treated with 0.1 to 100 ng/mL of HGF or KGF for up to 5 days. Cell cultures were assessed for proliferation, migration, and differentiation into myofibroblasts. Organ cultures were used to evaluate the effect of HGF and KGF on reepithelialization following a wound, epithelial morphology and stratification, keratocyte numbers directly beneath the wounded area, and differentiation into myofibroblasts. The 2 growth factors had opposite effects on the rate of reepithelialization, with HGF delaying and KGF accelerating epithelial coverage of the wound. Morphologic assessment showed that both growth factors affected the stratification and differentiation of the epithelium. Both factors stimulated proliferation of keratocytes in serum-free cell culture, although neither induced the appearance of myofibroblasts. This was in contrast to wounded organ cultures treated with 100 ng/mL HGF, in which large numbers of myofibroblasts were observed under the wound. Control corneas and those receiving KGF contained very few myofibroblasts. Keratocyte repopulation of the denuded area under the wound was enhanced in the presence of HGF but decreased in response to KGF. Hepatocyte growth factor and KGF appeared to have potent and often opposite effects on epithelial and stromal cells following a wound. Hepatocyte growth factor was more detrimental than KGF, resulting in an aberrant epithelium and mass differentiation of keratocytes into myofibroblasts. Inhibition of HGF may be an appropriate therapeutic intervention in the case of persistent epithelial defects and to prevent fibrosis following a corneal stromal wound such as can occur after refractive surgery.

Carrington LM ，Boulton M 《JOURNAL OF CATARACT AND REFRACTIVE SURGERY》