Effect Of Dexamethasone On Mast Cells And Collagen Fibrils In The Primary Developmental Pterygia

Objective:pterygium with high incidence is a condition characterized by epithelial overgrowth of the cornea, usually bilateral, and occupying a nasal interpalpebral location. It is thought to be an irritative phenomenon due to ultraviolet light. If the head of pterygium enlarges and encroaches onto the papillary area, it should reduce visual acuity and be removed surgically. Surgery is the crucial method in the treatments of pterygium. No method can prevent the recurrence completely. How to lower recurrence is still the mainly study. Dexamethasone (DX) as an effective treatment is applying in clinic for many years. However there is no credible basic study for its therapy mechanism. We observed the morphological characteristic of the primary developmental pterygia which sizes were more than 2mm onto the cornea. We studied the mast cells (MCs), collagen fibrils, histological pathology and pathological ultra-structural, and analyzed them. We aimed to estimate the curative effect of DX impersonally and comprehensively, and discover its therapy mechanism.Methods:1. Experiment groups Specimens of 33 eyes (28patients) were collected from the ophthalmic outpatient department, from July, in 2003, to December, in 2004. 33 eyes were divided into four groups randomly: P0, PI, P2, P3° P0: 8 eyes. No DX was injected before surgery. PI: 9 eyes. 0.4ml of 5mg/ml DX was injected once at the jugular of pterygium. One week later, the pterygium was excised. P2: 5 eyes. 0.4ml of 5mg/ml DX was injected twice at the same part as group PI, once a week. One week later, the pterygium was excised. P3: 11 eyes. 0.4ml of 5mg/ml DX was injected four times, once a week. One week later, the pterygium was excised. We collected normal bulbar conjunctiva as group C, 8 eyes (8 patients) were coming from the patients without other corneal and conjunctival disease.2. H.E. staining We made paraffin slices and observed the histopathological changes of the different groups' specimens by performing H.E. staining.3. MC examination Each specimen was performing Csaba staining, and observed the form and distributing of MCs. The numbers of MCs were counted under light microscopy at 400 magnification. The MCs counts were calculated as cells/five fields.4. Collagen fibrils examination We observed collagen fibrils' conformation under polarization microscope by 2.4.6-Trinitrophend -Sirius Red F3B staining, and counted the ratios of type III collagen to type I collagen by pathology- image analytic software of type imagepro plus 5.0.1.5. Transmission electron microscopy The pathological ultrastructures of pterygia were studied by transmission electron microscopy in group C, PO and P3.6. Follow-up after surgery We observed which one relapsed or not.Results:1. Clinic observation We could observe the head of pterygium coming into paleness, organization lesser and thinner, the edge of the head become thinner as membrane, and the blood vessels disappeared. And the body's blood vessels came to be atrophied partly.2. Results of H.E. staining In group PI, P2 and P3, the blood vessels of pterygia were reduced and little blood vessels near basilar membranes were atrophied. There was a decrease in the numbers of fibroblast cells, which of the body came into smaller, the nuclear were dense stained and the shapes were anomalistic. The numbers of inflammation cells were reduced. The representations were more obvious with more times of DX injections.3. MC examination There were significant differences in the comparisons of the numbers of MC in the heads and the bodies of each group between group PO, PI, P2, P3 and group C (PO.05), and the mean number of mast cells in group PO tissues was twice as high as that in group C. There were no significant differences between group PI, P2 and group PO (P>0.05), however the numbers of MCs were reduced with the more timesof DX injections. It was significant difference between the group P3 and group PO (PO.05).4. Collagen fibrils examination Ratios of type III collagen to type I collagen of the heads and the bodies were significant differences between group PO, PI, P2, P3 and group C (P<0.05). And it were significant differences between group PI, P2, P3 and group PO (P<0.05). The ratios were reduced with more times of DX injections.5. Correlative analysis between the numbers of MCs and the ratios of type III collagen to type I collagen There were significant correlations between the numbers of MCs and the ratios of type III collagen to type I collagen of the heads (r= 0.634, P<0.01) and the bodies of (r=0.618, P<0.01) pterygia.6. The result of transmission electron microscopy In group P3, Collagen fibrils around fibroblast cells were reduced. Rough endoplasmic reticulum in fibroblast cells dilated like pools and contained a great deal of lysosome and fat drops. All this showed that the fibroblast cells were not active, collagen excreted decreasingly, and the function of excreting collagen was reduced.7. Postoperative prognosis: The prognosis were not common absolutely (P<0.05). There was significant difference between group P2 and PO (P<0.05), and The prognosis of group P2 was better than it of group PO. It was highly significant difference between group P3 and PO (P<0.01), and it was better in group PO than in group PO.