Immuno-histochemical evaluation of conjunctival remodelling in vernal keratoconjunctivitis

In vivo laser scanning confocal microscopy of vernal keratoconjunctivitis

BACKGROUND

To demonstrate the morphological characteristics of vernal keratoconjunctivitis (VKC) by using in vivo laser scanning confocal microscope (LSCM).

DESIGN

Descriptive analysis of VKC by LSCM performed in EENT Hospital of Fudan University.

PARTICIPANTS

26 patients diagnosed as VKC and 26 age-matched healthy controls were enrolled in the study.

METHODS

The HRTII/RCM was used to examine bulbar conjunctiva, tarsal conjunctiva, superior limbus and inferior limbus.

MAIN OUTCOME MEASURES

The density of Langerhans cells and inflammatory cells in tarsal and bulbar conjunctiva were calculated. The morphology of Vogt Palisades was analysed and normal rate of Vogt Palisades at superior and inferior limbus was calculated, respectively.

RESULTS

Infiltration of a larger number of Langerhans cells and inflammatory cells could be identified in both bulbar conjunctiva and tarsal conjunctiva compared with normal subjects. Furthermore, the density of Langerhans cells in tarsal conjunctiva was significantly higher in tarsal form and mix form than that in bulbar form (P = 0.048). Normal Vogt Palisades were visible only in 15 and 23 eyes at superior and inferior limbus respectively. Abnormal Vogt Palisades were characterized by atrophy or absence of stromal papillae and disappearance of bright basal cells, accompanied with the infiltration of more Langerhans cells. At superior limbal area, bulbar form had the highest abnormal rate, followed by mix form, both were significantly higher than tarsal form (P = 0.005).

CONCLUSIONS

The in vivo morphological characteristics of conjunctiva and limbus in VKC included the infiltration of Langerhans cells and inflammatory cells in epithelium and stroma, and the destruction of Vogt Palisades.

Mast Cell Chymase Decreases the Barrier Function and Inhibits the Migration of Corneal Epithelial Cells

PURPOSE

We investigated the in vitro effects of human mast cell chymase on corneal epithelial cells.

METHODS

Human corneal epithelial cells were incubated with human chymase at activity levels that were likely to exist in the tears of patients with vernal keratoconjunctivitis.

RESULTS

Incubation of chymase resulted in a decrease of barrier function of corneal epithelium. Occludin protein was cleaved by chymase. In the wound assay, incubation with chymase resulted in an inhibition of cell migration.

CONCLUSION

Human chymase causes the proteolysis of occludin and fibronectin, resulting in a decrease of barrier function and inhibition of the migration of corneal epithelial cells.

Mechanisms of giant papillary formation in vernal keratoconjunctivitis

PURPOSE

Tissue remodeling, known to accompany exacerbation of bronchial asthma (BA) and characterized by thickening of reticular basement membrane, increased fibrosis, and angiogenesis, is believed to be an important mechanism in giant papillary formation in vernal keratoconjunctivitis (VKC). This study was conducted to confirm the difference of tissue remodeling between BA and VKC and to determine the most relevant factor for VKC exacerbation.

METHODS

Histopathologic analysis of conjunctival specimens from 6 patients with VKC and 4 normal controls was performed. Immunohistochemistry tests for collagen types 1, 3, and 5, fibronectin, laminin (a marker of the basement membrane of the epithelium or vessels), fibroblast (prolyl 4-hydroxylase), and alpha-smooth muscle actin (alpha-SMA) were performed. Morphometric analysis evaluated immunoreactive areas for collagens and fibronectin and the number of cell nuclei in VKC papillae and normal control specimens.

RESULTS

In histopathologic sections of VKC papillae, mononuclear cells were mainly observed in the central region and granulocytes preferentially in the peripheral stroma. Immunohistochemistry showed increased vascularity and existence of fibroblasts and alpha-SMA-positive cells in VKC papillae. Morphometric analysis showed that the number of cell nuclei in VKC papillae was 7.3 times higher versus in normal controls (P < 0.05). Furthermore, the immunoreactive area for fibronectin was 4.5 times larger versus in normal controls (P < 0.05), although collagens were not significantly different between the 2 groups.

CONCLUSION

Giant papillary formation in VKC is thought to occur in relation to tissue remodeling. However, the most relevant factor for the exacerbation of VKC seems to be inflammation rather than fibrosis.

Fibroblasts as local immune modulators in ocular allergic disease

Vernal keratoconjunctivitis (VKC), a severe form of ocular allergic disease, is characterized by the formation of giant papillae at the upper tarsal conjunctiva and corneal lesions that threaten vision. Recent evidence indicates that resident fibroblasts function as immune modulators in the pathogenesis of the chronic allergic inflammation associated with VKC. The T helper 2 (Th2) cell-derived cytokines interleukin (IL)-4 and IL-13 stimulate the migration and proliferation of conjunctival fibroblasts as well as protecting these cells from apoptotic cell death, effects that likely underlie the hyperplasia of fibroblasts that contributes to the formation of giant papillae. Conjunctival fibroblasts also synthesize extracellular matrix proteins and tissue inhibitors of metalloproteinases as well as down-regulate the expression of matrix metalloproteinases in response to these cytokines, effects that likely contribute to the excessive deposition of extracellular matrix that is characteristic of giant papillae. Stimulation of fibroblasts in the corneal stroma with the combination of a proinflammatory cytokine and either IL-4 or IL-13 results in up-regulation of the expression of the chemokine eotaxin and thymus- and activation-regulated chemokine as well as of vascular cell adhesion molecule-1, which together mediate the infiltration and activation of eosinophils and Th2 cells. Fibroblasts therefore appear to play a central role in the induction and amplification of ocular allergic inflammation and the consequent development of giant papillae and corneal disorders in individuals with VKC. Fibroblasts and fibroblast-derived factors thus represent new and potentially important therapeutic targets for treatment of the giant papillae and corneal disorders associated with VKC.

Immunopathogenesis of conjunctival remodelling in vernal keratoconjunctivitis

PURPOSE

To study the processes involved in mediating conjunctival remodelling in vernal keratoconjunctivitis (VKC) by investigating the expression of integrin receptors, epidermal growth factor receptor (EGFR), vascular endothelial growth factor (VEGF), transforming growth factor-beta(TGF-beta), basic fibroblast growth factor (bFGF), platelet-derived growth factor (PDGF), and Ki67 antigen, which is a marker for cell proliferation.

METHODS

Conjunctival biopsy specimens from 16 patients with active VKC and nine control subjects were studied by immunohistochemical techniques using monoclonal and polyclonal antibodies directed against the integrin alpha3 and alpha6 subunits, EGFR, VEGF, TGF-beta, bFGF, PDGF, and Ki67 antigen. The phenotype of inflammatory cells expressing growth factors was examined by double immunohistochemistry.

RESULTS

In the normal conjunctiva, very weak immunoreactivity was observed for EGFR and VEGF in epithelial cells, and for alpha3 and alpha6 integrin subunits on basal epithelial cells, and on vascular endothelial cells in the upper substantia propria. There was no immunoreactivity for the other antibodies. In VKC specimens, strong staining for alpha3 and alpha6 integrin subunits was observed on the membranes of basal and suprabasal epithelial cells, and all vascular endothelial cells. Immunoreactivity for Ki67 antigen was observed in the nuclei of the basal and suprabasal epithelial cells. Strong immunoreactivity was observed for EGFR in the deeper layers of the epithelium, and for VEGF in all epithelial cells. Inflammatory cells expressing EGFR, VEGF, TGF-beta, bFGF, and PDGF were noted in 8, 9, 11, 10, and 10 specimens, respectively. The majority of inflammatory cells expressing growth factors were eosinophils (45+/-4%) and monocytes/macrophages (35+/-4%).

CONCLUSIONS

Chronic conjunctival inflammation in VKC is associated with increased staining of alpha3, and alpha6 integrin subunits, EGFR, VEGF, TGF-beta, bFGF, and PDGF that might mediate conjunctival remodelling.