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Pterygium: clinical, histological and immunohistochemical aspects

Poster Details

First Author: S.Craitoiu ROMANIA

Co Author(s):    C. Mocanu   R. Manescu           

Abstract Details



Purpose:

The subject of this paper is of great interest since the elucidation of the etiopathogenesis of this disease can have significat clinical consequences for the surgical treatment (preventing the frequent post-surgery relapses); also, it can help the development of new non-surgical treatments to reduce relapses, severity of inflammation, tissular invasion, proliferation and angiogenesis.

Setting:

Emergency Clincal County Hospital of Craiova, Romania

Methods:

Pterygium is a lesion of the ocular surface, involving only one or both eyes. It has the form of a triangular strap-like fibrovascular tissue that lays over the epibulbar surface of the conjunctiva. Recently published data showed that the disease is an active process of cellular proliferation, ongoing connective tissue remodeling, angiogenesis and inflammation. Pterygium consists of epithelial hyperplasia accompanied by fibrovascular proliferation, originating at the corneo-conjunctival junction. It causes disconfort, lacrimation and photophobia. After surgical intervention, relapses are frequent. When pterygium takes a more aggresive course, it can cause blurred vision by inducing irregular astygmatism, injuries of the corneal stroma and obliteration of the visual axis, as well as ocular irritation through the inflammation of the ocular surface from its site. The subject of this paper is of great interest since the elucidation of the etiopathogenesis of this disease can have significat clinical consequences for the surgical treatment (preventing the frequent post-surgery relapses); also, it can help the development of new non-surgical treatments to reduce relapses, severity of inflammation, tissular invasion, proliferation and angiogenesis. The material used consisted of 18 pieces of surgical excision from human patients (fragments of pterygium), obtained from the Clinic of Ophthalmology of the County Emergency Hospital Nr. 1 Craiova. From a clinical perspective, nine of the patients were male and the rest were female; the patients' ages ranged between 58 and 81 years old. Ten more fragments of epibulbar conjunctiva were obtained during surgical procedures for cataract; these were used as control tissue. Pterygium fragments were treated with the regular method of paraffin inclusion and the resulting sections were stained with haematoxylin and eosin (HE), trichromic Goldner Szekely and trichromic van Gieson . The method employed for immunohistochemical tests was ABC/HRP technique (Avidin complexed with peroxidase biotinylated). During immunohistocemical study we used two antibodies: anti-human CD31 and anti-human VEGF. The intensity of staining is recorded as: • (+++), if staining is intensely positive or specifically scattered, clearly visible with small magnification; • (++), if staining is focal or of moderate intensity, clearly visible only with medium magnification; • (+), if staining is weak or very localized, clearly visible only with a large magnification; • (+-), if staining is very poor; • (-), if staining is negative.

Results:

We have examined under the microscope fragments of primary and relapsed pterygium from patients treated with surgical ablation and conjunctival autologous graft. This epithelium has a variable thickness, as it supplements the irregularities of the underlying stroma. In some areas the epithelium invaginates into the stroma and at this level there are increased numbers of goblet cells. The stroma of the pterygium's head is made of connective tissue, rich in fibrocytes and connective fibrils. Furthermore, there are many blood vessels. An inflammatory infiltrate can be seen on some sections, especially in the perivascular and periglandular areas. The study of immunoreactivity at CD31 has proved the presence of a much richer vascularization in the connective tissue of pterygium. The strongest reactivity to this marker was identified in the subepithelial region. The morphology of these vessels (small caliber, tortuous and branched blood vessels) is suggestive for the presence of an active angiogenesis. In all the cases studied, an immune reaction of the ptreygian tissue to VEGF was present and this reaction was more intense than in normal conjunctival tissue. From a calitative perspective, the immunoreaction to VEGF was heterogenous, and its intensity was different for every case.

Conclusions:

Pterygium is a condition with a rather increased prevalence with multiple post-surgery relapses and involving a range of clinical issues; in severe cases it reaches the corneal surface and induces vision impairment through irregular astigmatism, corneal stroma damage and obliteration of the visual axis. The histological aspects described will contribute to the clarification of some issues relating to the etiopathogeny of the condition primarily regarding post-surgery relapses. The study of vascular microdensity confirmed the existence of marked angiogenesis of pterygium, while VEGF overexpression particularly in the proliferative structures of the pterygium favors the causal involvement of this growth factor in pterygium pathogenesis. VEGF expression in the pterygium endothelial and stromal cells can induce angiogenic activity, demonstrated by increased vascular microdensity. This reactive response of the pterygium tissue proves on the one hand the proliferative-invasive, tumor-like nature of this condition. Moreover, this type of immunohistochemistry warrants the development of growth factors synthetic inhibitors which may allow for the reduction of the relapse rate, inflammation intesity, tissue invasiveness, proliferation and angiogenesis in pterygium. FINANCIAL INTEREST: NONE

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