Evidence of pterygial fibrous tissues derived from mesenchymal stem cells

Yongping LI; Zhe ZHU; Wenxin ZHANG; Lin LIU; Dan LIANG

ABSTRACT

BACKGROUND:

Pterygium is associated with local chronic inflammatory responses and chronic stimulation from external factors such as. sunlight and wind dust. Presently. there are various theories concerning the onset mechanism of pterygium, but these theories are not generally accepted.

OBJECTIVE:

To investigate histopathological chractefistics of pterygium and analyze the mulfipotent stem cell effects on the onset of pterygium

DESIGN:

An open experiment.

SETTING:

Zhongshan Ophthalmic Center of Sun Yat-sen University.MATERIALS Experiments were performed at the State Key Laboratory of Ophthalmology, Sun Yat-sen University from September 2006 to January 2007. 218 pterygial paraffin specimens following clinical and pathological diagnosis were obtained from Pathology Lab of Zhongshan Ophthalmic Center, Sun Yat-sea University.

METHODS:

Pterygial specimens harvested from clinical operations received morphology, immunohistochemistry and immunofluorescence under a confocal microscope.MAIN OUTCOME

MEASURES:

Morphology of ptorygium and expressions of CD34, vimentin (VIM), smooth muscle acfin (SMA), S- 100 in pterygium.

RESULTS:

Changes in morphology Fibroplasia and neovascularization were the main changes in pterygium. Fibroplasia wasdiverse in different regions, and two main phenomena were observed. First, the tissues arranged tightly like the scleral fiber.Secondly, in some loose region, some of spindle-shape, polygonal, asteroid fibroblast-like cells, arranging loosely, could be seen only. No apparent collagen fibers were identified between them. Immunohistochemistry were positive for CD34 in some region where the fibroblast actively proliferated, whereas fibrocytes in mature fibrous tissue were negatively stained.Immunohistochemisu'y was positive for VIM in a large fraction of fibrocytes, vascular endothelial cells, vessel wall and perithelial cells. SMA staining was positive in basophilous small blocks, spindle or irregular cell cluster. Of the 218 cases, 56 cases had smooth muscle. S-100 staining demonstrated that neurofilament protein and adipocytes were positive. Of the 218 cases, 44 cases had adipose tissue, Immunofluorescence showed that proliferative active cells were positive and stained green under a confocal microscope.

CONCLUSION:

The fibrous tissues in pterygium originate from mesenchymal stem cells, and can differentiate into smooth muscle and adipose tissue.