Effect of latanoprost and timolol on the histopathology of the human conjunctiva

Abstract

Aim: To investigate the effect of timolol and latanoprost on the extracellular matrix organisation, inflammatory infiltration, and expression of matrix metalloproteinases (MMPs) and tissue inhibitors of matrix metalloproteinases (TIMPs) in the human conjunctiva.

Methods: Conjunctival biopsies were obtained from the inferior fornix during routine cataract surgery from 20 patients with primary open-angle glaucoma, who had received a monotherapy either with timolol or latanoprost, and from 10 non-glaucomatous patients. Specimens were investigated by light microscopy, immunohistochemistry using antibodies against MMP-1,-3, TIMP-2,-3 and CD 68 antibodies and by quantitative transmission electron microscopy.

Results: The number of collagen fibres was significantly decreased in latanoprost-treated conjunctival specimens compared with timolol-treated eyes (p<0.01) but showed no difference to controls. Amorphous material was increased in both treated groups compared with controls (p<0.001) but was less in latanoprost-treated specimens compared with timolol-treated eyes (p<0.001). Optically clear spaces, probably containing glycosaminoglycans, were significantly reduced in both treated groups-with less of a reduction in latanoprost-compared with timolol-treated eyes (p<0.001). A marked upregulation of MMP-1 and MMP-3 and moderately increased staining for TIMP-2 and TIMP-3 was found in epithelial cells and subepithelial stromal cells of latanoprost-treated eyes. A moderate infiltration with macrophages and inflammatory cells was observed in timolol-treated eyes.

Conclusions: Latanoprost-treated conjunctival specimens showed a decreased stromal collagen density and a less pronounced inflammatory infiltration. The upregulation of MMP-1 and MMP-3 in latanoprost-treated eyes might explain the reduced extracellular matrix accumulation in the conjunctival stroma. Therefore, latanoprost therapy might have a more favourable effect on the outcome of glaucoma filtering surgery.

Figure 1. Immunohistochemical staining of MMP-1 (A–C) and MMP-3 (D–F), TIMP-2 (G–I) and TIMP-3 (J–L) in the conjunctival specimens of control and study groups.

Figure 2. Immunolocalisation of CD 68 indicating macrophages in the conjunctival tissue of eyes treated with timolol (A) and latanoprost (B).

Figure 3. Quantification analysis of extracellular matrix components in the conjunctival stroma: (A–C) electron micrograph showing collagen fibres (small arrow), amorphous material (large arrow), and optically clear spaces (arrowhead) in the control, timolol and latanoprost group: (D–F), original magnification 34 000×.

Figure 4. Mean percentage (%) of collagen fibres in the subepithelial and deep layer in the control group (white column), timolol group (grey column) and latanoprost group (black column); *p<0.05, **p<0.01, ***p<0.001.

Figure 5. Mean percentage (%) of amorphous material in the subepithelial and deep layer in the control (white column), timolol (grey column) and latanoprost group (black column); *p<0.05, **p<0.01, ***p<0.001.

Figure 6. Mean percentage (%) of empty spaces in the subepithelial and deep layer in the control-, (white column), timolol-, (grey column) and latanoprost group (black column); *p<0.05, **p<0.01, ***p<0.001.