Photodynamic Therapy Triggers Expression Of Haemopoietic Stem Cell Marker Cd34 Of Keratocytes

Abstract

Purpose: : Photodynamic therapy (PDT) may be a potential treatment alternative in therapy resistant infectious keratitis. PDT may eliminate the microorganisms from the infected cornea by damages caused through free oxygen radicals, or even by supporting different stages of activation of keratocytes and inflammatory cell response. The purpose of this study was to determine the impact of PDT on activation of human keratocytes in culture.

Methods: : Primary human corneal keratocytes were isolated by digestion in collagenase A (1 mg/ml) from human corneal buttons, and cultured in DMEM/Ham’s culture medium supplemented with 10% FCS. Keratocytes underwent illumination (670 nm) for 13 minutes following exposure to 0, 50, 100, 150, 200 and 250 nMol/ml concentrations of photosensitizer chlorin e6 (Ce6) in the culture medium. The day after treatment α-smooth-actin and CD34 expression of the cells was analysed using flow-cytometry (FACS).

Results: : Using Ce6 or illumination only, expression of α-smooth-actin or CD34 of the cells did not change significantly. Twenty-four hours after PDT the percentage of α-smooth-actin positive keratocytes decreased significantly (p<0.05) and the percentage of CD34 positive cells increased significantly (p<0.05) at concentrations higher than 50 nMol/ml of Ce6. Following PDT the percentage of α-smooth-actin/ CD34 positive cells was 81/ 20% using 50 nMol/ml, and 40/71% using 250 nMol/ml concentrations of Ce6.

Conclusions: : As a short term effect, photodynamic therapy seems to activate the dendritic interstitial cell system and inhibit myofibroblastic transformation of keratocytes in vitro.

Keywords: cornea: stroma and keratocytes • cornea: basic science • photodynamic therapy