Thrombin stimulates the proliferation of human retinal glial cells

Retinal glial cells may play a role in most of the proliferative retinopathies. Although glial cell proliferation is a frequent event in retinal pathobiology, no specific mitogens for human retinal glial cells are known. Using cultured retinal glial cells obtained from postmortem adult human eyes, we found that thrombin stimulates glial cell proliferation in a dose-dependent manner with a half-maximal concentration of 100 ng/ml (0.4 U/ml). Thus, thrombin may be a plasma-derived mitogen capable of stimulating retinal glial cells to proliferate when there is a breakdown of the blood-retinal barrier. We also observed that this proliferative response of retinal glia requires more than 6 h of continuous exposure to thrombin. This finding suggests that a thorough wash-out of a thrombin-containing infusate and/or the rapid inactivation of this molecule would prevent thrombin form exacerbating a proliferative disorder of the retina.