Human retinal pigment epithelium in vitro: influence of low oxygen tension, glucose and insulin.

Retinal pigment epithelium (RPE) cells migrating through the damaged retina into the vitreous body seem to play an important role for the pathogenesis of proliferative vitreoretinopathy (PVR) and other proliferative retina diseases. It is so far not known how the RPE cells are able to survive in the vitreous body without contact to the blood vessels of the choroid supplying them with oxygen and nutritive substances. To answer this question, we studied growth characteristics and sensitivity to glucose and insulin of human RPE cells, incubated with reduced oxygen partial pressure. In the first study, RPE cultures of 58 postmortem human eyes were grown with 5% O2/5% CO2 and with standard conditions (20% O2/5% CO2). The growth was assessed in five graded stages. Our data show that human RPE grows better under 5% oxygen than under 20% O2 (p < 0.0001). In consideration of this effect, we cultivated, in a further study, pigment epithelium of 49 postmortem human eyes with 5% oxygen and with 4 different glucose concentrations with and without addition of insulin. We found that glucose in higher concentrations was a potent stimulator of growth, whereas insulin was a modest stimulator when used alone. The combination of glucose and insulin was significantly more effective (p = 0.01) in the period of the first 7 days. These results suggest that proliferation of human RPE cells can be increased by oxygen reduction, glucose and insulin. These interactions may help in understanding the pathophysiology of retina damage and proliferative retina diseases like PVR.

Proliferation of corneal epithelial and endothelial cells in the trabecular region of human donor corneas in organ culture.

Thirty corneoscleral rings obtained after trephination of a 4- to 7.5-mm graft and 8 whole corneas with scleral rims were cultured up to 6 weeks. The corneal epithelium grew over the scleral rim and trabecula, and, after 3-4 weeks, was slowly invading the endothelial sheet. Endothelial cells did not show any evidence of migration unless the trabecula was removed. Even then, however, the endothelial growth was very limited and was soon suppressed by fast-growing epithelium.

Low oxygen prevents epithelial overgrowth of corneas in long-term organ culture.

Forth human corneo-scleral rings and 40 whole corneas with scleral rim were preserved in organ culture for up to six weeks in either normal (20%) or low (6%) oxygen concentration in the gas phase of the culture. Decreasing the oxygen prevented epithelial invasion of the inner side of the cornea without adversely affecting the condition of the endothelium. It is suggested that lower oxygen level might improve corneal preservation in organ culture.

Effect of low oxygen tension on the growth of bovine corneal endothelial cells in vitro.

The proliferation of bovine corneal endothelial cells cultured in low (6%) and normal (20%) oxygen concentration in the gas phase was compared. Low oxygen tension significantly stimulated cell multiplication and DNA synthesis of the cultured cells.