Culture of retinal pigment epithelial cells from subretinal fluid

Detection of Mycobacterium tuberculosis Genome in Subretinal Fluid of Patients with Latent Tuberculosis Infection

PURPOSE

To test our hypothesis that Mycobacterium tuberculosis (MTB) DNA may be present in retinal pigment epithelium (RPE) cells in individuals with latent tuberculosis (TB) infection.

METHODS

A total of 100 patients with rhegmatogenous retinal detachment (without any signs of endogenous uveitis in either eye) underwent pars plana vitrectomy (PPV) with internal tamponade. All were subjected to tuberculin skin test. None had manifest systemic TB disease. The subretinal fluid collected during surgery was subjected to multitargeted polymerase chain reaction (PCR) targeting three genes of MTB (IS6110, MPB64 and protein b).

RESULTS

In total, 16 patients had latent TB, of which TB PCR was positive in six patients.

CONCLUSIONS

We demonstrate presence of MTB genome in the subretinal fluid containing RPE cells from individuals with latent TB infection, who did not have any evidence of intraocular TB or manifest systemic TB disease, and suggest that MTB can be sequestrated in the RPE cells in latent TB.

Subretinal fluid in primary rhegmatogenous retinal detachment: physiopathology and composition

During retinal detachment, subretinal fluid is present, whose composition and physiopathology are still little known. Under normal conditions, osmotic and oncotic pressures help keep the retina in place, but the main retinal attachment force is provided by active transport in the pigment epithelium. Subretinal fluid composition varies according to detachment duration; total protein concentration in subretinal fluid increases with time. In addition, all proteins are qualitatively modified. The detached retina loses its oxygen supply, and it then uses the anaerobic pathway to degrade glucose. Thus, long-duration retinal detachments feature increased lactic acid and dextrose concentrations. Phospholipids are also increased in subretinal fluid, reflecting retinal degradation. This review presents data on the physiopathology and composition of the subretinal fluid in retinal detachments.

Secretion of plasminogen activators by cells cultured from subretinal fluid

Secretion of plasminogen activators was examined in 11 cells cultures from subretinal fluid of patients with retinal detachment. The plasminogen activator production was compared to 4 retinal pigment epithelial cell cultures from post-mortem donors with no known retinal pathology. Plasminogen activator activity was evaluated by zymography and was corrected for the total cell protein in the cultures. Cells from subretinal fluid had more proteolytic activity and secreted more active urokinase-type plasminogen activator than retinal pigment epithelial cells of donor origin. It is possible that cells from subretinal fluid are modulated by the conditions in subretinal fluid to secrete more urokinase-type plasminogen activator, generally considered to be a sign of invasive growth or that the subretinal fluid cultures contain other cell types than solely retinal pigment epithelial cells, such as pigmented macrophages, with an active plasminogen activator production. Alternatively, retinal pigment epithelial cells detached into the subretinal fluid may represent a selected population of retinal pigment epithelial cells with a more active extracellular proteolysis.