Ultrastructural and Fluid Flow Properties of Cultured Fetal Trabecular Meshwork Cells

Abstract

Purpose:: In Primary Open Angle Glaucoma (POAG), trabecular meshwork (TM) cells have been found to be more senescent and reduced in numbers than in normal eyes(1). Fetal TM may be a source of healthy cells for replacement of diseased or lost cells in POAG. The isolation, culture, and protein expression of fetal TM cells have been previously described from our lab(2). In the present study, we report the ultrastructural characteristics and fluid flow properties of these cells.

Methods:: Fetal and adult TM cells grown on permeable filters were processed by standard methods for transmission electron microscopy. Sections were cut using a diamond knife and ultrastructural features were examined with an electron microscope. Both fetal and adult cells were grown to confluency on permeable Millipore filters for permeability assays. Horseradish peroxidase (HRP) permeation was measured in six replicates of each cell type. The amount of permeation was quantified by measurement of the enzymatic product of HRP in the effluent by its absorption at 470 nm in a spectrophotometer.

Results:: Both fetal and adult TM cells were found to have multiple electron dense bodies, microvilli, and similar junctional proteins. The permeation of HRP across fetal and adult TM monolayers was 0.034 ± 0.008 ΔOD₄₇₀ and 0.049 ± 0.011 ΔOD₄₇₀, respectively (P = 0.02).

Conclusions:: Cultured fetal TM cells exhibited similar ultrastructural characteristics as their adult counterparts. However, fetal cells were less permeable to fluid flow then adult TM cells. From our prior and present results, cultured fetal TM cells have similar structural and protein expression characteristics as adult cells, however, they grow at a faster rate and for more extended passages. Fetal tissue may be a source of healthy TM cells for potential transplantation in POAG.

Keywords: trabecular meshwork