Identification of a Novel Cell Type in Primary Cultures of Human Trabecular Meshwork

Abstract

Abstract: : Purpose:During regular experiments with human trabecular meshwork (HTM) primary cell cultures we accidentally observed that a small number of cells can resume growth a few weeks after replicative senescence appears to have been reached. The purpose of this study is to investigate the ultrastructure of these cells. Methods:Two HTM cell lines were grown to reach replicative senescence. After cell division ceased, the cultures were maintained for 6 to 10 weeks until a small number of cells were observed to again initiate active replication and generate visible colonies. Two such colonies were analyzed by transmission electron microscopy. Results:Electron microscopic evaluation revealed features different from those of HTM cells or fibroblasts. These include a very large Golgi apparatus and the presence of bodies filled with glycogen granules that are released to the extracellular space. These bodies are also clearly visible outside of the cells by light microscopy because of their high refringence. Conclusion:A possible new cell type with growth pattern and ultrastructural features different from those of the normal HTM cells is present in HTM primary cultures. The presence of glycogen rich bodies similar to the precursors of lamellar bodies is somewhat suggestive of Schwalbe's line cells. The ability to proliferate after the other cells in the culture have reached replicative senescence suggests the possibility that these cells might represent possible HTM stem cells.

Keywords: 601 trabecular meshwork • 472 microscopy: electron microscopy • 553 regeneration