Cross-linked actin networks (CLANs) in bovine trabecular meshwork cells.

A cytoskeletal feature of human trabecular meshwork (HTM) cells in vitro and ex vivo is the presence of cross-linked actin networks (CLANs) that are abundant in a proportion of TM cells exposed to dexamethasone (DEX) and also in cells from glaucoma patients. We wished to determine whether CLANs were present in the bovine trabecular meshwork (BTM), whether they were similarly induced by dexamethasone and whether the structures were comparable to CLANs in HTM cells. Cultures of HTM and BTM cells and ex vivo dissections of BTM tissue were stained with phalloidin (F-actin) and propidium iodide (nuclei) and imaged by confocal microscopy, thereafter being subjected to image analysis. Some CLAN-like structures were identified in ex vivo BTM tissue cultured with and without DEX. However we found that BTM cells in culture produced abundant CLANs when exposed to DEX; comparable to the best response from HTM cells. The CLANs were of similar dimensions and morphology to those found in human cells and they had a similar half life of 2 or 3 days following the removal of DEX. This work demonstrates that BTM cells provide a suitable model for future investigations of CLAN formation and function. BTM cultures are sufficiently hardy to thrive in low serum and serum-free conditions so we were able to show that aqueous humor stimulates CLAN formation in the target cells. Future research is directed at identifying the aqueous component(s) responsible for CLAN production.