Transformation of human ciliary epithelial cells by simian virus 40: induction of cell proliferation and retention of beta 2-adrenergic receptors.

Abstract

Ciliary epithelial cells derived from human eye were successfully propagated through many generations after transformation with simian virus 40. The cell clone 8-SVHCE was isolated and characterized by immunoprecipitation and pharmacological studies that demonstrated the presence of several functional properties observed in the parent cells of this tissue. Immunoprecipitation revealed the presence of large tumor (T) antigen, and Southern blot analysis showed the incorporation of viral DNA into high molecular weight ciliary epithelial cell DNA. Studies of catecholamine-stimulated cellular cAMP production and of isoproterenol-dependent protein phosphorylation of vimentin in 8-SVHCE indicated the functional conservation of 6-adrenergic receptor-mediated processes that are thought to be important in the regulation of aqueous humor production by the ciliary epithelium in vivo.Ciliary epithelium (CE) in the mammalian eye is thought to play an essential role in the formation of aqueous humor. The composition of aqueous humor is largely dependent on the mechanism of active transport of plasma proteins and electrolytes in these cells. The rate of formation of aqueous humor is modulated by the sympathetic (adrenergic) system (1). The stroma in the ciliary processes is innervated by adrenergic fibers whose terminations remain close to the CE (2). Two structural features of these cells in vivo are (i) a structural polarity where the apical domain of a nonpigmented epithelial (NPE) cell faces the apical domain of a pigmented epithelial (PE) cell and (ii) a physiological, enzyme-based active transport system, Na+,K+-ATPase, located in the basolateral domains in both cell types. The relationship of the structural and physiological polarity in the CE to the regulation of ion transport (i.e., fluid flow from the stroma to the posterior chamber) is unclear.Previous studies (3-5) using crude membrane preparations from whole ciliary processes have indicated the presence of 8-adrenergic receptors in the ciliary epithelium of eyes from a variety of mammalian species. It is possible, however, that vascular endothelial cells from microvessels in the stroma of ciliary processes may have contributed to the stimulation of adenylate cyclase by 83-adrenergic receptors that was observed in these preparations. Attempts have been made to dissociate the CE cells from the stroma tissue to measure the properties and characteristics of the P-adrenergic receptor/ adenylate cyclase system in a mixed population of NPE and PE cells (6), after their separation in a density gradient (7), and in isolated NPE cells (8). In these studies, p-adrenergic receptors were found in both cell types. In addition, several attempts have been made to grow CE in tissue culture media after its dissociation and separation (9) from ciliary processes. Some of the differentiated characteristics ofhuman CE cells, such as their structural polarity and epithelial cell type, are retained in primary tissue cultures and have been studied by morphological and immunological...

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