DIFFERENTIATION AND ANGIOGENIC GROWTH-FACTOR MESSAGE IN 2 MAMMALIAN LENS EPITHELIAL-CELL LINES

Lens epithelial cells in culture can sometimes be induced to form sphe roid aggregates termed lentoid bodies, composed of cells exhibiting va rious characteristics of the more highly differentiated lens fiber cel ls. However, lentoid bodies are often slow to form, and the ability to produce them declines with serial subculture. It was therefore of int erest to establish and/or characterize lens epithelial cell lines capa ble of forming lentoid bodies. The differentiation state was assessed in lentoid bodies formed by each of two lens epithelial cell lines, th e transformed alphaTN4 cell line from mouse and the nontransformed N/N 1135A cell line from rabbit. Lentoid and monolayer cultures of each ce ll line were examined for transcripts of the lens-specific alphaA-crys tallin (''alphaA''), gammaD-crystallin (''gammaD''; formerly gamma1-cr ystallin) and MP26 genes. alphaTN4 lentoid bodies contained 2.5 times the alphaA RNA found in monolayer cells, but lacked detectable gammaD and MP26 RNA. None of the three markers were detected in either lentoi d or monolayer N/N1135A cultures grown under the conditions described. Lentoid body formation alone, therefore, does not indicate the extent of differentiation occurring. At least some of the changes in cell ad hesion occurring during lentoid body formation involve laminin-like an d fibronectin-like interactions, and are reminiscent of those observed during embryonic lens formation. Finally, vascular endothelial growth factor mRNA was absent from the lens but present in alphaTN4 cells, s uggestin a mechanism whereby the lens tumors of the founder mouse beca me vascularized.