IMMORTAL CELL-LINES ISOLATED FROM HEART DIFFERENTIATE TO AN ENDOTHELIAL-CELL LINEAGE IN THE PRESENCE OF RETINOIC ACID

Previously, we isolated a single line of transgenic mice which develop an enlarged heart due to the expression of the immortalizing gene, po lyomavirus large T antigen. Immortal cell lines were isolated from adu lt transgenic but not from nontransgenic hearts. All of the 24 cell li nes expressed vimentin and fibronectin but not desmin or myosin heavy chain. We conclude that the cell lines are of non-muscle origin. Six c ell lines were chosen for further study. All six cell lines demonstrat e profound morphological and biochemical effects when incubated with 1 0(-4) M to 10(-7) M retinoic acid. The retinoic acid-treated cell line s showed arrested cellular proliferation and aligned to form rows and vesicle-like structures. Cycloheximide inhibited these retinoic acid-i nduced changes, indicating a need for continued protein synthesis. Ret inoic acid-treated, but not untreated, cells lost expression of viment in and fibronectin, gained the ability to incorporate acetylated low d ensity lipoprotein, and expressed Factor VIII-related antigen. Retinoi c acid did not induce expression of desmin or myosin heavy chain. Incu bation of the cell lines with transforming growth factor beta1, dimeth yl sulfoxide, or phorbol esters had no biochemical or morphological ef fect. We conclude that these cell lines differentiate to an endothelia l lineage in the presence of retinoic acid.