ESTABLISHMENT AND CHARACTERIZATION OF A CONDITIONALLY IMMORTALIZED SMOOTH MUSCLE MYOMETRIAL-LIKE CELL-LINE/

A novel smooth muscle/myometrial-like cell line, SMU1-10, has been gen erated from the uterus of a H-2K(b)-tsA58 transgenic mouse carrying a thermolabile SV40 large T-antigen gene. These cells grow continuously when maintained at the permissive temperature (33 degrees C) for the S V40 large T-antigen but stop dividing when placed at the non-permissiv e temperature (39 degrees C) and ultimately die within 3 weeks. All of the SMU1-10 cells produce smooth muscle or-actin (SMAA) at both 33 de grees C and 39 degrees C. A subset of the cells also contain smooth mu scle gamma-actin (SMGA), a hallmark of smooth muscle differentiation, and the fraction of cells staining for this actin increases from about 1% when maintained for three days at 33 degrees C to as much as 30% a t 39 degrees C over the same length of time. However, the appearance o f SMGA in SMU1-10 cells appears to be regulated mainly at a post-trans criptional level since in situ hybridization indicates that all cells contain SMGA mRNA at both 33 degrees C and 39 degrees C. SMU1-10 cultu res also contain smooth muscle myosin heavy chain (SM-MHC) and SM22 al pha, both of which are only found in smooth muscle of the adult mouse. Three additional smooth muscle (myometrium)-related markers, connexin 43, the thromboxane A(2) receptor, and the progesterone receptor also are present in these cells. At the nonpermissive temperature for SV40 large T-antigen, the both level of SMGA mRNA and the number of cells staining for this actin are significantly increased in the presence of progesterone, a process that is similar to the upregulation of SMGA i n the myometrium late in pregnancy. Overall, SMU1-10 cells provides a potentially useful in vitro model system to study smooth muscle/myomet rial differentiation. (C) 1997 Wiley-Liss, Inc.