XXXX liver cells produce a diffusible activity which inhibits the differentiation of murine @entity189 and embryonic stem cells.

@entity1138 @entity189 @entity3457 @entity35 @entity1968
Many pluripotent @entity189 ( @entity189 ) cell lines and all embryonic stem (ES) cell lines have hitherto been maintained in the undifferentiated state only by culture on feeder layers of @entity1138 -treated embryonic fibroblasts. We now demonstrate that medium conditioned by incubation with @entity35 liver (BRL) cells prevents the spontaneous differentiation of such cells which occurs when they are plated in the absence of feeders. This effect is not mediated via cell selection but represents a fully reversible inhibitory action ascribed to a @entity3457 ( @entity3457 ). BRL-conditioned medium can therefore replace feeders in the propagation of homogeneous stem cell populations. Such medium also restricts differentiation in embryoid bodies formed via aggregation of @entity189 cells and partially inhibits @entity1968 -induced differentiation. The PSA4 @entity189 line gives rise only to extraembryonic endoderm-like cells when aggregated or exposed to @entity1968 in BRL-conditioned medium. This suggests that @entity3457 may be lineage-specific. @entity3457 is a dialysable, acid-stable entity of apparent molecular weight 20,000-35,000. Its actions are reproduced neither by insulin-like growth factor-II nor by transforming growth factor-beta. @entity3457 thus appears to be a novel factor exerting a negative control over embryonic stem cell differentiation.
