Subject: Why do we use bFGF for maintaining pluripotency of stem cells?

Hello,
I was wondering why is bFGF used to maintain pluripotency of stem cells? 
According to what limited information about the downstream effects of the MAPK 
pathway is known to me, it should bring about differentiation as well as cell 
proliferation. However, FGF is used all across the globe in labs involved in 
stem cell research for the maintenance of pluripotency. FGF is one of the many 
factors that is know to activate the RAS/ERK pathway, which is known to bring 
about differentiation, so how does its presence in the culture media prevent 
the stem cells from differentiating.

Re: Why do we use bFGF for maintaining pluripotency of stem cells?