Sh-sy5y differentiation help

I've been experimenting in shsy5y cell line and haven't had any problem so far. Now we're trying to differentiate them with retinoic acid. But it seems like something goes wrong and I don't know what. We use 10 mikromolar Retinoic acid with high glucose and %1 fbs. We saw some cells started to grow branches different than the undifferentiated ones. But most of the cells died and most of rest seems apoptotic. We have tried low glucose and low fbs in another plate. They seemed more enduring but the picture was the same as the other group. Most of them were apoptotic. I can't figure out what are we doing wrong. I did everything the same as I read I the literature but literature is not enough for most of the protocols. I hope someone give me an idea where should I look or what should I change in the procedure.