How do they make passage limited cells? - (Oct/18/2012 )

Does anyone know what technique companies use to make passage limited cells? I would like to order an engineered cell line and they have kits with passage limited cells (couple of divisions) included. I was wondering how they are able to do that.

one way is to irradiate the cells, which stops cell division. We have had such cells from perkin elmer eg http://www.perkinelmer.com/Content/TDLotSheet/ES-000-A12F_M1F-A12.pdf