I'm working with primary cultures, but fibroblast cells hinder efficient recovery. I have read that cholera toxin can be used to inhibit fibroblast growth.
You may use 'FibrOut' which is a proprietary combination of several biochemical compounds, antibodies, or specialty reagents, which prevent overgrowth of fibroblastic or contaminating cells, effectively increasing the yield of target cells. Each fibroblast growth inhibitory system is customized to be tissue-specific and cell-specific.
For more information about this product, you may want to refer to the link below.