Our laboratory has had problems with cardiac differentiation from iPSCs this autumn with different cell lines. Our differentiation results in these bubble cells (see image). These bubbles come from EB differentiation and small molecule monolayer differentiation. Only common molecule between the two is IWP4 which has been replaced with new batch with no different outcome. Different passages on iPSCs have been thawed with no effect. The problem is not cell-line specific.

Have you experienced this or do you have any ideas how to overcome this?