OPCs don't really require thyroid hormone in order to differentiate. They will more slowly differentiate when mitogens (PDGF/FGF) are withheld. Unfortunately I do not know of any media that does not contain progesterone and supports OPCS growth. The common media supliments or defined media such as neuro-basal A B27 and N2 contain progesterone. Is there a particulars reason you would like to avoid these hormones in your prep?

 The aim is not to avoid these hormones in the medium but avoid ethanol, in which these hormones are disolved.

I agree that T4 is not essential for OPC differentiation. As for progesterone, I am not sure whether it is definitely required for OPC differentiation. However, I noticed that rat OPCs could differentiate in the cortical neuron culture medium which mainly consists of neurobasal, 2%B27 and 2 mML-glutamine. Good luck!

I agree with Dr. Potter's recommendations. We also use the Barres Lab's protocol for solubilizing thyroid hormone. Unfortunately I cannot tell you what exactly is in B27 or N2, but EtOH is not listed in their formulations. It is likely that the progesterone is solubilized with the fatty acid content of the supplements, but I cannot confirm this. If you want to make up your own reagents, there are water-soluble forms of progesterone with a  2-hydroxypropyl-β-cyclodextrin carrier, but you may need to consider what effects cyclodextrins may have on cellular cholesterol.

Thank you everyone for answering this question. We recently noticed the effect of the lack of T4 and progesterone in the differentiation  of rat OPCs, and they do differentiate!!!