General inquiry regarding WNT activation

I've seen in the literature that researchers DO or DO NOT serum starve prior to treating with Wnt.  I am looking into performing some Wnt3a treatments.  Should I serum starve my cells prior to treating them?  I will be using recombinant Wnt3a.  Does it matter if using recombinant Wnt3a vs. L/Wnt3a conditioned medium?

Thanks!

James