it's clear that there's a problem here, but defunding the group is not an answer. that functionally amounts to fully privatizing the business, which is likely to lead to worse abuses. this is deeper, systemic and requires a different approach.
i am a strong proponent of abortion rights and medical research. however, i do believe that the potential sale of human body parts is an issue that is serious enough for congressional investigation. some proposed solutions that are better than defunding:
1) pass legislation that forces a public auditing of tissue donation costs. in fact, make it a regular thing. make the figures accountable. ensure that exact costs are precisely delineated. this is broader than planned parenthood - it should be applied to any situation where the possible profiting of selling human tissue is an issue. this is reasonable accountability, and should really exist anyways.
2) you could install the state as an intermediate in tissue donation, and have the recipients refund the state rather than the private party.