Do AgNOR counts reflect cellular ploidy or cellular proliferation? A study of trophoblastic tissue.

There is considerable debate as to whether AgNOR counts reflect cellular ploidy or cellular proliferation. Trophoblastic tissue from hydropic abortions and from hydatidiform moles offers an excellent model for analysing this problem. Thus, complete moles show considerable cell proliferation but are diploid, whilst partial moles show markedly less cell proliferation but are triploid: hydropic abortuses are diploid and show no cellular proliferation. AgNOR counts in villous cytotrophoblastic cells from hydropic abortions and from complete hydatidiform moles are similar, but those in partial hydatidiform moles are 50 per cent higher than in either hydropic abortions or complete moles. Thus, in non-neoplastic trophoblastic tissue AgNOR counts are clearly a reflection of ploidy rather than of cell proliferation.