Effect of transferrin on amphibian limb regeneration: a blastema cell culture study.

In order to study mitogenic control during axolotl limb regeneration, we have developed a primary blastema cell culture as a very sensitive bioassay for blastema mitogens. Transferrin, an iron-binding glycoprotein which has been shown to be the neurotrophic factor for muscle cells, is the mitogen which has been analysed in the present report. Addition of approximately 2 μg human transferrin/ ml of serum-free culture medium enhances blastema cell proliferation 11-fold over control levels and 2-fold over that produced by the addition of nerve extracts or purified growth factors extracted from nerve tissues (basic and acidic fetal growth factor, FGF). At a higher concentration (20 μg/ml), transferrin alone has no mitogenic effect unless the medium is also supplemented with FeCl3 (100 μM). The results are discussed with regard to the sensitivity of the blastema cell culture bioassay and in the context of the neurotrophic theory of urodele limb regeneration.