Organogenesis requires support of the vascular system and control of proliferation activity. VEGF, a selective
mitogen for vascular endothelial cells, is important for vessel development. PTEN, known as a tumor suppressor, regulates
cell size and modulates VEGF-mediated signaling on angiogenesis. However, it is not yet clear if PTEN controls tissue
mass by suppressing angiogenesis provoked by VEGF and their correlations in postnatal tissue development in vivo.
We used a primitive vertebrate, Japanese eel (Anguilla japonica), to study this question. Swim bladder gas glands (a somatic
tissue composed mainly by the capillaries) from normal eels or eels injected with hypophyseal factors were used to
examine the expression of VEGF A, PTEN, IGF-1, and Flk-1 by RT-PCR. Two forms of PTEN (PTEN a, long form, and
PTEN b, short form) cDNA have been cloned. There was no correlation between VEGF expression and gas gland tissue
mass while a negative correlation between PTEN expression and tissue mass was noted; further, a higher correlation between
the tissue mass and the ratio of VEGF to PTEN was shown. In summary, we have shown the involvement of VEGF
and PTEN in postnatal tissue development, the ratio of VEGF to PTEN may represent the growth status of the tissue.