Am. J. Respir. Cell Mol. Biol., Vol 13, No. 3, 09 1995, 262-270.
Expression of insulin-like growth factor receptors 1 and 2 in the developing lung and their relation to epithelial cell differentiation
B Maitre, A Clement, MC Williams and JS Brody
Pulmonary Center, Boston University School of Medicine, Massachusetts, USA.
Insulin-like growth factors (IGFs) and their receptors have been implicated
as regulators of cell differentiation and cell proliferation in a number of
systems and have been shown to play an important role in embryonic
development. In this study we examined expression of mRNA for IGF-I and
IGF-II, IGF binding protein 2 (IGFBP-2), and IGF receptors 1 (IGFR-1) and 2
(IGFR-2) during fetal lung development and in early postnatal and adult
lungs by the polymerase chain reaction (PCR). IGF-I mRNA was found in
embryonic and postnatal lungs at all ages as was IGFBP-2, whereas IGF-II
mRNA was present only in prenatal lungs. IGFR-1 was present in all but the
adult lungs. Lung epithelial cells expressed IGFR-1 at 14 days' gestation
but not at 18 days' gestation as measured by PCR and in situ hybridization.
Alveolar epithelial cells re- expressed IGFR-1 mRNA in the early postnatal
period but not in the adult lung. IGFR-2 was expressed by PCR and in situ
hybridization in 14- day embryonic epithelium, was not present at 18 days
or at birth, but was re-expressed at high levels in the early postnatal
alveolar wall. Immunocytochemical localization of IGFR-2 confirmed its
absence in the late fetal and newborn lung. It reappeared in alveoli,
exclusively in type 1 cells, in early postnatal and adult lungs. These
studies demonstrate the stage- and cell-specific appearance of IGF
receptors in the developing and postnatal lung. They also establish IGFR-2
as a marker of the mature alveolar type 1 cell.(ABSTRACT TRUNCATED AT 250
WORDS)
