The expression patterns of integrin subunits on human breast tissues obtained during pregnancy

Integrins have been shown to exert regulatory influences on mammary differentiation and morphogenesis in rodent experimental systems. We have, therefore, examined the expression patterns of integrin subunits on human breast tissues obtained at the 12th, 15th and 18th weeks of pregnancy. Myoepithelial cells were positive for all the integrin subunits examined. alpha2, alpha6 and beta4 showed increased and more defined labelling during pregnancy, indicating that myoepithelial cells and extracellular matrix strengthen their support for the expanding alveoli during pregnancy. Sub-populations of stromal cells were positive for alpha1, alpha3, alpha6, beta1 and beta4. On luminal epithelial cells, alpha1, alpha2, alpha3, alpha6 and beta1 were detectable. alpha2 showed a focal decrease, but the expression patterns of other integrins in luminal cells did not change during pregnancy. Therefore, the expression patterns of most integrins existing prior to pregnancy seem sufficient in this cell type to support the morphological and functional development during early pregnancy.