Temporal and spatial expression of laminin, collagen types IV and I and α 6/ β 1 integrin receptor in the developing rat parotid gland

Abstract

Abstract We have examined the temporal expression and cellular localization of the genes and proteins for the extracellular matrix (ECM) proteins laminin (B1, B2 and A chain), collagen types α1 (IV) and α1 (I) and the integrin receptor complex α6/β1, during parotid gland postnatal development. Laminin B1 and B2 isoforms and collagens α1 (IV) and α1 (I) mRNA steady-state levels were highest at ages 0, 7 and 14 days after birth and declined to the adult (90 days) level at 21 days and older. Laminin A chain transcripts were not detected at any age. Collagen α1 (IV) and laminin were localized in the basal membrane of the developing acinar and ductal cells, while collagen α1 (I) was localized in the stroma surrounding the cells. The amounts of these ECM components were high at the early stages of development and lower at later times. The pattern of expression of the α6/β1 integrin genes during development was similar to those of laminin and collagens α1 (IV) and α1 (I). Accumulations of mRNA were high at 0, 7 and 14 days after birth and lower at 21 days and older. High levels of β1 integrin were localized in the developing acinar and ductal cell membranes at early ages (7 days); lower amounts were present in the same distribution pattern at later stages of gland development. These data suggest that laminin B1 and B2 and collagen type α1 (IV) and α1 (I) are consistently coexpressed with the α6/β1 integrin receptor complex in the developing acinar and ductal cells during parotid gland postnatal development. Their expression is concomitant with the morphologic and proliferative changes occurring in these cells during this period.