CELL-SPECIFIC EXPRESSION OF FIBRONECTIN AND EIIIA AND EIIIB SPLICE VARIANTS AFTER OXYGEN INJURY

Cellular fibronectin (cFN) expression is characteristic of injured tis sues. Unlike plasma FN, cFN mRNA often contains the EIILA or EIIIB dom ains. We examined the lung cell-specific expression of total cFN mRNA. and the EIIIA and EIIIB splice variants in rabbits after acute oxygen injury. By in situ hybridization, control lung had low cFN mRNA. Afte r exposure to >95% oxygen, mRNAs for total cFN and EIIIA were noted pr imarily in alveolar macrophages and large-vessel endothelial cells. By 3-5 days recovery, cFN and EIIIA mRNA abundance was increased in alve olar septal cells (i.e., alveolar epithelial, interstitial, or endothe lial cells) and in some large-vessel endothelial cells but was low in bronchial epithelial cells. During recovery, EIIIB mRNA was low in alv eolar septal cells but was noted mainly in chondrocytes. Immunostainin g for EIIIA increased during recovery, paralleling the in situ hybridi zations. Because FN may modulate alveolar type II cell phenotype, we i nvestigated type II cell cFN mRNA expression in vivo. During recovery, neither isolated type II cells nor cells with surfactant protein C mR NA in vivo contained FN mRNA. In summary, these data suggest that cFN with the EIIIA domain has a role in alveolar cell recovery from oxygen injury and that type II cells do not express cFN during recovery.