Distribution and mRNA expression of tenascin-C in developing human lung

Tenascin-C is an extracellular matrix glycoprotein that is spatially expres sed during organogenesis, in inflammatory and fibrotic disorders, and in ne oplasms. The aim of this study was to analyze its expression in developing human lung tissues during pseudoglandular, canalicular, saccular, and alveo lar periods corresponding to Weeks 12 to 40. Lung tissues were obtained at autopsy from 34 nonmalformed cases. An immunohistochemical analysis and a m essenger RNA (mRNA) in situ hybridization method combined with light micros copy were used. The extent of tenascin-C immunoreactivity was scored as abs ent, low, moderate, or strong in and around different types of pulmonary ce lls. The immunohistochemical expression for tenascin-C was strong beneath t he airway epithelium, especially at the sites of airway subdivision during Weeks 12 to 23, whereas its expression was moderate or weak underneath alve olar and bronchiolar epithelia between Weeks 24 and 40. The expression for tenascin-C was strong in the intima of veins, especially in the canalicular period, i.e., Weeks 17 to 28. A moderate or strong immunoreactivity for te nascin-C was also observed around chondrocytes in every case studied during all periods. The increased expression of tenascin-C mRNA was most often se en in the cells below the airway epithelium. Taken together, tenascin-C is expressed in human lung during all developmental periods, and its expressio n is especially strong below the airway epithelium at the sites of airway s ubdivision.