In the extracellular matrix is a layer of attenuated fibroblasts which delineate an area equivalent to the basement membrane zone (BMZ). They are an anatomic unit of mesenchymal cells that interact with the overlying epithelium. Very little is known about this layer of cells. They are thought to be associated with differentiation, the BMZ and as sentinel cells which respond locally to inflammation or epithelial injury. Here we describe morphologic changes in the mesenchymal cell layer following naphthalene injury to mouse Clara cells. In controls, the attenuated fibroblast layer covers approximately 62% of the BMZ. The cells are 35u in diameter, 0.3u thick and exist 0.2u from the basal lamina (BL). More than 30% of the cell layer is in direct contact with the BL. Four days post naphthalene (DPN) injured Clara cells have sloughed, ciliated cells have squamated and are proliferating and differentiating to repair the tissue (LS Van Winkle et al Am J Physiol 269 L800-L818, 1995). We found increased number, length and thickness of attenuated fibroblasts at 4 DPN. They cover 80% of the BMZ and are increased in diameter to 43u with an average thickness of 1.8u. Their average distance from the BL is 0.3u but only 5% of the cell layer is in direct contact with the BL. Individual cells appear to be synthetically active, containing abundant rough endoplasmic reticulum. At 7 DPN, the attenuated fibroblast layer was unchanged. We conclude that the layer of attenuated fibroblasts appear to be in a quiescent state before injury. Following injury the cell layer responds by increasing in size, number and synthetic activity. This is consistent with the concept of attenuated fibroblasts acting as sentinel cells in response to epithelial injury.
|Original language||English (US)|
|State||Published - Mar 20 1998|
ASJC Scopus subject areas
- Agricultural and Biological Sciences (miscellaneous)
- Biochemistry, Genetics and Molecular Biology(all)
- Cell Biology