Tenascin in rat lung development: in situ localization and cellular
sources.
Zhao, Yun, and Stephen L. Young.
Research Service, Durham VAMC and Department of Medicine, Duke
University Medical Center, Durham, North Carolina 27710
APStracts 2:0084L, 1995.
Tenascin (TN) is a hexameric extracellular matrix glycoprotein that
may play an important role during lung development. TN protein is
temporally and spatially restricted during lung organogenesis. The
temporo-spatial and cellular expression of TN mRNA in lung remains
unclear. Localization of message expression of TN in rat lung tissue
was first investigated by using in situ hybridization performed with
an antisense RNA probe. TN mRNA was present primarily within the
mesenchyme of day 16 gestational age fetal rat lung tissue, whereas
immunoreactive TN protein was found along the basement membrane. In
postnatal day three rat lung tissue, TN mRNA was detected along
alveolar septal walls and was concentrated at secondary septal tips.
Expression of TN message was consistent with localization of
immunoreactive TN protein. Accumulation of TN mRNA in alveolar septal
tips suggests that mesenchyme may be the major source of TN mRNA. To
investigate the cellular source of TN in rat lung, we studied the
expression of TN in cultured rat lung fibroblasts, endothelial cells
and alveolar epithelial cells. Two TN isoforms, having molecular mass
of 230kDa and 180kDa, were in conditioned medium and in cellular
extracts of lung fibroblasts and endothelial cells. TN was secreted
and deposited in the extracellular matrix closely associated with the
surface of lung fibroblasts and endothelial cells. Lung alveolar
epithelial cells showed undetectable or barely detectable amounts of
TN. These studies demonstrated that TN isoforms are expressed not
only by lung fibroblasts, but also by lung endothelial cells. The
unique spatial localization of TN mRNA during lung development and
expression of TN by different lung cell types suggested TN may be
involved in matrix organization and cell-cell interactions during
lung development.
Received 23 January 1995; accepted in final form 9 May 1995.
APS Manuscript Number L18-5.
Article publication pending Am. J. Physiol. (Lung Cell. Mol.
Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 26 May 1995.