Biology Reference
In-Depth Information
27
Tissue Recombinants
to Study Extracellular Matrix Targeting
to Basement Membranes
Patricia Simon-Assmann and Michèle Kedinger
1. Introduction
The basement membrane that separates an epithelium or other parenchymal
tissues from the connective tissue has been postulated for a long time to be of
epithelial origin. Because of difficulties in interpreting results obtained mostly
by autoradiographic labeling at the light microscopy level, new analytical tools
and models were important to develop. In particular, Lipton
(1)
using an in
vitro coculture system was probably the first to provide evidence for a dual
origin of the basement membrane: indeed a distinct basement membrane structure
developed in myoblast cultures only after the addition of muscle fibroblasts.
Various experimental techniques are currently used to study the expression
of basement membrane molecules. They include immunohistochemistry, bio-
chemical approaches, or detection of transcripts by
in situ
hybridization on
isolated tissue compartments or cell lines. Apart from the minor limitations of
each model (such as cellular contamination in the case of isolated epithelial or
mesenchymal cell preparations, abnormal cell behavior or loss of differentia-
tion of cultured cells, threshold sensitivity), they all share a major drawback.
Indeed, the fact that a tissue compartment expresses a given basement
membrane molecule does not necessarily imply that this molecule is depos-
ited at the basement membrane region. Autoradiographic studies (incorpora-
tion of radioactive precursors) that circumvent this problem, unfortunately do
not allow discrimination between individual components. The strategy
designed by Sariola et al.
(2
,
3)
that is grafting of avascular murine embry-
onic kidneys onto quail chorioallantoic membrane deserves special attention.
The major advantage of this model is that it allows the authors to follow the
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