Publication: The ultrastructural composition of basement membranes in vivo
Authors
Miosge, Nicolai
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Publisher
Murcia : F. Hernández
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DOI
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info:eu-repo/semantics/article
Description
Abstract
The ultrastructure of basement membranes
has a homogeneous appearance. The enormous cell
biological importance of basement membranes and their
components f o r c e l l proliferation, migration and
differentiation implies that their composition is more
complex than their structure suggests. To elucidate the
molecular composition of basement membranes it1 vivo,
we optimised immunogold histochemistry to allow the
determination of the molecular arrangement of matrix
molecules.
Basically, we apply a mild fixation and embed the
tissues in the hydrophilic L R - G O ~T~h~is .p reserves the
basement membrane with a quality similar to freeze
substitution. The application of two antibodies directed
toward the C- and N-terminal ends of a molecule and
coupled to gold particles of different sizes allows
determination of the orientation of a molecule within the
basement membrane. We were able to demonstrate that
the molecular orientation of the laminin-l molecule
changes in the basement membrane according to cell
biological needs. We also showed that ultrastructurally
identical basement membranes like the ones of the
proximal and distal tubules of the kidney have a
differing molecular arrangement. Integrin a7 influences the molecular composition of the basement membranes
at the myotendinous junction. With the help of double
labelling at the ultrastructural level we could show that
nidogen-l is CO-localised with laminin-l and only found
in fully developed, mature basement membranes. In
general, laminin-l, nidogen-l and collagen type IV are
localised over the entire width of basement membranes,
with laminin-l and nidogen-l CO-localised, in
accordance with the current basement membrane
models.
Incidentally, our investigations warn us, that not
every matrix protein found at the light microscopic level
as a linear staining pattern underneath an epithelium
(basement membrane zone) is a real basement
membrane component when investigated at the ultrastructural level. Instead, one and the same molecule,
e.g. endostatin, can be a basement membrane component
in one organ and a matrix molecule in another.
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