Publication: The fibronexus in reactive and tumoral myofibroblasts: further characterisation by electron microscopy
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Date
2001
Authors
Eyden, B.
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Publisher
Murcia : F. Hernández
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DOI
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info:eu-repo/semantics/article
Description
Abstract
Forty two surgical specimens containing
myofibroblasts were studied to clarify the criteria for
identifying the fibronexus, an ultrastructural feature
regarded as a marker for myofibroblastic differentiation.
Granulation tissue, tumour stroma, fibro-proliferative
lesions (nodular fasciitis, myofibromatosis, inflammatory
myofibroblastic tumour) and malignancies
(myofibrosarcoma and fibrosarcoma) were studied.
Comparable results were found throughout these
specimens, although fibronexus junctions were better
developed in reactive compared with tumoral
myofibroblasts. By electron microscopy, myofibroblasts
were identified by abundant rough endoplasmic
reticulum, peripheral smooth-muscle myofilaments with
foca1 densities, and fibronexus junctions. The latter were
recognised as the points of convergence on the
myofibroblast surfaces of intracellular myofilaments and
extracellular fibronectin fibrils. The fibronectin fibrils
were often co-linear with myofilaments. Also,
fibronectin fibrils were dark-staining, straight and rigidlooking,
and had a longitudinal filamentous substructure.
A striking feature was the tendency of fibronectin fibrils
to project into the surrounding extracellular space, away
from the myofibroblast surface: in these respects, they
differed significantly from lamina ("basement
membrane"). The presence of fibronectin fibrils
correlated positively with fibronectin immunostaining by
light and electron microscopy. Laminin and collagen IV
showed variable and weak staining in the intercellular spaces in a minority of cases and never strongly stained
myofibroblast surfaces. The data emphasise that the
fibronexus has a number of distinctive features
permitting identification, and constitute a reference-point
for pathologists wishing to use electron microscopy to
refine light microscopy diagnoses of putative
myofibroblastic lesions. The role of the fibronexus in the
definition of the myofibroblast is discussed.
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