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tensegrity which will occupy us for the rest of the
chapter. Aside from that, the exact therapeutic implica-
tions of this discovery are as yet unclear.
Suffice it to say that fascia has long been thought to
be plastic or viscoelastic, but otherwise inelastic and
non-contractile. Both these shibboleths are being revised
in light of new research. According to Schleip, 'It is
generally assumed that fascia is solely a passive contrib-
utor to biomechanical behavior, by transmitting tension
which is created by muscles or other forces ... [but]
there are recent hints which indicate that fascia may be
able to contract autonomously and thereby play a more
active role.' 10 4
as we would normally understand it. The factors that
induce the long-duration, low-energy contraction of
these cells are: (1) mechanical tension going through the
tissues in question, and (2) specific cytokines and other
pharmacological agents such as nitric oxide (which
relaxes MFBs) and histamine, mepyramine, and oxyto-
cin (which stimulate contraction). Unexpectedly, neither
norepinephrine or acetylcholine (neurotransmitters
commonly used to contract muscle), nor angiotensin or
caffeine (calcium channel blockers) has any effect on
these MFBs. Many MFBs are located near capillary
vessels, the better to be in contact with these chemical
agents. 10 8
The contraction, when it occurs, comes on very slowly
compared to any muscle contraction, building over 20-
30 minutes and sustaining for more than an hour before
slowly subsiding. Based on the in vitro studies to date,
this is not a quick-reaction system, but rather one built
for more sustained loads, acting as slowly as it does
under fluid chemical stimulation rather than neural.
One aspect of the fluid environment is of course its pH,
and a lower, acidic pH in the matrix tends to increase
the contractility of these MFBs. uw,11 ° Therefore, activities
that produce pH changes in the internal milieu, such as
breathing pattern disorder, emotional distress, or acid-
producing foods, could induce a general stiffening in
the fascial body. Here ends this brief foray into chemis-
try, which is so well-covered elsewhere. 11 0
MFBs also induce contraction through the matrix in
response to mechanical loading, as would be expected.
With the slow response of these cells, it takes 15-
30 minutes or more before the fascia in question
gets more tense and stiff. This stiffness is a result of the
MFBs pulling on the collagen matrix and 'crimping' it
(Fig. 1.65).
The manner in which the MFB contracts and tenses
the fiber matrix of the ECM is instructive, and will lead
us into the wonderful world of tensegrity on a cellular
level.
Myofibroblasts
In fact, fascia can now be said to be contractile. But the
circumstances under which such a contraction is exerted
are limited and therefore quite interesting. We now
know that there is a class of cells in fascia that are capable
of exerting clinically significant contractile force in par-
ticular circumstances - enough, for instance, to influ-
ence low-back stability. 10 5 This class of cell has been
termed myofibroblasts (MFBs - see Fig. 1.47B). MFBs
represent a middle ground between a smooth muscle
cell (commonly found in viscera at the end of an auto-
nomic motor nerve) and the traditional fibroblast (the
cell that primarily builds and maintains the collagenous
matrix). Since both smooth muscle cells and fibroblasts
develop from the same mesodermal primordium, it
comes as little surprise (in retrospect, as usual) that the
body might find some use for the transitional cell
between the two, but some surprising characteristics of
these cells kept them from being recognized earlier.
Apparently, evolution found variable uses for such a
cell, as MFBs have several major phenotypes from
slightly modified fibroblasts to nearly typical smooth
muscle cells. 10 6
Chronic contraction of MFBs plays a role in chronic
contractures such as Dupuytren's contracture of the
palmar fascia or adhesive capsulitis in the shoulder. 10 4
MFBs are clearly very active during wound healing and
scar formation, helping to draw together the gap in the
metamembrane and build new tissue. 10 7 To be brief, we
will let the reader follow the references for these possi-
bly intriguing roles in body pathology so that we can
hew closely our stated goal of describing how fascia
works normally.
It is now clear that MFBs occur in healthy fascia, and
in fascial sheets in particular, such as the lumbar fascia,
fascia lata, crural fascia, and plantar fascia. They have
also been found in ligaments, the menisci, tendons, and
organ capsules. The density of these cells may vary posi-
tively with physical activity and exercise, but in any
case, the density is highly variable in different parts of
the body and among people.
One very surprising aspect of these cells is that -
unlike every other muscle cell in the body, smooth or
striated - they are not stimulated to contract via the
usual neural synapse. Therefore, they are beyond the
reach of conscious control, or even unconscious control
Fig. 1.65 A contracting myofibroblast (MFB) can produce visible
'crimping' on the in vitro substrate, demonstrating the ability of the
motive power of the MFB to affect the surrounding matrix. (Photo
provided by Dr Boris Hinz, Laboratory of Cell Biophysics, Ecole
Polytechnique Federate de Lausanne, Lausanne, Switzerland.)
54
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