Vol. 282, Issue 4, E851-E864, April 2002
Bone as an ion exchange system: evidence for a link between
mechanotransduction and metabolic needs
A.
Rubinacci1,
M.
Covini2,
C.
Bisogni2,
I.
Villa1,
M.
Galli2,
C.
Palumbo3,
M.
Ferretti3,
M. A.
Muglia3, and
G.
Marotti3
1 Bone Metabolic Unit, Scientific Institute H San Raffaele,
20132 Milano; 2 Department of Bioengineering, Politecnico of
Milano, 20133 Milano; and 3 Department of Morphological
Sciences Human Anatomy, University of Modena, 41100 Modena, Italy
To detect whether the
mutual interaction occurring between the osteocytes-bone lining cells
system (OBLCS) and the bone extracellular fluid (BECF) is affected by
load through a modification of the BECF-extracellular fluid (ECF;
systemic extracellular fluid) gradient, mice metatarsal bones
immersed in ECF were subjected ex vivo to a 2-min cyclic axial load of
different amplitudes and frequencies. The electric (ionic) currents at
the bone surface were measured by a vibrating probe after having
exposed BECF to ECF through a transcortical hole. The application of
different loads and different frequencies increased the ionic current
in a dose-dependent manner. The postload current density subsequently
decayed following an exponential pattern. Postload increment's
amplitude and decay were dependent on bone viability. Dummy and static
loads did not induce current density modifications. Because BECF is
perturbed by loading, it is conceivable that OBLCS tends to restore
BECF preload conditions by controlling ion fluxes at the bone-plasma interface to fulfill metabolic needs. Because the electric current reflects the integrated activity of OBLCS, its evaluation in transgenic mice engineered to possess genetic lesions in channels or matrix constituents could be helpful in the characterization of the mechanical and metabolic functions of bone.
osteocytes; bone lining cells; mineral homeostasis; mechanical
loading; fluid shear stress