AJP - Endocrinology and Metabolism, Vol 263, Issue 6 E1029-E1034, Copyright © 1992 by American Physiological Society
Disuse osteopenia is accompanied by downregulation of gene expression for bone proteins in growing rats
G. K. Wakley, J. S. Portwood and R. T. Turner
Department of Orthopedic Surgery, Mayo Clinic, Rochester, Minnesota 55905.
Unilateral sciatic neurectomy (USN) resulted in cortical osteopenia in
tibiae from the sciatic nerve-sectioned limb of growing rats. The bone
deficit resulted from decreased periosteal addition; there were no changes
in the indexes of bone resorption. The periosteal bone formation rate was
reduced in the nerve-sectioned limb within 7 days of sciatic neurectomy,
and this decrease persisted for at least 56 days. Steady-state mRNA levels
for bone proteins were determined in periosteum isolated from tibiae and
femurs 7 and 14 days after sciatic nerve section. Nerve section resulted in
decreased levels of mRNA for osteocalcin, alkaline phosphatase, and
possibly the prepro-alpha (I)-subunit of type I collagen (collagen). The
effects were more pronounced in tibiae than femurs, corresponding to the
greater degree of immobility induced by USN in the former bone. The results
demonstrate that decreased bone formation precedes establishment of disuse
cortical osteopenia in growing rats with no evidence for a change in bone
resorption. Furthermore, the decreased bone formation is associated with,
and may be due to, reduced mRNA levels for matrix proteins and other
important bone proteins.
