Hindlimb unloading in rat decreases preosteoblast proliferation
assessed in vivo with brdu dna incorporation..
Barou, Odile, Sabine Palle, Laurence Vico, Christian Alexandre, Marie
-H[umlaut]al[angstrom]ane Lafage-Proust.
Laboratoire de Biologie du Tissu Osseux, Saint-Etienne University,
France
APStracts 4:0229E, 1997.
Immobilization affects bone formation. However the mechanisms
regulating the decrease in osteoblast recruitment remain unclear. The
aim of our study was to determine in vivo osteoblastic proliferation
after short-term immobilization among the different bone
compartments. 12 Wistar 5-week-old rats were assigned to two groups:
6 tail-suspended animals for 6 days and their 6 age-related controls.
Osmotic minipumps, each containing 40mg bromodeoxyuridine (BrDU),
were implanted intraperitonealy at day 4 until sacrifice.
Histomorphometric measurements found a significant lower bone volume
in primary (ISP, -22%) and secondary spongiosa (IISP, -37%) in
unloaded rats as compared to their age-related controls. BrDU
immunohistochemistry showed that the proliferation capacity of
osteogenic precursors in I SP(-29%), preosteoblasts in II SP (-80%)
and in periosteum, as well as bone marrow cells (-40%) was lowered by
unloading. We demonstrated in vivo for the first time that 6-day
tail-suspension induced a significant decrease in proliferation of
periosteal and trabecular preosteoblasts in I SP and IISP as well as
in bone marrow cells.
Received 13 June 1997; accepted in final form 7 October 1997.
APS Manuscript Number E281-7.
Article publication pending Am. J. Physiol. (Endocrinol. Metab.).
ISSN 1080-4757 Copyright 1997 The American Physiological Society.
Published in APStracts on 29 October 1997