Site- and compartment-specific changes in bone with hindlimb unloading in mature adult rats

S. A. Bloomfield, Matthew Allen, H. A. Hogan, M. D. Delp

Research output: Contribution to journalArticle

94 Citations (Scopus)

Abstract

The purpose of this study was to examine site- and compartment-specific changes in bone induced by hindlimb unloading (HU) in the mature adult male rat (6 months old). Tibiae, femora, and humeri were removed after 14, 21, and 28 days of HU for determination of bone mineral density (BMD) and geometry by peripheral quantitative computed tomography (pQCT), mechanical properties, and bone formation rate (BFR), and compared with baseline (0 day) and aging (28 day) controls. HU resulted in 20%-21% declines in cancellous BMD at the proximal tibia and femoral neck after 28 day HU vs. 0 day controls (CON). Cortical shell BMD at these sites was greater (by 4%-6%) in both 28 day HU and 28 day CON vs. 0 day CON animals, and nearly identical to that gain seen in the weight-bearing humerus. Mechanical properties at the proximal tibia exhibited a nonsignificant decline after HU vs. those of 0 day CON rats. At the femoral neck, a 10% decrement was noted in ultimate load in 28 day HU rats vs. 28 day CON animals. Middiaphyseal tibial bone increased slightly in density and area during HU; no differences in structural and material properties between 28 day HU and 28 day CON rats were noted. BFR at the tibial midshaft was significantly lower (by 90%) after 21 day HU vs. 0 day CON; this decline was maintained throughout 28 day HU. These results suggest there are compartment-specific differences in the mature adult skeletal response to hindlimb unloading, and that the major impact over 28 days of unloading is on cancellous bone sites. Given the sharp decline in BFR for midshaft cortical bone, it appears likely that deficits in BMD, area, or mechanical properties would develop with longer duration unloading.

Original languageEnglish (US)
Pages (from-to)149-157
Number of pages9
JournalBone
Volume31
Issue number1
DOIs
StatePublished - 2002
Externally publishedYes

Fingerprint

Hindlimb Suspension
Bone and Bones
Bone Density
Tibia
Osteogenesis
Femur Neck
Humerus
Weight-Bearing
Femur

Keywords

  • Bone mineral density (BMD)
  • Bone strength
  • Histomorphometry
  • Microgravity
  • Quantitative computed X-ray tomography

ASJC Scopus subject areas

  • Physiology
  • Hematology

Cite this

Site- and compartment-specific changes in bone with hindlimb unloading in mature adult rats. / Bloomfield, S. A.; Allen, Matthew; Hogan, H. A.; Delp, M. D.

In: Bone, Vol. 31, No. 1, 2002, p. 149-157.

Research output: Contribution to journalArticle

Bloomfield, S. A. ; Allen, Matthew ; Hogan, H. A. ; Delp, M. D. / Site- and compartment-specific changes in bone with hindlimb unloading in mature adult rats. In: Bone. 2002 ; Vol. 31, No. 1. pp. 149-157.
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abstract = "The purpose of this study was to examine site- and compartment-specific changes in bone induced by hindlimb unloading (HU) in the mature adult male rat (6 months old). Tibiae, femora, and humeri were removed after 14, 21, and 28 days of HU for determination of bone mineral density (BMD) and geometry by peripheral quantitative computed tomography (pQCT), mechanical properties, and bone formation rate (BFR), and compared with baseline (0 day) and aging (28 day) controls. HU resulted in 20{\%}-21{\%} declines in cancellous BMD at the proximal tibia and femoral neck after 28 day HU vs. 0 day controls (CON). Cortical shell BMD at these sites was greater (by 4{\%}-6{\%}) in both 28 day HU and 28 day CON vs. 0 day CON animals, and nearly identical to that gain seen in the weight-bearing humerus. Mechanical properties at the proximal tibia exhibited a nonsignificant decline after HU vs. those of 0 day CON rats. At the femoral neck, a 10{\%} decrement was noted in ultimate load in 28 day HU rats vs. 28 day CON animals. Middiaphyseal tibial bone increased slightly in density and area during HU; no differences in structural and material properties between 28 day HU and 28 day CON rats were noted. BFR at the tibial midshaft was significantly lower (by 90{\%}) after 21 day HU vs. 0 day CON; this decline was maintained throughout 28 day HU. These results suggest there are compartment-specific differences in the mature adult skeletal response to hindlimb unloading, and that the major impact over 28 days of unloading is on cancellous bone sites. Given the sharp decline in BFR for midshaft cortical bone, it appears likely that deficits in BMD, area, or mechanical properties would develop with longer duration unloading.",
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