Full text of DOI:10.1359/jbmr.2002.17.6.1044

JOURNAL OF BONE AND MINERAL RESEARCH
Volume 17, Number 6, 2002
© 2002 American Society for Bone and Mineral Research
Changes in Bone Structure and Mass With Advancing Age
in the Male C57BL/6J Mouse
BERNARD P. HALLORAN,1 VIRGINIA L. FERGUSON,2 STEVEN J. SIMSKE,2 ANDREW BURGHARDT,3
LAURA L. VENTON,1 and SHARMILA MAJUMDAR3
ABSTRACT
To determine whether the mouse loses bone with aging and whether the changes mimic those observed in
human aging, we examined the changes in the tibial metaphysis and diaphysis in the male C57BL/6J mouse
over its life span using microcomputed tomography (␮CT). Cancellous bone volume fraction (BV/TV)
decreased 60% between 6 weeks and 24 months of age. Loss was characterized by decreased trabecular
number (Tb.N), increased trabecular spacing (Tb.Sp), and decreased connectivity. Anisotropy decreased while
the structure model index increased with age. Cortical bone thickness increased between 6 weeks and 6 months
of age and then decreased continuously to 24 months (؊12%). Cortical bone area (Ct.Ar) remained constant
between 6 and 24 months. Fat-free weight reached a peak at 12 months and gradually declined to 24 months.
Total mass lost between 12 and 24 months reached 10%. Overall, the age-related changes in skeletal mass and
architecture in the mouse were remarkably similar to those seen in human aging. Furthermore, the rapid early
loss of cancellous bone suggests that bone loss is not just associated with old age in the mouse but rather occurs
as a continuum from early growth. We conclude that the C57BL/6J male mouse maybe a useful model to study
at least some aspects of age-related bone loss in humans. (J Bone Miner Res 2002;17:1044–1050)
Key words: aging, bone, mouse, osteoporosis, bone structure
and low bone mass.(4–6) However, the question arises as to
whether mice lose bone with age and if so whether the
INTRODUCTION
GE-RELATED BONE loss occurs in both men and women
and is a major underlying cause of osteoporotic frac-
pattern of loss and change in bone architecture is similar to
that in human aging.
A
tures in the elderly.(1–3) Because of the increasing technical
ability to manipulate and study gene expression in the
mouse, there is a growing interest in and use of the aged
mouse as an animal model to study age-related bone loss in
humans. Indeed, because of the remarkable differences in
peak bone mass across mouse strains, much work is now
concentrated on seeking genetic loci associated with high
In humans, peak bone mineral density (BMD) as assessed
by quantitative computed tomography (QCT), and dual-
energy X-ray absorptiometry (DXA) is reached between the
ages of 10 and 19 years.(7,8) However, bone mineral content
(BMC) continues to increase to the age of 30–35 years as a
consequence of continued radial growth of the bone and
increased mineralization.(9) With further aging, BMD and
BMC decrease.(8,10–12) Aging is associated also with struc-
tural changes in bone.(13–22) Cancellous bone volume de-
The authors have no conflict of interest.
1Departments of Medicine and Physiology, University of California and Division of Endocrinology, Veterans Affairs Medical Center,
San Francisco, California, USA.
2Bioserve Space Technologies, University of Colorado, Boulder, Colorado, USA.
3Department of Radiology, University of California, San Francisco, California, USA.
1044

BONE STRUCTURE AND MASS IN THE AGING MOUSE
1045
creases, trabecular number (Tb.N) decreases, trabecular
spacing (Tb.Sp) increases, and cortical bone thins. Trabec-
ular thickness (Tb.Th) remains unchanged or decreases with
age.(16,20–22)
Preparation of bones
At the time of euthanasia the right tibia was removed and
cleaned of adherent tissue. Bones were defatted by sequential
extraction in ethanol and diethyl ether using a Soxhlet appa-
ratus and dried overnight at 95°C, and their length and fat-free
weight were determined before being submitted to ␮CT.
Studies in the female mouse, although limited, generally
show a decrease in bone mass with age.(23–25) Vertebral
mass is reported to peak around midlife (13 months) and
gradually decrease thereafter.(24) Middiaphyseal cortical
thickness and percent cortical area (Ct.Ar) in the femur also
decrease with age. Bone density in the femoral neck peaks
at 12 months and falls by 18% by 32 months.(25) However,
little is known about the structural or architectural changes
that occur in mouse bone during aging other than that
cancellous bone volume decreases. Furthermore, age-
related bone loss in the female mouse is complicated by
estrogen deficiency.(26,27) It is not clear to what extent the
reported changes in bone thickness and mass are a conse-
quence of aging per se or hormone deficiency.
In the male mouse, conventional bone histomorphometry
indicates that cancellous bone volume peaks around 12
months of age and then decreases by nearly 50% by extreme
old age.(24) Bergman et al.(28) report similar findings in the
femur of the Balb/c mouse between 4 and 24 months.
Perkins et al.(29) report that between 6 and 24 months
cortical thickness decreases by ϳ14% in both C57BL/6J
and Balb/c mice. However, data are not available on can-
cellous structure or architecture. Data are available on bone
changes with age in several senescence-accelerated mouse
models but these models do not necessarily represent the
normal course of bone aging.(30,31)
␮CT
The tibias were imaged using ␮CT (␮CT-20; Scanco
Medical AG, Bassersdorf, Switzerland) with a resolution of
18 ␮m in all three spatial dimensions.(34) The scans were
performed starting at the growth plate and extending into
the shaft distally in 18-␮m sections for a total of ϳ120
slices per scan. From this volume, 50 slices below the
growth plate, constituting 0.9 mm in length, were selected
for evaluation. This region of interest was chosen based on
preliminary observations indicating that in the older animals
all of the cancellous bone was found within this volume.
Distal regions were devoid of cancellous bone. The trabec-
ular part of the proximal tibia was identified semiautomat-
ically.(35) The gray-scale images were processed using a
low-pass filter (width of 0.5, support ϭ 1 pixel or kernel
size of 3 pixels) to remove noise, and a fixed threshold was
used to separate the bone and marrow phase. A second
image was obtained along the diaphysis to assess changes in
cortical bone structure. This scan was performed at a reso-
lution of 18 ␮m in all three spatial dimensions and consisted
of 10 18-␮m sections, starting 5 mm proximally from the
tibial-fibular junction. From this volume, six slices were
To determine whether changes in bone structure and mass selected for evaluation.
The bone from 6-week-old animals was less mineralized
occur in the aging male mouse and whether these changes
are similar to those in humans, we studied C57BL/6J male
mice from 1.5 to 24 months of age using microcomputed
tomography (␮CT). The data show that bone in the male
mouse undergoes substantial change with advancing age
and that the changes are remarkably similar to those in
human aging.
(as assessed by the gray-level intensities) than the bone in
older animals, which stayed relatively constant. Thus, a
different threshold was selected for the 6-week group com-
pared with the other age groups, all of which were analyzed
at an identical threshold level. To express the threshold units
in units of hydroxyapatite (HA) rather than arbitrary units,
to enable comparisons for later scans, and between scanners
we scanned a 97% pure HA phantom (BABI-HAP-D;
Berkeley Advanced Biomaterials, Inc., Berkeley, CA, USA)
using the same resolution and imaging set up. The gray level
of the HA was 17973.5, assuming 97% purity and the
density of pure HA to be 3 g/cm3, the threshold selected for
cortical bone was 0.955 gHA/cm3 for the 6-week-old ani-
mals and 1.01 gHA/cm3 for the other age groups, and the
threshold for trabecular bone was 0.584 gHA/cm3 for the
6-week-old animals and 0.743 gHA/cm3 for the others.
From the resulting binarized images of the trabecular re-
gion, structural parameters were computed. Bone volume
fraction (BV/TV), Tb.Th, Tb.N, and Tb.Sp were calculated
with the direct distance transformation method.(36) Using a
triangle meshing technique previously described,(36) degree
of anisotropy (DA)(36) and structure model index (SMI)(37)
were calculated. Connectivity density (Conn.Dn) was deter-
mined using the Euler method.(38)
MATERIALS AND METHODS
Animals
Forty-eight, 4-week-old male C57BL/6J mice (mean life
span, ϳ27 months) were obtained from The Jackson Lab-
oratory (Bar Harbor, ME, USA) and maintained in our
animal colony until they reached 1.5, 3, 5.5, 12, 18, and 24
months of age (n ϭ 8 mice/group).(32,33) Animals were
housed 4–5 mice/cage (Յ5.5 months of age) and 2–3 mice/
cage (Ͼ5.5 months of age) and were maintained on a 12:12
h light-dark cycle with access to water ad libitum and a
standard rodent diet (8640 Harlan Teklad 22/5 [W]; Harlan
Teklad, Madison, WI, USA) containing 1.13% calcium and
0.94% phosphorus. Mice were weighed periodically
throughout the study and killed by cervical dislocation. The
Animal Care and Use Committee at the University of Col-
orado at Boulder approved the protocol for this study.
The cortex was segmented using a low-pass filter and a
fixed threshold as described previously, and from the bina-
rized image cortical area Ct.Ar, medullary area (Me.Ar) and

1046
HALLORAN ET AL.
FIG. 2. Age-related changes in cancellous BV/TV (mean Ϯ SD) in
the proximal tibia. 1p Ͻ 0.001 and 2p Ͻ 0.05 compared with 12 months,
one-way ANOVA, and Dunnett’s test.
FIG. 1. Age-related changes in body weight (mean Ϯ SD).
cross-sectional area (X.Ar) were calculated and averaged months to 3.06 Ϯ 0.40 at 24 months of age (Fig. 4). Mineral
over all slices.
density of the cancellous bone as estimated from the gray
scale appeared to increase from 0.84 gHA/cm3 at 1.5
months to 1.2 gHA/cm3 at 12 months but then remained
relatively constant into old age.
Data analysis
Data are presented as mean Ϯ SD and analyzed using
one-way analysis of variance (ANOVA) and Dunnett’s post
hoc test using the 12-month-old animals as the control
group.
Analysis of the midtibial diaphysis is shown in Fig. 5.
Total bone area increased continuously from 1.5 to 12
months of age. Between 12 and 24 months, no change in
bone area was observed. Cortical thickness increased
from ϳ160 ␮m at 1.5 months to 230 ␮m at 5.5 months
and then decreased continuously to 185 ␮m at 24 months.
Between 12 and 24 months, thickness decreased by 12%.
Cortical bone area increased from 0.43 mm2 at 1.5
months to ϳ0.64 mm2 at 5.5 months and then remained
remarkably constant to 24 months. Me.Ar increased with
age (data not shown). Cortical density, as estimated from
the gray scale, appeared to increase from 1.84 gHA/cm3
at 1.5 months to 1.96 gHA/cm3 at 5.5 months and then
continued to increase gradually to 2.00 gHA/cm3 at 24
months (p Ͻ 0.05).
Three-dimensional images of the cancellous bone and
cross-sectional images of the cortical bone from animals
aged 1.5, 3, 5.5, 12, 18, and 24 months are shown in Fig. 6.
The loss of bone volume and decrease in anisotropy with
age in the cancellous compartment and the increase in
Me.Ar and cortical thinning in the diaphysis with age are
visually apparent.
RESULTS
The change in body weight with age is shown in Fig. 1.
Body weight reached a stable level by 12 months of age and
remained unchanged to 24 months of age.
Quantitative analysis of the proximal tibial metaphysis is
shown in Figs. 2–4. Cancellous bone volume decreased
continuously from 1.5 to 24 months of age (Fig. 2). Using
12 months as a basis from which to measure bone changes
(Dunnett’s test), aging from 12 to 24 months resulted in a
32% decrease in cancellous BV/TV (p Ͻ 0.05). Between 5.5
and 24 months, bone volume decreased by 52% (p Ͻ
0.001). Tb.N also decreased continuously, but the change
between 12 and 24 months was not significant (Fig. 3).
Between 5.5 and 24 months Tb.N decreased by 37% (p Ͻ
0.001). Tb.Sp increased continuously from 1.5 to 24 months
(Fig. 3). Between 12 and 24 months and between 5.5 and 24
months Tb.Sp increased by 41% and 64%, respectively.
Tb.Th increased roughly 18% between 1.5 and 5.5 months
but then remained relatively constant to 24 months (Fig. 3).
Conn.Dn, a measure of trabecular connectedness, decreased
continuously from 1.5 to 12 months, whereas beyond 12
months of age, Conn.Dn remained constant (Fig. 3). An-
isotropy, or the degree of asymmetry in trabecular bone
orientation, decreased from ϳ2.2 (highly oriented) at 5.5
months to 1.65 (less oriented) at 18 months (Fig. 4). The
The total fat-free weight and length of the tibia are reported
in Table 1. Fat-free weight reached a peak at 12 months and
gradually declined to 24 months. Total mass lost between 12
and 24 months reached 10% (p Ͻ 0.01). Length peaked be-
tween 3 and 5.5 months and did not change thereafter.
DISCUSSION
Our results show that both cancellous and cortical bone
SMI gradually increased (p Ͻ 0.02) from 2.76 Ϯ 0.23 at 1.5 undergo dramatic change during growth and aging in the male

BONE STRUCTURE AND MASS IN THE AGING MOUSE
1047
FIG. 3. Age-related changes in Tb.N, Tb.Sp,
Tb.Th, and Conn.Dn (mean Ϯ SD) in the prox-
imal tibia. 1p Ͻ 0.001, 2p Ͻ 0.005, 3p Ͻ 0.01,
and 4p Ͻ 0.05 compared with 12 months, one-
way ANOVA, and Dunnett’s test.
FIG. 4. Age-related changes in trabecular an-
isotropy and SMI (mean Ϯ SD) in the proximal
tibia. 1p Ͻ 0.001, 2p Ͻ 0.005, 3p Ͻ 0.01, and
4p Ͻ 0.05 compared with 12 months, one-way
ANOVA, and Dunnett’s test.
C57BL/6J mouse. They also reveal that the pattern of change significance until late in life when trabeculae undergo a
is remarkably similar to that observed in human aging.
In human aging, cancellous bone volume, Tb.N, and
sharp change from platelike to less platelike.(22)
We observe similar but not identical cancellous bone
Tb.Th decrease and Tb.Sp increases.(13–22) Furthermore, changes in the aging male mouse. Like in humans, cancel-
during the early stages of aging in the human there is a lous volume and Tb.N decrease and Tb.Sp increases with
preferred loss of horizontal trabeculae leading to an increase advancing age. However, unlike reports in the human Tb.Th
in anisotropy.(39) This is followed by a period of trabecular does not appear to decrease with age in the mouse, suggest-
perforation and an eventual decrease in anisotropy. In the ing that bone loss in this model is not a consequence of
human tibia, Tb.Th decreases with age but Tb.N shows only trabecular thinning at least in the proximal tibia. Also,
a small insignificant trend downward.(22) The SMI in the unlike humans, there does not appear to be a preferential
tibia gradually increases but the increase does not reach loss of horizontal trabeculae. Anisotropy decreases in a

1048
HALLORAN ET AL.
FIG. 5. Age-related changes in cross-sectional diaphyseal area (total bone area), cortical thickness, and Ct.Ar (mean Ϯ SD) 5 mm proximal to
the tibial-fibular junction. 1p Ͻ 0.001, 2p Ͻ 0.005, and 3p Ͻ 0.05 compared with 12 months, one-way ANOVA, and Dunnett’s test.
nearly continuous fashion in the mouse. Comparing the SMI
The timing of the changes in bone associated with aging
in humans and mice tibias is revealing. SMI values in the also is remarkably similar in mice and men. In humans, total
human proximal tibia gradually increase from 0.5 to 0.8 bone mass peaks between 30 and 40 years of age or assum-
(relatively platelike) between the ages of 10 and 70 years. ing a life span of 75–80 years, roughly halfway through life.
Between 70 and 90 years, they increase more sharply, We and others find that bone mass in the mouse also peaks
reaching peak values of ϳ1.5. SMI values in the male mouse around midlife (i.e., at 12–13 months).(24) Cancellous bone
are much higher (2.76, rodlike) to begin with and like in volume in the tibia reaches a peak at or before 1.5 months
humans, gradually increase with age (become more rodlike).
(5% of mean life span) in the mouse and then decreases
The differences between the human and mouse with rapidly. Unfortunately, cancellous measurements are lim-
respect to trabecular thinning and loss patterns may repre- ited in children and adolescent humans, but cancellous
sent differences in the mechanisms of bone loss, reflect the volume also may peak relatively early in human life (10–19
influences of dissimilarities in mechanical loading, be con- years or 20% of mean life span).(7,8) The other structural
sequent to differences in skeletal architecture between hu- parameters of cancellous bone have not been studied ade-
mans and C57BL/6J male mice, or be related to differences quately in young humans to make comparisons with mice.
in the skeletal sites analyzed (our data were collected from
The structural changes in cancellous bone that occur with
the tibia whereas most human data have been collected from postmaturational aging in the male mouse are similar to
the vertebrae). Interestingly, the serum concentration of those induced by ovariectomy in the female mouse.(44,45)
testosterone does not decrease with postmaturational aging Using a similar ␮CT approach to measure cancellous struc-
in the C57BL/6J male mouse.(40) Thus, androgen deficiency ture, ovariectomy results in a decrease in cancellous BV/
does not appear to play a role in age-related bone loss in this TV, Tb.Th, Tb.N, and Conn.Dn and an increase in Tb.Sp.
model. Regardless of the mechanisms, the changes in cancel- However, cortical thickness is reported to remain un-
lous bone with age are remarkably similar in humans and mice. changed in the ovariectomized animal.(45)
In contrast, the age-related change in cancellous bone in
the rat is radically different.(41) Vertebral bone volume and examine the different compartments, that is, trabecular and
Tb.Th increase with age and Tb.N remains unchanged. cortical bone, in our aging mouse model. However, it must
The use of ␮CT imaging in this model permits us to
With respect to cortical bone, human aging is associated be noted that the resolution of the ␮CT images was 18 ␮m,
with an increase in X.Ar because of continued periosteal and Tb.Th ranged from 42 to 50 ␮m in this model. Although
growth, a decrease in cortical thickness, an increase in this spatial resolution is ϳ1⁄
3
–1⁄
the trabecular dimensions,
2
cortical porosity, and a decrease in cortical density.(17–19) clearly, higher-resolution images would permit a more ac-
The same changes occur in the tibia from the male mouse curate estimate of the Tb.Th. Thus, the measures of thick-
with the exception of the decrease in cortical density as ness determined in this study may differ from those derived
estimated by the gray scale in our animals. X.Ar increases from histology. In fact, comparative studies between histol-
and cortical thickness decreases. The male mice appear to ogy and ␮CT have established that although there may be
differ from humans only in that cortical density appears to some resolution-dependent effects and ␮CT provides only
increase. This may be caused by the absence of cortical static structural information, compared with the cellular
remodeling in the mouse and the gradual increase in bone function that histology provides, ␮CT is a valid modality for
matrix mineralization that naturally occurs with time.(42,43) assessing trabecular structure in animal models and human
However, decreased density has been reported in the fem- specimens.(45–47) In images in which the spatial resolution
oral neck of female mice.(25) The reason for this discrepancy was lower (i.e., on the order of trabecular bone dimensions),
is not clear but may be related to gender and skeletal site. we have shown that despite the fact that measured param-

BONE STRUCTURE AND MASS IN THE AGING MOUSE
1049
FIG. 6. Representative (median) ␮CT images of the tibial diaphysis 5 mm proximal to the tibial-fibular junction (top) and cancellous bone in
the proximal tibia (bottom) from mice aged 5.5, 12, 18, and 24 months.
TABLE 1. EFFECT OF AGE ON FAT-FREE WEIGHT AND
ACKNOWLEDGMENTS
LENGTH OF THE TIBIA (MEAN Ϯ SD)
This work was supported by the Veterans Affairs Merit
Review program; the Research Evaluation & Allocation
Committee (REAC); and the Academic Senate Committee
on Research (COR) Committees at the University of Cali-
fornia, San Francisco; and the National Institutes of Health
(NIH) grant RO1-AG17762.
Age (months)
Fat-free weight (mg)
Length (mm)
1.5
3.0
5.5
12
18
24
24.3 ϩ 1.8 (p Ͻ 0.001)* 15.7 ϩ 0.3
30.1 ϩ 1.3 (p Ͻ 0.001)* 17.3 ϩ 0.1
34.8 ϩ 1.9
35.5 ϩ 2.5
34.9 ϩ 2.3
17.7 ϩ 0.3
17.9 ϩ 0.3
17.9 ϩ 0.3
17.7 ϩ 0.2
32.0 ϩ 2.2 (p Ͻ 0.01)*
REFERENCES
* One-way ANOVA and the Dunnett’s test, compared with the
1. Ensrud KE, Palermo L, Black DM, Cauley J, Jergas M, Orwoll
ES, Nevitt MC, Fox KM, Cummings SR 1995 Hip and calca-
neal bone loss increase with advancing age: Longitudinal
results from the study of osteoporotic fractures. J Bone Miner
Res 10:1778–1787.
12-month group.
eters in the limited resolution range differ from those
measured from very high resolution images, the correla-
tion between the measures is very good.(48,49) Therefore,
the trends of change in Tb.Th that we observe are clearly
valid, although the absolute magnitude may be prone to a
resolution-based bias. The measures of spacing and other pa-
rameters do not suffer from this resolution-based effect, how-
ever.
Collectively, our data suggest that the changes in skeletal
structure that occur during aging in the mouse are similar to
those that occur during human aging. Therefore, the mouse
may be a useful model to study at least some aspects of
age-related bone loss in humans. However, despite the
similarities in the age-related loss of bone in humans and
mice, the mechanisms responsible for loss may not be
identical. Differences in body mass, skeletal structure, and
life span may influence the dynamics of bone metabolism
and how bone is lost with aging.
2. Riggs BL, Melton LJ 1995 Osteoporosis, 2nd ed. Lippincott-
Raven, New York, NY, USA.
3. Orwoll ES, Bevan L, Phipps KR 2000 Determinants of bone
mineral density in older men. Osteoporos Int 11:815–821.
4. Chen C, Kalu DN 1999 Strain differences in bone density and
calcium metabolism between C3H/HeJ and C57BL/6J mice.
Bone 25:413–420.
5. Turner CH, Hsieh YF, Muller R, Bouxsein M, Baylink DJ, Rosen
CJ, Grynpas MD, Donahue LR, Beamer WG 2000 Genetic reg-
ulation of cortical and trabecular bone strength and microarchi-
tecture in inbred strains of mice. J Bone Miner Res 15:1126–1131.
6. Klein RF, Shea M, Gunness ME, Pelz GB, Belknap JK, Orwoll
ES 2001 Phenotypic characterization of mice bred for high and
low peak bone mass. J Bone Miner Res 16:63–71.
7. Bonjour JP, Theintz G, Buchs B, Slosman D, Rizzoli R 1991
Critical years and stages of puberty for spinal and femoral
bone mass accumulation during adolescence. J Clin Endocri-
nol Metab 73:555–563.
8. Yu W, Qin M, Xu L, van Kuijk C, Meng X, Xing X, Cao J,
Genant HK 1999 Normal changes in spinal bone mineral
density in a Chinese population. Osteoporos Int 9:179–187.

1050
HALLORAN ET AL.
9. Riggs BL 1991 Overview of osteoporosis. West J Med 154:
63–77.
osteoblastogenesis in murine model of accelerated senescence.
J Clin Invest 97:1732–1740.
10. Riggs BL, Wahner HW, Dunn WL, Mazes RB, Oxford KP, Melton 32. Goodrick CL 1975 Lifespan and inheritance of longevity of
inbred mice. J Gerontol 30:257–263.
33. Kunstyr I, Leuenberger HGW 1975 Gerontological data of
C57BL/6 mice. J Gerontol 30:157–162.
34. Ruegsegger P, Koler B, Muller R 1996 A microtomographic
system for the nondestructive evaluation of bone architecture.
Calcif Tissue Int 58:24–29.
LJ 1981 Differential changes in bone mineral density of the appen-
dicular and axial skeleton with aging. J Clin Invest 67:328–335.
11. Kalender WA, Felsenberg D, Louis O, Lopez O, Lopez P, Klotz
E, Osteaux M, Fraga J 1989 Reference values for trabecular and
cortical vertebral bone density in single and dual energy quanti-
tative computed tomography. Eur J Radiol 9:75–80.
35. Laib A, Barou O, Vico L, Lafage-Proust MH, Alexandre C, Ru¨eg-
segger P 2000 3D micro-computed tomography of trabecular and
cortical bone architecture with application to a rat model of immobi-
lization osteoporosis Med Biol Eng Comp 38:326–332.
36. Hildebrand T, Ru¨egsegger P 1997 A new method for the
model independent assessment of thickness in three-
dimensional images. J Microsc 185:67–75.
37. Hildebrand T, Ruegsegger P 1997 Quantification of bone
microarchitecture with the structure model index. Comput
Methods Biomech Biomed End 1:15–23.
38. Odgaard A 1997 Three-dimensional methods for quantifica-
tion of cancellous bone architecture. Bone 20:315–328.
39. Mosekilde L 1993 Vertebral structure and strength in vivo and
in vitro. Calcif Tissue Int 53:S121–S125.
40. Nelson JF, Latham KR, Finch CE 1975 Plasma testosterone
levels in C57BL/6J male mice: Effects of age and disease.
Acta Endocrinol 80:744–752.
41. Barbier A, Martel C, de Vernejoul MC, Tirode F, Nys M, Mocaer G,
Morieux C, Murakami H, Lachertz F 1999 The visualization and
evaluation of bone architecture in the rat using three-dimensional
X-ray computed tomography. J Bone Miner Res 17:37–44.
42. Parfitt AM 1993 Bone age, mineral density and fatigue dam-
age. Calcif Tissue Int 53:S82–S85.
43. Boyde A, Elliot JC, Jones SJ 1993 Stereology and histogram
analysis of backscattered electron images: Age changes in
bone. Bone 14:205–210.
44. Onoe Y, Miyaura C, Ito M, Ohta H, Nozawa S, Suda T 2000
Comparative effects of estrogen and raloxifene on B lypho-
poiesis and bone loss induced by sex steroid deficiency in
mice. J Bone Miner Res 15:541–549.
45. Alexander J, Bab I, Fish S, Muller R, Uchiyama T, Gronowicz G,
Nahounou M, Zhao Q, White D, Chorev M, Gazit D, Rosenblatt
M 2001 Human parathyroid hormone 1–34 reverses bone loss in
ovariectomized mice. J Bone Miner Res 16:1665–1673.
46. Balto K, Muller R, Carrington D, Dobeck J, Stashenko P 2000
Quantification of periapical bone destruction in mice by micro-
computed tomography. J Dent Res 79:35–40.
12. Orwoll ES, Oviatt SK, McClung MR, Deftos LJ, Sexton G
1990 The rate of bone mineral loss in normal men and the
effects of calcium and cholecalciferol supplementation. Ann
Intern Med 112:29–34.
13. Kleerkoper M, Villanueva AR, Stanciu J, Rao DS, Parfitt AM
1985 The role of three dimensional trabecular microstructure
in the pathogenesis of vertebral compression fractures. Calcif
Tissue Int 37:594–597.
14. Parfitt AM 1987 Age-related structural changes in trabecular
and cortical bone: Cellular mechanisms and biochemical con-
sequences. Calcif Tissue Int 36(Suppl 1):S123–127.
15. Parfitt AM 1987 Trabecular bone architecture in the pathogenesis
and prevention of fracture. Am J Med 82(Suppl 1B):68–72.
16. Mosekilde L 1989 Sex differences in age-related loss of ver-
tebral trabecular bone mass and structure. Bone 10:425–432.
17. Garn SM, Sullivan TV, Decker SA, Larkin FA, Hawthorn VM
1992 Continuing bone expansion and increasing bone loss
over a two decade period in men and women from a total
community sample. J Hum Biol 4:57–67.
18. Brockstedt H, Kassen M, Ericksen EF 1993 Age and sex
related changes in iliac cortical bone mass. Bone 14:681–691.
19. Martin B 1993 Aging and strength of bone as a structural
material. Calcif Tissue Int 53:S41–S46.
20. Majumdar S, Genant HK, Grampp S, Newitt DC, Truong VH,
Lin JC, Mathur A 1997 Correlation of trabecular bone struc-
ture with age, bone mineral density and osteoporotic status: In
vivo studies in the distal radius using high resolution magnetic
resonance imaging. J Bone Miner Res 12:111–118.
21. Mosekilde L 1998 The effect of modeling and remodeling on
human vertebral architecture. Tech Health Care 6:287–297.
22. Ding M, Hvid I 2000 Quantification of age-related changes in
the structure model type and trabecular thickness of human
tibial cancellous bone. Bone 26:291–295.
23. Silbermann M, Weiss A, Reznick AZ, Eilam Y, Szydel N,
Gershon D 1987 Age-related trend for osteopenia in femurs of
female C57BL/6 mice. Compr Gerontol A 1:45–51.
24. Bar-Shira-Maymon B, Coleman R, Cohen A, Steinhagen-
Thiessen E, Silbermann M 1989 Age related bone loss in
lumbar vertebrae of CW-1 female mice: A histomorphometric
study. Calcif Tissue Int 44:36–45.
25. Weiss A, Arbell I, Steinhagen-Thiessen E, Silbermann 1991
Structural changes in aging bone: Osteopenia in the proximal
femurs of female mice. Bone 12:165–172.
26. Nelson JF, Felicio L, Osterburg H, Finch C 1992 Differential
contribution of ovarian factors to age-related reduction in
plasma estradiol and progesterone during the estrus cycle of
C57BL/6J mice. Endocrinology 130:805–811.
47. Muller R, Van Campenhout H, Van Damme B, Van Der Perre
G, Dequeker J Hildebrand T, Ruegsegger P 1998 Morphomet-
ric analysis of human bone biopsies: A quantitative structural
comparison of histological sections and micro-computed to-
mography. Bone 23:59–66.
48. Majumdar S, Newitt D, Mathur A, Osman D, Gies A, Chiu E,
Lotz J, Kinney J, Genant H 1996 Magnetic resonance imaging
of trabecular bone structure in the distal radius: Relationship
with X-ray tomographic microscopy and biomechanics. Os-
teoporos Int 6:376–385.
49. Kothari M, Keaveny T, Lin J, Newit D, Genant HK, Majumdar
S 1998 Impact of special resolution on the prediction of
trabecular architecture parameters. Bone 22:437–443.
27. Gee DM, Flurkey K, Finch CE 1983 Aging and the regulation
of LH in C57BL/6J mice. Biol Reprod 28:598–603.
28. Bergman RJ, Gazit D, Kahn AJ, Gruber H, McDougall S,
Hahn TJ 1996 Age-related changes in osteogenic stem cells in
mice. J Bone Miner Res 11:568–577.
29. Perkins SL, Gibbons R, Kling S, Kahn AJ 1994 Age-related
bone loss in mice is associated with an increased osteoclast
progenitor pool. Bone 15:65–72.
Address reprint requests to:
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Veterans Affairs Medical Center 111N
4150 Clement Street
30. Kobayashi Y, Goto S, Tanno T, Yamazaki M, Moriya H 1998
Regional variation in the progression of bone loss in two different
mouse osteopenia models. Calcif Tissue Int 62:426–436.
San Francisco, CA 94121, USA
31. Jilka RL, Weinstein RS, Takahashi K, Parfitt AM, Manolagas Received in original form July 24, 2001; in revised form December
SC 1996 Linkage of decreased bone mass with impaired 4, 2001; accepted January 28, 2002.