A longitudinal analysis of urinary biochemical markers and bone mineral density in STR/Ort mice as a model of spontaneous osteoarthritis.
ABSTRACT To investigate the longitudinal changes both in the urinary concentrations of biochemical markers and in bone mineral density (BMD) during disease progression in the STR/Ort mouse model of osteoarthritis (OA).
Male STR/Ort mice were studied, with CBA mice used as nonarthritic controls. Radiographic evaluation and grading of the knee and measurements of urinary C-terminal crosslinking telopeptide of type II collagen (CTX-II), pyridinoline (Pyr), and deoxypyridinoline were performed between 8 weeks and 40 weeks of age. The BMD of the femoral shaft was measured from 20 weeks to 40 weeks of age and adjusted for body weight. Histologic evaluation and grading were performed at 40 weeks of age. STR/Ort mice were divided into 2 subgroups (STR OA and STR non-OA) based on histologic grading.
No significant differences between STR/Ort and CBA mice were observed for any biochemical marker or BMD at any time point. Urinary CTX-II levels and BMD in the STR OA subgroup were higher than those in the STR non-OA subgroup before radiographic changes of OA were apparent. Higher urinary Pyr levels in the STR OA subgroup were observed at the advanced stage of OA.
Urinary CTX-II could be a useful marker in the early diagnosis and predicting the progression of OA, and urinary Pyr may be a potential marker to assess the severity of OA at an advanced stage. An increase in BMD prior to the establishment of radiographic OA may be related to the induction of OA.
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ABSTRACT: To examine the role of connective tissue growth factor CCN2/CTGF (CCN2) in the maintenance of the articular cartilaginous phenotype, we analyzed knee joints from aging transgenic mice (TG) overexpressing CCN2 driven by the Col2a1 promoter. Knee joints from 3-, 14-, 40-, and 60-day-old and 5-, 12-, 18-, 21-, and 24-month-old littermates were analyzed. Ccn2-LacZ transgene expression in articular cartilage was followed by X-gal staining until 5 months of age. Overexpression of CCN2 protein was confirmed through all ages in TG articular cartilage and in growth plates. Radiographic analysis of knee joints showed a narrowing joint space and other features of osteoarthritis in 50% of WT, but not in any of the TG mice. Transgenic articular cartilage showed enhanced toluidine blue and safranin-O staining as well as chondrocyte proliferation but reduced staining for type X and I collagen and MMP-13 as compared with those parameters for WT cartilage. Staining for aggrecan neoepitope, a marker of aggrecan degradation in WT articular cartilage, increased at 5 and 12 months, but disappeared at 24 months due to loss of cartilage; whereas it was reduced in TG articular cartilage after 12 months. Expression of cartilage genes and MMPs under cyclic tension stress (CTS) was measured by using primary cultures of chondrocytes obtained from wild-type (WT) rib cartilage and TG or WT epiphyseal cartilage. CTS applied to primary cultures of mock-transfected rib chondrocytes from WT cartilage and WT epiphyseal cartilage induced expression of Col1a1, ColXa1, Mmp-13, and Mmp-9 mRNAs; however, their levels were not affected in CCN2-overexpressing chondrocytes and TG epiphyseal cartilage. In conclusion, cartilage-specific overexpression of CCN2 during the developmental and growth periods reduced age-related changes in articular cartilage. Thus CCN2 may play a role as an anti-aging factor by stabilizing articular cartilage.PLoS ONE 08/2013; 8(8):e71156. · 3.53 Impact Factor
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ABSTRACT: This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. The publisher does not give any warranty express or implied or make any representation that the contents will be complete or accurate or up to date. The accuracy of any instructions, formulae, and drug doses should be independently verified with primary sources. The publisher shall not be liable for any loss, actions, claims, proceedings, demand, or costs or damages whatsoever or howsoever caused arising directly or indirectly in connection with or arising out of the use of this material.Journal of Applied Animal Research 04/2011; 0.4(2-39):149-152. · 0.48 Impact Factor
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ABSTRACT: Osteoarthritis is a common joint disease that currently lacks disease-modifying treatments. Development of therapeutic agents for osteoarthritis requires better understanding of the disease and cost-effective in vivo models that mimic the human disease. Here, we analyzed the joints of STR/ort mice, a model for spontaneous osteoarthritis, for levels of inflammatory and oxidative stress markers and measured serum cytokines to characterize the local and systemic inflammatory status of these mice. Markers of low-grade inflammatory and oxidative stress-RAGE, AGE, S100A4, and HMGB1-were evaluated through immunohistochemistry. Of these, AGE and HMGB1 levels were elevated strongly in hyperplastic synovium, cartilage, meniscus, and ligaments in the joints of STR/ort mice compared with CBA mice, an osteoarthritis-resistant mouse strain. These increases (particularly in the synovium, meniscus, and ligaments) correlated with increased histopathologic changes in the cartilage. Serum analysis showed higher concentrations of several cytokines including IL1β, IL12p70, MIP1β, and IL5 in STR/ort mice, and these changes correlated with worsened joint morphology. These results indicate that STR/ort mice exhibited local and systemic proinflammatory conditions, both of which are present in human osteoarthritis. Therefore, the STR/ort mouse model appears to be a clinically relevant and cost-effective small animal model for testing osteoarthritis therapeutics.Comparative medicine 01/2011; 61(4):346-55. · 0.76 Impact Factor
ARTHRITIS & RHEUMATISM
Vol. 62, No. 2, February 2010, pp 463–471
© 2010, American College of Rheumatology
A Longitudinal Analysis of Urinary Biochemical Markers and
Bone Mineral Density in STR/Ort Mice as a Model of
Junichiro Sarukawa, Masaaki Takahashi, Mitsuhito Doi, Daisuke Suzuki, and Akira Nagano
Objective. To investigate the longitudinal changes
both in the urinary concentrations of biochemical mark-
ers and in bone mineral density (BMD) during disease
progression in the STR/Ort mouse model of osteoarthri-
Methods. Male STR/Ort mice were studied, with
CBA mice used as nonarthritic controls. Radiographic
evaluation and grading of the knee and measurements
of urinary C-terminal crosslinking telopeptide of type II
collagen (CTX-II), pyridinoline (Pyr), and deoxypyr-
idinoline were performed between 8 weeks and 40 weeks
of age. The BMD of the femoral shaft was measured
from 20 weeks to 40 weeks of age and adjusted for body
weight. Histologic evaluation and grading were per-
formed at 40 weeks of age. STR/Ort mice were divided
into 2 subgroups (STR OA and STR non-OA) based on
Results. No significant differences between STR/
Ort and CBA mice were observed for any biochemical
marker or BMD at any time point. Urinary CTX-II
levels and BMD in the STR OA subgroup were higher
than those in the STR non-OA subgroup before radio-
graphic changes of OA were apparent. Higher urinary
Pyr levels in the STR OA subgroup were observed at the
advanced stage of OA.
Conclusion. Urinary CTX-II could be a useful
marker in the early diagnosis and predicting the pro-
gression of OA, and urinary Pyr may be a potential
marker to assess the severity of OA at an advanced
stage. An increase in BMD prior to the establishment of
radiographic OA may be related to the induction of OA.
Osteoarthritis (OA) is one of the most common
and disabling disorders in the general population, and its
pathology is characterized by the degeneration of artic-
ular cartilage, sclerosis of subchondral bone, and osteo-
phyte formation. To date, radiographs are generally
used to define these features of OA in clinical practice
and in the research setting (1,2). Osteoarthritic changes
on radiographs, however, are detected in fairly advanced
stages of the disease, and relatively long examination
periods are needed to demonstrate significant changes
on successive radiographs (3). Therefore, it is often
difficult to diagnose OA at an earlier stage and to
monitor the disease status of OA using radiographs
To improve the diagnosis and monitoring of
arthritis, biochemical markers have been developed with
the aim of detecting changes in OA. Two major catego-
ries of molecules are used as biochemical markers of
arthritis: molecules of the extracellular matrix and pro-
teolytic enzymes or cytokines. Most of the molecules of
the extracellular matrix are related to cartilage and bone
metabolism. In particular, proteoglycans and type II
collagen are the major constituents of cartilage, and type
II collagen is localized almost exclusively in cartilage.
Therefore, urinary C-terminal crosslinking telopeptide
of type II collagen (CTX-II) may potentially represent a
specific marker for cartilage turnover (4,5). Pyridinoline
(Pyr) and its minor analog, deoxypyridinoline (D-Pyr),
are major crosslinks of mature collagen (6,7). Urinary
Pyr and D-Pyr have been used as markers of bone
metabolism. Because the tissue distribution of Pyr favors
cartilage in addition to its presence in bone, urinary Pyr
content may serve as a marker of both cartilage and
bone metabolism. D-Pyr is distributed almost exclusively
in the matrix of mature bone (8). Therefore, urinary
Junichiro Sarukawa, MD, Masaaki Takahashi, MD, Mitsuhito
Doi, MD, Daisuke Suzuki, MD, Akira Nagano, MD: Hamamatsu
University School of Medicine, Hamamatsu, Japan.
Address correspondence and reprint requests to Junichiro
Sarukawa, MD, Department of Orthopaedic Surgery, Hamamatsu
University School of Medicine, 1-20-1, Handayama, Higashi, Hama-
matsu, Shizuoka, Postal Code 431-3192, Japan. E-mail: firstname.lastname@example.org-
Submitted for publication September 25, 2008; accepted in
revised form October 9, 2009.
concentrations of Pyr and D-Pyr in patients with OA
may be affected by cartilage degeneration, synthesis of
osteophytes, and sclerosis of subchondral bone (7).
However, the relationship between changes in the levels
of ?1 biochemical marker and the progression of OA
over long-term periods is not yet fully clarified. This
problem stems from 2 reasons; one of these reasons is
the difficulty in diagnosing OA at an early stage, partic-
ularly before the radiographically detectable stage (9),
and the other reason is that changes in the progression
of OA are usually small and relatively long-term in
Over several decades, many animal models have
been developed to investigate the pathology of OA. For
example, degenerative changes can be induced by the
injection of chemicals or by surgical intervention (11–
13). In contrast to these models, STR/Ort mice experi-
ence spontaneous histologic degeneration in the medial
tibial plateau, which closely resembles that in human
OA. Approximately 85% of male STR/Ort mice show
signs of cartilage degeneration by 35 weeks of age (14).
Because the time course for the progression of OA in
STR/Ort mice is much shorter than that in humans, the
use of this model enables us to longitudinally investigate
the relationship between changes in biochemical mark-
ers and the onset and progression of OA in an acceler-
ated time frame.
Many factors, including obesity, previous injury,
and bone mineral density (BMD), have been related to
the pathogenesis of OA. Numerous cross-sectional stud-
ies have examined the relationship between BMD and
OA (15,16). In general, patients with radiographic OA
have higher BMD than individuals without OA; how-
ever, results differ somewhat according to the site of
BMD measurement and the specific joint groups af-
fected by OA. Few data are available on the longitudinal
changes in BMD in patients with radiographic OA.
In this study, we investigated the longitudinal
relationship between changes in the concentrations of
several biochemical markers and the onset and progres-
sion of OA in STR/Ort mice, as well as the relationship
of OA and BMD. We hypothesized 1) that the levels of
some potential biochemical markers change during dif-
ferent stages of OA development and establishment, and
that such changes elucidate cartilage and bone metabo-
lism during OA development, and 2) that high or low
BMD is associated with the development of OA.
MATERIALS AND METHODS
Animals. In this study, 8-week-old male STR/Ort mice
(n ? 22) and 8-week-old male CBA mice (n ? 12; used as
controls) were purchased from Charles River Japan (Yoko-
hama, Japan). The mice were housed individually in standard
mouse cages (room temperature 24°C; 12-hour light/12-hour
dark cycle) with free access to standard mouse food and tap
water. All experiments were performed according to the
protocol approved by the Animal Care and Use Committee of
Hamamatsu University School of Medicine.
Radiographic analysis. Prior to imaging and after
measuring their body weight, the mice were anesthetized by an
intraperitoneal injection of sodium pentobarbital. Radio-
graphs of the left and right knee joints were obtained in lateral
projections longitudinally at 8, 12, 16, 20, 24, 28, 32, 36, and 40
weeks, using a soft x-ray apparatus (M-60; Softex, Tokyo,
Japan). Exposure was for 20 seconds at 30 kV and 5 mA, and
the film was processed using an automatic film developer.
Radiographs were graded according to our original radio-
graphic grading scale for OA progression, as follows: grade 0 ?
no apparent change; grade 1 ? identification of sclerosis of
subchondral bone, or osteophyte formation, or joint space
narrowing (JSN), or calcification of the patellar tendon; grade
2 ? identification of any 2 of the grade 1 features; grade 3 ?
identification of any 3 of the grade 1 features; grade 4 ?
identification of all 4 grade 1 features (Figure 1A). These
features were characteristic of the osteoarthritic changes in
STR/Ort mice observed in previous studies (17–19). The values
for radiographic grading of the left and right knee joints were
averaged for each mouse and used in the statistical analysis.
A single observer who was blinded with regard to the
experimental group evaluated the radiographic grading.
Cohen’s kappa statistics were used to assess the intraob-
server and interobserver agreement of radiographic grading
by 2 readers. The kappa values for intraobserver and
interobserver agreement were 0.73 and 0.71, respectively.
These values are regarded as reliable enough for the method
used in the present study.
Bone densitometry. The BMD of the left and right
femoral shaft was measured longitudinally in all mice at 20, 24,
28, 32, 36, and 40 weeks of age, by dual x-ray absorptiometry
(DXA) with a Hologic QDR-1000 Plus system (Hologic,
Waltham, MA). Because a relatively long period of time is
required to measure BMD, and the mice need to be anesthe-
tized, which sometimes risks death, we avoided measuring
BMD before 20 weeks of age, because it has been reported that
OA developed in STR/Ort mice during the period from 20
weeks to 35 weeks of age (14,20). While under general
anesthesia, the mice were placed in a supine position with the
bilateral hind limb over the scanning surface and the hip, knee,
and ankle articulations in 90° flexion. The foot and proximal
tibia were secured to the machine with tape just outside the
scanning area; scans included the entire femur. In the resulting
scans, the region of interest (ROI) was defined as the femoral
shaft (middle 60% of the total femoral length). The values for
left and right femoral shaft BMD were averaged for each
mouse and used in the statistical analysis. To evaluate the
reproducibility of the DXA technique, the left femoral shaft
BMD of a mouse at 20 weeks of age was repositioned and
measured 7 times on the same day. The coefficient of variation
(CV) for scanning was 1.1%.
Histologic grading of OA. At 40 weeks of age, all mice
were killed, and the whole knee joints of all mice were
dissected and fixed in 10% neutral buffered formalin for 24
464SARUKAWA ET AL
hours. The specimens were decalcified in 10% EDTA for 2
weeks. After dehydration and embedding in paraffin, 10 serial
sections were prepared from the central region of the medial
tibial plateau in the sagittal plane, because it has been reported
that changes in OA occur more pronouncedly in the medial
tibiofemoral compartment than in other compartments of the
knee joints (21). Sections were stained with hematoxylin and
eosin and Safranin O. Grading of OA progression in the
medial tibiofemoral compartment was performed according to
the procedure described by Walton (14) and Schu ¨nke et al
(22), as follows: grade 0 ? no apparent changes, grade 1 ?
superficial fibrillation of articular cartilage, grade 2 ? defects
limited to uncalcified cartilage, grade 3 ? defects extending
into calcified cartilage, and grade 4 ? exposure of subchondral
bone at the articular surface (see Figure 2). The final grade was
determined as the highest grade in all sections, by a single
observer who was blinded with regard to the experimental
group. A mouse was defined as having histologic OA if the
histologic grade for at least 1 knee joint was ?2. Based on
these criteria for histologic OA, STR/Ort mice were further
categorized into 2 subgroups: STR OA (bilateral OA and
unilateral OA) and STR non-OA (no signs of OA). The kappa
Figure 1. A, Typical radiographs of the knees of mice in the lateral projection, representing the grades of radiographic
knee osteoarthritis (OA). The 4 features used in radiographic grading were osteophyte formation (OF), sclerosis of
subchondral bone (SS), calcification of the patellar tendon (CP), and joint space narrowing (JSN). The grades were
defined as follows: grade 0 ? no signs of OA, grade 1 ? identification of 1 of the 4 features, grade 2 ? identification
of any 2 of the 4 features, grade 3 ? identification of any 3 of the 4 features, and grade 4 ? identification of all 4 features.
Bar ? 1 mm. B and C, Time course of the progression of OA by radiographic grading in STR/Ort and CBA mice (B)
and mice in the STR OA and STR non-OA subgroups (C). The values for the radiographic grading of the left and right
knee joints were averaged for each mouse. Bars show the mean and SD. ? ? P ? 0.001 versus CBA; † ? P ? 0.01 versus
STR non-OA; ‡ ? P ? 0.001 versus STR non-OA.
Figure 2. Histologic sections representing the grades of degenerative lesions of articular cartilage. Degeneration of articular
cartilage was evaluated by systematic analysis of knee joints sectioned in a sagittal plane. Tissue sections were stained with
Safranin O and graded as follows: grade 0 ? no apparent changes, grade 1 ? superficial fibrillation of articular cartilage, grade
2 ? defects limited to uncalcified cartilage, grade 3 ? defects extending into calcified cartilage, and grade 4 ? exposure of
subchondral bone. Bar ? 200 ?m.
URINARY BIOCHEMICAL MARKERS AND BMD IN A MOUSE MODEL OF OA 465
values for intraobserver and interobserver agreement of histo-
logic grading were 0.91 and 0.83, respectively. These values are
regarded as reliable enough for this method.
Urine samples. At 8, 12, 16, 20, 24, 28, 32, 36, and 40
weeks of age, urine samples were collected from the mice by
keeping them overnight in metabolic cages for 24 hours. The
samples were centrifuged at 3,000 revolutions per minute for
10 minutes to remove debris, stored in aliquots, and frozen at
?30°C until assayed.
Measurement of urinary CTX-II. Urinary CTX-II lev-
els were measured by enzyme-linked immunosorbent assay
(Urine Pre-Clinical CartiLaps; Nordic Bioscience, Herlev,
Denmark) (5). The standard for CTX-II was a synthetic
peptide (EKGPDP) that was included in the kit. The levels of
CTX-II were corrected for urinary creatinine, measured enzy-
matically on an autoanalyzer (Hitachi, Tokyo, Japan) accord-
ing to the manufacturer’s protocol. The formula for calculating
the concentration was as follows: corrected CTX-II value
(?g/mmole creatinine) ? Urine Pre-Clinical CartiLaps (?g/
liter)/creatinine (mmole/liter). The intraassay and interassay
CVs for CTX-II were 5.7% and 9.4%, respectively.
Measurement of urinary Pyr and D-Pyr. Aliquots of
urine samples were hydrolyzed with an equal volume of 6N
HCl at 110°C for 20 hours. The levels of urinary Pyr and D-Pyr
were measured by high-performance liquid chromatography
directly linked to an automated sample preparation with
extraction columns (ASPEC) system (23). The external stan-
dard for Pyr and D-Pyr was isolated from human cortical bone
(24). In several studies, standards isolated from animal species
different from mice have been used to measure the levels of
urinary Pyr and D-Pyr in mice (25,26). The levels of urinary
Pyr and D-Pyr were corrected for creatinine. The formula for
calculating the concentration was as follows: corrected Pyr or
D-Pyr (nmoles/mmole creatinine) ? Pyr or D-Pyr (nmoles/
liter)/creatinine (mmoles/liter). The intraassay and interassay
CVs for Pyr were 6.4% and 8.3%, respectively, and those for
D-Pyr were 5.9% and 9.5%, respectively.
Statistical analysis. The Mann-Whitney U test was
used to assess differences in radiographic grading between
groups at each time point. Differences in BMD between the 2
groups, adjusted for body weight at each time point, were
assessed by analysis of covariance. A repeated-measures two-
way analysis of variance for urinary biochemical markers
determined whether there was an age effect, a group effect,
and a group-by-age interaction. When a group-by-age interac-
tion was significant, post hoc pairwise comparisons with Bon-
ferroni adjustment were conducted. Spearman’s correlation
coefficients were used to examine the correlation between the
2 measurements. P values less than 0.05 were considered
significant. SPSS version 11.0 statistical software was used for
all analyses (SPSS, Chicago, IL).
Histologic evaluation and categorization into
subgroups. Among the 24 joints of 12 control CBA mice
at 40 weeks of age, 21 joints (87.5%) were histologic
grade 0, and 3 joints (12.5%) were grade 1. Histologic
grades of ?2 were not identified in CBA mice. Among
the 44 joints of 22 STR/Ort mice at 40 weeks of age, 10
(22.7%) were histologic grade 0, 10 (22.7%) were grade
1, 4 (9.1%) were grade 2, 16 (36.4%) were grade 3, and
4 (9.1%) were grade 4. All 22 STR/Ort mice were
further categorized into 2 subgroups, with 16 in the STR
OA subgroup (histologic grade of ?2 for at least 1 knee
joint) and 6 in the STR non-OA subgroup (histologic
grade of 0 or 1 for both knee joints). In the STR OA
group, 9 mice had unilateral OA, and 7 mice had
bilateral OA (Table 1).
Changes in body weight. At the beginning of the
study, the body weights of the STR/Ort mice were
almost equal to those of the CBA mice. Although the
body weights of the STR/Ort and CBA mice increased
throughout the study period, those of the STR/Ort mice
were ?15% heavier than those of CBA mice older than
age 16 weeks. There were no differences in body weight
between mice in the STR OA and STR non-OA sub-
groups throughout the study period (data not shown).
Changes in radiographic grading. The radio-
graphic grades for the CBA mice did not increase
throughout the study period, while those for the STR/
Ort mice increased after 24 weeks of age. The radio-
graphic grades for the STR/Ort mice at 28, 32, 36, and 40
weeks of age were significantly higher (16.4-, 46.8-, 18.3-,
and 7.6-fold, respectively) than those for the CBA mice
(P ? 0.001 for all) (Figure 1B). The radiographic grades
for mice in both the STR OA and STR non-OA
subgroups increased gradually after 24 weeks of age. The
radiographic grades for mice in the STR OA subgroup at
28, 32, 36, and 40 weeks of age were significantly higher
in CBA and STR/Ort mice*
Histologic evaluation and grading of cartilage degeneration
(no. of joints/no. of mice)
no. of joints
STR OA unilateral, no.
STR OA bilateral, no.
* All mice in the STR osteoarthritis (OA) subgroup had OA of grade
?2, based on a histologic grading scale of 0–4 (see Materials and
Methods). STR/Ort mice were further categorized into 2 subgroups:
STR OA (unilateral and bilateral) and STR non-OA (no sign of OA).
466SARUKAWA ET AL
(2.7-, 2.1-, 2.2-, and 2.3-fold, respectively) than those for
mice in the STR non-OA subgroup (P ? 0.004, P ?
0.004, P ? 0.002, and P ? 0.001, respectively) (Figure
1C). The radiographic grading at 40 weeks of age
correlated with the histologic grading at 40 weeks of age
(r ? 0.788, P ? 0.001).
Changes in femoral shaft BMD adjusted for body
weight. In STR/Ort mice, femoral shaft BMD adjusted
for body weight increased gradually from 20 weeks to 28
weeks of age and reached a plateau thereafter. The
adjusted BMD in CBA mice increased gradually
throughout the study period. There were no significant
differences in the adjusted BMD between STR/Ort and
CBA mice at each time point (Figure 3A). In the STR
OA subgroup, the adjusted BMD increased gradually
from 20 weeks to 28 weeks of age and reached a plateau
thereafter. Meanwhile, the adjusted BMD in the STR
non-OA subgroup increased gradually from 20 weeks to
Figure 4. Time course of urinary C-terminal crosslinking telopeptide of type II collagen (CTX-II) levels (A and B), pyridinoline (Pyr) levels (C and
D), and deoxypyridinoline (D-Pyr) levels (E and F) in STR/Ort and CBA mice and mice in the STR osteoarthritis (OA) and STR non-OA subgroups.
All urinary biochemical markers were corrected for creatinine (creat). Bars show the mean ? SD. ? ? P ? 0.001 versus mice younger than age 4
weeks in the STR OA and STR non-OA subgroups; † ? P ? 0.05; ‡ ? P ? 0.01; § ? P ? 0.001, versus STR non-OA.
Figure 3. Time course of femoral shaft bone mineral density (BMD) adjusted for body weight in STR/Ort and
CBA mice (A), and mice in the STR osteoarthritis (OA) and STR non-OA subgroups (B). The values for the left
and right femoral shaft BMD were averaged for each mouse. Bars show the mean ? SD. † ? P ? 0.05; ‡ ? P
? 0.01, versus STR non-OA.
URINARY BIOCHEMICAL MARKERS AND BMD IN A MOUSE MODEL OF OA 467