Copyright 2003 by Institute of Pharmacology
EFFECTS OF DOXYCYCLINE ON DEVELOPMENTOF CHANGES IN HISTOMORPHOMETRIC PARAMETERS OFBONES INDUCED BY BILATERAL OVARIECTOMY IN RATS
Joanna Folwarczna, Maria Pytlik, Waldemar Janiec
Department of Pharmacology, Medical University of Silesia, Jagielloñska 4, PL 41-200 Sosnowiec, Poland
Effects of doxycycline on development of changes in histomorphometricparameters of bones induced by bilateral ovariectomy in rats. J. FOLWAR-CZNA, M. PYTLIK, W. JANIEC. Pol. J. Pharmacol., 2003, 55, 433–441.
Tetracyclines are considered potential medication for the treatment of
osteoporosis. The aim of the present study was to investigate the effects ofdoxycycline on development of unfavorable changes in bone histomor-phometric parameters induced by bilateral ovariectomy in rats. Doxycyclineat a dose of 20 mg/kg po daily was administered for 28 days to bilaterallyovariectomized and sham-operated 3-month-old Wistar rats. Bone histomor-phometric parameters of the tibia (transverse growth, width of periosteal andendosteal osteoid, area of the transverse cross-section of the diaphysis andarea of the transverse cross-section of the marrow cavity) and the femur(width of epiphyseal and metaphyseal trabeculae, width of epiphyseal carti-lage) were examined.
Bilateral ovariectomy caused symptoms of osteopenia in the rat bones.
Doxycycline counteracted the unfavorable changes in bone structure causedby estrogen deficiency. However, in the sham-operated rats doxycycline it-self induced deleterious effects in the trabecular bone. Key words: doxycycline, ovariectomy, osteoporosis, rat J. Folwarczna, M. Pytlik, W. JaniecINTRODUCTION
cline, IV. Ovariectomized group receiving doxycy-cline.
Doxycycline is a representative of broad-spec-
Bilateral ovariectomy or sham-operation were
trum tetracycline antibiotics, widely used both in
performed under ether anesthesia. A longitudinal
medical and dental practice. Numerous studies de-
incision was made inferior to the rib cage on the
monstrated that apart from their antimicrobial ac-
dorsolateral body wall. The ovaries were exteri-
tivity, tetracyclines exert pleiotropic effects on the
orized, ligated and excised. Rats subjected to the
host organism, leading to inhibition of connective
sham surgical procedure had only the ovaries exte-
tissue breakdown [14]. The most widely recog-
nized of those effects is the ability of tetracyclines
Treatment with doxycycline started three-four
to inhibit matrix metalloproteinases (collagenases,
days after the surgical procedure. Doxycycline (Doxy-
gelatinases) [14]. Tetracyclines incorporate to bones
cyclinum, Polfa, Poland) was administered daily by
and influence bone remodeling. They were re-
oral gavage for 4 weeks as doxycycline hydrochlo-
ported to affect the function of osteoclasts [4, 31,
ride at a dose equivalent to 20 mg/kg of doxycy-
cline daily. The control groups received 0.9% sa-
Tetracyclines are considered potential agents
line in the same volume of 2 ml/kg po daily. The
which could be applicable in the treatment of osteo-
porosis [14]. Although there are also data indicating
One day before the start and on the last day of
disadvantageous effects of tetracyclines on bones
administration of doxycycline or saline, the ani-
[36, 39], the favorable effects of tetracyclines were
mals were given tetracycline hydrochloride (20
described in experimental rickets [18], in osteope-
mg/kg ip) in order to mark the calcification front.
nia in experimental streptozotocin-induced diabetes
The next day, animals were sacrificed and the right
[15, 32] and in prednisolone-induced osteopenia
and left tibial and femoral bones and L-4 vertebra
[13]. Minocycline and a chemically modified tetra-
were prepared. In the isolated bones, mass and
cycline (CMT-8) were reported to exert advanta-
macrometric parameters were determined (length,
geous effects in osteopenia induced by ovariectomy
diameter of the diaphysis in the mid-length).
in rats [33, 43]. Doxycycline is more potent inhibi-
In order to determine the content of mineral
tor of collagenase than minocycline [14].
substances in bones, the L-4 vertebra, left tibia and
Postmenopausal osteoporosis is the most com-
femur were mineralized at the temperature of 620°C
mon type of the bone loss. The main pathogenic
factor of postmenopausal osteoporosis is a hormo-
The right femoral and tibial bones were used to
ne-dependent increase in bone resorption and ac-
prepare histological specimens. From the tibial
celerated loss of bone mass in the first 5–10 years
bone, transverse cross-sections were made, perpen-
after the menopause [26]. The model of bilaterally
dicularly to the long axis, starting from the point
ovariectomized rats mimics the changes occurring
where fibula grows into it. From the femoral bone,
in the skeletal system of postmenopausal women
a longitudinal section of the distal epiphysis was
due to estrogen deficiency [29, 44].
made, in the medial part, in the median plane. The
The aim of the present study was to examine the
sections were ground on the tarnished glass. The
effects of doxycycline on the histomorphometric
first preparation from the tibia remained unstained.
parameters of bones in rats with normal estrogen
The rest of the preparations were stained using the
level (sham-operated) and in rats with estrogen de-
Tripp and MacKay method (without decalcifica-
ficiency (bilaterally ovariectomized).
The histomorphometric measurements were made
MATERIALS and METHODS
using a microscope Optiphot-2 (Nikon), connectedthrough RGB camera (Cohu) to personal computer
The experiments were carried out on three-
(program Lucia G 4.51, Laboratory Imaging), with
month-old female Wistar rats, given distilled water
final magnifications of 200 and 500 times.
to drink and fed a standard diet ad libitum. The ani-
In the unstained preparation, the distance be-
mals were divided into 4 groups (n = 5–8): I. Sham-
tween the tetracycline stripes was measured, on the
operated control group, II. Ovariectomized control
periosteum side and on the marrow cavity side (pe-
group, III. Sham-operated group receiving doxycy-
riosteal and endosteal transverse growth).
DOXYCYCLINE, OVARIECTOMY AND BONE HISTOMORPHOMETRIC PARAMETERS
In the stained preparation of the transverse
Administration of doxycycline at a dose of 20
cross-section of the tibia, the width of the endosteal
mg/kg po daily for 28 days to the sham-operated
and periosteal osteoid was determined. In the longi-
rats resulted in lesser body mass gain and smaller
tudinal preparation from the femur, the width of
mass of the thymus in comparison with the sham-
epiphyseal cartilage and the width of trabeculae in
operated control group. There were no statistically
the epiphysis and metaphysis were measured.
significant changes in the examined parameters of
The area of the transverse cross-section of the
the skeletal system, with the exception of a de-
cortical bone in the tibial diaphysis and the area of
crease in the width of trabeculae in the femoral
the transverse cross-section of the marrow cavity in
epiphysis (by 10.4%, p < 0.05). The bone mineral
the tibia were measured in the stained preparation,
content to bone mass ratio for the L-4 vertebra was
with the use of a lanameter (magnification 50 times).
reduced by 6%. The changes may indicate slight
Results are presented as the mean ± SEM. Sta-
disorders in bone remodeling caused by doxycy-
tistical evaluation was performed using ANOVA
cline. The width of epiphyseal cartilage was insig-
and Student’s t-test for unpaired observations. When
nificantly narrower than that of the sham-operated
ANOVA revealed significant differences (p < 0.05),
further analysis was performed using Student’s
Administration of doxycycline at a dose of 20
t-test for unpaired observations.
mg/kg po daily for 28 days to the ovariectomizedrats did not statistically significantly affect thebody mass gain, mass of the uterus, mass of the
thymus or the examined macrometric parameters ofbones in comparison with the ovariectomized con-
Bilateral ovariectomy caused accelerated body
trol group. Contrary to the ovariectomized control
mass gain, a substantial decrease in the mass of the
rats, in the doxycycline-treated group there were no
uterus (by 75%) and an increase in the mass of the
significant decreases in the bone mineral content to
thymus (by 77%), as well as severe changes in the
bone mass ratio in the examined bones in compari-
skeletal system, in comparison with the group of
son with the sham-operated control group. The ra-
sham-operated control rats (Tab. 1). Significant de-
tios were higher by 3.6%, 4.8% and 5.2% in the
creases in the bone mineral content to bone mass
tibia, femur and L-4 vertebra, respectively, than in
ratios in the examined bones (by 6.5–9.9%) were
the ovariectomized control group. In the tibia, the
observed, indicating a decrease in bone mineral
width of periosteal and endosteal osteoid in the
doxycycline-treated ovariectomized rats statisti-
Although macrometric parameters of the long
cally significantly decreased (by 12.4% and 15%,
bones did not significantly change (data not shown),
respectively, p < 0.01) in comparison with the con-
the loss of estrogen due to ovariectomy affected the
trol group of ovariectomized rats. The transverse
investigated histomorphometric parameters. In the
cross section area of the marrow cavity and the ra-
tibial bone, increases in the width of periosteal and
tio of the transverse cross section area of the mar-
endosteal osteoid (by 16%, p < 0.001, and 9.5%, re-
row cavity to the transverse cross-section area of
spectively) in comparison with sham-operated con-
the diaphysis insignificantly decreased (by 8.3%),
trol rats were observed, which, when confronted
which may indicate the inhibition of the cortical
with an increase in the periosteal transverse growth
bone resorption. In the femur, the width of trabecu-
by 10.6% (statistically insignificant), may indicate
lae in the epiphysis and metaphysis increased by
increased bone formation. An increase (by 7.4%) in
6.6% and 8.1%, respectively, in comparison with
the transverse cross-section area of the marrow
the ovariectomized control group. There was also
cavity in the tibia may be the effect of the intensifi-
an insignificant decrease in the width of epiphyseal
cation of resorption processes in the cortical bone.
The width of trabeculae in the epiphysis and meta-physis of the femur decreased (by 18%, p < 0.01,
DISCUSSION
and 9.8%, respectively) in comparison with thesham-operated control rats, indicating the accelera-
Bilateral ovariectomy caused changes in the rat
tion of bone resorption. The width of epiphyseal
osseous system indicating the accelerated bone
cartilage insignificantly increased.
loss, which were documented by the decreases in
J. Folwarczna, M. Pytlik, W. JaniecTable 1. Effects of doxycycline (20 mg/kg po daily), administered for 4 weeks, on the histomorphometric parameters of bones in rats
II Ovariecto- III Sham-opera- IV Ovariectomi- ANOVA
370.41 ± 35.72 92.51 ± 6.73*** 388.87 ± 48.52 86.04 ± 6.66***
364.90 ± 19.65 645.77 ± 74.29** 265.53 ± 43.85* 607.14 ± 50.70*** p < 0.001
cortical bone in the tibial diaphysis (mm )
Transverse cross-section area of the tibial 0.751 ± 0.066
Transverse cross-section area of the tibial 0.179 ± 0.011
Results are presented as means ± SEM (n = 58). ANOVA and then Students t-test for unpaired observations were used for estima-
tion of statistical significance. NS not significant in ANOVA. * significantly different (t-test) from the sham-operated control group
(I); * p < 0.05, ** p < 0.01, *** p < 0.001. = significant difference (t-test) between the ovariectomized group treated with doxycycline
(IV) and the ovariectomized control group (II); == p < 0.01
the ratios of bone mineral content to bone mass as
increase in the transverse cross-section area of the
well as the investigated histomorphometric para-
marrow cavity in the tibia) was noted.
meters. In the cancellous bone (the trabeculae of
The observed changes are consistent with nu-
the femoral epiphysis and metaphysis), the intensi-
merous previous reports [28, 37, 43]. Estrogen de-
fication of bone resorption was observed. In the
ficiency leads to the increased rate of bone remod-
cortical bone, intensification of bone formation (an
eling (both resorption and formation), because es-
increase in the width of osteoid and transverse bone
trogen decreases a number of remodeling cycles by
growth) and intensification of bone resorption (an
attenuating the birth rate of osteoclasts and osteo-
DOXYCYCLINE, OVARIECTOMY AND BONE HISTOMORPHOMETRIC PARAMETERS
blasts from their respective progenitors [25]. The
inase activity in several rat models, including adju-
imbalance between bone resorption and formation
vant arthritis and periodontal disease [9].
in favor of the former observed in postmenopausal
Tetracyclines also affect the structure and activi-
osteoporosis is due to changes in the working life-
ty of osteoclasts [30, 31, 33, 41]. The influence on
span of osteoclasts and osteoblasts, as estrogen ex-
osteoclasts includes decreasing the ruffled border
erts pro-apoptotic effects on osteoclasts and anti-
area of osteoclasts and inducing retraction of osteo-
apoptotic effects on osteoblasts and osteocytes [25].
clasts, diminishing acid production and diminish-
Recent data indicate that estrogen may exert an in-
ing the secretion of lysosomal cysteine proteinases
hibitory effect on resorption activity of mature os-
(cathepsins), and inhibition of gelatinase activity
teoclasts due to inhibition of organic matrix degra-
[30, 31, 41]. From among proteolytic enzymes se-
dation by cysteine proteinases [27].
creted by osteoclasts into an extracellular resorp-
Administration of doxycycline at a dose of 20
tion lacuna, major roles in degradation of the or-
mg/kg po daily for 4 weeks to the sham-operated
ganic matrix (composed mainly of type I collagen)
rats only slightly affected the investigated parame-
have been suggested to be played by matrix metal-
ters of the skeletal system. There were no changes
loproteinases (particularly MMP-9 – gelatinase B)
in the cortical bone, but the changes were observed
and cysteine proteinases (particularly cathepsin K)
in the cancellous bone (a decrease in the bone mine-
[27]. Recent data suggest that organic matrix de-
ral content/bone mass ratio in the L-4 vertebra and
gradation by osteoclasts is initiated by matrix me-
a decrease in the width of trabeculae in the femoral
talloproteinases and continued by cysteine prote-
epiphysis), which indicate predominance of bone
inases [27]. Tetracyclines in vitro reduced the for-
mation of mature osteoclasts and induced apoptosis
The intensification of bone resorption demon-
of osteoclasts [4]. In in vivo experiments carried
strated in the present study is consistent with our
out on rats, minocycline impaired osteoid tissue re-
previous observation that doxycycline at a dose of
moval as well as a number and resorbing activity of
100 mg/kg po daily, administered to normal control
osteoclasts in a synchronized model of bone re-
rats, intensified bone resorption in the cancellous
modeling [22], and doxycycline suppressed surgi-
and cortical bone [13]. Administration of oxytetra-
cally induced recruitment of osteoclasts [19]. Doxy-
cycline to young rats was reported to cause an inhi-
cycline reduced alveolar bone loss occurring after
bition of mineralization and possibly intensifica-
periodontal surgery in rats and endodontal surgery
in dogs [8]. Tetracyclines inhibited alveolar bone
It should be emphasised that other reports de-
loss in experimental periodontitis induced by Por-
monstrated rather that tetracyclines caused inhibi-
phyromonas gingivalis in rats [5]. Minocycline was
tion of bone resorption. The inhibiting effect on
reported to reduce bone resorption in ovariecto-
bone resorption was demonstrated in vitro [6, 16,
mized aged rats [43, 44]. Doxycycline (100 mg
17] and in vivo [14, 22, 33, 44]. Tetracyclines are
daily for 3 months) decreased urinary excretion of
inhibitors of matrix metalloproteinases, among oth-
hydroxyproline (a bone resorption marker) in early
ers collagenases [14]. Collagenase has been postu-
lated to be involved in bone resorption [43]. Colla-
The increase in the resorbing activity in rat
genase, which is synthesized and secreted by osteo-
bones observed in the present study may be the re-
blasts in response to various hormones and factors,
sult of the used model of the in vivo experiment on
may degrade the barrier of non-calcified osteoid,
rats with normal processes of bone remodeling. In
allowing osteoclasts to reach the mineralized bone
our abovementioned study [13], doxycycline at the
surface lying below and start resorption of bone.
high dose of 100 mg/kg po daily also intensified
The activity of collagenase may limit the rate of
cortical bone formation, an effect not observed in
bone resorption [30]. Several chemically modified
the sham-operated rats in the present study. The
tetracyclines that did not inhibit collagenase were
dose used in the present study seems to be not high
poor inhibitors of bone resorption [4]. Doxycycline
enough to augment bone formation in rats with nor-
is the most potent metalloproteinase inhibitor
among antimicrobial tetracyclines [14]. The dose
Administration of doxycycline (20 mg/kg po
used in the present study (20 mg/kg po daily) was
daily for 4 weeks) to the ovariectomized rats caused
an effective dose inhibiting matrix metalloprote-
an improvement in bone status in comparison with
J. Folwarczna, M. Pytlik, W. Janiec
the ovariectomized control group. Although in the
However, the unfavorable effects of tetracy-
present study doxycycline itself seemed to unfa-
clines on the processes of bone formation were also
vorably affect bone remodeling, it counteracted the
described. For a long time it has been known that
accelerated bone loss caused by ovariectomy, both
tetracyclines exert disadvantageous side effects on
in the trabecular (vertebra) and total (tibia and fe-
the skeletal system, especially of children, leading
mur) bones, normalizing the ratios of bone mineral
to tooth discoloration and slowing of the longitudi-
content to bone mass in the investigated bones.
nal growth of bones [36, 39]. Administration of
Increases in the width of trabeculae in the femo-
doxycycline to young rats reduced the longitudinal
ral epiphysis and metaphysis, in comparison with
bone growth [10] and the content of calcium and
the ovariectomized control rats, may indicate inhi-
phosphorus in bones [12]. Oxytetracycline caused
bition of bone resorption or/and intensification of
the inhibition of calcification of the epiphyseal car-
bone formation in the cancellous bone. In the corti-
tilage in young rats [24]. Long-term administration
cal bone, the width of osteoid was significantly re-
of tetracycline led to disorders of bone growth and
duced. The thinning of the osteoid may indicate
maturation in adult oophorectomized rhesus mon-
either intensification of bone mineralization (im-
keys [36]. Effect of doxycycline on collagen syn-
provement in bone formation) or inhibition of bone
thesis in other cells was different than in bones;
matrix synthesis. As the transverse growth of the
doxycycline inhibited collagen synthesis by bovine
cortical bone in the tibia did not change in compari-
articular chondrocytes cultured in alginate (type II
son with the ovariectomized control group, the
collagen) [3] and in cultured human skin fibro-
former possibility seems to be more probable. Pro-
cesses of bone resorption in the tibia from the side
Estrogen prevents bone loss by blocking the
of the marrow cavity seemed to be inhibited in
production of proinflammatory cytokines in bone
comparison with the ovariectomized control rats.
marrow and bone cells. After natural or surgically
The inhibiting effect on bone resorption observed
evoked menopause, the main consequence of the
in the ovariectomized rats is consistent with many
increased cytokine production in bones is an ex-
abovementioned reports on tetracycline inhibition
pansion of the osteoclastic pool due to the in-
of bone resorption. The intensification of bone for-
creased formation of osteoclasts and prolongation
mation could also play a role in the beneficial effect
of their life-span. Enhanced cytokine production
of doxycycline on the bones of rats with estrogen
leads also to the increased activity of mature osteo-
clasts and increased osteoblastic activity. Among
The intensifying effect of tetracyclines on bone
the cytokines known to be regulated by estrogen
formation was observed in different experimental
are IL-1, IL-6, and TNFa [26]. Tetracyclines were
models, especially in experimentally induced disor-
reported to affect cytokine production. Tetracy-
ders of bone remodeling, for example in osteopenia
clines may protect rodents from lethal endotoxemia
caused by streptozotocin-induced diabetes [2],
and significantly reduce TNFa and IL-1 levels in
prednisolone-induced osteopenia [13] and osteope-
their serum [14]. Minocycline was reported to re-
nia in ovariectomized aged rats [43].
duce the expression of IL-6 mRNA in bones of
The favorable effects of tetracyclines in diabe-
ovariectomized aged rats after marrow ablation
tes-induced osteopenia were connected with im-
[42], indicating that tetracyclines may prevent the
provement of the impaired structure and function
recruitment of osteoclasts by suppressing IL-6 pro-
of osteoblasts, among others an increase in colla-
duction by osteoblasts [29]. A chemically modified
gen synthesis, which was demonstrated using ultra-
tetracycline (CMT-8) reduced the IL-6 gene ex-
structural cytochemical techniques and incorpora-
pression in IL-1 stimulated MC3T3 murine osteo-
tion of 3H-proline to osteoblasts and extracellular
blastic cells in culture [29]. The effects on cytokine
bone matrix [32, 34]. Minocycline increased the
production may contribute to the mechanism of fa-
expression of type I collagen mRNA in bones of
vorable effect of doxycycline on bones of ovariec-
ovariectomized aged rats after marrow ablation
[42]. Tetracyclines also reversed the inhibitory ef-
From among two major groups of proteolytic
fect of periodontal infection on collagen synthesis
enzymes secreted by osteoclasts suggested to par-
(expression of type I and type XII collagen mRNAs
ticipate in organic matrix degradation (matrix me-
talloproteinases and cysteine proteinases), only the
DOXYCYCLINE, OVARIECTOMY AND BONE HISTOMORPHOMETRIC PARAMETERS
activity of cysteine proteinases is regulated by es-
considered. US Food and Drug Administration ap-
trogen [27]. As doxycycline in the present study
proved the use of doxycycline in a subantimicro-
did not inhibit bone resorption in the sham operated
bial dose as an adjunct therapy in adult periodonti-
rats, it is possible that inhibition of the excessive
tis [14]. Long-term administration of doxycycline
bone resorption observed in the ovariectomized
in subantimicrobial dose (20 mg twice daily) in
rats was due to inhibition of secretion of cysteine
adult periodontitis did not result in detrimental shift
proteinases, whose activity might have been in-
in normal periodontal flora nor lead to the coloni-
zation or overgrowth of periodontal or opportunis-
The results of the present study indicating fa-
tic pathogens [7]. It is not known if such dosage
vorable effect of doxycycline on bones of ovariec-
would be safe and effective to inhibit excessive
tomized rats are consistent with the results obtained
in ovariectomized aged rats treated with mino-cycline. Minocycline (about 22 mg/kg daily for8 weeks) caused substantial stimulation of bone
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Athletic Code School District Wauzeka-Steuben 2012-2013 2012-2013 (Changes/Updates/Reminders) • A student’s record for code violations goes into effect immediately upon signing this athletic code, no matter the grade level or age of the athlete and stays with them through high school. • Parents and athletes need to look over the policies and rules for athleti
Gemeindeseite vom 31. Oktober 2008 Gemeinde Sevelen Gemeinderatsverhandlungen vom 27. Oktober 2008 Direkt unter Gemeindewappen platzieren: Null-Stern-Hotel Eine zweite Probenacht findet vom Freitag, 14. November auf den Samstag, 15. November 2008 statt. Dieser Anlass wird vor al em für die Medien lanciert, welche für Berichterstattungen rund um die Welt besorgt sein werden.