Increased local matrix metalloproteinase-8 expression in the periodontal connective tissues of smokers with periodontal disease.
ABSTRACT Matrix metalloproteinase (MMP)-8 has been associated with the progression of periodontitis, a common inflammatory disease of the supporting structures of the teeth, and with other degradative diseases. Tobacco smokers are at high risk of developing periodontitis that may progress more rapidly and respond poorly to treatment. Therefore, MMP-8 expression was determined by immunofluorescence staining in 60 random, computer-selected fields in the excised periodontal tissues of smokers and non-smokers, balanced for age, gender, and periodontal status. Immunofluorescence intensity, representing MMP-8 expression, in the periodontal tissues of smokers (30 fields from 6 subjects, mean 1154+/-124 units) was significantly higher than that in the periodontal tissues of non-smokers (30 fields from 6 subjects, mean 817+/-60 units; p < 0.05). Serum MMP-8 concentrations were measured by ELISA and compared in a larger group of smokers (n = 20) and age- and gender-balanced non-smokers (n = 20). Systemic MMP-8 concentrations in smokers and non-smokers were not significantly different (p > 0.05). A local tobacco-related increase in MMP-8 burden may contribute to periodontal disease progression in tobacco smokers. This finding may also have relevance to other tobacco-induced inflammatory diseases, such as vascular and pulmonary diseases.
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ABSTRACT: Matrix metalloproteinases (MMPs) and serine proteinases seem to be related to tissue destruction in periodontitis. The presence of MMPs in gingival crevicular fluid (GCF) and saliva, however, has not been studied comprehensively with the enzyme-linked immunosorbent assay (ELISA)-technique. We therefore examined the levels of MMP-1, -3, -8 and -9, and their endogenous inhibitor, tissue inhibitor of matrix metalloproteinases (TIMP-1), in GCF and saliva of patients with adult periodontitis (AP) and localized juvenile periodontitis (LJP). Elevated levels of MMP-1 were detected in LJP GCF compared to AP and control GCF. Elevated levels of TIMP-1 were also detected in LJP GCF in comparison to AP and control GCF. Higher MMP-8 levels were detected in AP GCF compared to LJP and control GCF. The relative low levels of MMP-3 were present in all studied GCF samples. Elevated levels of MMP-8 were further detected in saliva of AP compared to LJP and the controls. Both MMP-1 and TIMP-1 were detected in all studied saliva samples, but not significant differences were detected between the studied groups. Our ELISA-results confirm that (i) PMN MMP-8 and MMP-9 are the main collagenase and gelatinase in AP GCF, whereas GCF collagenase in LJP seems to be of the MMP-1-type; (ii) only low levels of TIMP-1, endogenous MMP-inhibitor, are present in AP GCF, which emphasises the importance of doxycycline as a possible adjunctive drug in the treatment of AP patients; (iii) tests based on specific antibodies against PMN MMPs, especially MMP-8, might serve as a reliable method of measuring and monitoring enzyme levels in GCF from different periodontitis patients.Journal Of Clinical Periodontology 01/1997; 23(12):1127-32. · 3.69 Impact Factor
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ABSTRACT: Periodontal inflammation is characterized by irreversible degradation of periodontal ligament collagen fibers leading to loss of tooth attachment. Cultured gingival keratinocytes and fibroblasts express, in vitro, various matrix metalloproteinases (MMPs) which can degrade fibrillar collagens. We hypothesized that several MMPs are also synthesized in vivo by sulcular epithelium, and analyzed the collagenolytic MMPs (MMP-2, -8, -13, and -14) and matrilysin (MMP-7) in gingival tissue specimens and gingival crevicular fluid from adult and localized juvenile periodontitis patients by in situ hybridization, immunohistochemistry, and Western immunoblotting. MMP-2, -7, -8, and -13 were expressed in gingival sulcular epithelium. MMP-7 and -13 were also located in fibroblasts and macrophages, and MMP-8 in neutrophils. MMP-8- and -13-positive cells/mm2 were higher in periodontitis gingiva when compared with healthy control tissue (p < 0.01). In periodontal diseases, gingival sulcular epithelium expresses several, rather than a single, collagenolytic MMPs, and this proteolytic cascade is evidently responsible for the tissue destruction characteristic of adult and juvenile periodontitis.Journal of Dental Research 01/2001; 79(12):1969-77. · 3.83 Impact Factor
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ABSTRACT: The influence of smoking behavior on the periodontal health condition was clinically and radiographically studied in 257 dentally aware adults in the age range 20-69 years, including 50 current smokers, 61 former smokers and 133 non-smokers. The clinical variables to be investigated were frequency of diseased sites > or =4 mm, frequency of gingival bleeding sites and plaque index. In addition, the periodontal bone height was radiographically assessed as a % of the dental root length. All variables were based on full-mouth examinations including all teeth and periodontia. The observations indicated an inferior periodontal health condition associated with smoking. This was evidenced by a significantly greater frequency of diseased sites and a significantly greater reduction of periodontal bone height in current smokers as compared to non-smokers. The condition of former smokers was intermediate between current smokers and non-smokers, suggesting that former smokers who have quit smoking have a better periodontal health condition than current smokers, although worse than that of non-smokers. The finding that former smokers exhibited less disease than current smokers suggests that smoking cessation may be beneficial and mitigate the untoward effects inflicted by smoking, allowing a normalization towards non-smoker conditions. Heavy exposure was consistently associated with more severe a condition than light exposure, suggesting that the relationship between smoking exposure and periodontal morbidity is dose-dependent. Altogether, the present observations identify a negative impact from smoking on periodontal health and provide further evidence that tobacco smoking is an avoidable risk for periodontal disease.Journal Of Clinical Periodontology 01/2000; 27(1):61-8. · 3.69 Impact Factor
Increased local matrix metalloproteinase-8 expression in the periodontal
connective tissues of smokers with periodontal disease
K.-Z. Liua,b,d, A. Hynesc, A. Mand, A. Alsagheerc, D.L. Singerc, D.A. Scotte,⁎
aDepartment of Oral Biology, University of Manitoba, Canada
bDepartment of Pathology, University of Manitoba, Canada
cDepartment of Dental Diagnostics and Surgical Sciences, University of Manitoba, Canada
dInstitute for Biodiagnostics, National Research Council, Winnipeg, MB, Canada
eDepartment of Periodontics, Endodontics and Dental Hygiene, University of Louisville, KY 40292, USA
Received 24 May 2006; accepted 26 May 2006
Available online 22 July 2006
Matrix metalloproteinase (MMP)-8 has been associated with the progression of periodontitis, a common inflammatory disease of the
supporting structures of the teeth, and with other degradative diseases. Tobacco smokers are at high risk of developing periodontitis that may
progress more rapidly and respond poorly to treatment. Therefore, MMP-8 expression was determined by immunofluorescence staining in 60
random, computer-selected fields in the excised periodontal tissues of smokers and non-smokers, balanced for age, gender, and periodontal status.
Immunofluorescence intensity, representing MMP-8 expression, in the periodontal tissues of smokers (30 fields from 6 subjects, mean 1154±124
units) was significantly higher than that in the periodontal tissues of non-smokers (30 fields from 6 subjects, mean 817±60 units; p<0.05). Serum
MMP-8 concentrations were measured by ELISA and compared in a larger group of smokers (n=20) and age- and gender-balanced non-smokers
(n=20). Systemic MMP-8 concentrations in smokers and non-smokers were not significantly different (p>0.05). A local tobacco-related increase
in MMP-8 burden may contribute to periodontal disease progression in tobacco smokers. This finding may also have relevance to other tobacco-
induced inflammatory diseases, such as vascular and pulmonary diseases.
© 2006 Elsevier B.V. All rights reserved.
Keywords: Collagen; MMP-8; Periodontitis; Smoking; Tobacco
The matrix metalloproteinase (MMP) family members are
endogenous calcium- and zinc-dependent enzymes that degrade
many major components of human tissues. MMP-mediated
tissue degradation is essential in embryonic development,
inflammation, wound healing, and all normal processes that
require tissue remodeling. Normally, an inflammatory response
is self-resolving and a balance between MMPs and their
endogenous inhibitors – the tissue inhibitors of matrix metal-
loproteinases (TIMPS) – ensure uncontrolled MMP-mediated
tissue damage does not occur . However, strong evidence
associates inappropriate or prolonged expression of MMPs,
including MMP-8, with the initiation and progression of several
important diseases with major inflammatory components, such
as various vascular diseases [1–3], inflammatory pulmonary
diseases [4–6], and periodontitis [7–10]. Cigarette consumption
is well established as a major risk factor for periodontal disease,
with smokers 2 to 14 times more likely to develop periodontitis
than non-smokers [11–16] and significant improvements in
periodontal healtharenoted on quitting [17,18].The detrimental
effects of smoking on periodontal tissues can be observed even
in young smokers [13,15].
MMP-8 is expressed in periodontal tissues, and has been
reported to be upregulated in the tissues of individuals with
inflammation and periodontitis [8–10]. MMP-8 is considered to
Biochimica et Biophysica Acta 1762 (2006) 775–780
E-mail address: firstname.lastname@example.org (D.A. Scott).
0925-4439/$ - see front matter © 2006 Elsevier B.V. All rights reserved.
represent an appropriate therapeutic target for the prevention
of periodontal disease progression [7,19–22]. Indeed, sub-
antibacterial doses of tetracycline family antibiotics, known
MMP-8 inhibitors, can be effective therapeutic adjuncts for the
treatment of periodontitis [7,23,24]. Furthermore, a chair side
test developed to estimate MMP-8 concentrations in gingival
crevicular fluid has been proposed as a diagnostic tool for active
Neutrophils, which infiltrate periodontal tissues and the
gingival sulcus in large numbers where they function to defend
against plaque bacteria, are a major cellular source of MMP-8
. Tobacco smoke and specific smoke components are
known to activate neutrophils . Additionally, the period-
ontium is a highly vascularized region, and it has been shown
that in vitro cigarette smoke condensate exposure leads to the
upregulation of MMP-8 gene activity in human endothelial cells
Therefore, we hypothesized that tobacco smoke-induced
dysregulation of MMP-8 expression may contribute to the
increased susceptibility of smokers to periodontitis. Local
(periodontal tissues) and systemic (serum) MMP-8 profiles in
smokers and non-smokers were thus examined.
2. Materials and methods
Human MMP-8 Quantikine ELISA kits were purchased from R&D
Systems (Minneapolis, MN, USA). Mouse IgG1anti-human MMP-8 antibody
(clone 115-13D2), normal goat serum, and bovine serum albumin were
obtained from Oncogene Research Products (San Diego, CA, USA). Antibody
monospecific for mouse immunoglobulin G, conjugated with fluoroscein
isothiocyanate was supplied by EMD Biosciences (San Diego, CA, USA).
Super Frost Plus slides were purchased from Fisher Scientific Co. (Ottawa,
ON, Canada). Isopentane, methanol, acetone, Tissue-Tek® O.C.T. compound,
and hematoxylin and eosin (H and E) stain were obtained from VWR
International Ltd. (Mississauga, ON, Canada). InSpeck microsphere image
intensity calibration kits were bought from Molecular Probes, Inc. (Eugene,
2.2. Measurement of systemic MMP-8 concentrations in smokers and
vein from 20 smokers (10 females and 10 males; mean age 37.3, s.d. 10.8 years)
−70 °C and stored until assayedfor MMP-8, as described below. Study approval
was provided by the local ethics committee.
Serum total MMP-8 concentrations were measured by using an MMP-8
ELISA kit. Serum assays were performed in duplicate, according to the
manufacturer's instructions (R&D Systems, Minneapolis, MN, USA). In brief,
samples and MMP-8 standards were added to microplates pre-coated with
antibody specifically recognizing both the pro- and active forms of MMP-8.
Following washing, bound MMP-8 was measured using a horse-radish
peroxidase-conjugated secondary anti-MMP-8 antibody, developed with hydro-
genperoxide andtetramethylbenzidine. Opticaldensity was measured at 450 nm
using a Bio-Rad Model 550 microplate reader and associated Microplate
Manager software (Bio-Rad Laboratories, Mississauga, ON, Canada). The
concentration of total MMP-8 was calculated from a calibration curve using
duplicate standard concentrations of MMP-8. The reported sensitivity of this
ELISA is 0.02 ng ml−1. The mean intra-assay coefficient of variation (CV),
determined by assaying the MMP-8 concentration in three serum samples in
by assaying three serum samples in duplicate in 40 separate assays, has been
in smokers and non-smokers were determined by t-test. Statistical significance
was set at p≤0.05. Serum MMP-8 levels in 60 individuals were found to range
from 5 to 134 ng ml−1by the ELISA manufacturer.
2.3. Periodontal tissue collection and processing
In a separate, smaller group of subjects, periodontal tissue samples were
obtained from specific sites in six smokers (aged 54, 62, 50, 34, 45, and 74
years) and six non-smokers (aged 72, 65, 62, 65, 41, and 75 years) matched for
disease severity and inflammation, as shown in Table 1 . Each site selected
exhibited evidence of periodontal destruction and current, moderate to severe
inflammation, defined by a gingival index of 2 or 3 according to Loe and Silness
. Subjects were in good general health, well schooled in proper oral hygiene
procedures, had previously completed non-surgical treatment, and were
scheduled for clinically necessary surgical treatment at the sites from which
periodontal tissue samples were obtained.
Subjects reporting to be non-smokers at the time of recruitment had their
smoking status validated by analysis of expired-air CO concentrations (PiCO
meter and PiCO Chart software, Bedfont Scientific Ltd. (Rochester, Kent,
UK). Non-smokers were required to exhibit an expired-air CO concentration
of <8 ppm .
During periodontal surgery mid-interproximal periodontal tissue samples
were removed and stored in normal saline until the procedure was completed.
After surgery, the tissues were snap frozen in isopentane, supercooled in liquid
nitrogen, then stored at −80 °C. The frozen specimens (n=12) were embedded
in Tissue-Tek® O.C.T. compound, sectioned consecutively at 10 μm in a
cryostat at −18 °C and mounted on Super Frost Plus slides. The tissue sections
were fixed in pre-cooled mixture solution consisted of methanol and acetone
(3:7) at −20 °C for 20 min. Again, study approval was provided by the local
Expired-air CO concentrations and clinical data from smoking and non-
smoking subjects are presented in Table 1.
2.4. Immunofluorescence staining
Tissue sections were pre-incubated in 10% normal goat serum in PBS in a
moist chamber for 30 min at room temperature, then incubated with mouse IgG1
monoclonal antibody against human MMP-8 (clone 115-13D2) at a working
dilution of 1:100 in PBS containing 1% BSA in a moist chamber at 37 °C for 90
min. This antibody recognizes both pro- and active isoforms of MMP-8.
Sections were washed (3×5 min), and incubated with secondary antibody
monospecific for mouse immunoglobulin G, conjugated with fluoroscein
isothiocyanate diluted in PBS-BSA at a final dilution of 1:100. In adjacent
negative control sections, the primary antibody was replaced by non-immune
goat serum diluted in 3% BSA. The sections were then examined using an
inverted Nikon Eclipse TS100 microscope equipped with Nikon Plan Fluor
Mean and (standard deviation) of expired-air CO concentrations and clinical
data from smoking and non-smoking subjects with chronic periodontitis
Non-smokers (n=6) Smokers (n=6)
Expired-air CO (ppm)
Smoking history (years)
Probing depth (mm)
Clinical attachment loss (mm)
Bleeding on probing (yes)
There were no statistically significant differences in clinical parameters between
smokers and non-smokers.
776K.-Z. Liu et al. / Biochimica et Biophysica Acta 1762 (2006) 775–780
objectives (Nikon, Tokyo, Japan), a Fluor filter set (Omega Optical, Brattleboro,
VT, USA) and a 300 W Xenon light source (Intracellular Imaging Inc,
Cincinnati, OH, USA). Tissue integrity and orientation was confirmed by
conventional hematoxylin and eosin staining of adjacent sections. The contrast
photomicrographs were taken by using an inverted Nikon Eclipse TS100
microscope, illuminated with a pre-centered 6V-30W halogenlamp. A Nikon
Ph1 DL lens was used, while the phase slider was set at 10–20–40 position at
the ELWD condenser.
2.5. Quantification and statistical analyses of immunofluorescence
A total of five optical fields from each sample (10 X magnification)
were randomly selected and captured by using a Cohu 2600 series CCD
camera (Cohu, Inc., Electronics Division, San Diego, CA, USA). InCytel
software (Intracellular Imaging Inc, Cincinnati, OH, USA) was employed for
the capture of fluorescence images. The fluorescence intensity from each
experiment was calibrated using the InSpeck microsphere image intensity
calibration kit (Molecular Probes, Inc., Eugene, OR, USA) as an external
intensity standard. The fluorescence intensities of these digital images were
measured and analyzed using Bersoft Image Measurement software (Bersoft
Inc., Toronto, ON, Canada). Image statistics were calculated based on the
whole image by selecting a consistent threshold in the image throughout the
calculation. Statistical differences between the fluorescence intensities of
smoker and non-smoker tissues were assessed by t-test (Origin 6.1,
OriginLab Corp., Northampton, MA, USA). Statistical significance was set
3.1. MMP-8 expression in periodontal tissues in smokers and
Representative photomicrographs of MMP-8-positive re-
gions of immunofluorescence staining, phase contrast micro-
scopy, and an adjacent hematoxylin- and eosin-stained
periodontal tissue section are shown in Fig. 1. As shown in
Fig.1C,thehighsensitivityofthefluorescence technique canbe
appreciated by the absorption of light at one wavelength with
zero-background, while the high resolution of fluorescence
technique was evidenced by an extremely small number of
fluorescing molecules (as few as 50 molecules per cubic
micron). Phase contrast microscopy allowed correlation of
MMP-8 positive regions with local histological features on the
same tissue section, as shown in Fig. 1B.
H and E staining (Fig. 1A) of an adjacent section revealed
a typical histological constitution of periodontal tissue, i.e.
the gingival epithelium that comprises the epithelial layer
that covers the external surface of the gingival and
underlying connective tissue composed of gingival fibers,
ground substance, and cells, including neural and vascular
elements. Most of the fluorescence labeled-MMP-8 regions
are found in the connective tissue, rather than the epithelial
A comparison of typical sections showing MMP-8-positive
regionsinthe periodontal tissuesofsmokersand non-smokersis
presented in Fig. 2. It is clear that the frequency of MMP-8-
positive regions in the tissues from smokers is higher than that
Measurement software) to quantify the fluorescence intensities
in the sections from both groups immunofluorescence inten-
sities, representing MMP-8 expression, were indeed signifi-
cantly higher in the periodontal tissues of smokers (mean 1154,
s.e. 124 units) compared to that of non-smokers (mean 817, s.e.
60 units; p<0.05), as shown in Fig. 3.
3.2. Systemic MMP-8 concentrations in smokers and
There was no statistically significant difference between the
Fig. 1. Representative photomicrography of hematoxylin and eosin staining (A);
phase contrast (B); and MMP-8-positive fluorescence staining (C); of adjacent
periodontal tissues from a non-smoker with periodontitis.
777K.-Z. Liu et al. / Biochimica et Biophysica Acta 1762 (2006) 775–780
13.9 ng ml− 1) and non-smokers (mean 1.5, s.d. 4.6 ng ml−1;
In the periodontium, in common with other tissues, increased
MMP-8 expression is associated with remodeling of extra-
nents,including collagendestruction [7,25,26,33].Furthermore,
a significant correlation between increased MMP-8 levels and
periodontal disease severity has been suggested . We
hypothesized that the significantly increased susceptibility of
tobacco smokers to the development and progression of perio-
dontitis [11–16] may be due, in part, to tobacco-induced in-
creases in local MMP-8 expression.
Indeed, MMP-8 activity has been found to be modified in
other organs and body fluids in tobacco smokers. For example,
following the induction of suction blisters on the upper arm,
Knuutinen et al.  noted an increased MMP-8 concentration
in the resulting fluid infiltrate in smokers compared to the
infiltrate in non-smokers. In addition, Betsuyaku et al.  have
shown increased MMP-8 and MMP-9 activity in the bronchial
alveolar lavage fluids of smokers with emphysema compared to
those without emphysema. With respect to the MMP-8 burden
in oral tissues and fluids, several studies have addressed the
potential correlation smoking status with MMP-8 concentra-
tions in the gingival crevicular fluid, an inflammatory tran-
speriodontal exudate. Soder et al.  reported a positive
correlation between elastase complexed to α1-antitrypsin and
MMP-8 concentrations in the gingival crevicular fluid of
smokers. However, these authors did not observe any difference
in gingival crevicular fluid MMP-8 levels between smokers and
non-smokers in individuals with various persistent periodontal
diseases. Persson et al.  have reported that MMP-8 levels
remained the same in the gingival crevicular fluid of smokers
following surgical treatment for periodontitis, whereas surgical
intervention resulted in decreased MMP-8 levels in non-
smokers, suggestive of a tobacco-induced MMP-8 burden.
Liede et al.  examined salivary MMP-8 concentrations in
327 smokers and 82 quitters who had taken part in a cancer
prevention study. MMP-8 levels were found to be lower in the
saliva of current smokers than in ex-smokers. It should be noted
that self-reports of non-smoking can often be unreliable .
Therefore, we herein extend the above findings by determining
MMP-8 expression levels directly in the periodontal tissues of
smokers and validated non-smokers exhibiting periodontal
MMP-8 exists as an inactive pro-form with a molecular
weight of approximately 85 kDa. MMP-8 becomes activated by
removal of the amino terminal pro-peptide . The antibody
we used in the present study can detect both pro-(85 kDa) and
active (64 kDa) forms of MMP-8. Therefore, the fluorescing
regions in the periodontal sections reveal both pro- and active
MMP-8. As demonstrated in Fig. 3, in 30 randomly assigned
fields of periodontal tissues of tobacco smokers (n=6), MMP-8
expression is significantly increased compared to expression in
the periodontal tissues of non-smokers (n=6).
By comparing immunofluorescence images with H and E-
stained tissue sections, we were able to determine the distri-
bution of MMP-8 within the periodontal tissues. As evidenced
by Fig. 1, the majority of MMP-8-specific fluorescence was
found in the connective tissues, rather than in the periodontal
epithelium. This statement holds true for both smokers and non-
Fig. 3. Mean (s.d.)aMMP-8-positive fluorescence intensities in the periodontal
tissues of smokers and non-smokers with periodontal tissue destruction.a5 fields
were randomly selected from the connective tissues of each of 6 smokers and 6
Fig. 2. Typical MMP-8-positive fluorescence imaging of periodontal tissues of
a smoker (A) and a non-smoker (B) with periodontitis.
778K.-Z. Liu et al. / Biochimica et Biophysica Acta 1762 (2006) 775–780
smokers, and is consistent with previous reports of MMP-8
immunoreactivity localized to a leukocyte-enriched inflamma-
tory cell infiltration in the connective tissue of human period-
ontitis-affected gingival tissues .
We did not address potential mechanisms by which MMP-8-
specific immunofluorescence is increased in smokers, but this is
an obvious area for future research. Similarly, we did not
examine the cellular sources or specific isoforms of MMP-8 in
the periodontal tissues, or the local expression of tissue inhibi-
tors of matrix. Such information will be important in developing
mechanistic hypotheses to explain the increased immunoreac-
tive MMP-8 found the in the periodontia of smokers.
MMP-8 is considered to be a key mediator of the irreversible
tissue destruction associated with periodontitis. Certainly,
neutrophils are a major cellular source of MMP-8, and a large
and persistent neutrophil influx is a hallmark of inflammatory
periodontal diseases . Additionally, expression of MMP-8
can be induced from several cell types found in the periodontia
by pro-inflammatory mediators such as IL-1 β and TNF-α
[41,42]. Furthermore, specific bacterial proteinases present in
gingival plaque can activate and process the PMN-type MMP-8
to active forms . Therefore, tobacco-induced degranulation
events in neutrophils; tobacco-induced alterations to the
microbial flora; and tobacco-induced increases in pro-inflam-
matory mediator burden could each, theoretically, influence
MMP-8 expression levels in the periodontal tissues of smokers.
Mechanisms of periodontal disease progression may well
differ significantly, or even fundamentally, between smokers
and non-smokers . For example, it is recognized that overt
inflammation is suppressed in the periodontal tissues of
smokers, despite increased susceptibility to periodontitis in
these subjects [44,45]. This is typified by a reduced bleeding
response in the gingival tissues of smokers likely due to a
chronic and reversible suppression of angiogenesis in response
to periodontal bacteria [17,44–46]. Thus, it is important to note
that periodontal tissues used in the present study were taken
from smoking and non-smoking groups that were balanced for
We also examined the systemic MMP-8 burden in a separate,
larger study population (n=40). While a trend towards elevated
serum levels of total MMP-8 was noted in the smokers, standard
deviations were large, and no statistically significant difference
in total MMP-8 concentrations was noted between smokers
(mean 7.8, s.d. 13.9 ng ml− 1) and non-smokers (mean 1.5, s.d.
4.6 ng ml− 1).
In summary, we have shown that there is a localized increase
in MMP-8 expression in the periodontal tissues of smokers.
While we have not shown collagen degradation directly, and we
acknowledge that the number of subjects providing periodontal
tissues was small (n=12), increased MMP-8 expression may
contribute to the increased susceptibility to periodontitis, in-
creased disease progression rates, and poorer response to
treatment known to occur in tobacco smokers compared to
a consequence of increased MMP-8 expression may also have
relevance to other tobacco-induced inflammatory diseases, such
as vascular and pulmonary diseases. Future studies that address
the cellular source of MMP-8; that differentiate MMP-8
isoforms; and that seek to elucidate the mechanisms underlying
a tobacco-related MMP-8 burden in periodontal tissues may be
To conclude, the finding of increased periodontal expression
of MMP-8 in tobacco smokers, compared to non-smokers, adds
further evidence that oral health professionals should be
encouraged to remain active in helping to reduce the burden
of tobacco use in their communities by advocating, advising and
facilitating smoking cessation among their patients.
We are most grateful to Randy Summers of the Institute for
Biodiagnostics, National Research Council, Winnipeg, Canada,
for his statistical advice. This study was funded, in part, by the
Manitoba Medical Service Foundation, and by the Centers for
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