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International Journal of General Medicine 2018:11 155–166
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ORIGINAL RESEARCH
open access to scientific and medical research
Open Access Full Text Article
http://dx.doi.org/10.2147/IJGM.S152873
The vitamin D receptor and the etiology of
RANTES/CCL-expressive fatty-degenerative
osteolysis of the jawbone: an interface between
osteoimmunology and bone metabolism
Johann Lechner1
Jürgen Aschoff2
Tatjana Rudi3
1Clinic for Integrative Dentistry,
Munich, Germany; 2Center for
Integrative Healing, Wuppertal,
Germany; 3Statistics at Institute
for Epidemiological Studies, Berlin,
Germany
Background: Recent research on vitamin D indicates that our current understanding of the
factors leading to chronic inflammation should be revised. One of the key mechanisms by
which microbial immunosuppression occurs is the suppression of one of the most common
endogenous cell nucleus receptors: the vitamin D receptor (VDR). Autoimmune diseases may be
correlated with VDR deactivation (VDR-deac) which occurs when the receptor is no longer able
to transcribe antimicrobial agents. Excess 1,25-dihydroxyvitamin D (1,25D) is not converted to
25-hydroxyvitamin D (25D); thus, high 1,25D levels may be accompanied by low 25D values.
Patients and methods: Since 1,25D promotes osteoclast activity and may thereby cause
osteoporosis, fatty-degenerative osteolysis of the jaw (FDOJ), as described by our team, may also
be associated with VDR-deac. In 43 patients, vitamin D conversion, immune system function
and the quality of bone resorption and formation in the jawbone were related factors that may
enhance chronic inflammatory processes. Here, we examine the relationship between immunology
and bone metabolism among 43 FDOJ patients and those with immune system diseases (ISDs).
Results: We provide a link between FDOJ, RANTES/CCL5 overexpression and VDR-deac.
Conclusion: The clinical data demonstrate the interaction between VDR-deac and proinflam-
matory RANTES/CCL5 overexpression in FDOJ patients.
Keywords: vitamin D receptor; chemokine RANTES/CCL5, osteopathy of the jawbone, immune
system diseases, osteoimmunology
Introduction
The etiology of chronic inflammatory diseases, such as rheumatoid arthritis, multiple
sclerosis, systemic lupus erythematosus and arteriosclerosis, has not been eluci-
dated. It is widely acknowledged that several factors are linked to the development
of such diseases, including genetic predisposition and environmental and dietary
factors. Recently, modern metagenomic research on intra- and extracellular genes
has shown that over the course of centuries, thousands of microbes have succeeded
in establishing themselves permanently in our bodies. A clever mechanism directed
to this end is the deactivation of the vitamin D receptor (VDR); intraphagocytic
bacteria produce ligands that deactivate the VDR. In turn, pathogenic bacteria have
developed mechanisms to alter and evade the host immune response.1,2 In this way,
interleukin (IL)-2 and interferon gamma (IFN-γ) switch off the body’s own innate
immunity which makes possible an immunogenic reaction, particularly in the case
of intracellular microorganisms.3 Researchers have found that autoimmune disease
Correspondence: Johann Lechner
Clinic for Integrative Dentistry,
Gruenwalder Str. 10A, 81547 Munich,
Germany
Tel +49 89 697 0129
Email drlechner@aol.com
Journal name: International Journal of General Medicine
Article Designation: Original Research
Year: 2018
Volume: 11
Running head verso: Lechner et al
Running head recto: VDR and the etiology of RANTES/CCL-expressive FDOJ
DOI: http://dx.doi.org/10.2147/IJGM.S152873
This article was published in the following Dove Press journal:
International Journal of General Medicine
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Lechner et al
markers can be greatly increased in the presence of chronic
mycobacterial infections.4 Advances in detection techniques
using improved genome-based cultivation methods are
highly likely to significantly expand the number of known
pathogens involved in chronic diseases.5–7 It is increasingly
recognized that bacteria can persist as cell wall-deficient
variants (otherwise known as L-forms)5–7 and as “per-
sistent” forms within metagenomic bacterial communi-
ties.8,9 By means of the VDR, 1,25-dihydroxyvitamin D3
(1,25[OH]2D3/1,25D) regulates the immune system which is
present in most immune cell types, particularly monocytes,
macrophages and dendritic cells.10 In general, the innate
immune system is enhanced and the adaptive immune sys-
tem is inhibited by 1,25D.11,12 Thus, an effective immune
response is heavily dependent on the vitamin D endocrine
system which is responsible for balancing inflammatory and
anti-inflammatory processes.13 The VDR transcribes over
1,400 genes which accounts for 4% of all human genes and
which are no longer able to be transcribed when the VDR
is deactivated. The VDR also affects parathormone and
calcium-sensitive receptors and is thus essential for main-
taining well-regulated calcium homeostasis in the bone.
Hence, the VDR is further implicated in systemic disorders
of calcium metabolism, as well as vitamin D utilization
in fatty-degenerative osteolysis of the jawbone (FDOJ).14
Research aims
The purpose of this article was to investigate the extent to
which deactivated VDR (VDR-deac) plays an etiological
role in the development of chronically altered metabolism
in the jawbone in a cohort of patients with immune system
diseases (ISDs). This article also attempts to provide further
insight with respect to the question of whether VDR-deac and
inflammatory cytokine overexpression in FDOJ areas may
function as a reinforcement loop in ISDs.
Materials and methods
The study presented herein was performed as a case-
control study and was deemed to be retrospective in nature.
Approval was granted by Institute for Medical Diagnostics
(IMD)-Berlin forensic accredited Institute DIN EN 15189/
DIN EN 17025. All patients provided their written consent
to participate in this study, and the samples and data were
collected in the course of routine practice, i.e., regular
oral surgery procedures. The study cohort of 43 patients
with FDOJ comprised of five groups consisting of patients
with various specialist-diagnosed ISDs: atypical facial
and trigeminal pain (n=9); neurodegenerative disorders
(multiple sclerosis and amyotrophic lateral sclerosis)
(n=5); tumors (breast cancer and prostate cancer) (n=5);
rheumatism (fibromyalgia and Lyme disease) (n=16); and
chronic fatigue syndrome (n=8). The patients’ average age
was 54.05 years (age range: 23–75 years). There was a
gender ratio (females to males) of 25:18. A control group
comprised of 19 patients without FDOJ, had an average
age of 54 years (age range: 38–71 years) and a gender
ratio (female to male) of 8:11. All patients were seeking
to uncover the etiology of their respective ISDs, including
possibly FDOJ-induced “silent inflammation” of the jaw-
bone. The serum values of 25-hydroxyvitamin D3 (25[OH]
D3/25D) and 1,25D were determined for the cohort. Follow-
ing the clinically necessary excision of FDOJ, conspicuous
FDOJ samples were analyzed for their cytokine content.
Serum vitamin D levels were analyzed in FDOJ group
(n=43). Cytokine levels in the jawbone were analyzed in
FDOJ group (n=43) and the control group (n=19).
The use of medications for the treatment of systemic
diseases was not generally regarded as an exclusion criterion.
Alcohol addiction, fetal alcohol syndrome or abuse of any
other drugs were additional exclusion criteria.15,16 Defined
exclusion criteria consisted of cortisone and bisphosphonate
use due to their effects on bone metabolism as well as cur-
rent or recent use of vitamin D preparations, i.e., within the
previous 14 days. The patients’ serum vitamin D levels were
correlated with the cytokine profiles of FDOJ areas of the
five patient groups.
Serum measurement of 25D and 1,25D
The analysis of 1,25D was carried out by means of the che-
miluminescence immunoassay IDS-iSYS 1,25 VitDXp with
the analytical device iSYS (International Decision Systems,
Minneapolis, MN, USA). The analysis of 25D levels was
carried out using the chemiluminescence immunoassay
LIAISON® 25 OH Vitamin D TOTAL with the LIAISON®
analyzer (DiaSorin, Saluggia, Italy).
Cytokine prole measurement in
jawbone osteolysis
The current treatment for FDOJ lesions consists of bony
cavity curettage.17,18 To elucidate a possible causative link
between FDOJ and VDR-deac at the Munich Clinic for Inte-
grative Dentistry (Munich, Germany), 43 patients with ISDs
who were also diagnosed with FDOJ underwent surgery on
the affected jaw area. Following the administration of local
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VDR and the etiology of RANTES/CCL-expressive FDOJ
anesthesia, the mucoperiosteal flap was folded over and the
cortical layer was removed. All patients exhibited FDOJ
within the bone marrow that was similar to FDOJ samples
described in the literature.19,20 In all 43 cases, surgery was
performed on edentulous jaw areas at the sites of former
wisdom teeth and the adjacent retromolar areas.
In 62 jawbone samples (43 FDOJ samples from the ISD
group and 19 healthy jawbone samples), seven mediating
factors were measured: fibroblast growth factor (FGF)-2,
IL-1 receptor antagonist (IL-1ra), IL-6, IL-8, monocyte
chemotactic protein (MCP)-1, tumor necrosis factor alpha
(TNF-α) and RANTES/CCL5 (R/C). The FDOJ clumps
with a volume of up to ½ cm3 were scooped out (Figure 1
shows a clinical example of their morphology), and these
pea-sized clumps of tissue were immediately placed in a
sterile container (Sarstedt micro-tube; ref. 72.692.005) which
was sealed and stored at –20°C until transportation to the
laboratory (IMD-Berlin, Berlin, Germany). There, the tissue
samples were mechanically comminuted, incorporated with
200 μL of protease buffer (Complete Mini Protease Inhibi-
tor Cocktail; Hoffmann-La Roche, Basel, Switzerland) and
homogenized. The homogenate was centrifuged for 15 min-
utes at 13,400 rpm, after which the supernatant was removed
and centrifuged for another 25 minutes at 13,400 rpm. The
determination of R/C was carried out in the supernatant of
the tissue homogenate using the Human Cytokine/Chemokine
Panel I (MPXHCYTO-60K; Millipore GmbH, Schwalbach,
Germany), according to the manufacturer’s protocol and
using the Luminex 200TM with xPonent® software (Luminex,
Austin, TX, USA).
Statistical analysis
The measured values obtained from the FDOJ and control
cohorts were subjected to descriptive statistical analyses
using SAS 9.4. The median, mean and distribution of the data
were determined to assess whether nonparametric or para-
metric tests were most appropriate. The difference between
the values of FDOJ patients and the general population was
assessed using Student’s t-test. Differences between the two
cohorts were determined using the Wilcoxon–Mann–Whitney
test. The differences between disease groups were tested
with the Kruskal–Wallis test. Statistical significance was
set at a P<0.05.
Results
Distribution of 1,25D and 25D in the
total cohort
For male and female adults, the elderly, and both sum-
mer and winter values, a mean level of 22–111 μg/L was
assumed for cholecalciferol 25D. The mean level of cal-
citriol 1,25D was assumed to be 18–64 ng/L for the same
distribution (standard values were obtained from German
Laborwerte Verzeichnis). In the recent literature,3,21 values
>45 are considered as suspicious, and for this reason the
upper reference value was set to 50 ng/L in our statistical
analyses. As is well known, only one-thousandth of the
amount of 1,25D is present in the blood when compared
to 25D. The distribution of these values in the total study
cohort (n=43) is shown in Figure 2.
The ratio of 25-hydroxy-(cholecalciferol)
and 1,25-dihydroxy-(calcitriol) vitamin
D3 in determining the deactivation of the
vitamin D receptor
We calculated the ratio of 1,25D (measured in ng/L) and 25D
(measured in μg/L) in 43 patients with systemic immunologi-
cal disorders (Figure 2), and clinically verified the presence
of FDOJ according to recommendations presented in the
literature.21 This may pose a problem, as there is a thousand-
fold difference in the concentrations of the two vitamins in
question. The direct detection of VDR-deac is not yet possible
in standard laboratories, however, since it is a cell nucleus
receptor that is found in the mitochondria. In practice, a sim-
ple reliable measurement is necessary to determine the status
of the complex system of vitamin D regulation. It is possible
to infer from the discussion in the relevant literature that a
ratio >1.3 may be considered as a reference value for VDR-
deac.22–24 The hypothesis that the mean value of the ratios in
the FDOJ group is ≤1.3 may be rejected (P<0.001). Further-
more, the descriptive analysis indicates that 34 patients with
ISDs from the FDOJ study cohort (n=43) showed VDR-deac.
As Figure 3 illustrates, in all five disease groups the mean
Figure 1 (A) Red oval shows location of fatty-degenerative osteolysis of the
jawbone; (B) 1:15 scale, morphology of fatty-degenerative osteolysis.
0.6 mm
AB
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Lechner et al
ratio was >1.3. Based on the Kruskal–Wallis test (P=0.6805),
it may be assumed that the main tendencies of the disease
groups do not differ. All the individual groups as well as the
cohort as a whole had values >1.3. This shows that, from the
cohort, VDR-deac was present in 34 patients with ISDs and
clinically verified FDOJ.
Figure 2 Distribution of 1,25D and 25D in the total study cohort (n=43).
Abbreviations: 1,25D, 1,25-dihydroxyvitamin D3; Def, deciency; 25D, 25-hydroxyvitamin D3.
1,25-Dihydroxy-Vit D: reference range 18–64 ng/L in serum
25-Hydroxy-Vit D: reference range 22–111 µg/L in serum
100
Def 25D
Def 1,25D Elevated 1,25D
Elevated 25D
3020 5040 7060 9080 110100 130120 150140
10
0
30
20
50
40
70
60
90
80
110
100
130
120
140
170 180160
Figure 3 In all ve disease groups, the 25D value is above the minimum threshold while the 1,25D value falls within the standard range. (Vitamin D values are shown as mean
values.) The distribution of the VDR ratio is greater than the assumed maximum of 1.3 (×10 in the graph) in all ve disease groups.
Abbreviations: 1,25D, 1,25-dihydroxyvitamin D3; 25D, 25-hydroxyvitamin D3; VDR, vitamin D receptor; MV, medium values; MS, multiple sclerosis; CFS, chronic fatigue
syndrome; Afp/TrigMS, atypical facial pain/trigeminal myofacial symptoms; Rheuma, rheumatic; norm, normal.
23 21 22 24 22
30
50
111
56.53
47.97
47.08
34.6
56.73
36.24
77.08
41.36
65.44
92
16
0
20
40
60
80
100
120
MV MS
(n=5)
Ratio
<13 (=1.3
×10)
MV Tumor
(n=5)
MV CFS
(n=8)
MV Rheuma
(n=16)
MV
Afp/TrigMS
(n=9)
Maximal
Norm
Minimal
Norm
Ratio 1,25-dihydroxy-Vit D:
25-hydroxy-Vit D ×10
1,25-Dihydroxy-Vit D (ng/L)
in serum
25-Hydroxy-Vit D (g/L)
in serum
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VDR and the etiology of RANTES/CCL-expressive FDOJ
Multiplex assay analysis of FDOJ
The multiplex assay analysis of the control group of 19
healthy jawbone samples indicated the following three
cytokines (in pg/mL): IL-1ra, 195.5 (SD ±569); FGF-2,
27.6 (SD ±59); and R/C, 149.9 (SD ±127). There were no
corresponding values found in the literature for these media-
tors in healthy jawbone. The mean values obtained for the
FDOJ cohort were noticeably higher than for the group of
healthy jawbone samples (in pg/mL): FGF-2, 622.8; IL-1ra,
616.6; and R/C, 4,590.8 (SD ±2,536.35). In Figure 4, the
hyperactivated signal transduction of R/C in the 43 FDOJ
samples of the cohort is shown (red bars) in comparison to
the 19 healthy jawbone samples (blue bars). Of particular
note, IL-6, IL-8 and TNF-α have extremely low values. These
cytokines are regarded as the “ignitors of humoral defense”,
and their absence may explain the cryptic and asymptomatic
character of FDOJ.
The cytokine profiles obtained from the FDOJ areas of
all five groups demonstrate a common pattern (Figure 5): on
one hand, there is a total paralysis of the immune system; on
the other, there is a one-sided derailment of FGF-2, IL-1ra
and MCP-1, and, in particular, the extreme overexpression
of R/C in all five ISD groups.
RANTES/CCL5 expression and the
vitamin D ratio
Based on the aims of this study, the correlation (value =0.13)
was calculated between R/C expression in the FDOJ samples
and VDR-deac. Using Spearman’s correlation, it was found
that this relationship was not significant (P=0.39). The scat-
ter plot diagram between R/C and VDR-deac is shown in
Figure 6. (See the “Limitations” section for various possible
causes.)
Discussion
The discussion of the study findings presented addresses four
factors concerning the possible etiological contribution of
ISDs: the serum content of 1,25D (ng/L); the serum content
of 25D (μg/L); the resulting calculated ratio; and the over-
expression of R/C (in pg/mL) in FDOJ. As noted previously,
microbes – including Mycobacterium tuberculosis, Borrelia
and Epstein-Barr virus (EBV) – downregulate VDR activity.
In the event, thereby, that the physiologically active 1,25D
form exceeds normal values, this may result in a correspond-
ing reduction of 25D. Consequently, more vitamin D experts
are beginning to reconsider vitamin D supplementation
among the general population.25
Serum levels of 1,25D and 25D in the
FDOJ cohort
Despite the recent surge in vitamin D supplementation, the
number of cases of chronic diseases has increased and is
expected to continue to rise.26 Interpretation of the results
presented in Figure 3 provides further supporting evidence
with respect to this phenomenon. The FDOJ–ISD cohort
exhibit the following relationships: the mean value of 1,25D
Figure 4 Comparison of the levels of seven cytokines obtained from 19 healthy jawbone samples with those from FDOJ samples from 43 patients with ISDs.
Abbreviations: FDOJ, fatty-degenerative osteolysis of the jaw; ISD, immune system disease; TNF-α, tumor necrosis factor alpha; MCP-1, monocyte chemotactic protein-1;
IL, interleukin; IL-1ra, IL-1 receptor antagonist; FGF-2, broblast growth factor-2; Norm, normal.
0 500
FGF-2
IL-1ra
IL-6
IL-8
MCP-1
TNF-α
RANTES/CCL5
1,000
622.8
616.6
202.4
101
231.1
7.5
132.5
20.3
6.3
149.9
4,756.8
11
27.6
196.5
1,500 2,500
pg/mL
2,000 3,000 3,500 4,000 4,500
Mean-FDOJ
Mean-Norm
5,000
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Lechner et al
of 71.11 ng/L (SD ±36.0) exceeds the maximum normal
reference value of 50 ng/L. At the same time, the mean value
of 25D of 41.4 μg/L (SD ±36.0) falls in the lower part of the
reference range of 111–22 μg/L (Figure 3). Accordingly,
an excess of the active hormone 1,25D, in contrast to 25D,
is present. Autoimmune diseases often correlate with high
1,25D values and low 25D values (which is associated with
a presumed “vitamin D deficiency”), and this is also the case
in the FDOJ study cohort exclusively affected by ISDs: low
25D levels are inversely correlated with high 1,25D levels.
Figure 5 Distribution of seven cytokines in the FDOJ samples obtained from ve disease groups: atypical facial and trigeminal pain (n=9); neurodegenerative disorders
(multiple sclerosis and amyotrophic lateral sclerosis) (n=5); tumors (breast cancer and prostate cancer) (n=5); rheumatism (bromyalgia and Lyme disease) (n=8); and
chronic fatigue syndrome (n=8). There was signicant overexpression of R/C in all groups; there were no statistically signicant differences between the individual groups
(Kruskal–Wallis).
Abbreviations: FDOJ, fatty-degenerative osteolysis of the jaw; R/C, RANTES/CCL5; TNF-α, tumor necrosis factor alpha; MCP-1, monocyte chemotactic protein-1;
IL, interleukin; IL-1ra, IL-1 receptor antagonist; FGF-2, broblast growth factor-2; Norm, normal; CFS, chronic fatigue syndrome; Afp-Trig, atypical facial pain-trigeminal
Neuralgia; NeuroDeg, neurogenerative diseases.
TNF-
RANTES/CCL5
pg/mL
RANTES/CCL5
Norm
MCP-1IL-8IL-6
CFS (n=8)
Rheumatic (n=16)
Tumor (n=5)
NeuroDeg (n=5)
Afp-Trig (n=9)
IL-1raFGF-2
0
1,000
2,000
3,000
4,000
5,000
6,000
Figure 6 Correlation (value/r=0.13) between R/C expression in the FDOJ samples and the VDR-deac levels. Spearman’s correlation coefcient is not signicant (P=0.39).
Abbreviations: R/C, RANTES/CCL5; FDOJ, fatty-degenerative osteolysis of the jaw; VDR-deac, VDR deactivation.
2,000
0
1
2
3
4
5
6
4,000
Vitamin D quotient
6,000
RANTES (pg/mL)
8,000 10,000
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VDR and the etiology of RANTES/CCL-expressive FDOJ
Consistent with the disease patterns exhibited by the FDOJ
cohort, abnormally low levels of the metabolite 25D are asso-
ciated with general mortality and an increased incidence of
at least 40 different chronic infections.27 Certainly, vitamin D
intake is often purported to confer immunosuppressive
effects. For instance, according to Arnson et al, “Vitamin D
affects the immune system on many levels and via a number
of mechanisms. Vitamin D has several immunosuppressive
properties and, on the whole, has such an effect”.28
The phenomenon of deactivation of
vitamin D receptor
The clinical evidence available for a wide range of autoim-
mune diseases shows that the innate immune function can
be induced by restoring VDR function.29 Bacteria-induced
ligands of the VDR deactivate this function. The infiltration
of microorganisms into the cell is known to occur in the case
of viruses. It is less known, however, whether bacteria can
migrate into the cell by shape changing. The conversion of
bacteria into so-called “cell wall-deficient forms” is a condi-
tion for their uptake within the cells. The bacteria that most
effectively infiltrate the cells at the VDR are well-known
agents of chronic infections (e.g., tuberculosis; borelliosis;
Chlamydia infections; infections caused by all forms of
herpes virus, EBV, cytomegaly virus; and Aspergillus sp.
infections). Intracellular bacteria can modulate cytokine
production30 and in monocytes and macrophages cytokine
activation markedly inhibits 1,25D/VDR gene transcrip-
tion. Capnines are the active substances produced by these
microbes and are capable of disabling the VDR. If VDR-deac
is present, it is increasingly likely that the body will not attack
its own tissues in autoimmune diseases; rather, antibodies are
produced that are directed against certain parts of the metage-
nome communities of microbes.31 Intracellular microbes
living in nuclear cells can interfere with DNA transcription
and repair mechanisms, allowing them to trigger many of the
dysfunctions associated with autoimmune diseases. Microbe
immunosuppression succeeds as a result of VDR suppres-
sion.32 Defects in VDR signal transduction have previously
been associated with bacterial infections and chronic inflam-
mation.33 As early as 2010, Proal et al31 reported that VDR
influences at least 1,400 genes, many of which are associated
with autoimmune disorders and cancer.34 In 2005, Wang et al35
used in silico emulation to demonstrate that the sulfonolipid
capnin, which is created by the biofilm bacterial species of
the genera Cytophaga, Capnocytophaga, Sporocytophaga
and Flexibacter, could bind to the VDR and thereby reduce
its activity.33 Published models predict that as the increased
concentrations of 1,25D accumulate in the nucleated cells,
they will increasingly occupy the ligand-binding pockets of
these receptors, thus displacing their endogenous ligands.36
The connection between deactivated
VDR and FDOJ: disrupted vitamin D
metabolism and pathological morphology
in the jawbone
Mandibular bone remodeling is mediated by inflammatory
factors such as cytokines and chemokines. Collectively, our
data strongly point toward R/C being an important molecule
for communication between osteoclasts and osteoblasts,
and shed new light on the functions of these chemokines in
osteoblast biology. Vitamin D and its receptor metabolism
also play an important role in bone resorption in immune-
mediated osteoporosis. In the case of FDOJ, previously
documented by our team,14 questions arise concerning not
only the effects but also the systemic causes of local areas of
FDOJ. Our data show that there is no statistically significant
correlation between FDOJ severity, expressed by the overex-
pression of R/C, and VDR-deac. Nevertheless, the presence
of VDR-deac in 34 FDOJ–ISD patients (79% of the study
cohort), in addition to insufficient wound healing and chronic
cytokine stimulation by root-filled teeth,37,38 may provide
further answers with respect to the disorders of jawbone
metabolism that arise in FDOJ. The aforementioned effects of
VDR-deac may provide a further explanation for the chronic
“silent inflammation” in the jaw, here referred to as FDOJ,
that we have repeatedly reported.14,18,37 At the same time, the
chemokine R/C is partly responsible for many ISDs – rheu-
matism, breast cancer, Hashimoto’s thyroiditis, melanomas,
multiple sclerosis, Amyotrophyic lateral sclerosis and so on;
it serves as a key pathogenic element, being overexpressed
by up to 35-fold in the affected jaw area.
We consider, therefore, the research findings of VDR
deactivation in the development of FDOJ to be illuminating.
VDR-deac also alters the balance of vitamin D-controlled
metabolism in the jawbone which can lead to osteolysis of
the trabecular structures and to the fatty transformation of
medullar spaces. Morphologically, FDOJ thus presents as
fatty clumps (Figures 1 and 7). The medullary bone lesion
evident in FDOJ is microscopically similar to aseptic, isch-
emic osteonecrosis.17 FDOJ appears to represent the transition
between the acute inflammation of a surgical dental wound
and a chronically inflamed, disturbed area of the jaw.
Bisphosphonate-related osteonecrosis of the jaw
(BRONJ) has been increasingly suspected as a potential
complication of bisphosphonate therapy, and the controversy
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Lechner et al
with regard to the association between osteonecrosis of the
jaw and bisphosphonates is a recent and growing problem.
While FDOJ is normally painless and without visible bone
loss, BRONJ is characterized by bone death wherein bone
is destroyed in the course of turnover.41 In contrast, the
upregulation of R/C secretion from osteoblasts in response
to the metabolism of FDOJ promotes osteoclast migration,
but may also induce migration of additional preosteoblasts to
the resorption site via a paracrine mechanism.42 In this way,
the process of bone modeling in the case of FDOJ is derailed
but not connected to bone loss.
Systemic signal transduction by
hyperactivated RANTES/CCL5 from
FDOJ areas
At the cellular level, chronic inflammation is characterized
by the infiltration of immunoinflammatory cells into the
target tissue which usually precedes tissue damage. In areas
of chronic inflammation, the production of cytokines by
infiltrating and local tissue cells overwhelms and exceeds the
regulatory mechanisms resulting in direct or indirect tissue
destruction via the activation of immune and inflammatory
cells. An imbalance between cytokines and their respective
inhibitors is characteristic of chronic inflammatory states.
Cytokines are involved in the induction of acute inflam-
matory events and later in the transition or persistence of
chronic inflammation. This means that cytokine-producing
mechanisms must be controlled in order to maintain healthy
conditions.39 FDOJ exhibits a metabolic derailment and an
associated chronic inflammatory input in the affected jaw
region, which overexpresses R/C by up to 35 times. This
compromises the maintenance of regular cell signaling,
thus causing persistent immune-mediated, metabolic and
hemodynamic disturbances. These chronic stimuli can
progress into diseases associated with local inflammation
such as rheumatism, neurodegenerative diseases, tumors,
chronic fatigue syndrome and facial pain (Figures 4 and 5).
FDOJ is characterized by these metabolic and immunologic
dysfunctions, with both adipocytes and macrophages being
important cellular sensors and also effectors of metabolic
derailments in bone metabolism. FDOJ constitutes its own
unique inflammatory phenomenon, since the cell response
is not bacterially or virally triggered but rather is initiated
by persistent metabolic derailments. The entity responsible
for these abacterial and aviral cell responses is primarily the
proinflammatory chemokine (R/C). As a result, systemically
relevant, dysregulated “signaling pathways” are activated
as shown in the five groups of ISDs described in this study.
Systemic cross-linking of VDR
deactivation and osteolysis in the
jawbone
Mice lacking the cathelicidin gene, which is reliably tran-
scribed by the VDR, exhibit longer wound-healing times
than their wild types.33 This effect is regulated by the VDR
only in humans and non-human primates, as the mouse cat-
helicidin gene does not possess a VDR binding site at the
promoter.34 Thus, VDR-deac has a negative effect on wound
healing. It may, therefore, be medically and systematically
necessary to study the relationship between VDR-deac and
bone metabolism in FDOJ. A previous study investigating
the relationship between R/C and 1,25D levels established
yet a further connection: R/C secretion from osteoblasts was
inhibited by hormones such as 25D and dexamethasone.42
This means that if the effect of 1,25D is switched off intra-
cellularly (i.e., if VDR-deac is present), the R/C level would
increase with a potentially negative immunomodulating effect
on ISD. High 1,25D values promote osteoclast activity.43 The
fact that excess 1,25D contributes to the successive formation
of FDOJ corresponds with the observation that FDOJ and
“vitamin D deficiency” are related. The research has shown
that in response to 1,25D, normal osteoclasts increase their
production of acid hydrolases and subsequently increase their
cell count. This means that osteoclast-mediated bone resorp-
tion is increased as a function of 1,25D. High 1,25D values,
in turn, are the result of chronic inflammation in conjunction
with VDR-deac. Therefore, it is the chronic inflammatory
process itself that causes osteoporosis and not “vitamin D
deficiency”. Low 25D values are only a consequence of the
aforementioned contexts. Attempts to promote healing in
Figure 7 (A) A cluster of dead fatty cells (white arrow) with small inammatory
cells observed in the medullary cavity of the jaw. (B) An FDOJ tissue sample with
complete fatty transformation of the cancellous portion of the jawbone (blue arrow).
Abbreviation: FDOJ, fatty-degenerative osteolysis of the jaw.
AB
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VDR and the etiology of RANTES/CCL-expressive FDOJ
FDOJ cases with excessive vitamin D supplementation are
thus immunologically counterproductive. From the interrela-
tions cited in the present study, it may be concluded that VDR-
deac is a possible cause of the severe osteolysis observed
in 34 of the 43 patients with FDOJ and of the extreme R/C
overexpression. An almost complete absence of “ignitors
of the immune system” (TNF-α and IL-6) in FDOJ areas
(Figure 4) is another reason for the ailing defense present
in those regions. Simultaneously, the VDR-deac prevents
1,25D from contributing to the expression of antimicrobial
peptides (AMPs), such as cathelicidin and beta-defensin,
which help to eliminate pathogens.44,45 In general, the innate
immune system is stimulated by 1,25D, and the adaptive
immune system is inhibited.46,47 Thus, an effective immune
response is highly dependent on the vitamin D3 endocrine
system responsible for the balance of proinflammatory and
anti-inflammatory elements. This relationship is illustrated by
Blaney et al48 in a study of 100 patients with autoimmune and
chronic diseases: 85% of patients showed 1,25D levels that
were >46.2 ng/L without hypercalcemia. Furthermore, large
and reliable studies conducted with Danish population data
found that the mean 1,25D value in a normal population was
29 ng/L with a standard deviation of 9.5. In addition, a review
of the literature49 confirmed the association of elevated 1,25D
levels with bone metabolism. It has been found that elevated
1,25D regulates VDR activity in the small intestine. This, in
turn, transcribes and multiplies the genes that transport cal-
cium and phosphorous across the intestinal epithelium. The
mucosal response, and calcium and phosphorus resorption,
is thus dependent on a competently activated VDR, while
increased 1,25D reduces VDR competence. The fact that
calcium and phosphorous resorption may be inhibited when
VDR activity is impaired by increased 1,25D is illustrated
by a study of Crohn’s disease patients with elevated 1,25D
levels and low bone mineral density.50 It was concluded
that treating the underlying chronic inflammation improved
the metabolic bone disease. Brot et al51 found that elevated
1,25D levels were associated with markedly reduced bone
density and bone content as well as increased bone turnover.
At levels >42 ng/L, 1,25D stimulates osteoclast activity in
the bone. This leads to osteoporosis development, tooth
fractures and soft tissue calcification.52 Accordingly, it was
found that a combination of high 1,25D and low 25D levels
is associated with the lowest bone mineral levels and poorest
bone health.50 The schematic overview in Figure 8 illustrates
the interconnection between VDR-deac, autoimmune and
systemic diseases, and FDOJ.
According to the existing theories on VDR-deac, our data
indicate that both systemic problems and local FDOJ may be
related to VDR-deac. Clinically, there may be an amplifica-
tion loop for both factors: VDR-deac may trigger the develop-
ment of FDOJ and ISDs; subsequently, FDOJ – which arises
as a result of VDR-deac – also leads to ISD development via
chronic R/C overexpression. The discussion concerning the
close relationship between bone metabolism, bone cells and
the immune system opens up a new interdisciplinary research
Figure 8 Interconnection between deactivated VDR, autoimmune and systemic diseases, disturbed bone metabolism and fatty-degenerative osteolysis of the jawbone with
an immunological amplication loop.
Abbreviations: FDOJ, fatty-degenerative osteolysis of the jaw; VDR, vitamin D receptor; 1,25(OH)2D, 1,25-dihydroxyvitamin D3; 25(OH)D, 25-hydroxyvitamin D3.
FDOJ
Autoimmune
disease
Osteoclasts
upregulated
Disturbed bone
metabolism
in jawbone
25(OH)D
downregulated
in serum
1,25(OH)2D
upregulated
in serum
Deactivated-VDR
Intracellular
bacteria/microbiome
Inflammatory
cytokine
RANTES/CCL5
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Lechner et al
field known as “osteoimmunology”.53 The data presented
here highlight the complexity of interwoven pathways and
the shared mechanisms involved in the cross talk between
the immune and bone systems. Emerging new homeostatic
networks define an interdisciplinary field of osteoimmunol-
ogy in which other organs and systems are functionally
interconnected.54 The conjunction of R/C overexpression
in FDOJ and the role of microbiota contributes to a proin-
flammatory cytokine milieu which drives bone resorption,
leading to changes in bone density and in bone phenotype.55
Based on the overexpression of the chemokine R/C in the
FDOJ cases presented here, further studies investigating
maxilla–mandibular osteoimmunology are recommended.
Conclusion
During the course of evolution, reactions to microbes have
resulted in finely tuned immune responses.56 The present
study brings the discussion on the subjects of the microbi-
ome, as well as intracellular infections, and dysregulations
of bone metabolism and signaling pathways into focus. We
detail the interconnection between deactivated VDR, auto-
immune and systemic diseases, disturbed bone metabolism
and FDOJ osteolysis. In doing so, attention is drawn to the
question of whether systemic cross-linking of VDR-deac and
FDOJ-derived R/C overexpression may be responsible for
the development of otherwise inexplicable systemic inflam-
matory reactions. We found that VDR-deac and metabolic
regulation in the mineral matrix of the jawbone, combined
with systemic dysregulated signal transduction, play a critical
role in the development of the inflammatory condition FDOJ.
Limitations
The limitations of the cross-sectional study presented
herein, in which vitamin D3 levels, cytokine levels and
FDOJ samples were collected concurrently, lie in the small
sample size employed. Futhermore, confounders were not
controlled. These include the duration of any underlying
disease, the duration of FDOJ, multimorbidity, medication
use and the administration of other therapies. Bias may
also be present in the determination of the VDR ratio. For
instance, values were collected only once for each partici-
pant and at different seasonal times, which is limiting given
that vitamin D levels are subject to natural fluctuations
throughout the year.
Future directions
In a cohort of 43 patients with FDOJ, on the one hand, and
ISDs, on the other, this study was able to demonstrate two
phenomena that present similar effects to those associated
with ISDs: aseptic osteolysis in the jawbone and the VDR-
deac. Although the evidence for causality presented remains
insufficient, our findings contribute to the expansion of the
current understanding of chronic aseptic osteolysis of the
jawbone, while also relating it to the immune system.
Acknowledgment
English-language translation and editing of this manuscript
were done by Natasha Gabriel.
Disclosure
The authors report no conflicts of interest in this work.
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