Int J Clin Exp Pathol 2019;12(9):3399-3407
www.ijcep.com /ISSN:1936-2625/IJCEP0098041

Original Article
Relationship between osteoporosis
and osteoarthritis based on DNA methylation
Ying Li, Bing Xie, Zhiqiang Jiang, Binbin Yuan
Department of Orthopedics, Guangdong Province Integrative Medicine Hospital, Foshan, China
Received June 5, 2019; Accepted July 23, 2019; Epub September 1, 2019; Published September 15, 2019
Abstract: The aim of this study was to investigate the relationship between osteoporosis and osteoarthritis by analyzing the DNA methylation in osteoporosis and osteoarthritis. The cancellous bone specimens were collected froma total of 12 hospitalized patients and divided into the osteoporosis group (OA), the osteoarthritis group (OP), theosteoporosis combined with osteoarthritis group (OA & OP), and the normal control group (N). The cancellous bone
specimens of each group were detected and the differences in gene expression profiles by the MeDIP-chip techniquewere compared. Compared with Group OA & OP, the methylation levels in Group OA and Group OP were statisticallyhigher, P < 0.05. In the microarray analysis, a total of 1,222 sites occurred hypermethylation. The analysis targetingthe differentially expressed genes between Group OA & OP and Group N revealed that group OA and group OP had 4common genes: PPIL3, NIF3L1, SMTN, and CALHM2. The level of genomic methylation is lower in the patients withosteoporosis and/or osteoarthritis. The common difference between osteoarthritis and osteoporosis is reflected insome specific promoters, which may participate in the processes of diseases through different pathways.
Keywords: Osteoporosis, osteoarthritis, mitochondria, DNA methylation

Introduction
Osteoarthritis (OA) and Osteoporosis (OP) areboth degenerative diseases. There is controversy about whether these two diseases areunrelated, positively related, or negatively related [1-3]. To find prevalence of osteoporosis(OP) in postmenopausal females with primaryknee osteoarthritis (OA) in India, where there is
widespread Vitamin D deficiency (VDD), Dhaon
et al. [4] considers that prevalence of osteoporosis in PMW with primary knee OA is similar tothat in the general population. Yoshimura et al.
[5] once reported, after 10 years of follow-up
study, that osteoporosis (OP) at the lumbar
spine might reduce the risk of subsequent OA
in women while not in men. Roux et al. [6] hasmentioned that hypertrophic osteophytes inlumbar osteoarthritis, to some extent, can reduce the incidence of lumbar fractures. However, the study did not explicitly state whether
OA was achieved by directly affecting the progress of OP. In clinical practice, there are manyelderly patients with OP and OA simultaneously.
Geusens et al. [7] has mentioned that the com-

mon insights about convergent and divergent
risk factors between OA and OP have resulted
in new conclusions on the roles of BMD, BMI,
falls, genetics, and epigenetics regarding thepathophysiology of diseases and increased
fracture risks in OP and OA. Abundant research
has proved the involvement of epigenetic mechanisms (post-translational modifications of histone tails, DNA methylation, and non-codingRNAs) in the differentiation of bone cells andmechanotransduction. Del Real et al. [8] points
out that various epigenetic abnormalities havebeen elucidated in patients with OP, OA, and/or
skeletal cancers, but the actual related pathogenetic roles are still not clear.
As a new research direction, the epigenetics
provides new ideas for exploring the relationship of OA with OP. The epigenetics includes the
DNA methylation, chromatin remodeling, histone modifications, or microRNA (miRNA). Its
regulatory effects include the genomic imprinting, maternal effects, gene silencing, or nucleolar dominance [9]. Current research has shownthat [10, 11] the occurrence and development

Osteoporosis and osteoarthritis based on DNA methylationof osteoporosis and osteoarthritis both involvea variety of epigenetic mechanisms. This study analyzed the genomic differences in the
mitochondrial characteristics, aiming to further
investigate the relationship between OP and
OA.
Materials and methods
Diagnostic criteria
The diagnosis of OP referred to the diagnostic
criteria issued by WHO: Bone Mineral Density(BMD) of L2-4 measured by the dual-energy
X-ray absorptiometry: T-value > -1.0 SD was
defined as normal, -1.0 SD > T value > -2.5 SD
was defined as bone loss; -2.5 SD > T value
was defined as OP; -2.5 SD > T value, combinedwith osteoporosis fractures, was defined assevere OP.
The diagnosis of OA referred to the diagnosis
and treatment guidelines of Osteoarthritis developed by the Chinese Society of Orthopedics
in 2007: 1. Repeated knee pain within the past
1 month; 2. X-ray images (standing or weightbearing position) showed the narrowing of joint
space, subchondral bone sclerosis and (or) cystic degeneration, and callus formation at theedge of joints; 3. The joint fluid (at least 2 times)
was clear and viscous, WBC < 2000/ml; 4.
Middle-aged and elderly patients (≥ 40 yearsold); 5. With morning stiffness ≤ 3 minutes; 6.
With the sound (feelings) of bone friction during
activities.
The patients with the item 1+2 or 1+3+5+6 or
1+4+5+6 can be diagnosed as knee osteoarthritis.
Inclusion criteria
1. Menopausal female patients, with menopause for more than 1 year, aged 55-75 years old; 2. Patients meeting the above diagnostic criteria of western medicine and traditional Chinese medicine syndrome and diagnosed as knee osteoarthritis; 3. Volunteers
with complete relevant information, can sign
the informed consent, and agree to retain bone
specimens.
Exclusion criteria
1. with severe heart, liver, kidney, or other system diseases, mental illness, or cancer; 2. with
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secondary osteoporosis, history of acute trauma, knee meniscus injury, lateral collateral ligament injury, cruciate ligament injury, traumatic synovitis, or hematoma of knee(s); 3. withheart, liver, kidney, or other systemic diseases,
mental illness, or cancer during treatment; 4.
combined with rheumatic bronchitis, rheumatoid arthritis, gout, or other painful joint diseases; 5. with bone marrow/hematopoietic diseases.
Case data
A total of 12 female patients from March 2015
to December 2015 were selected, aging 60-70
years and meeting the above standards. These
12 patients were divided into Group OA (n = 3),
Group OP (n = 3), Group OA & OP (n = 3), andGroup N (n = 3). The bone mineral density ofeach patient was measured using a bone densitometer (GE LUNAR Prodigy, USA, cv = 1.0%).
Before the study, all the patients signed theinformed consent. The age and weight ratio of
each group was strictly controlled to make itstatistically insignificant.
Specimen collection and preservation
1 cm3 of lumbar spinal cancellous bone was
sampled during lumbar surgery, placed in afreeze-dried tube, and preserved at -80°C.
Analysis of methylation chips
The Arraystar Human RefSeq Promoter Microarray was selected and Shanghai Kangcheng
Co. Ltd. was commissioned for the gene chiphybridization. It is a chip that can detect apparent methylation and the binding sites of transcription factors within the promoter region of
the RefSeq gene. The chip uses approximately
180,000 probes to cover approximately 23,148
gene promoter regions with 210 bp as the gap(the designed region is approximately -1300 bp
to +500 bp of TSS). The specific method was asfollows:
Extraction and Fragmentation of genomic DNA:The genomic DNA (gDNA) was extracted using
the DNeasy Blood & Tissue Kit (69506, QIAGEN,
Fremont, CA) and the purified DNA was thenquantified and evaluated using the NanoDrop
ND-1000 (Thermo Scientific, Massachusetts,USA), with 10 cycles of Bioruptor sonicator(diagenode, Liege, Belgium) in the “low” mode
Int J Clin Exp Pathol 2019;12(9):3399-3407

Osteoporosis and osteoarthritis based on DNA methylation(30 seconds “ON” and 30 seconds “OFF”) tointerrupt the genomic DNA to approximately
200-1000 bp. Agarose gel (EEO015, Gene
Company LTD, Hong Kong, China) electrophoresis was then performed to detect gDNA and cutDNA.
Immunoprecipitation: (1) 1 μg of ultrasoundcleaved genomic DNA was immunoprecipitatedusing a 5-methylcytosine mouse monoclonal
antibody (MAB-31HMC-100, diagenode, Liege,
Belgium). (2) The DNA was denatured at 94°C
for 10 min and then rapidly placed onto ice
for overnight culture with 1 μL of primary antibody and 400 μL of immunoprecipitation buffer (0.5% BSA in PBS) at 4°C. (3) The antibody-bound DNA fragments were recovered
and then mixed with 200 μL of mouse antiIgG magnetic beads (11201D, Invitrogen, California, USA) for 2 h at 4°C. (4) After the hybridization with antibodies, the mixture waswashed 5 times at 4°C. (5) After washing, thebeads were resuspended in a TE buffer containing 0.25% SDS and 0.25 mg/mL proteinase
K (127149304, QIAGEN, Fremont, CA) at 65°C
for 2 hr and then cooled to room temperature.
The MeDIP DNA was recovered using the
Qiagen MinElute columns (QIAGEN, Fremont,CA).
DNA Labeling and Chip Hybridization: (1) The
purified DNA was quantified using NanoDrop
ND-1000. (2) After labeling the DNA using the
Roche Dual-Color DNA Labeling Kit (the experimental procedure referred to the standard
Roche MeDIP-chip regulations), 1 μg of DNA
and 10 D of Cy5-9mer primer (IP sample) or
the Cy3-9mer primer (Input sample) were incubated at 98°C for 10 min, after that, 100 pmolof dNTPs and 100 U of Klenow fragment wereadded and mixed at 37°C for 2 h (PCR:MJ
Mini, BIO-Rad, California, USA). (3) 0.1-time volume of 0.5M EDTA (E7889-100ml, Sigma,
Missouri, USA) was added to terminate thereaction, and the labeled DNA was recovered
with isopropanol or ethanol. (4) The labeled
DNA and the chips were hybridized at 42°C for
16 to 20 h in a hybridization cassette using the
Roche hybridization kit (Hybridization SystemNimblegen Systems, Inc., Madison, WI, USA).
(5) After the hybridization was completed, thechip was washed using the Roche washing buffer pack (Nimblegen Systems, Inc., Madison,
WI, USA).

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Analysis of chip data
Methylation Enrichment and Binding Site Determination: Starting from the standardized log
2-ratio data, a sliding window (1500 bp) provided by NimbleScan v2.5 (Roche-NimbleGen)
was used to determine the binding sites foranalyzing the MeDIP-chip data. A one-sided
Kolmogorov-Smirnov (KS) test was used todetermine whether these probes had a significant normal distribution to the ratio of the logarithm of the probes on the other arrays. Eachprobe can obtain a P-value of log 10 from thewindow KS test surrounding a particular probe.
If the P values of several neighboring probes
were significantly above a set threshold, thisregion can then be considered to be a peak.
The peak data file was thus obtained from the Pvalue data file. NimbleScan was used to detect
the peak by searching the minimum P value
which had at least 2 probes above the threshold, and the peaks within the 500 bp in distance were merged.
Analysis of differentially enriched peaks using
the median method: When comparing the differentially enriched areas between two groupsof samples, the ratio of average logarithm, 2 ofeach probe in each group, was calculated first(for example, the experimental group and thecontrol group) to calculate the M’ value (the calculation method referred to the formula). NimbleScan Sliding Window was then re-run todetermine the binding site algorithm to find thedifferentially enriched peaks.
M’ = Average (log2 MeDIPE/Input E) - Average(log2 MeDIPC/Input C)
The criteria of NimbleScan algorithm for identifying the differential enhanced peaks (DEPs)
were as follows: at least one of the two samples
had a median ≥ 0.3, (M’) > 0; at least half theprobes of one peak-corresponded two samples
had a coefficient of variation ≤ 0.8.
Statistical analysis
SPSS22.0 was used for the statistical analysis.
The data obtained from the experiments werefirst tested for the normal distribution andhomogeneity of variance. The data with normal
distribution and homogeneity of variance wereexpressed as the mean ± standard deviation.
The comparison of mean values among groups

Int J Clin Exp Pathol 2019;12(9):3399-3407

Osteoporosis and osteoarthritis based on DNA methylation
Table 1. Comparison of lumbar bone mineral_density among different groups (g/cm2, x ± s)
Group
OA
OP
OA & OP
N

n
3
3
3
3

Lumbar BMD (g/cm2)
1.22±0.09
0.59±0.14Δ
0.62±0.19Δ
1.12±0.11

Note: The data followed the normal distribution with auniform variance. LSD test, Δindicates P < 0.05 between
group OA and group N; when compared with group OP. α= 0.05.

was performed using one-way analysis of variance (one-way ANOVA). The pairwise comparison of mean values among groups used the
LSD test. The data with non-normal distribution
and heterogeneity of variance were expressedas the median (P25-P75). Multiple comparisons among groups used the Kruskal-Wallis
test, with P < 0.05 (bilateral) considered as statistical significance.
Results
Analysis of general information
The one-way analysis of variance for the bonemineral density among groups was F = 16.53, P= 0.001 < 0.05, indicating statistical significance in the bone mineral density among thegroups while comparable. The LSD examination
targeting the lumbar spine BMD revealed significance, the lumbar spine BMDs in Group OP
and group OA & OP were significantly lower thanGroup OA and Group N (N) (P < 0.05). There wascomparability among the groups. No statisticalsignificance was observed in the bone mineraldensity between group OA and group N, OP, or
OA & OP, P > 0.05, and the baseline characteristic was consistent (Table 1).
Analysis of specimen quality
Analysis of Sample-related Coefficient Matrix:
The matrix analysis of each specimen in all thegroups showed that the relationship among thespecimens of different groups was relatively
consistent, among which the relationship coefficients of the specimens in Group OA, GroupOP, and Group N were all above 90% (Figure 1).
Sizes of DNA fragments: After the genomic DNA
was fragmented, the fragmented DNA of eachsample was quantified using NanoDrop ND3402

1000, and then we examined the size agarose
gel electrophoresis. The results showed thatthe sizes of the DNA fragments ranged from
200 to 1000 bp and met the requirements offollow-up experiment (Figure 2).
Analysis of differences in DNA methylationlevelsThe one-way analysis of variance (ANOVA) was
performed to compare the average DNA methylation level among the groups. F = 22.95, P =0.000 < 0.05. There were differences in the
DNA methylation level among groups and there was comparability among groups. The LSD
test showed that Group N had more of a statistical significance in the DNA methylationlevel than Group OA, Group OP, and group OA &OP (P < 0.05). The DNA methylation level inGroup N was significantly higher than the othergroups. Compared with group OA & OP, themethylation levels in group OA and group OP
were higher than group OA & OP (P < 0.05) andthe differences were statistically significant.
The comparison of the mean DNA methylationlevel between Group OA and Group OP showedno statistical significance, P > 0.05, indicatingthat the mean DNA methylation level between
Group OA and Group OP was comparable (Table
2).
Analysis of methylation chip results
Many studies have confirmed that transcriptional inhibition of promoter downstream genes
is related to the methylation of promoters and it
is known that mammalian promoters with different GC content have different methylation
profiles. Based on the CpG ratio, the GC content, and the length of the CpG enrichment
region, the promoters can be divided into thefollowing three categories: high CpG-density
promoter (HCP), low CpG-density promoter(LCP), and intermediate CpG-density promoter(ICP). Most ICP are methylated either in theactive state or in the inactive state, which
implies that the low density of methylated cytosine does not hinder the gene activity, so it isconsidered that only the methylation of HCP
and ICP is considered to be meaningful. Compared with Group OP and group OA, the CpG
island of 1222 gene promoters occurred hypermethylation (P < 0.05), among which 501
were on LCP, 191 were on ICP, and 530 were on
HCP (Figure 3); most of the differential genes
Int J Clin Exp Pathol 2019;12(9):3399-3407

Osteoporosis and osteoarthritis based on DNA methylation

Figure 1. Analysis of relationship coefficient matrix of specimens among different groups.

analyzed and classified by the GO typing forthe enrichment test. It can be seen that thegenes involved in methylation involve almost all
major biological processes and common signal
pathways.
Comparison of differential genes

Figure 2. Agarose gel electrophoresis analysis ofsizes of genomic DNA fragments of each specimen(BP).

were located on chr l, chr 3, chr l1, chr l6, chr l7,
and chr l9 (Figure 3). The above genes were3403

The comparison of the methylated genes in
HCP and ICP among groups revealed that there
were 644 differential genes in Group OA, 669
differential genes in Group OP, and 492 differential genes in Group OA & OP than Group N.
The comparative analysis of differentially expressed genes in Group OA & OP and Group N
revealed 4 common differential genes in these
Int J Clin Exp Pathol 2019;12(9):3399-3407

Osteoporosis and osteoarthritis based on DNA methylation
Table 2. DNA_ methylation levels in different
groups (%, x ± s)
Group
OA
OP
OA & OP
N

n
3
3
3
3

Level of DNA methylation (%)
3.47±0.13Δ,▲,◆
3.39±0.53Δ,▲
2.02±0.29Δ
5.04±0.64

Note: The data followed the normal distribution with auniform variance. The average DNA methylation level
among groups was analyzed by one-way ANOVA: F =22.95, P < 0.05. The pairwise comparison of DNA methylation level among groups was performed using the LSD
test, Δindicates P < 0.05 when compared with group N;▲
indicates P < 0.05 when compared with group OA & OP;◆
indicates P > 0.05 when compared with group OP. α =0.05.

two groups (NIF3L1 coexisted in HCP and ICP):
PPIL3, NIF3L1, SMTN, and CALHM2, among
which PPIL3, NIF3L1, and SMTN were all located in HCP. The specific information of differential genes is as follows (Table 3).
Discussion
The concept of epigenetics was first proposedby Waddington CH in 1942, who consideredepigenetics as a discipline for studying themechanisms of biological development. In the
middle of 1970s, the concept proposed by R.
Holliday [12] was that epigenetics studied theexpression changes of heritable genes thatwere caused by non-DNA sequence changes.
With the continuous progress of epigenetic
studies, it has revealed that the occurrence
and development of many systemic diseases,
such as tumors, degenerative diseases, nervous system diseases, or cardiovascular diseases, have very close relationship with epigenetics. Related mechanisms cover suchfields as post-translation histone modification,
miRNA-mediated post-transcription regulation,
and DNA methylation [13]. DNA methylation ismainly a process of adding the methyl group to
DNA molecules. In mammalian cells, DNA methylation predominantly occurs on the cytosine(C) of dinucleic acid in cytosine and guanylate(CpG) [14, 15]. Under the action of catalytic
enzymes, DNA methyltransferase can move themethyl group (S-adenosylmethionine) to the 5thcarbon atom (cytosine in the DNA duplex) andform the 5-methyl Cytosine (5-m C), and this is
the process of DNA methylation. The DNA methyltransferases (DNMTs) that can catalyze this3404

reaction include: DNMT1, DNMT3A, DNMT3B,
and DNMT3L, among which DNMT1, DNMT3A,
and DNMT3B can directly catalyze the methylation reaction while DNMT3L mainly catalyzes
other transferases to complete this activity. In
eukaryotes, DNA methylation has three states,
namely sustained hypomethylation, induced
demethylation, and hypermethylation.
In the genome, CpG is the site that maintains
methylation and both the C-terminus in 5’-CpG3’ and 3’-GpC-5’ of the DNA duplex are methylated. The CpG islands is one CpG cluster being
composed of a large number of unmethylated
CpGs, most of which are present in the transcription start site and promoter of structuralgenes. The hypermethylation of DNA firstcauses the 3D changes of the major groove inthe DNA duplex and then blocks the DNA binding activity of methylation-sensitive transcription factors (TFs, including E2F, CREB, AP2,cMyc/Myn, NF-kB, cMyb, or ETS), thus causing
gene silencing.
Zhang et al. [16] studied the interaction between DNA methylation and osteogenic differentiation of MSCs. The osteogenesis model of
MSCs was pretreated with 5-azacytidine 24
hours before the induction of osteogenic differentiation. The results revealed that as the DNA
methylation modification of the whole genome
was continuously reduced, the osteogenic differentiation efficiency was also significantly
improved. The determination targeting the fluctuation of methylation modification level on the
key regulatory osteogenic differentiation geneDlx5 at the single gene level revealed that after
the CpG island shore on the Dlx5 gene was pretreated, its methylation level was significantly
lower than other sites. Del Real et al. [17] studied the hMSCs obtained from the femoral headof females undergoing hip replacement due to
hip fractures and hip osteoarthritis and used
the Infinium 450 K Bead Array to explore the
DNA methylation. The transcriptome analysis
was accomplished by RNA sequencing. The
genomic analysis shows that most differentially-methylated loci are located in the genomic
region with enhancer activities while far awayfrom the genosomes and promoters. These
regions are associated with the genes that are
differentially expressed in the pathways andrich in the growth of hMSC and the differentiation of osteoblasts. The hMSCs obtained fromInt J Clin Exp Pathol 2019;12(9):3399-3407

Osteoporosis and osteoarthritis based on DNA methylation

Figure 3. Type and chromosome distribution of 1222 hypermethylated promoters in group OA and OP. A: Distributionof promoter types; B: Chromosome distribution.

role of the miR-22 osteoclasts,
indicating that miRNAs not only
Peak PeakPeak
Gene
Promoter
Chromosome
play roles in osteoclastogenesis
ID
Score
DM Value
Name Classification
but also play positive regulatory
975
3.61 0.455965469 PPIL3
HCP
chr2
roles in the bone resorption pro3494 2.69 0.239787114 NIF3L1
HCP
chr2
cess [19]. Other studies have
2071 2.52 0.212739393 SMTN
HCP
chr22
shown epigenetic dysregulation of1773 2.59 0.170241887 CALHM2
ICP
chr10
many genes and pathways in OA,
including some OA-susceptible
genes. In addition, the CpG methfractured patients showed the proliferation andylation in OA is related to the histological severity [20]. Alvarez et al. [21] demonstrated theupregulation of enhanced osteoblast driverrole of hypoxia in regulating the expressions of
RUNX2/OSX. In addition, they also showed the
anabolic and catabolic genes, as well as thesigns of accelerated methylation aging.
effects on the changes of DNA methylation.
According to certain studies regarding genomic
These results further support the role of epiexpression profiling, the inactivation and mugenetics in osteoarthritis and critically highlighttation in the miRNA coding regions may be
the complex relationship between the physioinvolved in the pathogenesis of OP. Regardlesslogical environment of chondrocytes and theof the upregulation or inhibition of miRNAs, it isprocess of osteoarthritis, as well as the effects
undeniable that significant changes happen inon therapeutic intervention and the underthe expressions of multiple miRNAs in the OA
standing of the pathophysiology of OA.
and OP cells. Therefore, the profile of the exAlthough the reasons for inter-group differencpressions of specific miRNAs in such patientses and specific mechanisms have not been
can be seen as new markers for the diagnosis
clarified yet, the expression significance ofof cartilage lesions.
other related genes on OA or OP has been iniAccording to Nicolas, inhibiting the endogenous
tially verified. Reppe et al. [22] considered thatmiR-22 in the OA chondrocytes can inhibit thebones exposed to stress or not showed differexpressions of IL-1β and MMP-13 by increasingent gene expressions, reflecting the differencthe expressions of PPARα and BMP-7, therees in bone turnover and remodeling; the comby increasing the content of proteoglycan thatparative histological analysis among group N,
can protect the cartilages [18]. Certain in vitro
group OP, and group OA revealed the transcripstudies by Mizoguchi have confirmed that thetomics, DNA methylation of epigenomics, proabsence of specific Dicer enzymes will induceteomics, and metabonomics. These studies,
the inhibition of osteoclast-mediated bone resalong with the genome-wide association studorption. The cause of this process reflects theies, in vitro observations, and transgenic aniTable 3. Basic information of differential genes

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Int J Clin Exp Pathol 2019;12(9):3399-3407

Osteoporosis and osteoarthritis based on DNA methylation
mal models, have identified a number of genes
and gene products that function through the
Wnt and other signaling systems and are closely related to bone density and fractures. Delgado-Calle et al. [23] studied the genome-wide
methylation profile of the bones in patientswith hip OA and OP, and the final results suggested that the genome-wide methylation analysis of bone samples revealed the regions withdifferential methylation in OP and OA. These
regions are rich in the genes associated withcell differentiation and skeletal embryogenesis, such as those in the homoeotic superfamily, suggesting the presence of developmental
components predisposed to these diseases.

Zhujiang (2012J2200037); Foshan Scienceand Technology Innovation Platform Construction Projects (2013 AG100022).

Conclusions[1]

This study reveals that the patients with OP/OA
have low levels of genomic methylation. The
common difference between OA and OP is incertain specific promoters. These genes involve
almost all in vivo biological processes and lay
the theoretical foundation for further exploring
the molecular regulation mechanisms. Four differential genes (PPIL3, NIF3L1, SMTN, andCALHM2) have been identified in OA/OP compared with Group N, which may be involved in
the development of diseases through different
pathways, and it also confirms that OA and OP
have certain relationship at the level of gene
methylation, which provides theoretical basis
for the common pathogenesis of these two diseases. However, due to the small number ofsamples and the large number of genes in thisexperiment, there may be some bias in screening common differential genes. We believe thatwith the continuous progress of research, therelationship between OA and OP will be further
revealed, and more problems will arouse everyone’s attention and thinking. At the same time,
it will have very important significance toward
the diagnosis or related treatment researchagainst diseases.
Acknowledgements
This study was funded by the Natural Science
Foundation Projects of Guangdong Province(2014A030313748); Science and Technology
Plan Projects of Guangdong Province (2013B021800162); Scientific Research Projects ofGuangdong Provincial Bureau of Traditional
Chinese Medicine (20141040); Science andTechnology Rising Star Projects of Guangzhou
3406

Disclosure of conflict of interest
None.
Address correspondence to: Bing Xie, Departmentof Orthopedics, Guangdong Province Integrative Medicine Hospital, No. 13 Pomegranate Road Haizhuqu District, Foshan 528200, China. Tel: +86 75786207632; Fax: +86 75786207629; E-mail: bingxiedoc@163.com

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