Mutational landscape and genetic signatures of cell-free DNA in tumour-induced osteomalacia

Tumour‐induced osteomalacia (TIO) is a very rare paraneoplastic syndrome with bone pain, fractures and muscle weakness, which is mostly caused by phosphaturic mesenchymal tumours (PMTs). Cell‐free DNA (cfDNA) has been regarded as a non‐invasive liquid biopsy for many malignant tumours. However, it has not been studied in benign tumours, which prompted us to adopt the targeted next‐generation sequencing approach to compare cfDNAs of 4 TIO patients, four patients with bone metastasis (BM) and 10 healthy controls. The mutational landscapes of cfDNA in TIO and BM groups were similar in the spectrum of allele frequencies and mutation types. Markedly, deleterious missense mutations in FGFR1 and loss‐of‐function mutations in MED12 were found in 3/4 TIO patients but none of BM patients. The gene ontology analysis strongly supported that these mutated genes found in TIOs would play a potential role in PMTs' process. The genetic signatures and corresponding change in expression of FGFR1 and FGF23 were further validated in PMT tissues from a test cohort of another three TIO patients. In summary, we reported the first study of the mutational landscape and genetic signatures of cfDNA in TIO/PMTs.

Estrogen Receptors (ESRs) Mutations in Adolescent Idiopathic Scoliosis: A Cross-Sectional Study

Background

Adolescent idiopathic scoliosis (AIS) is the most common spinal deformity, but its etiology is unclear. Multiple genetic mutations have been reported to be associated with AIS.

Material/Methods

We enrolled a cohort of 113 surgically treated AIS patients with available parental subjects from the Peking Union Medical College Hospital. We performed whole-exome sequencing in 10 trio families and whole-genome sequencing in 103 singleton patients. Luciferase assay was used to detect the functional alterations of candidate ESR1 and ESR2 variants.

Results

Using a de novo strategy, a missense variant in ESR1 (c.868A>G) was selected as a candidate gene for AIS. The main Cobb angle of this patient was 41° (T6–T10). Another potential pathogenic variant in ESR2 (c.236T>C) was identified. The main curve of the patient was 45° at T10–L3. The transactivation capacities of the mutated ESR1 and ESR2 protein were both significantly decreased (p=0.026 and 0.014, respectively).

Conclusions

Potential pathogenic variants in ESR1 and ESR2 were identified in 113 AIS patients, suggesting that genetic mutations in ESR1/2 were associated with the risk of AIS.

Posterior only instrumented fusion provides incomplete curve control for early-onset scoliosis in type 1 neurofibromatosis

Background

The mid-long term outcomes of posterior spinal fusion in pediatric neurofibromatosis type 1 (NF-1) patients are rarely reported, so does the effectiveness of itsorthopeidc maintenance function. This study aims to evaluate the mid-long term surgical outcomes of posterior only instrumented spinal fusion for early-onset scoliosis (EOS) in NF-1 patients.

Methods

A retrospective review was performed on a cohort of 10 NF-1 patients having EOS from 2008 to 2014 in our hospital, the age averaged at 7.8 years old when they underwent posterior only instrumented spinal fusion for their EOS. Both general clinical data and surgical specific data of the patients were collected and reviewed, and the dystrophic progression of EOS was evaluated during the follow-up.

Results

The average duration of follow-up was 54 months (24 to 88 months). All patients underwent posterior only instrumented spinal fusion at 1 stage. The primary curves of EOS were thoracic in 9 cases and 1 patient had lumbar scoliosis. Preoperative major curve was significantly corrected (from 66.1 to 31.1 degrees). However, the major curve deteriorated significantly to 40.1 degrees on average at the end of the follow-up. The T1-S1 distance increased 2.8 cm on average and kept increasing at a rate of 0.6 cm/year during the follow-up.

Conclusions

Posterior only fusion surgery was not a good option to treat the EOS in NF-1 patients despite the relatively short segments involvement in the disease. The maintenance of orthopedic effect after treatment was not satisfactory.

Genetic and molecular mechanism for distinct clinical phenotypes conveyed by allelic truncating mutations implicated in FBN1

BACKGROUND

The molecular and genetic mechanisms by which different single nucleotide variant alleles in specific genes, or at the same genetic locus, cause distinct disease phenotypes often remain unclear. Allelic truncating mutations of FBN1 could cause either classical Marfan syndrome (MFS) or a more complicated phenotype associated with Marfanoid-progeroid-lipodystrophy syndrome (MPLS).

METHODS

We investigated a small cohort, encompassing two classical MFS and one MPLS subjects from China, whose clinical presentation included scoliosis potentially requiring surgical intervention. Targeted next generation sequencing was performed on all the participants. We analyzed the molecular diagnosis, clinical features, and the potential molecular mechanism involved in the MPLS subject in our cohort.

RESULTS

We report a novel de novo FBN1 mutation for the first Chinese subject with MPLS, a more complicated fibrillinopathy, and two subjects with more classical MFS. We further predict that the MPLS truncating mutation, and others previously reported, is prone to escape the nonsense-mediated decay (NMD), while MFS mutations are predicted to be subjected to NMD. Also, the MPLS mutation occurs within the glucogenic hormone asprosin domain of FBN1. In vitro experiments showed that the single MPLS mutation p.Glu2759Cysfs*9 appears to perturb proper FBN1 protein aggregation as compared with the classical MFS mutation p.Tyr2596Thrfs*86. Both mutations appear to upregulate SMAD2 phosphorylation in vitro.

CONCLUSION

We provide direct evidence that a dominant-negative interaction of FBN1 potentially explains the complex MPLS phenotypes through genetic and functional analysis. Our study expands the mutation spectrum of FBN1 and highlights the potential molecular mechanism for MPLS.

Whole-Genome Methylation Analysis of Phenotype Discordant Monozygotic Twins Reveals Novel Epigenetic Perturbation Contributing to the Pathogenesis of Adolescent Idiopathic Scoliosis

Background: Adolescent idiopathic scoliosis (AIS) is a complex disease affecting a large number of teenagers, especially in female. This study reveals novel epigenetic perturbation to the pathogenesis of AIS.

Methods: A female monozygotic (MZ) twin pair discordant for AIS were examined for whole-exome sequencing and epigenome difference. Sets of differentially methylated regions (DMRs) were validated using MethylTarget™ method in 20 AIS female patients and 20 healthy female controls.

Results: Few exome difference but several potential DMRs were found between the MZ twins. We identified 313 hypermethylated DMRs and 397 hypomethylated DMRs, respectively. Most of them were enriched in the MAPK and PI3K-Akt signaling pathway, which may contribute to the discordance of AIS. Several DMRs related to scoliosis genes were tested, and the NDN: TSS-DMR (chr15:23932133-23932304, hg19) was confirmed in additional samples. The methylation level of this DMR was significantly higher in the AIS group than in the control group (p = 0.04).

Conclusions: We described the epigenome difference in an AIS female discordant MZ twin pair using Whole Genome Bisulfite Sequencing (WGBS). The NDN: TSS-DMR had higher methylation level in female AIS, which can help elucidate the potential etiology of AIS.

Urine Proteomics Profiling and Functional Characterization of Knee Osteoarthritis Using iTRAQ Technology

Osteoarthritis (OA) is a degenerative chronic disease affecting the whole joint structures. With the increment in life expectancy and aging population, OA has become one of the largest socioeconomic burdens, associated with pain and loss of joint function. However, early laboratory tests of OA are still lacking. Therefore, new diagnostic tests for this disease are urgently needed. In this study, to gain an insight into the pathogenesis and the potential biomarkers of OA, we implemented a comparative urine proteomics study on OA patients and health people using iTRAQ-based mass spectrometry technology. Western blotting was used to validate the relative changes in urine protein levels for four of the identified proteins. We constructed a comprehensive urine proteome profile of the OA patients and identified 102 proteins differently changed in abundance. Forty-six proteins were upregulated and 56 proteins were significantly downregulated in OA patients. Furthermore, the proteins, COL-4, MMP9, adiponectin, and BBOX1 were validated through Western blots, which can serve as valuable candidate biomarkers and help to illustrate the pathogenesis of OA. These findings may provide clues for promising biomarkers for the early diagnosis and also offer a theoretical basis for the early treatment of OA.

TBX6 missense variants expand the mutational spectrum in a non-Mendelian inheritance disease

Congenital scoliosis (CS) is a birth defect with variable clinical and anatomical manifestations due to spinal malformation. The genetic etiology underlying about 10% of CS cases in the Chinese population is compound inheritance by which the gene dosage is reduced below that of haploinsufficiency. In this genetic model, the trait manifests as a result of the combined effect of a rare variant and common pathogenic variant allele at a locus. From exome sequencing (ES) data of 523 patients in Asia and two patients in Texas, we identified six TBX6 gene-disruptive variants from 11 unrelated CS patients via ES and in vitro functional testing. The in trans mild hypomorphic allele was identified in 10 of the 11 subjects; as anticipated these 10 shared a similar spinal deformity of hemivertebrae. The remaining case has a homozygous variant in TBX6 (c.418C>T) and presents a more severe spinal deformity phenotype. We found decreased transcriptional activity and abnormal cellular localization as the molecular mechanisms for TBX6 missense loss-of-function alleles. Expanding the mutational spectrum of TBX6 pathogenic alleles enabled an increased molecular diagnostic detection rate, provided further evidence for the gene dosage-dependent genetic model underlying CS, and refined clinical classification.

Modified PUMC classification for adolescent idiopathic scoliosis

BACKGROUND

The original Peking Union Medical College (PUMC) classification of adolescent idiopathic scoliosis (AIS) is one system to combine each type with corresponding surgical fusion guidance, presenting comparable interobserver reliability, and reproducibility with Lenke classification. However, during its application in previous over 10 years, we found 2 main problems of this classification, which required modification.

PURPOSE

(1) To evaluate the interobserver and intraobserver reliability, (2) to assess the effects of the added fusion criteria of proximal thoracic (PT) curve on improving postoperative shoulder balance of the modified PUMC classification of AIS.

STUDY DESIGN/SETTING

Retrospective analysis of our AIS cohort and prospective validation of its effectiveness.

PATIENT SAMPLE

Fifty sets of preoperative radiographs of AIS patients were randomly chosen from our AIS database. Furthermore, 46 consecutive AIS cases with PT curve were enrolled who underwent surgeries in our center from July 2007 to July 2013, with at least 2-year follow-up.

OUTCOME MEASURES

The classification results of 50 sets of preoperative radiographs by 5 surgeons. The shoulder balance was evaluated using radiographic shoulder height.

METHODS

Five surgeons independently evaluated and classified presurgical radiographs of 50 AIS patients based on the modified PUMC classification. Inter- and intraobserver reliabilities were calculated. Furthermore, the post-op shoulder balance was investigated in 46 consecutive cases of AIS with PT curve who were treated strictly based on the modified PUMC classification.

RESULTS

The Kappa coefficients of inter- and intraobserver reliability of the overall modified PUMC classification are 0.889 and 0.865, respectively. The Kappa coefficients of inter- and intraobserver reliability for the type II are 0.791 and 0.746, respectively. In addition, the shoulder balance rate of the 46 AIS patients with PT curve at the final follow-up was 95.7%.

CONCLUSIONS

Modified PUMC classification presents incremental improvement compared to our original published version, with high interobserver and intraobserver reliability and better performance of postoperative shoulder balance. Furthermore, the modified PUMC classification provides corresponding surgical fusion guidance for each subtype. Multicenter prospective studies with larger samples are still needed to further improve this system.

Ankylosing spondylitis: etiology, pathogenesis, and treatments

Ankylosing spondylitis (AS), a common type of spondyloarthropathy, is a chronic inflammatory autoimmune disease that mainly affects spine joints, causing severe, chronic pain; additionally, in more advanced cases, it can cause spine fusion. Significant progress in its pathophysiology and treatment has been achieved in the last decade. Immune cells and innate cytokines have been suggested to be crucial in the pathogenesis of AS, especially human leukocyte antigen (HLA)‑B27 and the interleukin‑23/17 axis. However, the pathogenesis of AS remains unclear. The current study reviewed the etiology and pathogenesis of AS, including genome-wide association studies and cytokine pathways. This study also summarized the current pharmaceutical and surgical treatment with a discussion of future potential therapies.

Efficacy of bisphosphonates in patients with synovitis, acne, pustulosis, hyperostosis, and osteitis syndrome: a prospective open study

OBJECTIVES

To evaluate the clinical efficacy of bisphosphonates treatment for spinal bone marrow oedema (BME) in patients with synovitis, acne, pustulosis, hyperostosis, and osteitis (SAPHO) syndrome.

METHODS

SAPHO syndrome patients presenting to Peking Union Medical College Hospital from 2015 to 2016 were recruited. Patients were administered pamidronate disodium 1 mg/kg/d intravenously, for 3 days, at baseline and 3 months later. The symptoms were evaluated using the Visual Analog Score (VAS) for pain, and other clinical measures including, spinal BME scores, β-crosslaps, osteocalcin, and inflammatory factors, were collected.

RESULTS

A total of 30 patients (20 women and 10 men) with a median age of 47.2 (interquartile range 8.8) years were recruited. In a short time, the patients showed a significant decrease in VAS (before vs. after; first treatment: 5.70±1.62 vs. 2.30±1.29 cm, second treatment: 4.03±1.88 vs. 2.17±1.23 cm) and β-crosslaps (first treatment: 0.4441±0.1923 vs. 0.0859±0.0374 pg/ml, second treatment: 0.2891±0.1983 vs. 0.0962±0.0324 pg/ml) (all p<0.05). At 12-month follow-up, compared with the baseline, we noticed a significant drop in the VAS (5.70±1.62 vs. 2.43±1.25 cm), erythrocyte sedimentation rate (28.87±25.26 vs. 18.00±18.65 mm/h), high-sensitivity C-reactive protein level (11.76±10.19 vs. 5.84±5.88 mg/L), osteocalcin (2.30±1.27 vs. 1.65±0.80 ng/ml), and BME (30.50±24.09 vs. 22.13±27.79) (all p<0.05). No one had serious adverse events.

CONCLUSIONS

Bisphosphonates can significantly and rapidly relieve symptoms in patients with SAPHO syndrome and have a long-term effect on inflammation and spinal BME. We suggest that bisphosphonates could be used as the first-line therapeutic drug for SAPHO syndrome, especially in patients with spinal BME.

TBX6 compound inheritance leads to congenital vertebral malformations in humans and mice

Congenital vertebral malformations (CVMs) are associated with human TBX6 compound inheritance that combines a rare null allele and a common hypomorphic allele at the TBX6 locus. Our previous in vitro evidence suggested that this compound inheritance resulted in a TBX6 gene dosage of less than haploinsufficiency (i.e. <50%) as a potential mechanism of TBX6-associated CVMs. To further investigate this pathogenetic model, we ascertained and collected 108 Chinese CVM cases and found that 10 (9.3%) of them carried TBX6 null mutations in combination with common hypomorphic variants at the second TBX6 allele. For in vivo functional verification and genetic analysis of TBX6 compound inheritance, we generated both null and hypomorphic mutations in mouse Tbx6 using the CRISPR-Cas9 method. These Tbx6 mutants are not identical to the patient variants at the DNA sequence level, but instead functionally mimic disease-associated TBX6 variants. Intriguingly, as anticipated by the compound inheritance model, a high penetrance of CVM phenotype was only observed in the mice with combined null and hypomorphic alleles of Tbx6. These findings are consistent with our experimental observations in humans and supported the dosage effect of TBX6 in CVM etiology. In conclusion, our findings in the newly collected human CVM subjects and Tbx6 mouse models consistently support the contention that TBX6 compound inheritance causes CVMs, potentially via a gene dosage-dependent mechanism. Furthermore, mouse Tbx6 mutants mimicking human CVM-associated variants will be useful models for further mechanistic investigations of CVM pathogenesis in the cases associated with TBX6.

Change in the cause of inpatient mortality after arthroplasty: a retrospective study

Background

Although arthroplasty has been proved to be a safe and effective procedure, data regarding inpatient mortality rates associated with arthroplasty in China is unclear. We aimed to investigate the inpatient mortality rate after arthroplasty and the determinants of mortality at our center to ensure improved perioperative management.

Methods

This retrospective study included all patients who underwent arthroplasty at our center. Clinical data of mortality patients were collected. The incidence and the causes of inpatient mortality after arthroplasty were analyzed.

Results

A total of 4176 total knee arthroplasties, 2164 total hip arthroplasties, and 1031 femoral head replacements were performed. A rapid growth in surgery volume was observed, and more than 50% of the surgeries were performed in the last 5 years. The overall inpatient mortality rate is 0.3%; however, the mortality rate even decreased in the last 5 years. The cause of death changed over time. Pneumonia has become the leading cause of death in the past 5 years instead of cardiovascular complications.

Conclusions

Arthroplasty is a safe and effective procedure associated with a relatively low inpatient mortality in China. And inpatient mortality does not increase as the growing surgery volume due to improvement of perioperative management. However, patients presenting with risk factors and those undergoing non-elective procedures demonstrated a relatively high incidence of postoperative complications, particularly pneumonia.

The Progress of CRISPR/Cas9-Mediated Gene Editing in Generating Mouse/Zebrafish Models of Human Skeletal Diseases

Genetic factors play a substantial role in the etiology of skeletal diseases, which involve 1) defects in skeletal development, including intramembranous ossification and endochondral ossification; 2) defects in skeletal metabolism, including late bone growth and bone remodeling; 3) defects in early developmental processes related to skeletal diseases, such as neural crest cell (NCC) and cilia functions; 4) disturbance of the cellular signaling pathways which potentially affect bone growth. Efficient and high-throughput genetic methods have enabled the exploration and verification of disease-causing genes and variants. Animal models including mouse and zebrafish have been extensively used in functional mechanism studies of causal genes and variants. The conventional approaches of generating mutant animal models include spontaneous mutagenesis, random integration, and targeted integration via mouse embryonic stem cells. These approaches are costly and time-consuming. Recent development and application of gene-editing tools, especially the CRISPR/Cas9 system, has significantly accelerated the process of gene-editing in diverse organisms. Here we review both mice and zebrafish models of human skeletal diseases generated by CRISPR/Cas9 system, and their contributions to deciphering the underpins of disease mechanisms.

Mental health of patients with adolescent idiopathic scoliosis and their parents in China: a cross-sectional survey

BACKGROUNDS

Adolescent idiopathic scoliosis (AIS) is an adolescent onset spinal deformity, which can negatively affect the mental health of these patients. But no studies about their parental mental health have been reported so far. In this study, the parental mental health of AIS patients and the associated risk factors were evaluated by a cross-sectional survey.

METHODS

64 AIS patients who underwent conservative or surgical treatments in our hospital from April 2017 to March 2018, and their parents were enrolled in the AIS group. 85 parents of healthy children were enrolled in the control group. Depression and anxiety were separately assessed using the Patient Health Questionnaire (PHQ-9) and the Generalized Anxiety Disorder 7-item scale (GAD-7). Spearman correlation coefficients were first estimated to investigate the relationships among the parental PHQ-9/GAD-7 scores and the patient's PHQ-9/GAD-7 scores in the AIS group. Then, the morbidities of the parental probable major depressive disorder (pMDD, PHQ score ≥ 10) and probable general anxiety disorder (pGAD, GAD-7 score ≥ 10) were compared between the AIS and control groups. Third, the potential risk factors for parental pMDD or pGAD in the AIS group were compared using the chi-squared test or Student's t-test, respectively. Finally, the uneven distributive variates were analyzed using the binary logistic regression model.

RESULTS

Both parental depression and anxiety were moderately associated with those of the patients (r = 0.448~0.515, p < 0.01) in the AIS group, respectively. The morbidities of parental pMDD and pGAD in the AIS group were 14.1%, significantly higher than those in the control group (pMDD = 4.7%, p = 0.045; pGAD = 3.5%, p = 0.019). A Cobb angle of the major curve ≥50° (p = 0.034, odds ratio [OR] = 8.264), patients with pMDD (p = 0.018, OR = 17.576), and low education level of the parents (p = 0.026, OR = 0.122) were the risk factors of parental pMDD. Household income < 8000 rmb/month was the risk factor for parental pGAD (p = 0.021).

CONCLUSIONS

The morbidities of pMDD and pGAD in parents of AIS patients were higher than those in parents of healthy children. Parental depression and anxiety were closely associated with their children's depression and anxiety. Therefore, the parental mental health of AIS patients should be paid attention to, especially for those parents with risk factors.

The Relationship Between Dural Ossification and Spinal Stenosis in Thoracic Ossification of the Ligamentum Flavum

BACKGROUND

Dural ossification represents a difficult problem in the surgical management of thoracic ossification of the ligamentum flavum. Few studies have focused on this condition because of the relatively low prevalence. We speculated that dural ossification occurs only when spinal stenosis of patients with thoracic ossification of the ligamentum flavum progresses. Herein, we aimed to determine the relationship between dural ossification and spinal stenosis in thoracic ossification of the ligamentum flavum.

METHODS

In this study, 123 consecutive patients with ossification of the ligamentum flavum were retrospectively analyzed. Sixty-seven patients were ultimately included and were divided into a group that had dural ossification and a group that did not have dural ossification. Patient characteristics and radiographic data were recorded. The cross-sectional area occupying ratio ([1 - cross-sectional area of the narrowest level/normal cross-sectional area] × 100%) was measured and was calculated by 3 independent observers, followed by statistical analysis.

RESULTS

The 2 groups were comparable with respect to sex, age, body mass index, and distribution of the segment with maximum compression. The mean cross-sectional area occupying ratio (and standard deviation) in the T9-T12 subgroup in the group with dural ossification (63.4% ± 8.6%) was significantly higher (p < 0.001) than that in the group without dural ossification (30.7% ± 10.4%). The overall interobserver reliability for measurements of the cross-sectional area occupying ratio (interclass correlation coefficient, 0.976) was excellent. Thus, the cross-sectional area occupying ratio could be used as an indicator to distinguish between patients with ossification of the ligamentum flavum who did and did not have dural ossification, with a high diagnostic value, in the T9-T12 subgroup. A cross-sectional area occupying ratio of >55% (sensitivity of 81.5% and specificity of 100%), the "ossification zone," was indicative of dural ossification in patients with ossification of the ligamentum flavum, whereas a value of <45% (sensitivity of 100% and specificity of 89.7%) was considered safe. Moreover, ratios between 45% and 55% were considered to be in the "gray zone."

CONCLUSIONS

The results of this study indicate that the severity of spinal stenosis was significantly associated with dural ossification in ossification of the ligamentum flavum and the cross-sectional area occupying ratio may be used as an indicator of dural ossification in the lower thoracic spine.

CLINICAL RELEVANCE

The diagnosis of dural ossification was based on the intraoperative evidence, and the results could help spine surgeons to prepare for the surgical procedure.

TBX6-associated congenital scoliosis (TACS) as a clinically distinguishable subtype of congenital scoliosis: further evidence supporting the compound inheritance and TBX6 gene dosage model

PURPOSE

To characterize clinically measurable endophenotypes, implicating the TBX6 compound inheritance model.

METHODS

Patients with congenital scoliosis (CS) from China(N = 345, cohort 1), Japan (N = 142, cohort 2), and the United States (N = 10, cohort 3) were studied. Clinically measurable endophenotypes were compared according to the TBX6 genotypes. A mouse model for Tbx6 compound inheritance (N = 52) was investigated by micro computed tomography (micro-CT). A clinical diagnostic algorithm (TACScore) was developed to assist in clinical recognition of TBX6-associated CS (TACS).

RESULTS

In cohort 1, TACS patients (N = 33) were significantly younger at onset than the remaining CS patients (P = 0.02), presented with one or more hemivertebrae/butterfly vertebrae (P = 4.9 × 10^‒8), and exhibited vertebral malformations involving the lower part of the spine (T8-S5, P = 4.4 × 10^‒3); observations were confirmed in two replication cohorts. Simple rib anomalies were prevalent in TACS patients (P = 3.1 × 10^‒7), while intraspinal anomalies were uncommon (P = 7.0 × 10^‒7). A clinically usable TACScore was developed with an area under the curve (AUC) of 0.9 (P = 1.6 × 10^‒15). A Tbx6^{-/mh (mild-hypomorphic)} mouse model supported that a gene dosage effect underlies the TACS phenotype.

CONCLUSION

TACS is a clinically distinguishable entity with consistent clinically measurable endophenotypes. The type and distribution of vertebral column abnormalities in TBX6/Tbx6 compound inheritance implicate subtle perturbations in gene dosage as a cause of spine developmental birth defects responsible for about 10% of CS.

LncRNA-PCAT1 targeting miR-145-5p promotes TLR4-associated osteogenic differentiation of adipose-derived stem cells

This study was aimed to explore the differential expression of long noncoding RNAs (lncRNA)‐PCAT1, miR‐145‐5p and TLR4 in osteogenic differentiation via the Toll‐like receptor (TLR) signalling pathway and consequently determine the potential molecular mechanism. The mRNAs and pathways related to the osteogenic differentiation in human adipose‐derived stem cells (hADSCs) were analysed by bioinformatics. The MiRanda and TargetScan database were employed to detect the potential binding sites of miRNAs on lncRNAs and mRNAs. The differential expression of lncRNA‐PCAT1, miR‐145‐5p and TLR4 were detected by qRT‐PCR. Rrelated protein expression was analysed by Western blot. The targeted relationships between lncRNA‐PCAT1, miR‐145‐5p and TLR4 were verified by dual‐luciferase reporter assay. Alkaline phosphatase (ALP) activity and ARS staining assays were used to measure the impacts exerted by lncRNA PCAT1, miR‐145‐5p and TLR4 mRNA on osteogenic differentiation. After the induction of osteoblast differentiation, the expression of lncRNA‐PCAT1 and TLR4 increased, while the expression of miR‐145‐5p decreased. Dual‐luciferase reporter assay confirmed the targeted relationship between lncRNA‐PCAT1, miR‐145‐5p, and TLR4. LncRNA‐PCAT1 negatively regulated miR‐145‐5p and positively regulated TLR4. Knockdown of lncRNA‐PCAT1 or TLR4 decreased the expression of osteogenic differentiation‐related proteins, reduced the ALP and ARS levels and the activity of the TLR signalling pathway. MiR‐145‐5p could reverse the effects of PCAT1 and TLR4 in hADSCs osteogenic differentiation. LncRNA‐PCAT1 negatively regulated miR‐145‐5p, which promoted TLR4 expression to promote osteogenic differentiation by activating the TLR signalling pathway.

Decrease of MiR-31 induced by TNF-α inhibitor activates SATB2/RUNX2 pathway and promotes osteogenic differentiation in ethanol-induced osteonecrosis

PURPOSE

Suppressed osteogenic differentiation is considered a main cause of ethanol-induced osteonecrosis. Tumor necrosis factor α (TNF-α) and miR-31 have been reported to be involved in the osteogenic induction. This study aimed to explore a possible molecular mechanism regulating osteogenic differentiation in ethanol-induced osteonecrosis bone marrow stromal stem cells (BMSCs).

METHODS

Alizarin red staining was used to examine the level of mineralization in osteogenic differentiation process. Alkaline phosphatase assay was applied to the validation of ALP level which was essential to bone mineralization. The level of osteogenesis markers was determined by western blot assay, whereas the fluctuations of messenger RNA levels were tested by quantitative real-time polymerase chain reaction. Microarray analysis was conducted to identify differentially expressed genes, because the possible target relationship was predicted and validated by miRBase and luciferase reporter assay, respectively. Colony forming unit of fibroblast assay was used to observe the proliferation of BMSCs.

RESULTS

BMSCs from patients with ethanol-induced osteonecrosis exhibited weaker osteogenic differentiation and proliferation abilities. TNF-α inhibitor added in the osteogenic medium significantly enhanced the osteogenic differentiation ability and BMSCs proliferation ability. TNF-α by regulating miR-31 downregulated the expressions of RUNX2 and SATB2, two contributors of osteoblast differentiation, further suppressed osteogenic differentiation. On the contrary, TNF-α inhibitor could promote osteogenic differentiation in BMSCs from patients with ethanol-induced osteonecrosis.

CONCLUSION

TNF-α inhibitor could downregulate miR-31 expressions, which directly promoted SATB2 and RUNX2 expressions and enhanced osteogenic differentiation of BMSCs from patients with ethanol-induced osteonecrosis.