Heterozygous deletion of LRP5 gene in mice alters profile of immune cells and modulates differentiation of osteoblasts

Clinical and Genetic Features of Chinese Adult Patients With Chronic Non-Bacterial Osteomyelitis: A Single Center Report

Objectives

Chronic non-bacterial osteomyelitis (CNO) is a rare polygenic autoinflammatory bone disease. We aimed to characterize the clinical manifestations and gene variants of Chinese adult patients with CNO.

Methods

By reviewing data of all CNO patients being diagnosed and followed up at the Center for Adult Autoinflammation Diseases, Department of Rheumatology, Peking Union Medical College Hospital, clinical and genetic features of these patients were evaluated and concluded.

Results

The median age of disease onset was 19 (6-64) years old, and adult-onset was observed in 6 (60%) patients. The mean time of diagnosis delay was 92 ± 78 months. The common symptoms were bone pain (10, 100%), fever (9, 90%), and arthritis (6, 60%). In total, there were 54 skeletal lesions, and each patient had no less than 2 lesions. The most frequently affected sites included lower limbs (20.5%), mandible, vertebrae and pelvis (17.5%, separately). Variants of 4 genes were detected in our study including COL1A1, PSTPIP1, LRP5 and CLCN7. In seven patients who were treated with combination therapy containing tumor necrosis factor (TNF) α inhibitors, five (55.6%) had a complete response and 2 (44.4%) had a partial response.

Conclusion

This is the first and largest case series of CNO in the Chinese adult patients. Four novel genetic mutations potentially associated with CNO were identified. Notably, CNO should be considered in the differential diagnosis of adult patients with long disease course and recurrent multifocal osteomyelitis of unknown cause, and these patients might benefit from combination therapy containing TNFα inhibitors.

Identification of Critical Genes and lncRNAs in Osteolysis after Total Hip Arthroplasty and Osteoarthritis by RNA Sequencing

Total hip arthroplasty (THA) is a cost-effective treatment for osteoarthritis (OA), and osteolysis is a common complication of THA. This study was aimed at exploring the relevant molecular biomarkers for osteolysis after THA. We performed RNA sequence to identify and characterize expressed mRNAs and lncRNAs in OA and osteolysis. Differentially expressed mRNAs (DEmRNAs) and lncRNAs (DElncRNAs) in OA and osteolysis were acquired, as well as shared DEmRNAs/DElncRNAs in OA and osteolysis and osteolysis-specific DEmRNAs/DElncRNAs. Then, shared and osteolysis-specific DElncRNA-DEmRNA coexpression networks were constructed to further investigate the function of DElncRNAs and DEmRNAs in OA and osteolysis. In total, 343 DEmRNAs and 25 DElncRNAs in OA, 908 DEmRNAs and 107 DElncRNAs in osteolysis, and 406 DEmRNAs and 46 DElncRNAs between OA and osteolysis were acquired. A total of 136 shared DEmRNAs and 9 shared DElncRNAs in OA and osteolysis and 736 osteolysis-specific DEmRNAs and 103 osteolysis-specific DElncRNAs were acquired. Then, 128 shared DElncRNA-DEmRNA coexpression pairs and 522 osteolysis-specific DElncRNA-DEmRNA coexpression pairs were identified. The present study highlighted the roles of four interaction pairs, including two shared lncRNA-mRNA interaction pairs in OA and osteolysis (AC111000.4 and AC016831.6), which may function in the immune process of OA and osteolysis by regulating CD8A and CD8B, respectively, and two osteolysis-specific interaction pairs (AC090607.4-FOXO3 and TAL1-ABALON), which may play an important role in osteoclastogenesis.

Risk of Wnt/β-catenin signalling pathway gene polymorphisms in primary Sjögren's syndrome

OBJECTIVE

To explore genetic polymorphisms of the Wnt/β-catenin signalling pathway in primary SS (PSS).

METHODS

We included 98 patients with PSS and 165 healthy volunteers. Genomic DNA was extracted from peripheral blood samples. Through an open-array platform of low density, we genotyped 25 polymorphisms from 14 genes (WISP1, DKK1, SOST, FRZB, LRP1, LRP4, LRP5, LRP6, GSKB, ADAMTS5, GDF5, FMN2, ADIPOQ and COL11A1) involved in the Wnt/β-catenin signalling pathway. We compared the allelic and genotypic frequencies with Fisher's exact test and logistic regression analysis adjusted by age, gender and individual admixture, as well as bootstrap-resampling analysis. We assessed the gene-gene interaction by the multifactor dimensionality reduction method.

RESULTS

We found a positive significant association with four polymorphisms: LRP5 rs606989, FRZB rs409238, GSK3B rs2037547 and ADIPOQ rs2241766. All of them conferred risk for PSS, being the highest among subjects carrying three to four risk alleles (P < 0.001). According to a multifactor dimensionality reduction analysis, the best models included the LRP5 (rs606989), FRZB (rs409238) and ADIPOQ (rs2241766) polymorphisms.

CONCLUSION

LRP5, FRZB and ADIPOQ genes related in the Wnt/β-catenin signalling pathway increased the risk of PSS. Further research is needed to establish their functional role in this clinical entity.

Retinoic acid disrupts osteogenesis in pre-osteoblasts by down-regulating WNT signaling

The skull bones are formed by osteoblasts by intramembranous ossification. WNT signaling is a regulator of bone formation. Retinoic Acid (RA) act as a teratogen affecting craniofacial development. We evaluated the effects of RA on the differentiation and mineralization of MC-3T3 cells, and on the expression of WNT components. MC-3T3 were cultured with or without 0.5 μM RA in osteogenic medium and mineralization was assessed by alizarin red staining. The expression of osteogenic marker genes and WNT genes was evaluated at several time points up to 28 days. RA significantly inhibited MC-3T3 mineralization (p < 0.01), without affecting ALP activity or Alp gene expression. Both parameters gradually increased in time. During culture, RA stimulated Runx2 expression at 14 and 28 days compared to the respective controls (p < 0.05). Also, RA significantly reduced Sp7 expression at days 14 and 21 (p < 0.05). Simultaneously, RA significantly reduced the expression of the WNT genes cMyc, Lef1, Lrp5, Lrp6 and Wnt11 compared to the controls (p < 0.05). In contrast, RA increased the expression of the WNT inhibitors Dkk1 at day 21 and Dkk2 at days 14 and 21 (p < 0.01). Our data indicate that RA disrupts osteogenic differentiation and mineralization by inhibiting WNT signaling.

Activation of GPR30 promotes osteogenic differentiation of MC3T3-E1 cells: An implication in osteoporosis

Osteoporosis is an age-related disease characterized by reduced bone volume and disturbed bone metabolism. Novel therapies to rescue or prevent reduced bone mass by guiding the differentiation of pluripotent bone marrow stromal cells away from adipocyte differentiation and toward osteoblastic differentiation may serve as a valuable treatment option against osteoporosis. Estrogen has long been recognized as a key effector of bone formation and mineralization, but the exact mechanisms involved remain poorly understood. In the present study, we investigated the role of the estrogen-specific G protein-coupled receptor 30 (GPR30/GPER) using its specific agonist G1 in MC3T3-E1 preosteoblast cells. Our findings demonstrate that expression of GPR30 is upregulated during osteoblast differentiation and that agonism of GPR30 significantly increases some key markers of mineralization including alkaline phosphatase, osteocalcin, osterix, and type I collagen. We also demonstrate that GPR30 agonism upregulates expression of Runx2, which is recognized as an essential transcription factor involved in bone formation. Additionally, through a series of adenosine monophosphate-activated protein kinase (AMPK)-inhibition experiments using compound C, we show that the positive effects of GPR30 on mineralization and differentiation of preosteoblasts are mediated through the AMPK/anti-acetyl-CoA carboxylase (ACC) pathway. Taken together, the findings of the present study demonstrate the potential of GPR30 as a novel target for the treatment and prevention of osteoporosis.