The role of CKIP-1 in osteoporosis development and treatment

CKIP-1-Loaded Cartilage-Affinitive Nanoliposomes Reverse Osteoarthritis by Restoring Chondrocyte Homeostasis

Osteoarthritis (OA) is a chronic joint disease characterized by cartilage imbalance and disruption of cartilage extracellular matrix secretion. Identifying key genes that regulate cartilage differentiation and developing effective therapeutic strategies to restore their expression is crucial. In a previous study, we observed a significant correlation between the expression of the gene encoding casein kinase-2 interacting protein-1 (CKIP-1) in the cartilage of OA patients and OA severity scores, suggesting its potential involvement in OA development. To test this hypothesis, we synthesized a chondrocyte affinity plasmid, liposomes CKIP-1, to enhance CKIP-1 expression in chondrocytes. Our results demonstrated that injection of CAP-Lipos-CKIP-1 plasmid significantly improved OA joint destruction and restored joint motor function by enhancing cartilage extracellular matrix (ECM) secretion. Histological and cytological analyses confirmed that CKIP-1 maintains altered the phosphorylation of the signal transduction molecule SMAD2/3 of the transforming growth factor-β (TGF-β) pathway by promoting the phosphorylation of the 8T, 416S sit. Taken together, this work highlights a novel approach for the precise modulation of chondrocyte phenotype from an inflammatory to a noninflammatory state for the treatment of OA and may be broadly applicable to patients suffering from other arthritic diseases.

CGK733 alleviates ovariectomy-induced bone loss through blocking RANKL-mediated Ca2+ oscillations and NF-κB/MAPK signaling pathways

Osteoporosis is a prevalent systemic metabolic disease in modern society, in which patients often suffer from bone loss due to over-activation of osteoclasts. Currently, amelioration of bone loss through modulation of osteoclast activity is a major therapeutic strategy. Ataxia telangiectasia mutated (ATM) inhibitor CGK733 (CG) was reported to have a sensitizing impact in treating malignancies. However, its effect on osteoporosis remains unclear. In this study, we investigated the effects of CG on osteoclast differentiation and function, as well as the therapeutic effects of CG on osteoporosis. Our study found that CG inhibits osteoclast differentiation and function. We further found that CG inhibits the activation of NFATc1 and ultimately osteoclast formation by inhibiting RANKL-mediated Ca2+ oscillation and the NF-κB/MAPK signaling pathway. Next, we constructed an ovariectomized mouse model and demonstrated that CG improved bone loss in ovariectomized mice. Therefore, CG may be a potential drug for the prevention and treatment of osteoporosis.

Research Progress in Function and Regulation of E3 Ubiquitin Ligase SMURF1

Smad ubiquitylation regulatory factor 1 (Smurf1) is an important homologous member of E6-AP C-terminus type E3 ubiquitin ligase. Initially, Smurf1 was reportedly involved in the negative regulation of the bone morphogenesis protein (BMP) pathway. After further research, several studies have confirmed that Smurf1 is widely involved in various biological processes, such as bone homeostasis regulation, cell migration, apoptosis, and planar cell polarity. At the same time, recent studies have provided a deeper understanding of the regulatory mechanisms of Smurf1's expression, activity, and substrate selectivity. In our review, a brief summary of recent important biological functions and regulatory mechanisms of E3 ubiquitin ligase Smurf1 is proposed.

Recent Progress in Hyaluronic-Acid-Based Hydrogels for Bone Tissue Engineering

Hydrogel-based bone tissue engineering is a potential strategy for treating bone abnormalities and fractures. Hyaluronic acid (HA) is a natural polymer that is widely distributed in the human body and plays a significant role in numerous physiological processes such as cell migration, tissue hydration, and wound healing. Hydrogels based on HA and its derivatives have gained popularity as potential treatments for bone-related diseases. HA-based hydrogels have been extensively studied for their ability to mimic the natural extracellular matrix of bone tissue and provide a suitable microenvironment for cell support and tissue regeneration. The physical and chemical properties of HA can be modified to improve its mechanical strength, biocompatibility, and osteogenic potential. Moreover, HA-based hydrogels combined with other biomaterials in the presence or absence of bioactive agents have been investigated as a means of improving the mechanical properties and bioactivity of the hydrogel scaffold. Therefore, HA-based hydrogels have shown great promise in bone tissue engineering due to their biocompatibility, osteogenic activity, and ability to mimic the natural extracellular matrix of bone tissue. Overall, this review provides a comprehensive overview of the current state of the art in HA-based hydrogels for bone tissue engineering, highlighting the key advances, challenges, and future directions in this rapidly evolving field.

CKIP-1 mediates P. gingivalis-suppressed osteogenic/cementogenic differentiation of periodontal ligament cells partially via p38 signaling pathway

Objectives

Casein kinase 2 interacting protein-1 (CKIP-1) is a versatile player involved in various biological processes. However, whether CKIP-1 mediates the osteogenic/cementogenic differentiation of periodontal ligament cells (PDLCs) under Porphyromonas gingivalis (Pg) stimulation remains unknown.

Material and Methods

The effect of Pg on PDLC differentiation was first verified. CKIP-1 expression in Pg-infected PDLCs or in PDL of apical periodontitis (AP) mice was detected. The changes of CKIP-1 during PDLC differentiation was also determined. PDLC differentiation capacity in CKIP-1 knockout (KO) mice and CKIP-1-silenced PDLCs with or without Pg stimulation were further studied. Inhibitor was finally applied to verify the involvement of p38 signaling pathway in PDLC differentiation.

Results

The suppression effect of Pg on PDLC differentiation was demonstrated. CKIP-1 increased in the PDL of AP mice and Pg-induced PDLCs, and decreased gradually during PDLC differentiation. Increased OSX and RUNX2 expression in PDL were observed in CKIP-1 KO mice. Also, CKIP-1 silencing facilitated and rescued Pg-inhibited PDLC differentiation. Inhibitor for p38 signaling pathway blocked CKIP-1 silencing-facilitated PDLC differentiation.

Conclusions

CKIP-1 mediated the osteogenic/cementogenic differentiation of PDLCs partially through p38 signaling pathway, which may provide evidence for the regeneration of periodontal hard tissues damaged by Pg.

Characterization of Fecal Microbiomes of Osteoporotic Patients in Korea

An imbalanced gut microbiome has been linked to a higher risk of many bone-related diseases. The objective of this study was to discover biomarkers of osteoporosis (OP). So, we collected 76 stool samples (60 human controls and 16 OP patients), extracted DNA, and performed 16S ribosomal ribonucleic acid (rRNA) gene-based amplicon sequencing. Among the taxa with an average taxonomic composition greater than 1%, only the Lachnospira genus showed a significant difference between the two groups. The Linear Discriminant Effect Size analysis and qPCR experiments indicated the Lachnospira genus as a potential biomarker of OP. Moreover, a total of 11 metabolic pathways varied between the two groups. Our study concludes that the genus Lachnospira is potentially crucial for diagnosing and treating osteoporosis. The findings of this study might help researchers better understand OP from a microbiome perspective. This research might develop more effective diagnostic and treatment methods for OP in the future.

The effect of QiangGuYin on osteoporosis through the AKT/mTOR/autophagy signaling pathway mediated by CKIP-1

Osteoporosis is a systemic bone disease characterized by decreased bone mass and deterioration of bone microstructure, which leads to increased bone fragility and increased risk of fractures. Casein kinase 2 interacting protein 1 (CKIP-1, also known as PLEKHO1) is involved in the biological process of bone formation, differentiation and apoptosis, and is a negative regulator of bone formation. QiangGuYin (QGY) is a famous TCM formula that has been widely used in China for the clinical treatment of postmenopausal osteoporosis for decades, but the effect in regulating CKIP-1 on osteoporosis is not fully understood. This study aimed to explore the potential mechanism of CKIP-1 participating in autophagy in bone cells through the AKT/mTOR signaling pathway and the regulatory effect of QGY. The results in vivo showed that QGY treatment can significantly improve the bone quality of osteoporotic rats, down-regulate the expression of CKIP-1, LC3II/I and RANKL, and up-regulated the expression of p62, p-AKT/AKT, p-mTOR/mTOR, RUNX2 and OPG. It is worth noting that the results in vitro confirmed that CKIP-1 interacts with AKT. By up-regulating the expression of Atg5 and down-regulating the p62, the level of LC3 (autophagosome) is increased, and the cells osteogenesis and differentiation are inhibited. QGY inhibits the combination of CKIP-1 and AKT in osteoblasts, activates the AKT/mTOR signaling pathway, inhibits autophagy, and promotes cell differentiation, thereby exerting an anti-osteoporosis effect. Therefore, QGY targeting CKIP-1 to regulate the AKT/mTOR-autophagy signaling pathway may represent a promising drug candidate for the treatment of osteoporosis.

Cortical bone thickness of the distal radius predicts the local bone mineral density

AIMS

The distal radius is a major site of osteoporotic bone loss resulting in a high risk of fragility fracture. This study evaluated the capability of a cortical index (CI) at the distal radius to predict the local bone mineral density (BMD).

METHODS

A total of 54 human cadaver forearms (ten singles, 22 pairs) (19 to 90 years) were systematically assessed by clinical radiograph (XR), dual-energy X-ray absorptiometry (DXA), CT, as well as high-resolution peripheral quantitative CT (HR-pQCT). Cortical bone thickness (CBT) of the distal radius was measured on XR and CT scans, and two cortical indices mean average (CBTavg) and gauge (CBTg) were determined. These cortical indices were compared to the BMD of the distal radius determined by DXA (areal BMD (aBMD)) and HR-pQCT (volumetric BMD (vBMD)). Pearson correlation coefficient (r) and intraclass correlation coefficient (ICC) were used to compare the results and degree of reliability.

RESULTS

The CBT could accurately be determined on XRs and highly correlated to those determined on CT scans (r = 0.87 to 0.93). The CBTavg index of the XRs significantly correlated with the BMD measured by DXA (r = 0.78) and HR-pQCT (r = 0.63), as did the CBTg index with the DXA (r = 0.55) and HR-pQCT (r = 0.64) (all p < 0.001). A high correlation of the BMD and CBT was observed between paired specimens (r = 0.79 to 0.96). The intra- and inter-rater reliability was excellent (ICC 0.79 to 0.92).

CONCLUSION

The cortical index (CBTavg) at the distal radius shows a close correlation to the local BMD. It thus can serve as an initial screening tool to estimate the local bone quality if quantitative BMD measurements are unavailable, and enhance decision-making in acute settings on fracture management or further osteoporosis screening. Cite this article: Bone Joint Res 2021;10(12):820-829.

Ckip-1 Mediates P. gingivalis-Suppressed Cementoblast Mineralization

Porphyromonas gingivalis is responsible for the destruction of cementum in patients with periodontitis and periapical periodontitis. However, research about the effects of P. gingivalis on cementoblast mineralization and the underlying mechanism is still lacking. Casein kinase 2 interacting protein 1 (Ckip-1) is a scaffold protein that interacts with various proteins and signals to regulate different cell functions, such as cell morphology, apoptosis, and differentiation. In this study, we verified the suppressive effects of P. gingivalis and lipopolysaccharide (Pg-LPS) on OCCM-30 mineralization. We also showed that Ckip-1 gradually decreased during OCCM-30 mineralization but increased with the aggravation of Pg-induced inflammation. However, it remained unchanged when cells were stimulated with Pg-LPS, regardless of the concentration and incubation time. Then, more cellular cementum and enhanced Osterix expression were observed in Ckip-1 knockout mice when compared with the wild-type mice. Meanwhile, Ckip-1 silencing significantly enhanced cementoblast mineralization with or without P. gingivalis-associated inflammation. The trend was opposite when Ckip-1 was overexpressed. Finally, we found that the p38, Akt, and Wnt pathways were activated, while the Erk1/2 pathway was inhibited when Ckip-1 was silenced. The opposite results were also observed in the Ckip-1 overexpression group. Furthermore, we proved that cell mineralization was weakened when p38, Akt inhibitors were applied and strengthened when the Erk1/2 pathway was inhibited. In summary, Ckip-1 is upregulated underP. gingivalis-induced inflammation and negatively regulates cementoblast mineralization partially through mitogen-activated protein kinases and Akt signaling pathways, which may contribute to the restoration of cementum destroyed by P. gingivalis.

CKIP-1 contributes to osteogenic differentiation of mouse bone marrow mesenchymal stem cells

Background: Osteogenesis greatly depends on the differentiation of bone marrow mesenchymal stem cells (BMSCs). CKIP-1 is considered to be a negative regulator of BMSCs. Methods: We established a CKIP-1 knockout mouse model, then isolated and cultured BMSCs from wild-type and knockout groups. Results: Our data demonstrated that CKIP-1 knockout significantly increased bone structure in the experimental mouse model and enhanced BMSC proliferation. CKIP-1 knockout contributed to osteoblastic and adipogenic differentiation. Furthermore, CKIP-1 regulated osteogenesis in BMSCs via the MAPK signaling pathway, and BMSCs from the CKIP-1 knockout mice were effective in repairing the skull defect null mice. Conclusion: Our results concluded that silencing of CKIP-1 promoted osteogenesis in experimental mice and increased BMSCs differentiation via upregulation of the MAPK signaling pathway.

The construction of a novel xenograft bovine bone scaffold, (DSS)6-liposome/CKIP-1 siRNA/calcine bone and its osteogenesis evaluation on skull defect in rats

Background

Xenograft bone scaffolds have advantages such as mechanical strength, sufficient source and safety. Combined with siRNA properly targeting CKIP-1, a negative regulator of osteogenesis, may contribute to the repair result of calcine bone alone.

Methods

Herein, we constructed a novel xenograft bovine bone scaffold namely (DSS)6-liposome/CKIP-1 siRNA/calcine bone, the characteristics of which were investigated by confirming the effect of (DSS)6-liposome, observing the appearance and testing mechanical strength of calcine bone, and observing the combined result of CKIP-1 siRNA by FAM immunofluorescence. In addition, cytotoxicity by CCK-8 and LDH activity of L929 ​cells and MC3T3-E1 osteoblasts cultured with the scaffold were tested in vitro, primary osteoblasts proliferation, the mRNA expressions of CKIP-1, ALP, COL1-α and OCN, the protein expressions of CKIP-1, BMP-2, COL-1 and Runx2 and calcium nodules were also determined by CCK-8, RT-qPCR, western-blot and Alizarin Red staining in vitro. Then, we successively established the skull defect model for evaluating the repair result of the novel scaffold by HE staining of 2, 4, 8 and 12 weeks, immumohistochemical stainings of 2, 4, 8 and 12 weeks such as ALP, COL-1α and OCN, Mirco-CT scanning of 4 and 12 weeks and the relative parameters and so on in vivo.

Results

It indicated that (DSS)6-liposome/CKIP-1 siRNA/calcine bone could successfully knock down the CKIP-1 mRNA and protein expressions, promote osteoblasts proliferation with the little cytotoxicity in vitro, increase the protein expressions of BMP-2, COL-1 and Runx2 in vitro, increase mRNA expressions of ALP, COL-1α and OCN in vitro and in vivo, and have a better bone defect repair effect with few side effects in rats after 12 weeks.

Conclusion

Our research indicates (DSS)6-liposome/CKIP-1 siRNA/calcine bone could repair skull defects well in rats, and it may lay the foundation of applicating the novel xenograft bone scaffold in the clinical.

The Translational potential of this article

These findings provide evidence that (DSS)6- liposome/CKIP-1 siRNA/calcine bone could be used as a novel xenograft bone scaffold for osteogenesis with the good safety.

Casein Kinase 2-Interacting Protein-1 Alleviates High Glucose-Reduced Autophagy, Oxidative Stress, and Apoptosis in Retinal Pigment Epithelial Cells via Activating the p62/KEAP1/NRF2 Signaling Pathway

Background

Casein kinase 2-interacting protein-1 (CKIP-1) has been proved to be associated with complications of diabetes. Diabetic retinopathy is a main diabetic complication which usually leads to blindness. The current study aims to investigate the role of CKIP-1 in high glucose-treated retinal pigment epithelial (RPE) cells which is a component of blood-retinal barriers.

Methods

The RPE cells, ARPE-19, are treated with high glucose to mimic the diabetic stimulation. CKIP-1 was overexpressed in ARPE-19 cells to evaluate its effects on autophagy, oxidative stress, and apoptosis induced by high glucose treatment, using Western blot, immunofluorescence, and flow cytometry assays, respectively.

Results

CKIP-1 was expressed at a lower level in high glucose-treated cells than in normal glucose cells. Overexpression of CKIP-1 enhanced the Nrf2 translocation to the nucleus. Furthermore, high glucose-induced autophagy, oxidative stress, and apoptosis were inhibited after overexpression of CKIP-1. Also, CKIP-1 regulates the p62/Keap1/Nrf2 signaling, which might be the potential mechanism in this model.

Conclusion

In conclusion, CKIP-1 may be a potential therapeutic target that protects RPE cells from injury and subsequent diabetic retinopathy induced by high glucose.

Fibrinolysis as a target to enhance osteoporotic fracture healing by vibration therapy in a metaphyseal fracture model

Aims

Fibrinolysis plays a key transition step from haematoma formation to angiogenesis and fracture healing. Low-magnitude high-frequency vibration (LMHFV) is a non-invasive biophysical modality proven to enhance fibrinolytic factors. This study investigates the effect of LMHFV on fibrinolysis in a clinically relevant animal model to accelerate osteoporotic fracture healing.

Methods

A total of 144 rats were randomized to four groups: sham control; sham and LMHFV; ovariectomized (OVX); and ovariectomized and LMHFV (OVX-VT). Fibrinolytic potential was evaluated by quantifying fibrin, tissue plasminogen activator (tPA), and plasminogen activator inhibitor-1 (PAI-1) along with healing outcomes at three days, one week, two weeks, and six weeks post-fracture.

Results

All rats achieved healing, and x-ray relative radiopacity for OVX-VT was significantly higher compared to OVX at week 2. Martius Scarlet Blue (MSB) staining revealed a significant decrease of fibrin content in the callus in OVX-VT compared with OVX on day 3 (p = 0.020). Mean tPA from muscle was significantly higher for OVX-VT compared to OVX (p = 0.020) on day 3. Mechanical testing revealed the mean energy to failure was significantly higher for OVX-VT at 37.6 N mm (SD 8.4) and 71.9 N mm (SD 30.7) compared with OVX at 5.76 N mm (SD 7.1) (p = 0.010) and 17.7 N mm (SD 11.5) (p = 0.030) at week 2 and week 6, respectively.

Conclusion

Metaphyseal fracture healing is enhanced by LMHFV, and one of the important molecular pathways it acts on is fibrinolysis. LMHFV is a promising intervention for osteoporotic metaphyseal fracture healing. The improved mechanical properties, acceleration of fracture healing, and safety justify its role into translation to future clinical studies.

Cite this article: Bone Joint Res 2021;10(1):41–50.

High expression of the CKIP-1 gene might promote apoptosis through downregulation of the Ras/ERK signalling pathway in the intestinal type of gastric cancer

Objective

To investigate the effect of the casein kinase 2 interacting protein 1 (CKIP-1) on the apoptosis of the intestinal type of gastric cancer (GC).

Methods

The levels of CKIP-1 protein and the rates of apoptosis were measured in tissue samples of the intestinal type of GC and human GC cell lines. The rate of apoptosis and the protein levels of B cell lymphoma-2 (Bcl-2), Bcl-2 associated X protein (Bax), cleaved cysteinyl aspartate specific protease 3 (cleaved caspase-3), cleaved caspase-9, rat sarcoma (Ras), extracellular signal-regulated kinase 1 and 2 (ERK1/2) and phosphorylated extracellular signal-regulated kinase 1 and 2 (p-ERK1/2) were analysed in SGC7901 cells expressing CKIP-1 short hairpin RNA (shRNA; knockdown) and SGC7901 cells overexpressing CKIP-1.

Results

The levels of CKIP-1 protein were significantly lower in the intestinal type of GC tissues compared with the samples of intestinal metaplasia. Both the levels of CKIP-1 protein and the levels of apoptosis decreased gradually with decreasing cell differentiation in the intestinal type of GC tissue and cell lines; and they were positively correlated. In the CKIP-1 shRNA group, the rate of apoptosis and the levels of Bax, cleaved caspase-3 and cleaved caspase-9 were decreased; and the levels of Bcl-2, Ras and the ratio of p-ERK/ERK were increased, compared with the control group. Opposite results were observed in the CKIP-1 overexpression group.

Conclusion

High levels of CKIP-1 protein may promote apoptosis in the intestinal type of GC, possibly via the downregulation of the Ras/ERK signalling pathway.

Let-7i-5p functions as a putative osteogenic differentiation promoter by targeting CKIP-1

MicroRNA (miRNA) is an endogenous regulatory small molecule RNA. Growing evidence shows that miRNA plays an important regulatory role in gene expression. Although miRNA is a more intensive regulatory noncoding RNA in recent years, few studies have investigated the regulation of targeting genes involved in bone repair. Meanwhile, as a negative bone regulator, previous studies showed that casein kinase 2-interacting protein 1 (CKIP-1) is closely associated with bone formation and regeneration. However, the gene knockout method may not be suitable for clinical application. Therefore, it was hypothesized that miRNA molecules can inhibit the expression of CKIP-1 and ultimately promote the osteogenesis process. The present study revealed that let-7i-5p plays an important role in the process of fracture healing by inhibiting the expression of CKIP-1. Related research provides a novel gene target for fracture healing.

Supplementary information

The online version of this article (10.1007/s10616-020-00444-1) contains supplementary material, which is available to authorized users.

The role of gut microbiota in bone homeostasis

Aims

The effect of the gut microbiota (GM) and its metabolite on bone health is termed the gut-bone axis. Multiple studies have elucidated the mechanisms but findings vary greatly. A systematic review was performed to analyze current animal models and explore the effect of GM on bone.

Methods

Literature search was performed on PubMed and Embase databases. Information on the types and strains of animals, induction of osteoporosis, intervention strategies, determination of GM, assessment on bone mineral density (BMD) and bone quality, and key findings were extracted.

Results

A total of 30 studies were included, of which six studies used rats and 24 studies used mice. Osteoporosis or bone loss was induced in 14 studies. Interventions included ten with probiotics, three with prebiotics, nine with antibiotics, two with short-chain fatty acid (SCFA), six with vitamins and proteins, two with traditional Chinese medicine (TCM), and one with neuropeptide Y1R antagonist. In general, probiotics, prebiotics, nutritional interventions, and TCM were found to reverse the GM dysbiosis and rescue bone loss.

Conclusion

Despite the positive therapeutic effect of probiotics, prebiotics, and nutritional or pharmaceutical interventions on osteoporosis, there is still a critical knowledge gap regarding the role of GM in rescuing bone loss and its related pathways.

Cite this article: Bone Joint Res 2021;10(1):51–59.

Casein kinase 2 interacting protein 1 positively regulates caudal-related homeobox 1 in intestinal-type gastric cancer

BACKGROUND

Gastric cancer (GC) is one of the most common malignancies, and intestinal-type GC is the main histopathologic type of GC in China. We previously reported that casein kinase 2 interacting protein 1 (CKIP-1) acts as a candidate tumor suppressor in intestinal-type GC. CKIP-1 participates in the regulation of multiple signaling pathways, including the Wnt/β-catenin pathway, of which caudal-related homeobox 1 (CDX1) may be a downstream target gene. The purpose of this study was to investigate the relationship between CKIP-1 and CDX1 in intestinal-type GC.

METHODS

Sixty-seven gastroscopy biopsy specimens and surgically resected gastric specimens were divided into four groups: gastric mucosa group, intestinal metaplasia (IM) group, dysplasia group, and intestinal-type GC group. The expression levels of CKIP-1 and CDX1 were detected in these groups and GC cell lines, and the correlations between these expression levels were analyzed. SGC7901 and BGC823 cells were divided into CKIP-1 shRNA groups and CKIP-1 over-expression groups, and CDX1 expression was detected. β-Catenin expression was detected in intestinal-type GC tissue samples and CKIP-1 shRNA and CKIP-1 over-expression SGC7901 cells, and its correlation with CKIP-1 expression in intestinal-type GC tissue was analyzed. The Wnt/β-catenin pathway inhibitor DKK-1 and activator LiCl were incubated with SGC7901 cells, BGC823 cells, and CKIP-1 shRNA and CKIP-1 over-expression SGC7901 and BGC823 cells, following which CDX1 and Ki-67 expression were detected.

RESULTS

The expression levels of CKIP-1 and CDX1 were lower in patients with intestinal-type GC than in patients with IM and dysplasia (both P < 0.05). CKIP-1 and CDX1 expression levels were positively correlated in IM, dysplasia, and intestinal-type GC tissue and cell lines (r = 0.771, P < 0.01; r = 0.597, P < 0.01; r = 0.654, P < 0.01; r = 0.811, P < 0.01, respectively). CDX1 expression was decreased in the CKIP-1 shRNA groups and increased in the CKIP-1 over-expression groups of SGC7901 and BGC823 cells compared to that in the corresponding control groups (both P < 0.05). CKIP-1 expression was negatively correlated with β-catenin expression in intestinal-type GC patients (r = -0.458, P < 0.01). Compared to the control group, β-catenin expression was increased in the CKIP-1 shRNA SGC7901 cell group and decreased in the CKIP-1 over-expression SGC7901 cell group (P < 0.05). CDX1 expression was increased in SGC7901 and BGC823 cells treated with DKK-1, DKK-1 increased CDX1 expression and decreased Ki-67 expression in the CKIP-1 shRNA group; the opposite result was observed in SGC7901 and BGC823 cells treated with LiCl, and LiCl decreased CDX1 expression and increased Ki-67 expression in the CKIP-1 over-expression group (both P < 0.05).

CONCLUSIONS

Through the Wnt/β-catenin signaling pathway, CKIP-1 may positively regulate CDX1 in intestinal-type GC.

Inflammation-mediated age-dependent effects of casein kinase 2-interacting protein-1 on osteogenesis in mesenchymal stem cells

BACKGROUND

The casein kinase 2-interacting protein-1 (CKIP-1) is important in the development of osteoblasts and cardiomyocytes. However, the effects of CKIP-1 on osteoblast precursor mesenchymal stem cells (MSCs) remain unclear. This study aimed to determine whether CKIP-1 affects osteogenic differentiation in MSCs and explore the relationship of CKIP-1 and inflammation.

METHODS

Bone marrow MSCs of CKIP-1 wild type (WT) and knockout (KO) mice were cultivated in vitro. Cell phenotype was analyzed by flow cytometry, colony formation was detected to study the proliferative ability. Osteogenic and adipogenic induction were performed. The osteogenic ability was explored by alizarin red staining, alkaline phosphatase (ALP) staining and ALP activity detection. Quantitative real-time polymerase chain reaction (qRT-PCR) was carried out to determine the mRNA expression levels of osteoblast marker genes. The adipogenic ability was detected by oil red O staining. Content of the bone was analyzed to observe the differences of bone imaging parameters including trabecular bone volume/tissue volume (BV/TV), bone surface area fraction/trabecular BV, trabecular number (Tb.N), and trabecular spacing (Tb.sp). Interleukin (IL)-1β was injected on WT mice of 2 months old and 18 months old, respectively. Difference in CKIP-1 expression was detected by RT-PCR and western blot. The relationship between CKIP-1 and inflammation was explored by RT-PCR and western blot.

RESULTS

ALP assays, alizarin red staining, and qRT-PCR showed that MSCs derived from CKIP-1 KO mice exhibited a stronger capability for osteogenesis. Micro-computed tomography detection showed that among 18-month-old mice, CKIP-1 KO mice presented significantly higher bone mass compared with WT mice (P = 0.02). No significant difference was observed in 2-month-old mice. In vivo data showed that expression of CKIP-1 was higher in the bone marrow of aging mice than in young mice (4.3-fold increase at the mRNA level, P = 0.04). Finally, the expression levels of CKIP-1 in bone marrow (3.2-fold increase at the mRNA level, P = 0.03) and cultured MSCs were up-regulated on chronic inflammatory stimulation by IL-1β.

CONCLUSIONS

CKIP-1 is responsible for negative regulation of MSC osteogenesis with age-dependent effects. Increasing levels of inflammation with aging may be the primary factor responsible for higher expression levels of CKIP-1 but may not necessarily affect MSC aging.

Gut microbiome and osteoporosis: a review

Osteoporosis (OP) is a chronic metabolic bone disease characterized by the decrease of bone tissue per unit volume under the combined action of genetic and environmental factors, which leads to the decrease of bone strength, makes the bone brittle, and raises the possibility of bone fracture. However, the exact mechanism that determines the progression of OP remains to be underlined. There are hundreds of trillions of symbiotic bacteria living in the human gut, which have a mutually beneficial symbiotic relationship with the human body that helps to maintain human health. With the development of modern high-throughput sequencing (HTS) platforms, there has been growing evidence that the gut microbiome may play an important role in the programming of bone metabolism. In the present review, we discuss the potential mechanisms of the gut microbiome in the development of OP, such as alterations of bone metabolism, bone mineral absorption, and immune regulation. The potential of gut microbiome-targeted strategies in the prevention and treatment of OP was also evaluated.

Cite this article: Bone Joint Res 2020;9(8):524–530.

A Synthetic Peptide, CK2.3, Inhibits RANKL-Induced Osteoclastogenesis through BMPRIa and ERK Signaling Pathway

The skeletal system plays an important role in the development and maturation process. Through the bone remodeling process, 10% of the skeletal system is renewed every year. Osteoblasts and osteoclasts are two major bone cells that are involved in the development of the skeletal system, and their activity is kept in balance. An imbalance between their activities can lead to diseases such as osteoporosis that are characterized by significant bone loss due to the overactivity of bone-resorbing osteoclasts. Our laboratory has developed a novel peptide, CK2.3, which works as both an anabolic and anti-resorptive agent to induce bone formation and prevent bone loss. We previously reported that CK2.3 mediated mineralization and osteoblast development through the SMAD, ERK, and AKT signaling pathways. In this study, we demonstrated the mechanism by which CK2.3 inhibits osteoclast development. We showed that the inhibition of MEK by the U0126 inhibitor rescued the osteoclast development of RAW264.7 induced by RANKL in a co-culture system with CK2.3. We observed that CK2.3 induced ERK activation and BMPRIa expression on Day 1 after stimulation with CK2.3. While CK2.3 was previously reported to induce the SMAD signaling pathway in osteoblast development, we did not observe any changes in SMAD activation in osteoclast development with CK2.3 stimulation. Understanding the mechanism by which CK2.3 inhibits osteoclast development will allow CK2.3 to be developed as a new treatment for osteoporosis.

Angelica polysaccharide promotes proliferation and osteoblast differentiation of mesenchymal stem cells by regulation of long non-coding RNA H19: An animal study

Objectives

Osteoporosis is a systemic bone metabolic disease, which often occurs among the elderly. Angelica polysaccharide (AP) is the main component of angelica sinensis, and is widely used for treating various diseases. However, the effects of AP on osteoporosis have not been investigated. This study aimed to uncover the functions of AP in mesenchymal stem cell (MSC) proliferation and osteoblast differentiation.

Methods

MSCs were treated with different concentrations of AP, and then cell viability, Cyclin D1 protein level, and the osteogenic markers of runt-related transcription factor 2 (RUNX2), osteocalcin (OCN), alkaline phosphatase (ALP), bone morphogenetic protein 2 (BMP-2) were examined by Cell Counting Kit-8 (CCK-8) and western blot assays, respectively. The effect of AP on the main signalling pathways of phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT) and Wnt/β-catenin was determined by western blot. Following this, si-H19#1 and si-H19#2 were transfected into MSCs, and the effects of H19 on cell proliferation and osteoblast differentiation in MSCs were studied. Finally, in vivo experimentation explored bone mineral density, bone mineral content, and the ash weight and dry weight of femoral bone.

Results

The results revealed that AP significantly promoted cell viability, upregulated cyclin D1 and increased RUNX2, OCN, ALP, and BMP-2 protein levels in MSCs. Moreover, we found that AP notably activated PI3K/AKT and Wnt/β-catenin signalling pathways in MSCs. Additionally, the relative expression level of H19 was upregulated by AP in a dose-dependent manner. The promoting effects of AP on cell proliferation and osteoblast differentiation were reversed by H19 knockdown. Moreover, in vivo experimentation further confirmed the promoting effect of AP on bone formation.

Conclusion

These data indicate that AP could promote MSC proliferation and osteoblast differentiation by regulating H19.

Cite this article: X. Xie, M. Liu, Q. Meng. Angelica polysaccharide promotes proliferation and osteoblast differentiation of mesenchymal stem cells by regulation of long non-coding RNA H19: An animal study. Bone Joint Res 2019;8:323–332. DOI: 10.1302/2046-3758.87.BJR-2018-0223.R2.

Casein Kinase 2 Interacting Protein-1 Suppresses Glioma Cell Proliferation via Regulating the AKT/GSK3β/β-Catenin Pathway

Objective

Casein kinase 2 interacting protein-1 (CKIP-1) has exhibited multiple functions in regulating cell proliferation, apoptosis, differentiation, and cytoskeleton. CKIP-1 also plays an important role as a critical regulator in tumorigenesis. The aim of this study is to further examine the function of CKIP-1 in glioma cells.

Methods

The expression level of CKIP-1 protein was determined in gliomas tissues and cell lines by immunohistochemistry stain and western blotting while the association of CKIP-1 expression with prognosis was analyzed by Kaplan-Meier method and compared by log-rank test. CKIP-1 was overexpressed or silenced in gliomas cell lines. CCK-8, colony formation assay, and BrdU incorporation assay were used to determine cell proliferation and DNA synthesis. Cell cycle and apoptosis rate were determined with fluorescence-activated cell sorting (FACS) method. Then, expression of key members in AKT/GSK3β/β-catenin pathway was detected by western blot analysis.

Results

In the present study, we reported new evidence that CKIP-1 was reversely associated with the proliferation of glioma cells and survival in glioma patients. Additionally, the overexpressed CKIP-1 significantly inhibited glioma cell proliferation. Further experiments revealed that CKIP-1 functioned through its antiproliferative and proapoptotic activity in glioma cells. Importantly, mechanistic investigations suggested that CKIP-1 sharply suppressed the activity of AKT by inhibiting the phosphorylation, markedly downregulated the phosphorylated GSK3β at Ser9, and promoted β-catenin degradation.

Conclusions

Overall, our results provided new insights into the clinical significance and molecular mechanism of CKIP-1 in glioma, which indicated CKIP1 might function as a therapeutic target for clinical treatment of glioma.

Insights into siRNA Transfection in Suspension: Efficient Gene Silencing in Human Mesenchymal Stem Cells Encapsulated in Hyaluronic Acid Hydrogel

Small interfering RNAs (siRNAs) are powerful tools for post-transcriptional gene silencing, which offers enormous opportunities for tissue engineering applications. However, poor serum stability, inefficient intracellular delivery, and inevitable toxicity of transfection reagents are the key barriers for their clinical translation. Thus, innovative strategies that allow safe and efficient intracellular delivery of the nucleic acid drugs at the desired site is urgently needed for a smooth clinical translation of therapeutically appealing siRNA-based technology. In this regard, we have developed an innovative siRNA transfection protocol that employs a short incubation time of just 5 min. This allows easy transfection in suspension followed by transplantation of the cells in a hyaluronic acid (HA) hydrogel system. We also report here the unique ability of siRNA to bind HA that was quantified by siRNA release and rheological characterization of the HA-hydrogel. Such interactions also showed promising results to deliver functional siRNA in suspension transfection conditions within 30 min using native HA, although removal of excess HA by centrifugation seem to be essential. In the 2D experiments, suspension transfection of hMSCs with RNAiMAX resulted in ≈90% gene silencing (with or without removal of the excess reagent by centrifugation), while HA demonstrated a modest ≈40% gene silencing after removal of excess reagent after 30 min. Transplantation of such transfected cells in the HA-hydrogel system demonstrated an improved knockdown (≈90% and ≈60% with RNAiMAX and HA respectively after 48 h), with lower cytotoxicity (up to 5-days) as determined by PrestoBlue assay. The gene silencing efficiency in the 2D and 3D conditions were also confirmed at the protein levels by Western blot analysis. We postulate this novel transfection method could be applied for in vivo applications as it allows minimal manipulation of cells that are to be transplanted and reduce toxicity.