Targeting osteoblastic casein kinase-2 interacting protein-1 to enhance Smad-dependent BMP signaling and reverse bone formation reduction in glucocorticoid-induced 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.

Metabolomics analysis of the potential mechanism of Yi-Guan-Jian decoction to reverse bone loss in glucocorticoid-induced osteoporosis

BACKGROUND

Glucocorticoid-induced osteoporosis (GIOP) is a disease in which long-term use of glucocorticoid causes bone loss, deterioration of bone microstructure and fracture. Currently, clinical drugs targeting this disease have certain side effects. There is still a need to find effective drugs with fewer side effects. The theory of traditional Chinese medicine suggests that YGJ has therapeutic effect on GIOP, but it has not been explained. Therefore, this study aims to explore the protective effect of YGJ on GIOP mouse models and elucidate the underlying mechanism through LC-MS-based metabolomics analysis.

METHODS

The general condition of 8 week age male C57BL/6J mice was recorded after 8 weeks of treatment with dexamethasone (DEX) and YGJ. Bone-related parameters and bone morphology were determined by Micro-CT. HE staining was used to observe the pathological changes of bone tissue. Serum levels of bone metabolism markers were detected by ELISA. Liver metabolomics analysis was conducted to search for the significant markers of anti-GIOP of YGJ and the metabolic pathway affecting it.

RESULTS

After treatment, YGJ significantly reversed the weight loss caused by DEX; increase the number of bone trabecular in ROI region, significantly improve the bone-related parameters of GIOP mice, and increase the levels of alkaline phosphatase and osteocalcin. In the study of metabolic mechanism, YGJ reversed 24 potential markers in GIOP mice. These included cortisol, 3-hydroxybutyric acid, taurine, esculin and uric acid, which are closely associated with osteoporosis. Topological analysis results showed that YGJ had the most significant effect on taurine and hypotaurine metabolism, with - log10 (P) > 2.0 and Impact > 0.4.

CONCLUSIONS

Yi-Guan-Jian decoction can increase bone density and improve bone microstructure by regulating the levels of alkaline phosphatase and osteocalcin and reverse bone loss in GIOP mouse model. The underlying metabolic mechanism may be related to taurine and hypotaurine metabolic pathway.

Osteoporosis Due to Hormone Imbalance: An Overview of the Effects of Estrogen Deficiency and Glucocorticoid Overuse on Bone Turnover

Osteoporosis is a serious health issue among aging postmenopausal women. The majority of postmenopausal women with osteoporosis have bone loss related to estrogen deficiency. The rapid bone loss results from an increase in bone turnover with an imbalance between bone resorption and bone formation. Osteoporosis can also result from excessive glucocorticoid usage, which induces bone demineralization with significant changes of spatial heterogeneities of bone at microscale, indicating potential risk of fracture. This review is a summary of current literature about the molecular mechanisms of actions, the risk factors, and treatment of estrogen deficiency related osteoporosis (EDOP) and glucocorticoid induced osteoporosis (GIOP). Estrogen binds with estrogen receptor to promote the expression of osteoprotegerin (OPG), and to suppress the action of nuclear factor-κβ ligand (RANKL), thus inhibiting osteoclast formation and bone resorptive activity. It can also activate Wnt/β-catenin signaling to increase osteogenesis, and upregulate BMP signaling to promote mesenchymal stem cell differentiation from pre-osteoblasts to osteoblasts, rather than adipocytes. The lack of estrogen will alter the expression of estrogen target genes, increasing the secretion of IL-1, IL-6, and tumor necrosis factor (TNF). On the other hand, excessive glucocorticoids interfere the canonical BMP pathway and inhibit Wnt protein production, causing mesenchymal progenitor cells to differentiate toward adipocytes rather than osteoblasts. It can also increase RANKL/OPG ratio to promote bone resorption by enhancing the maturation and activation of osteoclast. Moreover, excess glucocorticoids are associated with osteoblast and osteocyte apoptosis, resulting in declined bone formation. The main focuses of treatment for EDOP and GIOP are somewhat different. Avoiding excessive glucocorticoid use is mandatory in patients with GIOP. In contrast, appropriate estrogen supplement is deemed the primary treatment for females with EDOP of various causes. Other pharmacological treatments include bisphosphonate, teriparatide, and RANKL inhibitors. Nevertheless, more detailed actions of EDOP and GIOP along with the safety and effectiveness of medications for treating osteoporosis warrant further investigation.

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.

E3 Ubiquitin Ligase-Mediated Regulation of Osteoblast Differentiation and Bone Formation

The ubiquitin–proteasome system (UPS) is an essential pathway that regulates the homeostasis and function of intracellular proteins and is a crucial protein-degradation system in osteoblast differentiation and bone formation. Abnormal regulation of ubiquitination leads to osteoblast differentiation disorders, interfering with bone formation and ultimately leading to osteoporosis. E3 ubiquitin ligases (E3) promote addition of a ubiquitin moiety to substrate proteins, specifically recognizing the substrate and modulating tyrosine kinase receptors, signaling proteins, and transcription factors involved in the regulation of osteoblast proliferation, differentiation, survival, and bone formation. In this review, we summarize current progress in the understanding of the function and regulatory effects of E3 ligases on the transcription factors and signaling pathways that regulate osteoblast differentiation and bone formation. A deep understanding of E3 ligase-mediated regulation of osteoblast differentiation provides a scientific rationale for the discovery and development of novel E3-targeting therapeutic strategies for osteoporosis.

Advances in the occurrence and biotherapy of osteoporosis

Osteoporosis (OP) is a bone metabolic disease, is characterized by degeneration of bone structure and decreased bone mass. It happens in more than 1/3 women and 1/5 men of over than 50 years old, which affects the health and lives of people. The main mechanism of OP is mainly that the dynamic balance between the bone formation and resorption is broken, so that bone resorption is more than bone formation. It is prone to result in bone metabolism disorder. There are many precipitating factor such as elder age, low hormone level, genetic factors and bad hobbies. At the same time, the occurrence of the OP and its complications has different degrees of impact on people's quality of life. Based on the current understanding of the OP, we summarized the etiology, current clinical drugs and potential targeting therapy for OP. Although the research have made many progress in explore what is the novel mechanism and how to improve the effect, there are still many problems in the treatment method that limit its application prospects and need to be solved. In this review, we mainly focus on the mechanism of OP and related research on the targeted treatment of OP. Hopefully, our summary will provide a reference to develop some novel strategies for the target therapy of OP.

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.

Targeting long noncoding RNA PMIF facilitates osteoprogenitor cells migrating to bone formation surface to promote bone formation during aging

Rationale: The migration of mesenchymal osteoprogenitor cells (OPCs) to bone formation surface is the initial step of osteoblastogenesis before they undergo osteoblast differentiation and maturation for governing bone formation. However, whether the migration capacity of OPCs is compromised during aging and how it contributes to the aging-related bone formation reduction remain unexplored. In the present study, we identified a migration inhibitory factor (i.e., long noncoding RNA PMIF) and examined whether targeting lnc-PMIF could facilitate osteoprogenitor cells migrating to bone formation surface to promote bone formation during aging.

Methods: Primary OPCs from young (6-momth-old) and aged (18-momth-old) C57BL/6 mice and stable lnc-PMIF knockdown/overexpression cell lines were used for in vitro and in vivo cell migration assay (i.e., wound healing assay, transwell assay and cell intratibial injection assay). RNA pulldown-MS/WB and RIP-qPCR were performed to identify the RNA binding proteins (RBPs) of lnc-PMIF. Truncations of lnc-PMIF and the identified RBP were engaged to determine the interaction motif between them by RNA pulldown-WB and EMSA. By cell-based therapy approach and by pharmacological approach, small interfering RNA (siRNA)-mediated lnc-PMIF knockdown were used in aged mice. The cell migration ability was evaluated by transwell assay and cell intratibial injection assay. The bone formation was evaluated by microCT analysis and bone morphometry analysis.

Results: We reported that the decreased bone formation was accompanied by the reduced migration capacity of the bone marrow mesenchymal stem cells (BMSCs, the unique source of OPCs in bone marrow) in aged mice. We further identified that the long non-coding RNA PMIF (postulated migration inhibitory factor) (i.e., lnc-PMIF) was highly expressed in BMSCs from aged mice and responsible for the reduced migration capacity of aged OPCs to bone formation surface. Mechanistically, we found that lnc-PMIF could bind to human antigen R (HuR) for interrupting the HuR-β-actin mRNA interaction, therefore inhibit the expression of β-actin for suppressing the migration of aged OPCs. We also authenticated a functionally conserved human lncRNA ortholog of the murine lnc-PMIF. By cell-based therapy approach, we demonstrated that replenishing the aged BMSCs with small interfering RNA (siRNA)-mediated lnc-PMIF knockdown could promote bone formation in aged mice. By pharmacological approach, we showed that targeted delivery of lnc-PMIF siRNA approaching the OPCs around the bone formation surface could also promote bone formation in aged mice.

Conclusion: Toward translational medicine, this study hints that targeting lnc-PMIF to facilitate aged OPCs migrating to bone formation surface could be a brand-new anabolic strategy for aging-related osteoporosis.

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.

MicroRNA-29b Promotes Subchondral Bone Loss in TMJ Osteoarthritis

Abnormal subchondral bone remodeling plays important roles during osteoarthritis (OA) pathology. Recent studies show that bone marrow mesenchymal stem cells (BMSCs) in osteoarthritic subchondral bones exhibit a prominent pro-osteoclastic effect that contributes to abnormal subchondral bone remodeling; however, the pathologic mechanism remains unclear. In the present study, we used a mouse model with OA-like change in the temporomandibular joint (TMJ) induced by an experimentally unilateral anterior crossbite (UAC) and found that the level of microRNA-29b (miR-29b), but not miR-29a or miR-29c, was markedly lower in BMSCs from subchondral bones of UAC mice as compared with that from the sham control mice. With an intra-articular aptamer delivery system, BMSC-specific overexpression of miR-29b by aptamer-agomiR-29b rescued subchondral bone loss and osteoclast hyperfunction in UAC mice, as demonstrated by a significant increase in bone mineral density, bone volume fraction, trabecular thickness, and the gene expression of osteocalcin and Runx2 but decreased trabecular separation, osteoclast number and osteoclast surface/bone surface, and the gene expression of cathepsin K, Trap, Wnt5a, Rankl, and Rank as compared with those in the UAC mice treated by aptamer-NC (all P < 0.05). In addition, BMSC-specific inhibition of miR-29b by aptamer-antagomiR-29b exacerbated those responses in UAC mice. Notably, although it primarily affected miR-29b levels in the subchondral bone (but not in cartilage and synovium), BMSC-specific overexpression of miR-29b in UAC mice largely rescued OA-like cartilage degradation, including decreased chondrocyte density, cartilage thickness, and the percentage areas of proteoglycans and type II collagen, while BMSC-specific inhibition of miR-29b aggravated these characteristics of cartilage degradation in UAC mice. Moreover, we identified Wnt5a, but not Rankl or Sdf-1, as the direct target of miR-29b. The results of the present study indicate that miR-29b is a key regulator of the pro-osteoclastic effects of BMSCs in TMJ-OA subchondral bones and plays important roles in the TMJ-OA progression.

Prostatic epithelial cells and their high expressions of CKIP-1 affect the TGF-β1 expression levels which might reduce the scar formation in remodeling stage at prostatic urethral wounds after wound repair

Objective

There are less scar formations in some wounds after wound repair. Our earlier study had shown that the amount of collagen fibers in canine prostatic urethra wound were less than in bladder neck wound after 2-μm laser resection of the prostate (TmLRP) and partial bladder neck mucosa at 4 weeks. The purpose of this study was to observe the amount of scar tissue and characterize the probable causes of “less scar healing” in prostatic urethra wound.

Methods

A total of 12 healthy adult male crossbred canines underwent resection of prostate and partial bladder neck mucosa using 2-μm laser. The prostatic urethra and bladder neck wound specimens were harvested at 3, 4, 8 and 12 weeks after operation, respectively. The histopathologic characteristics were observed by hematoxylin and eosin(HE)staining, and the expression of transforming growth factor-β₁ (TGF-β₁) and casein kinase-2 interacting protein-1 (CKIP-1) were examined by immunohistochemistry in prostatic urethra and bladder neck wound, respectively. Overexpressed CKIP-1 human prostate epithelial cells (BPH-1 cells) were established and the expression of TGF-β₁ was detected by Western blotting. Furthermore, a non-contact co-culture system of BPH-1 cells and human fibroblast (HFF-1) cells was used to observe the effects of BPH-1 cell and their high CKIP-1 levels on the expression of TGF-β₁ in HFF-1 in vitro.

Results

The histology showed that there were a large number of prostatic epithelium and a small amount of scar tissue in prostatic urethra wound, while no epithelial cells and more scar tissue in bladder neck wound at 4, 8 and 12 weeks after repair. There were a higher expression level of TGF-β₁ in prostate epithelial cells and fibroblasts and a lower expression level of CKIP-1 in prostate epithelial cells at 3 weeks after surgery in prostatic urethral wound. Compared to week 3, the TGF-β₁ expression decreased both in prostate epithelial cells and fibroblasts at 4, 8 and 12 weeks in prostatic urethral wound (p < 0.05 or p < 0.01). The CKIP-1 expression increased in prostate epithelial cells at 4, 8 and 12 weeks compared to 3 weeks in prostatic urethra wound (p < 0.01). A higher TGF-β1 expression level of fibroblasts was observed in bladder neck wound at 3 weeks. And there was no significant change in the expression of TGF-β₁ of fibroblasts in 3, 4, 8 and 12 weeks after operation in bladder neck wound. Both the prostate urethra and bladder neck wound fibroblasts showed weak expression of CKIP-1 and there was no significant change in 3, 4, 8 and 12 weeks. The vitro experiments showed that the TGF-β₁ expression in BPH-1 cells with CKIP-1 overexpression decreased 25% compared with control group (p < 0.05). Furthermore, the expression of TGF-β₁ in HFF-1 cells of co-cultured group decreased by 20% compared with Control group (p < 0.05); the expression of TGF-β₁ in HFF-1 cells of overexpression co-culture group were reduced by 15% compared with co-cultured group (p < 0.01).

Conclusions

A large number of prostate epithelial cells in prostatic urethra wound may be one of the causes of less formation of scar tissue after repair. The prostate epithelial cells might reduce expression level of TGF-β₁ by raising CKIP-1 expression and inhibit expression of TGF-β₁ in peripheral fibroblasts at remodeling stage to reduce the excessive proliferation of fibrous cells and the excessive scar formation.

Physiological functions of CKIP-1: From molecular mechanisms to therapy implications

The casein kinase 2 interacting protein-1 (CKIP-1, also known as PLEKHO1) is initially identified as a specific CK2α subunit-interacting protein. Subsequently, various proteins, including CPα, PAK1, Arp2/3, HDAC1, c-Jun, ATM, Smurf1, Rpt6, Akt, IFP35, TRAF6, REGγ and CARMA1, were reported to interact with CKIP-1. Owing to the great diversity of interacted proteins, CKIP-1 exhibits multiple biologic functions in cell morphology, cell differentiation and cell apoptosis. Besides, these functions are subcellular localization, cell type, and regulatory signaling dependent. CKIP-1 is involved in biological processes consisting of bone formation, tumorigenesis and immune regulation. Importantly, deregulation of CKIP-1 results in osteoporosis, tumor, and atherosclerosis. In this review, we introduce the molecular functions, biological processes and promising of therapeutic strategies. Through summarizing the intrinsic mechanisms, we expect to open new therapeutic avenues for CKIP-1.

Intracellular attenuation of BMP signaling via CKIP-1/Smurf1 is essential during neural crest induction

The neural crest is induced at the neural plate border during gastrulation by combined bone morphogenetic protein (BMP), fibroblast growth factor (FGF), and Wnt signaling. While intermediate BMP levels are critical for this induction, secreted BMP inhibitors are largely absent from the neural plate border. Here, we propose a morphogen model in which intracellular attenuation of BMP signaling sets the required intermediate levels to maintain neural crest induction. We show that the scaffold protein casein kinase interacting protein 1 (CKIP-1) and ubiquitin ligase Smad ubiquitin regulatory factor 1 (Smurf1) are coexpressed with BMP4 at the chick neural plate border. Knockdown of CKIP-1 during a critical period between gastrulation and neurulation causes neural crest loss. Consistent with specific BMP modulation, CKIP-1 loss suppresses phospho-Smads 1/5/8 (pSmad1/5/8) and BMP reporter output but has no effect on Wnt signaling; Smurf1 overexpression (OE) acts similarly. Epistasis experiments further show that CKIP-1 rescues Smurf1-mediated neural crest loss. The results support a model in which CKIP-1 suppresses Smurf1-mediated degradation of Smads, uncovering an intracellular mechanism for attenuation of BMP signaling to the intermediate levels required for maintenance of neural crest induction.

The role of CKIP-1 in osteoporosis development and treatment

Osteoporosis is a systemic skeletal disorder characterized by reduced bone mass and deterioration of bone microarchitecture, which results in increased bone fragility and fracture risk. Casein kinase 2-interacting protein-1 (CKIP-1) is a protein that plays an important role in regulation of bone formation. The effect of CKIP-1 on bone formation is mainly mediated through negative regulation of the bone morphogenetic protein pathway. In addition, CKIP-1 has an important role in the progression of osteoporosis. This review provides a summary of the recent studies on the role of CKIP-1 in osteoporosis development and treatment.

Cite this article: X. Peng, X. Wu, J. Zhang, G. Zhang, G. Li, X. Pan. The role of CKIP-1 in osteoporosis development and treatment. Bone Joint Res 2018;7:173–178. DOI: 10.1302/2046-3758.72.BJR-2017-0172.R1.

CKIP-1 serves as a negative regulator and correlates with the degree of differentiation in gastric cancer

Gastric cancer (GC) is one of the most commonly diagnosed malignancies worldwide. CKIP-1 is a casein kinase-2 α-subunit (CK2α) interacting protein. Though previous reports have shown that CKIP-1 plays a critical role in several types of cancers, hardly there are any studies that examined the role of CKIP-1 in the progression of GC. Our present study aimed to investigate the role of CKIP-1 in GC. Results demonstrated low-level expression of CKIP-1 in GC tissues and cell lines. Moreover, knockdown of CKIP-1 promoted cell proliferation, migration, and invasion in GC cell lines, whereas CKIP-1 overexpression inhibited proliferation, migration, and invasion in the cells. Altogether, our data suggests that CKIP-1 may act as a novel tumor suppressor gene in GC and is related to GC differentiation.