Ucma, a direct transcriptional target of Runx2 and Osterix, promotes osteoblast differentiation and nodule formation

Unique cartilage matrix-associated protein inhibits osteoclast differentiation by alleviating RANKL-induced reactive oxygen species

Unique cartilage matrix-associated protein (UCMA) is a γ-carboxyglutamic acid-rich secretory protein primarily expressed in adult cartilage. UCMA promotes osteoblast differentiation and reduces high glucose-induced reactive oxygen species (ROS) production in osteoblasts; however, its role in osteoclasts remains unclear. Since Ucma is not expressed in osteoclasts, treatment with recombinant UCMA protein (rUCMA) was employed to investigate the effect of UCMA on osteoclasts. The rUCMA-treated osteoclasts exhibited significantly reduced osteoclast differentiation, resorption activity, and osteoclast-specific gene expression. Moreover, rUCMA treatment reduced RANKL-induced ROS production and increased the expression of antioxidant genes in osteoclasts. This study demonstrates that UCMA effectively inhibits RANKL-stimulated osteoclast differentiation and oxidative stress.

Regulation of Immune Inflammation and Promotion of Periodontal Bone Regeneration by Irisin-Loaded Bioactive Glass Nanoparticles

Clinical solutions of bone defects caused by periodontitis involve surgical treatment and subsequent anti-infection treatment using antibiotics. Such a strategy faces a key challenge in that the excessive host immune response results in the damage of periodontal tissues. Consequently, it is of great importance to develop novel periodontitis treatment that allows the regulation of the host immune response and promotes the generation of periodontal tissues. Irisin has a good bone regeneration ability and could reduce the inflammatory reaction by regulating the differentiation of macrophages. In this study, we loaded irisin onto bioactive glass nanoparticles (BGNs) to prepare a composite, irisin-BGNs (IR-BGNs) with anti-inflammatory, bacteriostatic, and tissue regeneration functions, providing a novel idea for the design of ideal materials for repairing oral tissue defects caused by periodontitis. We also verified that the IR-BGNs had better anti-inflammatory properties on RAW264.7 cells compared to irisin and BGNs alone. Strikingly, when hPDLCs were stimulated with IR-BGNs, they exhibited increased expression of markers linked to osteogenesis, ALP activity, and mineralization ability in comparison to the negative control. Furthermore, on the basis of RNA sequencing results, we validated that the p38 pathway can contribute to the osteogenic differentiation of the IR-BGNs. This work may offer new thoughts on the design of ideal materials for repairing oral tissue defects.

Hydrolyzed Collagen Tripeptide Promotes Longitudinal Bone Growth in Childhood Rats via Increases in Insulin-Like Growth Factor-1 and Bone Morphogenetic Proteins

Previous studies have reported that collagen tripeptide (CTP) derived from collagen hydrolysate has various beneficial effects on health by protecting against skin aging and improving bone formation and cartilage regeneration. Collagen-Tripep20TM (CTP20), which is a low-molecular-weight CTP derived from fish skin, contains a bioactive CTP, Gly-Pro-Hyp >3.2% with a tripeptide content >20%. Herein, we investigated the osteogenic effects and mechanisms of CTP20 (<500 Da) on MG-63 osteoblast-like cells and SW1353 chondrocytes. And we measured promoting ratio of the longitudinal bone growth in childhood rats. First, CTP20 at 100 μg/mL elevated the proliferation (15.0% and 28.2%), alkaline phosphatase activity (29.3% and 32.0%), collagen synthesis (1.25- and 1.14-fold), and calcium deposition (1.18- and 1.15-fold) in MG-63 cells and SW1353, respectively. In addition, we found that CTP20 could promote the longitudinal growth and height of the growth plate of the tibia in childhood rats. CTP20 enhanced the protein expression of insulin-like growth factor-1 (IGF-1) in MG-63 and SW1353 cells, and in the growth plate of childhood rats, along with Janus Kinase 2, and signal transducer and activator of transcription 5 activation in MG-63 and SW1353 cells. CTP20 also elevated the expression levels of bone morphogenetic proteins (BMPs) in MG-63 and SW1353 cells and in the growth plates of childhood rats. These results indicate that CTP20 may promote the endochondral ossification and longitudinal bone growth, through enhancing of IGF-1 and BMPs. (Clinical Trial Registration number: smecae 19-09-01).

Growth dynamics and molecular bases of evolutionary novel jaw extensions in halfbeaks and needlefishes (Beloniformes)

Evolutionary novelties-derived traits without clear homology found in the ancestors of a lineage-may promote ecological specialization and facilitate adaptive radiations. Examples for such novelties include the wings of bats, pharyngeal jaws of cichlids and flowers of angiosperms. Belonoid fishes (flying fishes, halfbeaks and needlefishes) feature an astonishing diversity of extremely elongated jaw phenotypes with undetermined evolutionary origins. We investigate the development of elongated jaws in a halfbeak (Dermogenys pusilla) and a needlefish (Xenentodon cancila) using morphometrics, transcriptomics and in situ hybridization. We confirm that these fishes' elongated jaws are composed of distinct base and novel 'extension' portions. These extensions are morphologically unique to belonoids, and we describe the growth dynamics of both bases and extensions throughout early development in both studied species. From transcriptomic profiling, we deduce that jaw extension outgrowth is guided by populations of multipotent cells originating from the anterior tip of the dentary. These cells are shielded from differentiation, but proliferate and migrate anteriorly during the extension's allometric growth phase. Cells left behind at the tip leave the shielded zone and undergo differentiation into osteoblast-like cells, which deposit extracellular matrix with both bone and cartilage characteristics that mineralizes and thereby provides rigidity. Such bone has characteristics akin to histological observations on the elongated 'kype' process on lower jaws of male salmon, which may hint at common conserved regulatory underpinnings. Future studies will evaluate the molecular pathways that govern the anterior migration and proliferation of these multipotent cells underlying the belonoids' evolutionary novel jaw extensions.

Improvement of Estrogen Deficiency Symptoms by the Intake of Long-Term Fermented Soybeans (Doenjang) Rich in Bacillus Species through Modulating Gut Microbiota in Estrogen-Deficient Rats

Traditionally made doenjang (TMD) produced by the long-term fermentation of soybeans with salt may improve symptoms of estrogen deficiency. We aimed to evaluate the effects of four TMD types, containing low and high amounts of Bacillus species and biogenic amines (HBHA, HBLA, LBHA, and LBLA), on energy, glucose, and lipid metabolism, by altering the gut microbiota in estrogen-deficient ovariectomized (OVX) rats. Their mechanisms were also examined. The OVX rats were divided into the control, cooked soybean (CSB), HBHA, LBHA, HBLA, and LBLA groups. Sham-operated rats were the normal control group. Serum 17β-estradiol concentrations were similar among all OVX groups. Tail skin temperatures, which are indicative of hot flashes, were higher in the control than the HBHA and HBLA groups and were similar to the normal control group. Weight gain and visceral fat mass were lower in the TMD and CSB intake groups but not as low as in the normal control group. Lean body mass showed a trend opposite to that of visceral fat in the respective groups. The hepatic triglyceride content decreased with the TMD intake compared to the control and CSB groups. mRNA expressions of the peroxisome proliferator-activated receptor-γ (PPAR-γ) and carnitine palmitoyltransferase-1 in the TMD and CSB groups were as high as in the normal control group, and the PPAR-γ mRNA expression was more elevated in the HBLA group than in the normal control group. The morphology of the intestines improved in the TMD groups compared to the control, and the HBHA and HBLA groups showed an enhanced improvement compared to the CSB group. The HBHA, HBLA, and LBHA groups increased the α-diversity of the cecal microbiota compared to the control. Akkermenia and Lactobacillus were higher in the HBLA and LBLA groups compared to the control. The expression of the estrogen, forkhead box proteins of the class-O subgroup, and insulin-signaling pathways were lower in the control group, and HBHA and HBLA prevented their decrement. In conclusion, long-term treatment with TMD containing high amounts of Bacillus potentially improves estrogen deficiency symptoms more than unfermented soybeans.

Probable Treatment Targets for Diabetic Retinopathy Based on an Integrated Proteomic and Genomic Analysis

Purpose

Using previously approved medications for new indications can expedite the lengthy and expensive drug development process. We describe a bioinformatics pipeline that integrates genomics and proteomics platforms to identify already-approved drugs that might be useful to treat diabetic retinopathy (DR).

Methods

Proteomics analysis of vitreous humor samples from 12 patients undergoing pars plana vitrectomy for DR and a whole genome dataset (UKBiobank TOPMed-imputed) from 1330 individuals with DR and 395,155 controls were analyzed independently to identify biological pathways associated with DR. Common biological pathways shared between both datasets were further analyzed (STRING and REACTOME analyses) to identify target proteins for probable drug modulation. Curated target proteins were subsequently analyzed by the BindingDB database to identify chemical compounds they interact with. Identified chemical compounds were further curated through the Expasy SwissSimilarity database for already-approved drugs that interact with target proteins.

Results

The pathways in each dataset (proteomics and genomics) converged in the upregulation of a previously unknown pathway involved in DR (RUNX2 signaling; constituents MMP-13 and LGALS3), with an emphasis on its role in angiogenesis and blood-retina barrier. Bioinformatics analysis identified U.S. Food and Drug Administration (FDA)-approved medications (raltitrexed, pemetrexed, glyburide, probenecid, clindamycin hydrochloride, and ticagrelor) that, in theory, may modulate this pathway.

Conclusions

The bioinformatics pipeline described here identifies FDA-approved drugs that can be used for new alternative indications. These theoretical candidate drugs should be validated with experimental studies.

Translational Relevance

Our study suggests possible drugs for DR treatment based on an integrated proteomics and genomics pipeline. This approach can potentially expedite the drug discovery process by identifying already-approved drugs that might be used for new indications.

Exosomal miR-29a Derived from Bone Marrow Mesenchymal Stem Cells Promotes Mouse Bone Development and Formation

Bone undergoes constant remodeling during development, and the maintenance of its function requires a dynamic balance between bone formation and resorption by osteoclasts. With unique bone resorption capabilities, as large multinucleated cells, osteocytes participate in bone remodeling and they are produced by the mononuclear/macrophage cells under activation of Wnt and Runx2. The mechanism underlying osteogenesis remains unclear. We investigated the impact of exosomal miR-29a derived from BMSCs on bone development and formation. In this study, BMSCs were transfected and then injected into mice followed by analysis of femur and skull development and regeneration by HE staining and CT scanning, and the expression of DKK1, Runx-2, and osteogenic biomarkers (Osterix, Satb2, ALP, and BSP) by western blot and RT-qPCR. Compared with mice in miR-29a inhibitor group, the femur and skull of mice in miRNA NC group were more complete. miR-29a derived from BMSCs induced a decrease of DKK1 expression and increase of the expression of β-catenin and osteogenic transcription factors. In conclusion, this study demonstrates that BMSC-derived exosomes miR-29a facilitates osteogenesis in mice through inhibition of DKK1 expression.

Alleviation of Metabolic Disturbance by Substituting Kanjang High in Bacillus for Salt through Modulation of Gut Microbiota in Estrogen-Deficient Rats

A high salt intake may exacerbate menopausal symptoms and substituting for different types of traditionally made kanjang (TMK; soy sauce) may prevent it. This study examined whether substituting salt with lyophilized TMK containing low and high Bacillus and biogenic amines in a high-fat diet might modulate the menopausal symptoms and the energy, glucose, and lipid metabolism in ovariectomized (OVX) rats. They were categorized into salt (Control), TMK with high Bacillus and low biogenic amines (HBLB), TMK with high Bacillus and high biogenic amines (HBHB), TMK with low Bacillus and low biogenic amines (LBLB), and TMK with low Bacillus and high biogenic amines (LBHB). Sham-operated rats consumed the same diet as the Control. HBLB, HBHB, and LBHB prevented increased tail skin temperature compared to the Control. HBHB and HBLB partially inhibited the increased weight gain and abdominal fat mass by reducing the food efficiency without changing the serum 17β-estradiol concentrations. Serum glucose and insulin concentrations and the insulin resistance index by the homeostatic model assessment for insulin resistance showed a positive association for weight gain. HBLB and HBHB decreased the serum malondialdehyde and tumor-necrosis factor-α levels. Hepatic triglyceride storage was lower in all TMK groups than in the Control, while hepatic glycogen accumulation was higher in the HBLB, HBHB, and LBHB groups than in the Control and LBLB groups. Accordingly, the mRNA expression of peroxisome proliferator-activated receptors-γ(PPAR-γ) was higher in the HBLB and HBHB groups compared to the Control, and that of fatty acid synthase was opposite to PPAR-γ expression. However, HBLB and HBHB improved dyslipidemia and insulin resistance compared to the Control, but their improvement did not reach that of the Normal-control. The acetic acid concentrations in the portal vein were lower in the LBLB than in the Control, while the butyric acid contents were higher in the LBHB and HBLB groups than in the Control. HBHB, HBLB, and LBHB elevated Akkermansia and Lactobacillus, and HBLB and LBLB increased Bacteroides and Ruminococcus compared to the Control. Polycyclic aromatic hydrocarbon degradation, bile acid synthesis, and unsaturated fatty acid biosynthesis were significantly higher in the HBLB group than in the Control group. In conclusion, substituting salts to TMK with a high Bacillus content regardless of the bioamine contents partially improved the menopausal symptoms and metabolic disturbance in estrogen-deficient animals.

Bone Marrow Mesenchymal Stem Cell-Exosomes (BMSC-ExO) Promote Osteogenic Differentiation In Vitro and Osteogenesis In Vivo by Regulating miR-318/Runt-Related Transcription Factor 2 (RUNX2)

Primary osteoporosis (PMOP) is characterized by bone mass reduction and bone microstructure destruction, increased bone fragility and prone to fracture, which is partially caused by ovarian dysfunction and decreased estrogen content. Bone marrow mesenchymal stem cell exosomes (BMSC-ExO) can improve PMOP. In this study, BMSC-EXO was used to study the role and function of miR-318 and Runx2 in PMOP. Human osteogenitor cells were isolated from PMOP patients with primary osteoporosis. After BMSC-exo treatment, miR-318 and Runx 2 level was tested by RT-qPCR and Western blot. In addition, mice in OVX group were treated with BMSC-ExO (bilateral ovaries were removed) to observe the effect of BMSC-ExO on bone tissue. Our results showed that BMSC-exo treatment significantly decreased miR-318 level, upregulated RUNX2 expression and increased ALP activity. In addition, BMSC-exo administration ameliorated the declined bone mass and bone formation in osteoporotic femurs in OVX mice. In conclusion, BMSC-Exo enhances Runx2 levels by down-regulation of miR-318, thereby promoting osteogenic differentiation of osteogenitor cells, providing new potential therapeutic targets for treating PMOP.

Sp7 Action in the Skeleton: Its Mode of Action, Functions, and Relevance to Skeletal Diseases

Osteoblast differentiation is a tightly regulated process in which key transcription factors (TFs) and their target genes constitute gene regulatory networks (GRNs) under the control of osteogenic signaling pathways. Among these TFs, Sp7 works as an osteoblast determinant critical for osteoblast differentiation. Following the identification of Sp7 and a large number of its functional studies, recent genome-scale analyses have made a major contribution to the identification of a "non-canonical" mode of Sp7 action as well as "canonical" ones. The analyses have not only confirmed known Sp7 targets but have also uncovered its additional targets and upstream factors. In addition, biochemical analyses have demonstrated that Sp7 actions are regulated by chemical modifications and protein-protein interaction with other transcriptional regulators. Sp7 is also involved in chondrocyte differentiation and osteocyte biology as well as postnatal bone metabolism. The critical role of SP7 in the skeleton is supported by its relevance to human skeletal diseases. This review aims to overview the Sp7 actions in skeletal development and maintenance, particularly focusing on recent advances in our understanding of how Sp7 functions in the skeleton under physiological and pathological conditions.

Protection against Osteoporosis by Fermented Mulberry Vinegar Supplementation via Inhibiting Osteoclastic Activity in Ovariectomized Rats and Osteoclastic Cells

Menopause increases the osteoporosis risk, to which phytoestrogen intake can be beneficial. This study hypothesized that mulberry vinegar had a preventive effect on osteoporosis by decreasing osteoclastic activity. The hypothesis was tested in ovariectomized (OVX) rats and RANKL-differentiated osteoclast cells. OVX rats were given 0(OVX-CON), 0.5(OVX-MVL), 1(OVX-MVM), and 2(OVX-MVH) fermented mulberry vinegar (MV) mL/kg body weight (BW) daily for 12 weeks. Sham-operated rats had no MV supplementation (Normal-CON). The osteoporosis-related biomarkers were measured, and Micro-CT determined the bone mass of the femur. RANKL-differentiated Raw 264.7 cells were treated with MV (0–100 μg/mL). The cell viability, osteoporosis-related mRNA expression, and protein contents were measured. MV contained Acetobacter pasteurianus (7.31 log CFU/mL), citric acid (106 mg/mL), lactic acid (19.2 mg/mL), acetic acid (15.0 mg/mL), and rutin (0.36 mg/mL). OVX-MVM elevated the serum 17β-estradiol concentration similar to the Normal-CON group, but it did not prevent the decrease in uterine weight. OVX-MVM prevented the increase in osteoclastic-related parameters, including cathepsin K(CtsK), receptor activator of NF-κB ligand (RANKL), and tartrate-resistant acid phosphatase (TRAP) in the circulation. OVX-MVH also lowered C-telopeptide of type Ⅰ collagen as much as the Normal-CON group (p < 0.05). By contrast, OVX-MVH increased the serum osteoprotegerin concentration, an inhibitor of osteoclasts, better than the Normal-CON group (p < 0.05). These changes were integrated to alter the bone mineral density (BMD) in Micro-CT analysis: OVX-MVM and OVX-MVH prevented BMD decrease after OVX as much as the Normal-CON. In RANKL-differentiated osteoclast cells, the MV treatment for 24 and 48 h decreased RANKL-induced differentiation in osteoclast cells dose-dependently up to 100 µg/mL. Its decrease was related to inhibiting the TRAP activity and reducing TRAP-positive multinucleated cells during the five-day administration of RANKL. MV treatments also decreased mRNA expression of osteoclast-related genes (TRAP, Ctsk, OSCAR, and NFATc1). MV suppressed the protein contents of NFATc1 and c-FOS-related osteoclast. In conclusion, MV intake (1 mg/kg bw) protected against BMD loss mainly by inhibiting the osteoclastic activity (RANKL/RANK/TRAP) in OVX rats. MV may develop as a functional food for anti-osteoporosis in menopausal women.

Vitamin K-Dependent Proteins in Skeletal Development and Disease

Vitamin K and Vitamin K-dependent proteins (VKDPs) are best known for their pivotal role in blood coagulation. Of the 14 VKPDs identified in humans to date, 6 play also important roles in skeletal biology and disease. Thus, osteocalcin, also termed bone Gla-protein, is the most abundant non-collagenous protein in bone. Matrix Gla protein and Ucma/GRP on the other hand are highly abundant in cartilage. Furthermore, periostin, protein S, and growth arrest specific 6 protein (GAS 6) are expressed in skeletal tissues. The roles for these VKDPs are diverse but include the control of calcification and turnover of bone and cartilage. Vitamin K plays an important role in osteoporosis and serum osteocalcin levels are recognized as a promising marker for osteoporosis. On the other hand, matrix Gla protein and Ucma/GRP are associated with osteoarthritis. This review focuses on the roles of these three VKDPs, osteocalcin, matrix Gla protein and Ucma/GRP, in skeletal development and disease but will also summarize the roles the other skeletal VKDPs (periostin, protein S and GAS6) in skeletal biology.

C-C chemokine receptor type 6 modulates the biological function of osteoblastogenesis by altering the expression levels of Osterix and OPG/RANKL

Circulating inflammatory factors affect osteoblast and osteoclast formation and activity in osteoporosis. Estrogen affects the migration of Th17 cells via the C-C chemokine receptor type 6 (CCR6) and C-C chemokine ligand 20 (CCL20) signaling pathways to modulate bone metabolism; however, it is unclear whether and how CCR6 modulates bone homeostasis. In the present study, CCR6 knockout (CCR6^-/-) mice were selected to investigate the effects of CCR6 in the regulation of homeostasis of osteoblasts and osteoclasts. Primary osteoblasts were isolated from the calvarium of newborn CCR6^-/- or wild-type mice, followed by osteoblastic differentiation culture in vitro. CCR6 deletion reduced osteoblast activity in terms of alkaline phosphatase (ALP) activity and inhibited osteoblast mineralization according to the results of Alizarin Red S staining, whereas it did not affect the proliferation of osteoblasts. CCR6 deletion inhibited Osterix mRNA expression in osteoblasts during the late stage of mineralization in vitro, while it did not affect mRNA expression levels of runt-related transcription factor 2 (Runx2) and Collagen-1. The ratio of osteoprotegerin (OPG) /receptor activator of nuclear factor κ-Β ligand (RANKL) mRNA level in osteoblasts was decreased by CCR6 deficiency in the culture treated with 1,25(OH)2D3/PGE2, while there was no effect observed in the normal culture environment. The results provide novel insights, such as that CCR6 deletion suppresses osteoblast differentiation by downregulating the expression levels of the transcription factor Osterix, and indirectly promotes osteoclast production by increasing transcription of RANKL. This may be one of the mechanisms via which CCR6 deletion regulates bone metabolism.

Signaling Pathway and Transcriptional Regulation in Osteoblasts during Bone Healing: Direct Involvement of Hydroxyapatite as a Biomaterial

Bone defects and periodontal disease are pathological conditions that may become neglected diseases if not treated properly. Hydroxyapatite (HA), along with tricalcium phosphate and bioglass ceramic, is a biomaterial widely applied to orthopedic and dental uses. The in vivo performance of HA is determined by the interaction between HA particles with bone cells, particularly the bone mineralizing cells osteoblasts. It has been reported that HA-induced osteoblastic differentiation by increasing the expression of osteogenic transcription factors. However, the pathway involved and the events that occur in the cell membrane have not been well understood and remain controversial. Advances in gene editing and the discovery of pharmacologic inhibitors assist researchers to better understand osteoblastic differentiation. This review summarizes the involvement of extracellular signal-regulated kinase (ERK), p38, Wnt, and bone morphogenetic protein 2 (BMP2) in osteoblastic cellular regulation induced by HA. These advances enhance the current understanding of the molecular mechanism of HA as a biomaterial. Moreover, they provide a better strategy for the design of HA to be utilized in bone engineering.

Role of emerging vitamin K‑dependent proteins: Growth arrest‑specific protein 6, Gla‑rich protein and periostin (Review)

Vitamin K‑dependent proteins (VKDPs) are a group of proteins that need vitamin K to conduct carboxylation. Thus far, scholars have identified a total of 17 VKDPs in the human body. In this review, we summarize three important emerging VKDPs: Growth arrest‑specific protein 6 (Gas 6), Gla‑rich protein (GRP) and periostin in terms of their functions in physiological and pathological conditions. As examples, carboxylated Gas 6 and GRP effectively protect blood vessels from calcification, Gas 6 protects from acute kidney injury and is involved in chronic kidney disease, GRP contributes to bone homeostasis and delays the progression of osteoarthritis, and periostin is involved in all phases of fracture healing and assists myocardial regeneration in the early stages of myocardial infarction. However, periostin participates in the progression of cardiac fibrosis, idiopathic pulmonary fibrosis and airway remodeling of asthma. In addition, we discuss the relationship between vitamin K, VKDPs and cancer, and particularly the carboxylation state of VKDPs in cancer.

Recent Advances of Osterix Transcription Factor in Osteoblast Differentiation and Bone Formation

With increasing life expectations, more and more patients suffer from fractures either induced by intensive sports or other bone-related diseases. The balance between osteoblast-mediated bone formation and osteoclast-mediated bone resorption is the basis for maintaining bone health. Osterix (Osx) has long been known to be an essential transcription factor for the osteoblast differentiation and bone mineralization. Emerging evidence suggests that Osx not only plays an important role in intramembranous bone formation, but also affects endochondral ossification by participating in the terminal cartilage differentiation. Given its essentiality in skeletal development and bone formation, Osx has become a new research hotspot in recent years. In this review, we focus on the progress of Osx's function and its regulation in osteoblast differentiation and bone mass. And the potential role of Osx in developing new therapeutic strategies for osteolytic diseases was discussed.

Unique cartilage matrix-associated protein inhibits the migratory and invasive potential of triple-negative breast cancer

Triple-negative breast cancer (TNBC) that lacks expression of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2) is a breast cancer subtype with very aggressive metastasis and poor prognosis. Unique cartilage matrix-associated protein (UCMA) is a vitamin K-dependent protein (VKDP) with a high-density γ-carboxyglutamic acid (Gla) domain due to the action of vitamin K. UCMA promotes osteoblast differentiation and mineral deposition in bone and suppresses calcification in vessels. However, correlation between UCMA and TNBC is unknown. This study investigated the inhibitory effect of UCMA on TNBC cell in vitro migration, invasion, and colony formation in addition to in vivo tumorigenesis. Cell migration and invasion significantly decreased in Ucma-overexpressing MDA-MB-231 and 4T1 cells compared to the mock control cells. Also, colony formation and the number of colonies significantly decreased in Ucma-overexpressing MDA-MB-231 and 4T1 cells. These results indicate that UCMA significantly inhibits the migration, invasion, and colony formation of TNBC cells. In an in vivo xenograft mouse model, tumor growth significantly decreased in mice bearing Ucma-overexpressing TNBC cells compared to the mock control cells, indicating that UCMA reduced in vivo tumor growth, similar to the inhibitory role of UCMA in vitro. Survival analysis using publicly available database showed that high UCMA expression significantly correlated with favorable relapse-free survival in TNBC patients compared to those with the other VKDPs, matrix Gla protein (MGP) and osteocalcin (OCN). Collectively, this study suggests that UCMA is a promising new therapeutic agent for TNBC.

The Bone-Vasculature Axis: Calcium Supplementation and the Role of Vitamin K

Calcium supplements are broadly prescribed to treat osteoporosis either as monotherapy or together with vitamin D to enhance calcium absorption. It is still unclear whether calcium supplementation significantly contributes to the reduction of bone fragility and fracture risk. Data suggest that supplementing post-menopausal women with high doses of calcium has a detrimental impact on cardiovascular morbidity and mortality. Chronic kidney disease (CKD) patients are prone to vascular calcification in part due to impaired phosphate excretion. Calcium-based phosphate binders further increase risk of vascular calcification progression. In both bone and vascular tissue, vitamin K-dependent processes play an important role in calcium homeostasis and it is tempting to speculate that vitamin K supplementation might protect from the potentially untoward effects of calcium supplementation. This review provides an update on current literature on calcium supplementation among post-menopausal women and CKD patients and discusses underlying molecular mechanisms of vascular calcification. We propose therapeutic strategies with vitamin K2 treatment to prevent or hold progression of vascular calcification as a consequence of excessive calcium intake.

DGCR5 induces osteogenic differentiation by up-regulating Runx2 through miR-30d-5p

BACKGROUND

Postmenopausal osteoporosis (PMOP) is a metabolic bone disease caused by unbalance between osteoblast bone formation and osteoclast bone resorption. In this study, the moderating effect of DGCR5 on osteogenic differentiation and its role in PMOP was assessed.

METHODS

The expression levels of DGCR5, miR-30d-5p, and Runt-related transcription factor 2 (Runx2) mRNA and protein were determined by qRT-PCR and western blot, separately. The bone marrow human mesenchymal stem cells (hMSCs) were isolated from bone marrow of patients with PMOP or the healthy control. ALP activity and bone mineral density (BMD) were detected to reflect the osteogenic differentiation status. RIP and RNA pull-down assay were performed to explore the combination and interaction between DGCR5 and miR-30d-5p.

RESULTS

Compared with the healthy control group (n = 20), DGCR5 was down-regulated in hMSCs from patients with PMOP (n = 20). Overexpression of DGCR5 induced osteogenic differentiation of hMSCs. DGCR5 up-regulated the expression of Runx2 through miR-30d-5p. DGCR5 up-regulated the expression of Runx2 through miR-30d-5p to induce osteogenic differentiation of hMSCs.

CONCLUSION

DGCR5 negatively regulates miR-30d-5p, and it up-regulates Runx2 through miR-30d-5p, thereby inducing osteogenic differentiation of hMSCs, which may help to delay PMOP development.

miR‑204‑5p inhibits the occurrence and development of osteoarthritis by targeting Runx2

One of the hallmarks of osteoarthritis (OA) development is endochondral ossification, in which Runt-related transcription factor-2 (Runx2) is aberrantly expressed. Runx2 was previously identified to be regulated by microRNA-204-5p (miR-204-5p). The aim of the present study was to investigate the potential function of miR-204-5p regulating Runx2 during the development of OA and the underlying molecular mechanism. The expression levels of miR-204-5p and Runx2 were determined in tissue specimens. Rat OA models were established by transecting the anterior and posterior cruciate ligaments and removing the meniscus. Rats were treated with miR-204-5p agomir and miR-204-5p negative control (NC). All in vitro experiments were performed using rat primary chondrocytes and the SW-1353 human bone chondrosarcoma cell line. It was identified that the expression of miR-204-5p was significantly decreased, whereas Runx2 was significantly increased, in human OA tissues compared with in non-OA tissues, and levels were inversely associated with each other in primary chondrocytes and chondrosarcoma cells. Overexpression of miR-204-5p decreased the proliferation of chondrocytes and SW-1353 cells. Using a luciferase reporter assay, Runx2 was identified to be a direct target of miR-204-5p in chondrocytes and overexpressed miR-204-5p altered the expression of collagens II, X and matrix metalloproteinase (MMP)-1 and MMP-13 in primary chondrocytes and SW-1353 cells. Histological analysis revealed that miR-204-5p treatment ameliorated the OA-like phenotype that is reflected by assessment of cartilage thickness and Mankin's score. Runx2 expression was gradually increased as the rats increased in age. At 10 weeks of miR-204-5p agomir treatment, altered expression levels of collagens II and X, cartilage oligomeric matrix protein fragment, aggrecan, MMP-1 and MMP-13 were observed in the treatment group compared with the NC group. In conclusion, the results of the present study indicated that miR-204-5p decreases chondrocyte proliferation and ameliorates the OA-like phenotype in rats with surgically induced OA by targeting Runx2.

Upper zone of growth plate and cartilage matrix associated protein protects cartilage during inflammatory arthritis

Background

ADAMTS aggrecanases play a major role in cartilage degeneration during degenerative and inflammatory arthritis. The cartilage-specific secreted protein Upper zone of growth plate and cartilage matrix associated protein (Ucma) has been shown to block ADAMTS-triggered aggrecanolysis in experimental osteoarthritis. Here we aimed to investigate whether and how Ucma may affect cartilage destruction and osteophyte formation in the context of inflammatory arthritis.

Methods

Ucma–ADAMTS5 protein interactions were studied using slot blot and solid phase binding assays. Chondrocyte cultures were stimulated with ADAMTS5 or IL-1β in the presence or absence of Ucma and aggrecanolysis was assessed by neoepitope formation. Arthritis was induced by transfer of K/BxN serum into wild-type (WT), Ucma-deficient and WT mice treated with recombinant Ucma. Cartilage proteoglycan loss and cartilage damage was assessed by safranin-O stain, aggrecanase-induced neoepitope formation and histomorphometry, respectively. Osteophytes were assessed by histomorphometry, micro-computed tomography, RNA in-situ hybridisation for collagen10a1 and osteocalcin, and staining for TRAP activity. Gene expression analyses were performed using real-time RT-PCR.

Results

Ucma physically interacted with ADAMTS5 and blocked its aggrecanase activity in chondrocyte cultures. Ucma was highly expressed in the articular cartilage and in osteophytes during arthritis. Ucma had no effect on inflammation and bone erosion. In contrast, Ucma-deficient mice developed significantly more severe cartilage proteoglycan loss and cartilage destruction. Conversely, treatment with Ucma inhibited cartilage degeneration in arthritis. Ucma effectively inhibited ADAMTS5-triggered or IL-1β-triggered aggrecanolysis in vitro and in vivo. Furthermore, osteophyte formation was reduced in Ucma-deficient mice.

Conclusions

These results indicate that Ucma inhibits aggrecanolysis by physical interaction with ADAMTS5 and protects from cartilage degeneration in inflammatory arthritis. Ucma therefore represents an interesting novel and specific target for preventing cartilage degradation in the context of inflammatory arthritis.

Electronic supplementary material

The online version of this article (10.1186/s13075-018-1583-2) contains supplementary material, which is available to authorized users.

Vitamin K‑dependent proteins involved in bone and cardiovascular health (Review)

In postmenopausal women and elderly men, bone density decreases with age and vascular calcification is aggravated. This condition is closely associated with vitamin K2 deficiency. A total of 17 different vitamin K-dependent proteins have been identified to date. Vitamin K-dependent proteins are located within the bone, heart and blood vessels. For instance, carboxylated osteocalcin is beneficial for bone and aids the deposition of calcium into the bone matrix. Carboxylated matrix Gla protein effectively protects blood vessels and may prevent calcification within the vascular wall. Furthermore, carboxylated Gla-rich protein has been reported to act as an inhibitor in the calcification of the cardiovascular system, while growth arrest-specific protein-6 protects endothelial cells and vascular smooth muscle cells, resists apoptosis and inhibits the calcification of blood vessels by inhibiting the apoptosis of vascular smooth muscle cells. In addition, periostin may promote the differentiation, aggregation, adhesion and proliferation of osteoblasts. Periostin also occurs in the heart and may be associated with the reconstruction of heart function. These vitamin K-dependent proteins may exert their functions following γ-carboxylation with vitamin K, and different vitamin K-dependent proteins may exhibit synergistic effects or antagonistic effects on each other. In the cardiovascular system with vitamin K antagonist supplement or vitamin K deficiency, calcification occurs in the endothelium of blood vessels and vascular smooth muscle cells are transformed into osteoblast-like cells, a phenomenon that resembles bone growth. Both the bone and cardiovascular system are closely associated during embryonic development. Thus, the present study hypothesized that embryonic developmental position and tissue calcification may have a certain association for the bone and the cardiovascular system. This review describes and briefly discusses several important vitamin K-dependent proteins that serve an important role in bone and the cardiovascular system. The results of the review suggest that the vascular calcification and osteogenic differentiation of vascular smooth muscle cells may be associated with the location of the bone and cardiovascular system during embryonic development.

Ucma/GRP inhibits phosphate-induced vascular smooth muscle cell calcification via SMAD-dependent BMP signalling

Vascular calcification (VC) is the process of deposition of calcium phosphate crystals in the blood vessel wall, with a central role for vascular smooth muscle cells (VSMCs). VC is highly prevalent in chronic kidney disease (CKD) patients and thought, in part, to be induced by phosphate imbalance. The molecular mechanisms that regulate VC are not fully known. Here we propose a novel role for the mineralisation regulator Ucma/GRP (Upper zone of growth plate and Cartilage Matrix Associated protein/Gla Rich Protein) in phosphate-induced VSMC calcification. We show that Ucma/GRP is present in calcified atherosclerotic plaques and highly expressed in calcifying VSMCs in vitro. VSMCs from Ucma/GRP^−/− mice showed increased mineralisation and expression of osteo/chondrogenic markers (BMP-2, Runx2, β-catenin, p-SMAD1/5/8, ALP, OCN), and decreased expression of mineralisation inhibitor MGP, suggesting that Ucma/GRP is an inhibitor of mineralisation. Using BMP signalling inhibitor noggin and SMAD1/5/8 signalling inhibitor dorsomorphin we showed that Ucma/GRP is involved in inhibiting the BMP-2-SMAD1/5/8 osteo/chondrogenic signalling pathway in VSMCs treated with elevated phosphate concentrations. Additionally, we showed for the first time evidence of a direct interaction between Ucma/GRP and BMP-2. These results demonstrate an important role of Ucma/GRP in regulating osteo/chondrogenic differentiation and phosphate-induced mineralisation of VSMCs.

A Dual Role of Upper Zone of Growth Plate and Cartilage Matrix-Associated Protein in Human and Mouse Osteoarthritic Cartilage: Inhibition of Aggrecanases and Promotion of Bone Turnover

OBJECTIVE

Cartilage damage and subchondral bone changes are closely connected in osteoarthritis. Nevertheless, how these processes are interlinked is, to date, incompletely understood. This study was undertaken to investigate the mechanistic role of a cartilage-derived protein, upper zone of growth plate and cartilage matrix-associated protein (UCMA), in osteoarthritis-related cartilage and bone changes.

METHODS

UCMA expression was assessed in healthy and osteoarthritic human and mouse cartilage. For analysis of cartilage and bone changes, osteoarthritis was induced by destabilization of the medial meniscus (DMM) in wild-type (WT) and Ucma-deficient mice. UCMA-collagen interactions, the effect of UCMA on aggrecanase activity, and the impact of recombinant UCMA on osteoclast differentiation were studied in vitro.

RESULTS

UCMA was found to be overexpressed in human and mouse osteoarthritic cartilage. DMM-triggered cartilage changes, including increased structural damage, proteoglycan loss, and chondrocyte cell death, were aggravated in Ucma-deficient mice compared to WT littermates, thereby demonstrating the potential chondroprotective effects of UCMA. Moreover, UCMA inhibited ADAMTS-dependent aggrecanase activity and directly interacted with cartilage-specific collagen types. In contrast, osteoarthritis-related bone changes were significantly reduced in Ucma-deficient mice, showing less pronounced osteophyte formation and subchondral bone sclerosis. Mechanistically, UCMA directly promoted osteoclast differentiation in vitro.

CONCLUSION

UCMA appears to link cartilage with bone changes in osteoarthritis by supporting cartilage integrity as an endogenous inhibitor of aggrecanases while also promoting osteoclastogenesis and subchondral bone turnover. Thus, UCMA represents an important link between cartilage and bone in osteoarthritis.

Silk Fibroin-Alginate-Hydroxyapatite Composite Particles in Bone Tissue Engineering Applications In Vivo

The aim of this study was to evaluate the in vivo bone regeneration capability of alginate (AL), AL/hydroxyapatite (HA), and AL/HA/silk fibroin (SF) composites. Forty Sprague Dawley rats were used for the animal experiments. Central calvarial bone (diameter: 8.0 mm) defects were grafted with AL, AL/HA, or AL/HA/SF. New bone formation was evaluated by histomorphometric analysis. To demonstrate the immunocompatibility of each group, the level of tumor necrosis factor (TNF)-α expression was studied by immunohistochemistry (IHC) and quantitative reverse transcription polymerase chain reaction (qRT-PCR) at eight weeks post implantation. Additionally, osteogenic markers, such as fibroblast growth factor (FGF)-23, osteoprotegerin (OPG), and Runt-related transcription factor (Runx2) were evaluated by qPCR or IHC at eight weeks post implantation. The AL/HA/SF group showed significantly higher new bone formation than did the control group (p = 0.044) and the AL group (p = 0.035) at four weeks post implantation. Additionally, the AL/HA/SF group showed lower relative TNF-α mRNA levels and higher FGF-23 mRNA levels than the other groups did at eight weeks post implantation. IHC results demonstrated that the AL/HA/SF group had lower TNF-α expression and higher OPG and Runx2 expression at eight weeks post implantation. Additionally, no evidence of the inflammatory reaction or giant cell formation was observed around the residual graft material. We concluded that the AL/HA/SF composite could be effective as a scaffold for bone tissue engineering.

Tensile stress stimulates the expression of osteogenic cytokines/growth factors and matricellular proteins in the mouse cranial suture at the site of osteoblast differentiation

Mechanical stress promotes osteoblast proliferation and differentiation from mesenchymal stem cells (MSCs). Although numerous growth factors and cytokines are known to regulate this process, information regarding the differentiation of mechanically stimulated osteoblasts from MSCs in in vivo microenvironment is limited. To determine the significant factors involved in this process, we performed a global analysis of differentially expressed genes, in response to tensile stress, in the mouse cranial suture wherein osteoblasts differentiate from MSCs. We found that the gene expression levels of several components involved in bone morphogenetic protein, Wnt, and epithelial growth factor signalings were elevated with tensile stress. Moreover gene expression of some extracellular matrices (ECMs), such as cysteine rich protein 61 (Cyr61)/CCN1 and galectin-9, were upregulated. These ECMs have the ability to modulate the activities of cytokines and are known as matricellular proteins. Cyr61/CCN1 expression was prominently increased in the fibroblastic cells and preosteoblasts in the suture. Thus, for the first time we demonstrated the mechanical stimulation of Cyr61/CCN1 expression in osteogenic cells in an ex vivo system. These results suggest the importance of matricellular proteins along with the cytokine-mediated signaling for the mechanical regulation of MSC proliferation and differentiation into osteoblastic cell lineage in vivo.

The effect of mesoporous bioglass on osteogenesis and adipogenesis of osteoporotic BMSCs

This study evaluated the effect of mesoporous bioglass (MBG) dissolution on the differentiation of bone marrow mesenchymal stem cells (BMSCs) derived from either sham control or ovariectomized (OVX) rats. MBG was fabricated by evaporation-induced self-assembly method. Cell proliferation was tested by Cell Counting Kit-8 assay, and cytoskeletal morphology was observed by fluorescence microscopy. Osteogenic differentiation was evaluated by alkaline phosphatase (ALP) staining and activity, Alizarin Red staining, while adipogenic differentiation was assessed by Oil Red-O staining. Quantitative real-time PCR and Western blot analysis were taken to evaluate the expression of runt-related transcription factor 2 (Runx2) and proliferator-activated receptor-γ (PPARγ). We found that MBG dissolution (0, 25, 50, 100, 200 µg/mL) was nontoxic to BMSCs growth. Sham and OVX BMSCs exhibited the highest ALP activity in 50 µg/mL of MBG osteogenic dissolution, except that sham BMSCs in 100 µg/mL showed the highest ALP activity on day 14. Runx2 was significantly upregulated after 100 µg/mL of MBG stimulation in sham and OVX BMSCs for 7 and 14 days, except that 25 µg/mL showed highest upregulation effect on OVX BMSCs at day 7. PPARγ was downregulated after MBG stimulation. The protein level of Runx2 from the sham BMSCs group was significantly upregulated after lower doses (25 and 50 µg/mL) of MBG stimulation, whereas PPARγ was downregulated in the sham and OVX BMSCs group. Thus, both the osteogenic and adipogenic abilities of BMSCs were damaged under OVX condition. Moreover, lower concentration of MBG dissolution can promote osteogenesis but inhibit adipogenesis of the sham and OVX BMSCs. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 3004-3014, 2016.

Ossification of the posterior ligament is mediated by osterix via inhibition of the β-catenin signaling pathway

Ossification of the posterior longitudinal ligament (OPLL) involves ectopic calcification of the spinal ligament preferentially at the cervical spine. OPLL is associated with different diseases and occurs by endochondral ossification, which is associated with the activity of different transcription factors. However, the pathogenesis of OPLL remains unclear. Here, we investigated the role of osterix (Osx), a transcription factor that functions downstream of Runx2 and is an important regulator of osteogenesis, in the process of OPLL in a dexamethasone (Dex)-induced model of spinal ligament ossification. Our results showed that Osx is upregulated in patients with OPLL and during the ossification of ligament cells in parallel with the upregulation of osteogenic markers including osteocalcin (OCN), alkaline phosphatase (ALP) and collagen-1 (Col-1). Dex-induced ossification of ligament cells was associated with the downregulation and inactivation of β-catenin, and these effects were offset by Osx knockdown. Activation of β-catenin signaling abolished the effect of Dex on ossification and the upregulation of osteogenic markers. Taken together, our results suggest that OPLL is mediated by Osx via a mechanism involving the Wnt/β-catenin signaling pathway, providing a basis for further research to identify potential targets for the treatment of OPLL.

Induction of fibrillin-2 and periostin expression in Osterix-knockdown MC3T3-E1 cells

Osteoporosis is the most common age-related bone disease that is characterized by an imbalance between osteoblasts for bone formation and osteoclasts for bone resorption. Anti-catabolic drugs have been developed to inhibit osteoclast activity and to prevent bone loss in osteoporosis. However, because it is difficult to increase bone mass in osteoporotic bone, it would be beneficial to simultaneously enhance osteoblast function and thus form bone. Osterix (Osx) is an essential transcription factor for osteoblast differentiation. To date, many studies have focused on discovering Osx target genes and on increasing osteoblast differentiation. However, Osx targets and the mechanisms controlling osteoblast differentiation, are not well known. Here, we generated stable Osx-knockdown cell lines by employing shRNA in MC3T3-E1 osteoblastic cells. Stable Osx-knockdown osteoblasts exhibited a significant reduction in cell differentiation and nodule formation, which was similar to the reduced osteoblast activity observed in an Osx-deficient mouse model. Using an Affymetrix GeneChip microarray, we determined the differential gene expression profile in response to Osx knockdown, which provided insight into molecular mechanisms underlying osteoblast differentiation. Of 2743 genes with roles in cell differentiation, 15 were upregulated and 2 were downregulated in Osx-knockdown osteoblasts. In particular, the expression of fibrillin-2 and periostin was significantly increased in Osx-knockdown osteoblasts compared to that in control cells, as validated by RT-PCR and quantitative real-time PCR. Finally, this study showed differential gene expression profiles for Osx-mediated osteoblast differentiation, suggesting that fibrillin-2 and periostin will be target candidates of Osx in osteoblast differentiation.

Inhibition of osteoblast differentiation by aluminum trichloride exposure is associated with inhibition of BMP-2/Smad pathway component expression

Bone morphogenetic protein-2 (BMP-2)/Smad signaling pathway plays an important role in regulating osteoblast (OB) differentiation. OB differentiation is a key process of bone formation. Aluminum (Al) exposure inhibits bone formation and causes Al-induced bone disease. However, the mechanism is not fully understood. To investigate whether BMP-2/Smad signaling pathway is associated with OB differentiation in aluminum trichloride (AlCl₃)-treated OBs, the primary rat OBs were cultured and exposed to 0 (control group, CG), 1/40 IC₅₀ (low-dose group, LG), 1/20 IC₅₀ (mid-dose group, MG), and 1/10 IC₅₀ (high-dose group, HG) of AlCl₃ for 24 h, respectively. We found that the expressions of OB differentiation markers (Runx-2, Osterix and ALP) and BMP-2/Smad signaling pathway components (BMP-2, BMPR-IA, p-BMPR-IA, BMPR-II, p-Smad1/5/8 and p-Smad1/5/8/4) were all decreased in AlCl₃-treated OBs compared with the CG. These results indicated that inhibition of OB differentiation by AlCl₃ was associated with inhibition of BMP-2/Smad pathway component expression. Our findings provide a novel insight into the mechanism of AlCl₃-induced bone disease.

Effect of apatite formation of biphasic calcium phosphate ceramic (BCP) on osteoblastogenesis using simulated body fluid (SBF) with or without bovine serum albumin (BSA)

Although biphasic calcium phosphate ceramic (BCP) holds promise in therapy of bone defect, surface mineralization prior to implantation may improve the bioactivity to better integrate with the host. Immersion in simulated body fluid (SBF) and bovine serum albumin-simulated body fluid (BSA-SBF) are common methods to form apatite interface layer. This study was intended to investigate the effect of SBF and BSA-SBF treatment on the bioactivity of BCP in vitro. In this study, osteoblasts were grown on BCP with or without treatment of SBF or BSA-SBF, and detected with general observation, scanning electron microscope (SEM), cell proliferation assay, morphology observation, viability assay, alkaline phosphatase (ALP) activity assay, and osteogenic specific gene expression of alkaline phosphatase (ALPL), bone gamma-carboxyglutamate (gla) protein (BGLAP), bone morphogenetic protein 2 (BMP2), bone sialoprotein (BSP), type I collagen (COLI) and runt-related transcription factor 2 (RUNX2) after culture of 2, 5 and 8days. As the results shown, BCP pre-incubated in SBF and BSA-SBF up-regulated ALP activity and osteogenic related genes and proteins, which testified the positive effect of SBF and BSA-SBF. Especially, BSA-SBF enhanced the cell growth significantly. This study indicated that treatment by BSA-SBF is of importance for BCP before clinical application.

Gla-rich protein is involved in the cross-talk between calcification and inflammation in osteoarthritis

Osteoarthritis (OA) is a whole-joint disease characterized by articular cartilage loss, tissue inflammation, abnormal bone formation and extracellular matrix (ECM) mineralization. Disease-modifying treatments are not yet available and a better understanding of osteoarthritis pathophysiology should lead to the discovery of more effective treatments. Gla-rich protein (GRP) has been proposed to act as a mineralization inhibitor and was recently shown to be associated with OA in vivo. Here, we further investigated the association of GRP with OA mineralization-inflammation processes. Using a synoviocyte and chondrocyte OA cell system, we showed that GRP expression was up-regulated following cell differentiation throughout ECM calcification, and that inflammatory stimulation with IL-1β results in an increased expression of COX2 and MMP13 and up-regulation of GRP. Importantly, while treatment of articular cells with γ-carboxylated GRP inhibited ECM calcification, treatment with either GRP or GRP-coated basic calcium phosphate (BCP) crystals resulted in the down-regulation of inflammatory cytokines and mediators of inflammation, independently of its γ-carboxylation status. Our results strengthen the calcification inhibitory function of GRP and strongly suggest GRP as a novel anti-inflammatory agent, with potential beneficial effects on the main processes responsible for osteoarthritis progression. In conclusion, GRP is a strong candidate target to develop new therapeutic approaches.