Osteogenic effect of crocin in human periodontal ligament stem cells via Wnt/β-catenin signaling

OBJECTIVES

Crocin is a major class of medicinal components in saffron. This study aimed to determine whether crocin directly promotes the proliferation and osteogenic differentiation of human periodontal ligament stem cells (PDLSCs) in vitro and in vivo.

MATERIALS AND METHODS

CCK8 cell proliferation assay, reverse transcription quantitative polymerase chain reaction (RT-qPCR), Western blot analysis and Alizarin Red staining were performed in PDLSCs using crocin as a stimulant. DKK1 was used to selectively inhibit Wnt/β-catenin signaling, and Western blotting was performed to investigate the underlying mechanism. The PDLSCs were mixed with calcium phosphate cement and implanted into nude mice subcutaneously to study the effect of crocin on PDLSC osteogenic differentiation in vivo.

RESULTS

The CCK-8 assay showed that crocin did not promote the proliferation of PDLSCs. Treatment with 400 μM crocin significantly promoted PDLSC mRNA levels of ALP, COL1 and OCN; RUNX2 and BMP2 protein expression; mineralized nodule formation in vitro and in vivo; and ALP activity in tissues in vivo. In addition, crocin significantly promoted the phosphorylation of β-catenin and cyclin D1. DKK1 inhibits Wnt/β-catenin activation and partially reverses crocin-mediated promotion of PDLSC osteogenic differentiation.

CONCLUSION

Crocin may contribute to the regeneration of periodontal bone tissue.

Mesenchymal stem cells for subchondral bone marrow lesions: From bench to bedside

Subchondral bone marrow lesions (BMLs) are areas of disease within subchondral bone that appear as T1 hypointense and T2 hyperintense ill-defined areas of bone marrow on magnetic resonance imaging. The most common bone marrow lesions include subchondral lesions related to osteoarthritis, osteochondral defects, and avascular necrosis. Emerging therapies include autologous biologic therapeutics, in particular mesenchymal stem cells (MSCs), to maintain and improve cartilage health; MSCs have become a potential treatment option for BMLs given the unmet need for disease modification. Active areas in the preclinical research of bone marrow lesions include the paracrine function of MSCs in pathways of angiogenesis and inflammation, and the use of bioactive scaffolds to optimize the environment for implanted MSCs by facilitating chondrogenesis and higher bone volumes. A review of the clinical data demonstrates improvements in pain and functional outcomes when patients with knee osteoarthritis were treated with MSCs, suggesting that BM-MSCs can be a safe and effective treatment for patients with painful knee osteoarthritis with or without bone marrow lesions. Preliminary data examining MSCs in osteochondral defects suggest they can be beneficial as a subchondral injection alone, or as a surgical augmentation. In patients with hip avascular necrosis, those with earlier stage disease have improved outcomes when core decompression is augmented with MSCs, whereas patients in later stages post-collapse have equivalent outcomes with or without MSC treatment. While the evidence for the use of MSCs in conditions with associated bone marrow lesions seems promising, there remains a need for continued investigation into this treatment as a viable treatment option.

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Common BMLs include osteoarthritis, osteochondral defects, and avascular necrosis.

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Patients with knee osteoarthritis treated with MSCs show improved pain and function.

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MSCs used as subchondral injection or surgical augmentation in osteochondral defects

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Improved outcomes of early hip avascular necrosis after core decompression with MSCs

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Additional preclinical and clinical evidence of MSCs as treatment for BMLs is needed.

Therapeutic perspectives of exosomes in glucocorticoid-induced osteoarthrosis

Exosomes are widely involved in a variety of physiological and pathological processes. These important roles are also hidden in the physiological processes related to bone. Chondrocytes, osteoblasts, synovial fibroblasts, and bone marrow mesenchymal stem cells produce and secrete exosomes, thereby affecting the biology process of target cells. Furthermore, in the primary pathogenesis of osteoarthrosis induced by steroid hormones, mainly involve glucocorticoid (GC), the exosomes have also widely participated. Therefore, exosomes may also play an important role in glucocorticoid-induced osteoarthrosis and serve as a promising treatment for early intervention of osteoarthrosis in addition to playing a regulatory role in malignant tumors. This review summarizes the previous results on this direction, systematically combs the role and therapeutic potential of exosomes in GC-induced osteoarthrosis, discusses the potential role of exosomes in the treatment and prevention of GC-induced osteoarthrosis, and reveals the current challenges we confronted.

MiRNA-320a-5p contributes to the homeostasis of osteogenesis and adipogenesis in bone marrow mesenchymal stem cell

Objective

A number of miRNAs and their targets were dragged in the differentiation of bone marrow mesenchymal stem cells (BMSCs). We aimed to elaborate the underlying molecular mechanisms of miRNA-320a in the osteoblast and adipocyte differentiation.

Methods

Trauma-induced osteonecrosis of the femoral head (TIONFH) and normal control samples (n = 10 for each group) were collected, followed by miRNA chip analysis to identify the differentially expressed miRNAs. H&E staining was used to observe the pathological development of TIONFH. Lentiviral vector was used for overexpression and inhibition of miRNA-320a in vitro. Quantitative real-time PCR (qPCR), Western blotting and immunohistochemistry staining were employed to determine the expression of interested genes at mRNA or protein level. Luciferase report assay was employed to determine the binding of miRNA-320a and RUNX2. Alkaline phosphatase (ALP) and Alizarin red staining were performed to observe the osteogenesis and Oil red O staining were conducted to visualize the adipogenesis.

Results

Expression of miRNA-320a was up-regulated while RUNX2 expression was down-regulated in TIONFH than Normal control. Luciferase report assay confirmed that miRNA-320a directly targeted to the 3′UTR of RUNX2. miRNA-320a overexpression significantly declined the expressions of osteogenesis-related markers: RUNX2, OSTERIX, Collagen I, Osteocalcin and Osteopontin. ALP and Alizarin red staining confirmed the inhibition function of miRNA-320a in osteogenesis of BMSCs. miRNA-320a inhibition significantly decreased the expression of adipogenesis-related markers: AP2, C/EBPα, FABP4 and PPARγ. Oil Red O staining confirmed the miRNA-320a inhibition reduced adipogenesis of BMSCs.

Conclusions

miRNA-320a inhibits osteoblast differentiation via targeting RUNX2 and promotes adipocyte differentiation of BMSCs.

Platelet-Derived Growth Factor-Functionalized Scaffolds for the Recruitment of Synovial Mesenchymal Stem Cells for Osteochondral Repair

Cartilage regeneration is still a challenge for clinicians because of avascularity, denervation, load-bearing, synovial movement, and the paucity of endogenous repair cells. We constructed a multilayered osteochondral bionic scaffold and examined its repair capacity using a rabbit osteochondral defect model. The cartilage phase and interface layer of the scaffold were prepared by freeze-drying, whereas the bone phase of the scaffold was prepared by high-temperature sintering. The three-phase osteochondral bionic scaffold was formed by joining the hydroxyapatite (HAp) and silk fibroin (SF) scaffolds using the repeated freeze-thaw method. Different groups of scaffolds were implanted into the rabbit osteochondral defect model, and their repair capacities were assessed using imaging and histological analyses. The cartilage phase and the interface layer of the scaffold had a pore size of 110.13 ± 29.38 and 96.53 ± 33.72 μm, respectively. All generated scaffolds exhibited a honeycomb porous structure. The polydopamine- (PDA-) modified scaffold released platelet-derived growth factor (PDGF) for 4 weeks continuously, reaching a cumulative release of 71.74 ± 5.38%. Synovial mesenchymal stem cells (SMSCs) adhered well to all scaffolds, but demonstrated the strongest proliferation ability in the HSPP (HAp-Silk-PDA-PDGF) group. Following scaffold-induced chondrogenic differentiation, SMSCs produced much chondrocyte extracellular matrix (ECM). In in vivo experiments, the HSPP group exhibited a significantly higher gross tissue morphology score and achieved cartilage regeneration at an earlier stage and a significantly better repair process compared with the other groups (P < 0.05). Histological analysis revealed that the new cartilage tissue in the experimental group had a better shape and almost filled the defect area, whereas the scaffold was nearly completely degraded. The new cartilage was effectively fused with the surrounding normal cartilage, and a substantial amount of chondrocyte ECM was formed. The SF/HAp three-layer osteochondral bionic scaffold exhibited favorable pore size, porosity, and drug sustained-release properties. It demonstrated good biocompatibility in vitro and encouraging repair effect at osteochondral defect site in vivo, thereby expected to enabling the repair and regeneration of osteochondral damage.

Mesenchymal stromal cells for osteonecrosis

Osteonecrosis (ON) is an acquired debilitating skeletal disorder, which is caused by a multitude of traumatic and non-traumatic etiological factors. Vascular damage, mechanical stress and increased intraosseous pressure have been discussed as contributors to ON. The optimal treatment of ON remains to be determined, since the current gold standard, core decompression, is insufficiently effective. Specific properties of mesenchymal stromal cells (MSCs) provide the rationale for their assessment in advanced stages of ON: Osteoinductive potential has been demonstrated and MSC preparations of suitable quality for use as medicinal products have been developed. Here we review the scant information on the use of allogeneic or autologous MSCs in advanced ON as well as potentially supportive data from pre-clinical studies with autologous bone marrow mononuclear cells (auto BM-MNCs), which have been studied quite extensively and the presumed therapeutic effect of which was attributed to the rare MSCs contained in these cell products. Outcomes in clinical trials with MSCs and auto-BM-MNCs remain preliminary and non-definitive, at best promising, with respect to their pharmacological effect. Clearly, though, the application of any of these cell therapies was technically feasible and safe in that it was associated with low complication rates. The heterogeneity of cell type and source, study protocols, cell manufacturing, cell properties, cell doses and surgical techniques might contribute to inconsistent results.

miR-155-5p regulates mesenchymal stem cell osteogenesis and proliferation by targeting GSK3B in steroid-associated osteonecrosis

microRNAs (miRNAs) have recently been recognized as playing an important role in bone-associated diseases. This study investigated whether the reduced miR-155-5p in steroid-associated osteonecrosis of the femoral head (ONFH) attenuated osteogenic differentiation and cell proliferation by targeting GSK3B. Bone marrow was collected from the proximal femurs of patients with steroid-associated ONFH (n = 10) and patients with new femoral neck fracture (n = 10) and mesenchymal stem cells (MSCs) were isolated. The expression profile, the biological function of miR-155-5p, and the interaction between miR-155-5p and GSK3B were investigated by cell viability measurement, western blot, real-time polymerase chain reaction, luciferase reporter assay, and Alizarin Red S (ARS) staining of MSCs. The MSCs that were obtained from the femoral neck fracture group and from the steroid-associated ONFH group were transfected with or without miR-155-5p. We found that, in ONFH samples, the level of mature miR-155-5p was significantly lower than that of control samples. By inhibiting GSK3B, miR-155-5p promoted the nuclear translocation of β-catenin, increased the expression of osteogenesis-related genes, and facilitated the proliferation and differentiation of MSCs. Restoring the expression of GSK3B in MSCs partially reversed the effect of miR-155-5p. These findings suggest that reduced miR-155-5p in steroid-associated ONFH attenuates osteogenic differentiation and cell proliferation by increased levels of GSK3B and inhibition of Wnt signaling.

Crocin promotes osteogenesis differentiation of bone marrow mesenchymal stem cells

Crocin has plentiful pharmacological effects, but its role in osteogenesis differentiation of bone marrow mesenchymal stem cells (BMSCs) is unexplored. This study explored the effect of crocin on osteogenesis differentiation, in order to provide evidence for its clinical application. In cell experiments, human BMSCs (hBMSCs) were induced by osteogenesis differentiation medium or crocin. In animal experiments, steroid-induced osteonecrosis of the femoral head (SANFH) rat models was established using lipopolysaccharide (LPS) plus methylprednisolone (MPS), and then treated with crocin. The osteogenesis differentiation capacity of hBMSCs was analyzed by alkaline phosphatase (ALP) and alizarin red S staining. Histopathological changes in rat femoral head tissues were observed by hematoxylin and eosin (H&E) staining. The expression levels of RUNX2, COL1A1, OCN, and GSK-3β in hBMSCs and rat femoral head tissues were measured by quantitative real-time polymerase chain reaction (qRT-PCR) or western blot (WB) analysis. ALP and alizarin red S staining demonstrated that LAP activity and calcium nodules were increased in hBMSCs treated with crocin. From H&E staining results, femoral head tissues of SANFH models showed typical osteonecrosis, which could be ameliorated by crocin. WB and qRT-PCR assays detected that the expression levels of RUNX2, COL1A1, and OCN in hBMSCs and femoral head tissues of models were obviously increased after crocin treatment, while GSK-3β phosphorylation was reduced. In general, the action of crocin was concentration-dependent. Crocin might be beneficial to the recovery of SANFH through accelerating osteogenesis differentiation of BMSCs, which might be a novel therapy for related diseases.

Sodium lactate promotes stemness of human mesenchymal stem cells through KDM6B mediated glycolytic metabolism

Mesenchymal stem cells (MSCs) are an important cell source for tissue homeostasis and repair due to their stemness characteristic. Lots of intrinsic signaling pathways have been reported to regulate MSC stemness, but the extrinsic signals such as sodium lactate, particularly in physiological conditions, are poorly understood. Herein, we evaluated the effect of sodium lactate on human MSC stemness regulation by examining colony-forming ability, energy metabolism, multi-lineage differentiation ability, and pluripotent gene and protein expression. The underlying mechanism was further investigated with gene knockdown as well as small molecule interference and rescue experiments. We found that: (1) low concentration (1 mM) of sodium lactate promoted the stemness of human MSCs; (2) the upregulation of glycolysis was responsible for the MSC stemness promotion; (3) lysine demethylase 6B (KDM6B) was the key regulator which mediated sodium lactate-induced glycolysis and human MSC stemness enhancement. This study indicated that sodium lactate played an important role in human MSC stemness maintenance in physiological conditions, which could be related to KDM6B mediated metabolic regulation. It would provide new insight into stem cell biology, and contribute to cell transplantation and tissue regeneration strategies.

CD41-deficient exosomes from non-traumatic femoral head necrosis tissues impair osteogenic differentiation and migration of mesenchymal stem cells

Non-traumatic osteonecrosis of the femoral head (ONFH) is clinically a devastating and progressive disease without an effective treatment. Mesenchymal stem cells (MSCs) transplantation has been used to treat ONFH in early stage, but the failure rate of this therapy is high due to the reduced osteogenic differentiation and migration of the transplanted MSCs related with pathological bone tissues. However, the mechanism responsible for this decrease is still unclear. Therefore, we assume that the implanted MSCs might be influenced by signals delivered from pathological bone tissue, where the exosomes might play a critical role in this delivery. This study showed that exosomes from ONFH bone tissues (ONFH-exos) were able to induce GC-induced ONFH-like damage, in vivo and impair osteogenic differentiation and migration of MSCs, in vitro. Then, we analyzed the differentially expressed proteins (DEPs) in ONFH-exos using proteomic technology and identified 842 differentially expressed proteins (DEPs). On the basis of gene ontology (GO) enrichment analysis of DEPs, fold-changes and previous report, cell adhesion-related CD41 (integrin α2b) was selected for further investigation. Our study showed that the CD41 (integrin α2b) was distinctly decreased in ONFH-exos, compared to NOR-exos, and downregulation of CD41 could impair osteogenic differentiation and migration of the MSCs, where CD41-integrin β3-FAK-Akt-Runx2 pathway was involved. Finally, our study further suggested that CD41-affluent NOR-exos could restore the glucocorticoid-induced decline of osteogenic differentiation and migration in MSCs, and prevent GC-induced ONFH-like damage in rat models. Taken together, our study results revealed that in the progress of ONFH, exosomes from the pathological bone brought about the failure of MSCs repairing the necrotic bone for lack of some critical proteins, like integrin CD41, and prompted the progression of experimentally induced ONFH-like status in the rat. CD41 could be considered as the target of early diagnosis and therapy in ONFH.

Identification of potential miRNA biomarkers for traumatic osteonecrosis of femoral head

Traumatic osteonecrosis of femoral head (TONFH) is a common orthopedic disease caused by physical injury in hip. However, the unclear pathogenesis mechanism of TONFH and lacking of simple noninvasive early diagnosis method cause the necessity of hip replacement for most patients with TONFH. In this study, we aimed to identify circulating microRNAs (miRNAs) by integrated bioinformatics analyses as potential biomarker of TONFH. mRNA expression profiles were downloaded from the Gene Expression Omnibus database. Then we combined two miRNA screen methods: Weighted gene co-expression network analysis and fold change based differentially expressed miRNAs analysis. As a result, we identified 14 key miRNAs as potential biomarkers for TONFH. Besides, 302 target genes of these miRNAs were obtained and the miRNA-mRNA interaction network was constructed. Furthermore, the results of Kyoto Encyclopedia of Gene and Genome pathway analysis, Gene Ontology function analysis, protein-protein interaction (PPI) network analysis and PPI network module analysis showed close correlation between these 14 key miRNAs and TONFH. Then we established receiver operating characteristic curves and identified 6-miRNA signature with highly diagnosis value including miR-93-5p (area under the curve [AUC] = 0.93), miR-1324 (AUC = 0.92), miR-4666a-3p (AUC = 0.92), miR-5011-3p (AUC = 0.92), and miR-320a (AUC = 0.89), miR-185-5p (AUC = 0.89). Finally, the results of quantitative real-time polymerase chain reaction confirmed the significantly higher expression of miR-93-5p and miR-320a in the serum of patients with ONFH. These circulating miRNAs could serve as candidate early diagnosis markers and potential treatment targets of TONFH.

The potential roles of circular RNAs in osteonecrosis of the femoral head (Review)

Circular RNAs (circRNAs) are categorized as non-coding RNAs that, unlike widely known canonical linear RNAs, form a covalently closed continuous loop without 5′ or 3′ polarities, which enables them to resist digestion by RNA exonucleases. Although the functions of circRNAs remain largely unknown, accumulated evidence has demonstrated that circRNAs can act as microRNA sponges, which allows them to regulate numerous biological processes and disease mechanisms, including apoptosis, angiogenesis, invasion, metastasis and stem cell differentiation. Although research into circRNAs is in its infancy, studies have identified critical roles for circRNAs in the initiation and progression of disease. The present study delineated the characteristics and functions of circRNAs, and focused on the potential relationship between circRNAs and osteonecrosis of the femoral head (ONFH). CircRNAs represent a novel avenue for studying the mechanisms underlying ONFH as well as possible treatments.