Platelet-derived growth factor BB mediates the glioma-induced migration of bone marrow-derived mesenchymal stem cells by promoting the expression of vascular cell adhesion molecule-1 through the PI3K, P38 MAPK and NF-κB pathways

Angiogenesis in heterotopic ossification: From mechanisms to clinical significance

Heterotopic ossification (HO) refers to the formation of pathologic bone in nonskeletal tissues (including muscles, tendons or other soft tissues). HO typically occurs after a severe injury and can occur in any part of the body. HO lesions are highly vascularized. Angiogenesis, which is the formation of new blood vessels, plays an important role in the pathophysiology of HO. Surgical resection is considered an effective treatment for HO. However, it is difficult to completely remove new vessels, which can lead to the recurrence of HO and is often accompanied by significant problems such as intraoperative hemorrhage, demonstrating the important role of angiogenesis in HO. Here, we broadly summarize the current understanding of how angiogenesis contributes to HO; in particular, we focus on new insights into the cellular and signaling mechanisms underlying HO angiogenesis. We also review the development and current challenges associated with antiangiogenic therapy for HO.

Glioma-associated mesenchymal stem cells

Recent studies have revealed that glioma-associated mesenchymal stem cells play instrumental roles in tumorigenesis and tumour progression and cannot be ignored as a cellular component of the glioma microenvironment. Nevertheless, the origin of these cells and their roles are poorly understood. The only relevant studies have shown that glioma-associated mesenchymal stem cells play a large role in promoting tumour proliferation, invasion and angiogenesis. This review provides a comprehensive summary of their discovery and definition, origin, differences from other tissue-derived mesenchymal stem cells, spatial distribution, functions and prognostic and therapeutic opportunities to deepen the understanding of these cells and provide new insight into the treatment of glioma.

Endothelial Cells Promote Migration of Mesenchymal Stem Cells via PDGF-BB/PDGFRβ-Src-Akt in the Context of Inflammatory Microenvironment upon Bone Defect

Homing of mesenchymal stem cells (MSCs) to the defect site is indispensable for bone repair. Local endothelial cells (ECs) can recruit MSCs; however, the mechanism remains unclear, especially in the context of the inflammatory microenvironment. This study was aimed to investigate the role of ECs in MSCs migration during the inflammatory phase of bone repair. The inflammatory microenvironment was mimicked in vitro via adding a cytokine set (IL-1β, IL-6, and TNF-α) to the culture medium of ECs. The production of PDGF-BB from ECs was measured by ELISA. Transwell and wound healing assays were employed to assess MSCs migration toward ECs and evaluate the implication of PDGF-BB/PDGFRβ. A series of shRNA and pathway inhibitors were used to screen signal molecules downstream of PDGF-BB/PDGFRβ. Then, mouse models of femoral defects were fabricated and DBM scaffolds were implanted. GFP⁺ MSCs were injected via tail vein, and the relevance of PDGF-BB/PDGFRβ, as well as screened signal molecules, in cell homing was further verified during the early phase of bone repair. In the mimicked inflammatory microenvironment, MSCs migration toward ECs was significantly promoted, which could be abrogated by pdgfrb knockout in MSCs. Inhibition of Src or Akt led to negative effects analogous to pdgfrb knockout. Blockade of JNK, MEK, and p38 MAPK had no impact. Meanwhile, the secretion of PDGF-BB from ECs was evidently motivated by the inflammatory microenvironment. Adding recombinant PDGF-BB protein to the culture medium of ECs phenocopied the inflammatory microenvironment with regard to attracting MSCs, which was abolished by pdgfb, src, or akt in MSCs. Moreover, pdgfb knockout suppressed the expression and phosphorylation of Src and Akt in migrating MSCs. Src knockout impaired Akt expression but not vice versa. In vivo, reduced infiltration of CD31⁺ ECs was correlated with diminished PDGF-BB in local defect sites, and silencing pdgfb, src, or akt in MSCs markedly hampered cell homing. Together, these findings suggest that in the inflammatory microenvironment, MSCs migrate toward ECs via PDGF-BB/PDGFRβ and the downstream Src-Akt signal pathway.

Growth factors-based beneficial effects of platelet lysate on umbilical cord-derived stem cells and their synergistic use in osteoarthritis treatment

Poor viability of mesenchymal stem cells (MSCs) at the transplanted site often hinders the efficacy of MSCs-based therapy. Platelet lysate (PL) contains rich amounts of growth factors, which benefits cell growth. This study aimed to explore how human PL benefits umbilical cord-derived MSCs (huc-MSCs), and whether they have synergistic potential in osteoarthritis (OA) treatment. As quality control, flow cytometry and specific staining were performed to identify huc-MSCs, and ELISA was used to quantify growth factors in PL. CCK-8 and flow cytometry assays were performed to evaluate the effects of PL on the cell viability and cell cycle progression of huc-MSCs. Wound healing and transwell assays were conducted to assess the migration of huc-MSCs. RNA sequencing, real time PCR, and Western blot assays were conducted to explore the growth factors-based mechanism of PL. The in vitro results showed that PL significantly promoted the proliferation, cell cycle, and migration of huc-MSCs by upregulating relevant genes/proteins and activating beclin1-dependent autophagy via the AMPK/mTOR signaling pathway. The main growth factors (PDGF-AA, IGF-1, TGF-β, EGF, and FGF) contributed to the effects of PL in varying degrees. The in vivo data showed that combined PL and huc-MSCs exerted significant synergistic effect against OA. The overall study determined the beneficial effects and mechanism of PL on huc-MSCs and indicated PL as an adjuvant for huc-MSCs in treating OA. This is the first report on the growth factors-based mechanism of PL on huc-MSCs and their synergistic application. It provides novel knowledge of PLʹs roles and offers a promising strategy for stem cell-based OA therapy by combining PL and huc-MSCs.

Shp2 activation in bone marrow microenvironment mediates the drug resistance of B-cell acute lymphoblastic leukemia through enhancing the role of VCAM-1/VLA-4

B-cell acute lymphoblastic leukemia (B-ALL) is immune to the chemotherapy-induced apoptosis as a result of the protection of bone marrow mesenchymal stromal cells (BMSCs). However, the precise underlying mechanism of such protection remains unclear so far. In this experiment, protein tyrosine phosphatase 2 (Shp2), which was encoded by the PTPN11 gene, was highly expressed in BMSCs of the newly diagnosed and the recurrent B-ALL patients. The plasmid-induced (including Shp2 E76K) Shp2 activation in BMSCs (Shp2-activated BMSCs) markedly increased the BMSCs-mediated resistance of leukemia cells both in vitro and in vivo. Additionally, studies in vitro suggested that, the expression of vascular cell adhesion molecule 1 (VCAM-1) was markedly up-regulated in Shp2-activated BMSCs, and VCAM-1 expression in BMSCs of B-ALL patients was negatively correlated with Shp2 expression. Down-regulation of VCAM-1 in BMSCs using siRNA reversed the resistance of CCRF-SB cells mediated by the Shp2-activated BMSCs. As for the molecular mechanism, the PI3K/AKT pathway mediated the regulation of VCAM-1 by Shp2. Blocking the very late antigen-4 (VLA-4) by antibodies in CCRF-SB cells dramatically reversed the resistance of CCRF-SB cells mediated by the Shp2-activated BMSCs, and decreased the adhesion effects of both CCRF-SB cells and BMSCs. In conclusion, Shp2 activation in BMSCs up-regulates VCAM-1 expression through increasing the PI3K/AKT phosphorylation level, and targeting the VCAM-1/VLA-4 signaling may serve as a clinically relevant mechanism to overcome the BMSCs-mediated chemoresistance of B-ALL cells.

Vascular endothelial growth factor A/Vascular endothelial growth factor receptor 2 axis promotes human dental pulp stem cell migration via the FAK/PI3K/Akt and p38 MAPK signalling pathways

AIM

To investigate the effects of vascular endothelial growth factor A (VEGFA) and the underlying molecular mechanisms on the migration of human dental pulp stem cells (hDPSCs).

METHODOLOGY

The expression of VEGFA in inflammatory pulp tissue and lipopolysaccharide (LPS)-stimulated dental pulp cells was examined by immunofluorescence staining and qRT-PCR. The migration of hDPSCs was detected using transwell migration and wound healing assays. The activation of FAK, PI3K, Akt and p38 signalling was evaluated by Western blot analysis. Silence RNA (siRNA) technology was utilized to knockdown the expression of VEGFR1 (Flt-1) and VEGFR2 (Flk-1/KDR). PF573228 (inhibitor of FAK), LY294002 (inhibitor of PI3K), SB203580 (inhibitor of p38) and SU5416 (inhibitor of VEGFR2) were employed to investigate the effect of VEGFA on the migratory mechanism of hDPSCs. Data were analysed statistically using the Student's t-test or one-way ANOVA.

RESULTS

The expression levels of VEGFA in inflammatory pulp tissue in vivo and LPS-stimulated dental pulp cells in vitro were significantly greater than those in the control groups (P < 0.05). Vascular endothelial growth factor A promoted the migration of hDPSCs in a concentration-dependent manner. Several signalling pathways, including FAK, PI3K, Akt and p38, were activated by VEGFA in a dose- and time-dependent manner in hDPSCs. The VEGFA-induced migration of hDPSCs was significantly inhibited with drug inhibitors such as PF573228, LY294002, SB203580 or SU5416 (P < 0.05). These signalling pathways activated by VEGFA stimulation were significantly suppressed by pre-treatment with inhibitor of VEGFR2 (SU5416) or transfection with siRNA of VRGFR2 (P < 0.05) but not VEGFR1 siRNA.

CONCLUSIONS

Vascular endothelial growth factor A/VEGFR2 axis promoted the migration of hDPSCs via the FAK/PI3K/Akt and p38 MAPK signalling pathways. These findings reveal a novel molecular mechanism for cell migration of hDPSCs, which may contribute to the remodelling of pulp tissue and dentine.

Inhibition of SUMO-specific protease 1 induces apoptosis of astroglioma cells by regulating NF-κB/Akt pathways

SUMO-specific protease 1 (SENP1) is an important regulation protease in the protein desumoylation, which was shown to have a prooncogenicrole in many types of cancer. However, the mechanism of action for SENP1 in astrocytoma is not yet clear. Astrocytoma is the most frequent one among various neurogliomas, of which a subtype known as glioblastoma multiforme (GBM) is the most malignant brain glioma and seriously influences the life quality of the patients. In this study, the expression of SENP1 was detected in 28 cases of various grades of astrocytoma and 6 cases of normal human tissues. The results showed that the expression of SENP1 was positively correlated with the malignant grades. Besides, the NF-κB and Akt signaling pathways in GBM tissues were activated. Cytological experiments indicated that knock-down of endogenous SENP1 promoted cell apoptosis. Further research confirmed that downexpression of SENP1 could inhibit the phosphorylation of IκBα and Akt, and also the expression of its downstream regulation factors Bcl-xL and cyclinD1. These results delineate a key role for SENP1 in astrocytoma development, suggesting it may be a potential new therapeutic target inastrocytoma.

TNF-α enhances vascular cell adhesion molecule-1 expression in human bone marrow mesenchymal stem cells via the NF-κB, ERK and JNK signaling pathways

The migration of circulating mesenchymal stem cells (MSCs) to injured tissue is an important step in tissue regeneration and requires adhesion to the microvascular endothelium. The current study investigated the underlying mechanism of MSC adhesion to endothelial cells during inflammation. In in vitro MSC culture, tumor necrosis factor-α (TNF-α) increased the level of vascular cell adhesion molecule-1 (VCAM-1) expression in a dose-dependent manner. The nuclear factor-κB (NF-κB), extracellular signal-regulated kinase (ERK) and c-Jun N-terminal kinase (JNK) signaling pathway inhibitors, pyrrolidine dithiocarbamate (PDTC), U0126 and SP600125, respectively, suppressed VCAM-1 expression induced by TNF-α at the mRNA and protein levels (P<0.05). TNF-α augmented the activation of NF-κB, ERK and JNK, and promoted MSC adhesion to human umbilical vein endothelial cells; however, the inhibitors of NF-κB, ERK and JNK did not affect this process in these cells. The results of the current study indicate that adhesion of circulating MSCs to the endothelium is regulated by TNF-α-induced VCAM-1 expression, which is potentially mediated by the NF-κB, ERK and JNK signaling pathways.

Shikonin Inhibits the Migration and Invasion of Human Glioblastoma Cells by Targeting Phosphorylated β-Catenin and Phosphorylated PI3K/Akt: A Potential Mechanism for the Anti-Glioma Efficacy of a Traditional Chinese Herbal Medicine

Shikonin is an anthraquinone derivative extracted from the root of lithospermum. Shikonin is traditionally used in the treatment of inflammatory and infectious diseases such as hepatitis. Shikonin also inhibits proliferation and induces apoptosis in various tumors. However, the effect of shikonin on gliomas has not been fully elucidated. In the present study, we aimed to investigate the effects of shikonin on the migration and invasion of human glioblastoma cells as well as the underlying mechanisms. U87 and U251 human glioblastoma cells were treated with shikonin at 2.5, 5, and 7.5 μmol/L and cell viability, migration and invasiveness were assessed with CCK8, scratch wound healing, in vitro Transwell migration, and invasion assays. The expression and activity of matrix metalloproteinase-2 (MMP-2) and matrix metalloproteinase-9 (MMP-9) and the expression of phosphorylated β-catenin (p-β-catenin) and phosphorylated PI3K/Akt were also checked. Results showed that shikonin significantly inhibited the cell proliferation, migration, invasion, and expression of MMP-2 and MMP-9 in U87 and U251 cells. The expression of p-β-catenin showed contrary trends in two cell lines. It was significantly inhibited in U87 cells and promoted in U251 cells. Results in this work indicated that shikonin displayed an inhibitory effect on the migration and invasion of glioma cells by inhibiting the expression and activity of MMP-2 and -9. In addition, shikonin also inhibited the expression of p-PI3K and p-Akt to attenuate cell migration and invasion and MMP-2 and MMP-9 expression in both cell lines, which could be reversed by the PI3K/Akt pathway agonist, insulin-like growth factor-1 (IGF-1).

CRM197 in Combination With shRNA Interference of VCAM-1 Displays Enhanced Inhibitory Effects on Human Glioblastoma Cells

CRM197 is a naturally nontoxic diphtheria toxin mutant that binds and inhibits heparin-binding epidermal growth factor-like growth factor. CRM197 serves as carrier protein for vaccine and other therapeutic agents. CRM197 also inhibits the growth, migration, invasion, and induces apoptosis in various tumors. Vascular cell adhesion molecule-1 (VCAM-1) is an important cell surface adhesion molecule associated with malignancy of gliomas. In this work, we aimed to investigate the role and mechanism of CRM197 combined with shRNA interference of VCAM-1 (shRNA-VCAM-1) on the migration, invasion, and apoptosis of glioblastoma cells. U87 and U251 human glioblastoma cells were treated with CRM197 (10 µg/ml) and shRNA interfering technology was employed to silence VCAM-1 expression. Cell viability, migration, invasiveness, and apoptosis were assessed with CCK8, Transwell and Annexin V-PE/7-AAD staining. Activation of cleaved caspase-3, 8, and 9, activity of matrix metalloproteinase-2/9 (MMP-2/9), and expression of phosphorylated Akt (p-Akt) were also checked. Results showed that CRM197 and shRNA-VCAM-1 not only significantly inhibited the cell proliferation, migration, invasion, but also promoted the apoptosis of U87 and U251 cells. Combined treatment of both displayed enhanced inhibitory effects on the malignant biological behavior of glioma cells. The activation of cleaved caspase-3, 8, 9 was promoted, activity of MMP-2 and MMP-9 and expression of p-Akt were inhibited significantly by the treatment of CRM197 and shRNA-VCAM-1 alone or in combination, indicating that the combination of CRM197 with shRNA-VCAM-1 additively inhibited the malignant behavior of human glioblastoma cells via activating caspase-3, 8, 9 as well as inhibiting MMP-2, MMP-9, and Akt pathway.

Neural differentiation of mesenchymal stem cells influences their chemotactic responses to stromal cell-derived factor-1α

Mesenchymal stem cells (MSCs) are proposed as a promising source for cell-based therapies in neural disease. Although increasing numbers of studies have been devoted to the delineation of factors involved in the migration of MSCs, the relationship between the chemotactic response and the differentiation status of these cells is still unclear. In the present study, we demonstrated that MSCs in varying neural differentiation states display various chemotactic responses to stromal cell-derived factor-1α (SDF-1α). The chemotactic responses of MSCs under different differentiation stages in response to SDF-1α were analyzed by Boyden chamber, and the results showed that cells of undifferentiation, 24-h preinduction, 5-h induction, and 18-h maintenance states displayed a stronger chemotactic response to SDF-1α, while 48-h maintenance did not. Further, we found that the phosphorylation levels of PI3K/Akt, ERK1/2, SAPK/JNK, and p38MAPK are closely related to the differentiation states of MSCs subjected to SDF-1α, and finally, inhibition of SAPK/JNK signaling significantly attenuates SDF-1α-stimulated transfilter migration of MSCs of undifferentiation, 24-h preinduction, 18-h maintenance, and 48-h maintenance, but not MSCs of 5-h induction. Meanwhile, interference with PI3K/Akt, p38MAPK, or ERK1/2 signaling prevents only cells at certain differentiation state from migrating in response to SDF-1α. Collectively, these results demonstrate that MSCs in varying neural differentiation states have different migratory capacities, thereby illuminating optimization of the therapeutic potential of MSCs to be used for neural regeneration after injury.

Astragaloside IV inhibits platelet-derived growth factor-BB-stimulated proliferation and migration of vascular smooth muscle cells via the inhibition of p38 MAPK signaling

Astragaloside IV (AS-IV), the major active component extracted from Astragalus membranaceus, has been demonstrated to exhibit protective effects on the cardiovascular, immune, digestive and nervous systems; thus, has been widely used in traditional Chinese medicine. Abnormal proliferation and migration of vascular smooth muscle cells (VSMCs) is closely associated with the initiation and progression of cardiovascular diseases, including atherosclerosis and restenosis. However, the effects of AS-IV on VSMCs remain unknown. For the first time, the present study demonstrated that AS-IV markedly suppressed platelet-derived growth factor (PDGF)-BB-stimulated cellular proliferation and migration of HDMEC-a human dermal VSMCs (HDVSMCs). Further investigation into the underlying molecular mechanisms demonstrated that the administration of AS-IV attenuated the PDGF-BB-stimulated switch of HDVSMCs into a proliferative phenotype. Furthermore, AS-IV inhibited the PDGF-BB-induced expression of cell cycle-associated proteins, as well as the upregulation of matrix metalloproteinase (MMP)2, but not MMP9. In addition, AS-IV was shown to downregulate the activation of p38 mitogen-activated protein kinase (MAPK) signaling induced by PDGF-BB in HDVSMCs. Therefore, the observations of the present study indicate that AS-IV inhibits PDGF-BB-stimulated VSMC proliferation and migration, possibly by inhibiting the activation of the p38 MAPK signaling pathway. Thus, AS-IV may be useful for the treatment of vascular diseases.