Inhibiting expression of Cxcl9 promotes angiogenesis in MSCs-HUVECs co-culture

Multi-walled carbon nanotubes reversing the bone formation of bone marrow stromal cells by activating M2 macrophage polarization

Multi-walled carbon nanotubes (MWCNTs) are an excellent bone tissue repair material both in vitro and in vivo. The interactions between MWCNTs and single type of cells of bone tissue, including osteoblasts, bone marrow stromal cells (BMSCs) or osteoclasts, have been extensively studied. However, the interactions between MWCNTs with different types of cells in the bone microenvironment remain elusive. Bone microenvironment is a complex system composed of different types of cells, which have interactions between each other. In this work, the effects of MWCNTs on bone microenvironment were firstly studied by culture of MWCNTs with BMSCs, osteoblasts, osteoclasts, macrophages and vascular endothelial cells, respectively. Then, co-culture systems of macrophages-BMSCs, macrophages-calvaria and macrophages-BMSCs-vascular endothelial cells were treated with MWCNTs, respectively. The osteogenic differentiation of BMSCs and osteoblasts was inhibited when these two types of cells were cultured with MWCNTs, respectively. Strikingly, when co-culture MWCNTs with BMSCs and macrophages, the osteogenesis of BMSCs was promoted by inducing the M2 polymerization of macrophages. Meanwhile, MWCNTs promoted the bone formation in the osteolysis model of calvaria ex vivo. In addition, the formation of osteoclasts was inhibited, and angiogenesis was increased when treated with MWCNTs. This study revealed the inconsistent effects of MWCNTs on single type of bone cells and on the bone microenvironment. The results provided basic research data for the application of MWCNTs in bone tissue repair.

Phosphoserine-loaded chitosan membranes promote bone regeneration by activating endogenous stem cells

Bone defects that result from trauma, infection, surgery, or congenital malformation can severely affect the quality of life. To address this clinical problem, a phosphoserine-loaded chitosan membrane that consists of chitosan membranes serving as the scaffold support to accommodate endogenous stem cells and phosphoserine is synthesized. The introduction of phosphoserine greatly improves the osteogenic effect of the chitosan membranes via mutual crosslinking using a crosslinker (EDC, 1-ethyl-3-(3-dimethyl aminopropyl)-carbodiimide). The morphology of PS-CS membranes was shown by scanning electron microscopy (SEM) to have an interconnected porous structure. The incorporation of phosphoserine into chitosan membranes was confirmed by energy dispersive spectrum (EDS), Fourier Transforms Infrared (FTIR), and X-ray diffraction (XRD) spectrum. The CCK8 assay and Live/Dead staining, Hemolysis analysis, and cell adhesion assay demonstrated that PS-CS membranes had good biocompatibility. The osteogenesis-related gene expression of BMSCs was higher in PS-CS membranes than in CS membranes, which was verified by alkaline phosphatase (ALP) activity, immunofluorescence staining, and real-time quantitative PCR (RT-qPCR). Furthermore, micro-CT and histological analysis of rat cranial bone defect demonstrated that PS-CS membranes dramatically stimulated bone regeneration in vivo. Moreover, H&E staining of the main organs (heart, liver, spleen, lung, or kidney) showed no obvious histological abnormalities, revealing that PS-CS membranes were no additional systemic toxicity in vivo. Collectively, PS-CS membranes may be a promising candidate for bone tissue engineering.

Analysis of Cytokine Levels in Meibum and Clinical Correlations with Meibomian Gland Dysfunction

Objectives. This study is aimed at investigating the difference of meibum chemokines in MGD subjects with different degrees of MGD and the correlations of meibum chemokines with ocular surface parameters. Methods. Twenty MGD subjects (MQ $\text{score}>8$ ) and twenty MGD subjects (MQ $\text{score}\le 8$ ) were enrolled to examine ocular surface parameters, including meibomian gland function (MGE, MQ meibograde, and lid margin), tear stability (NIKBUT, FBUT, and LLT), tear secretion (SIT and TMH), OSDI questionnaire, and CFS. These subjects also obtained meibum samples, and then meibum chemokines (MIG, IFN-γ, IL-8, IP-10, and MCP-1) were examined and analyzed the correlations with ocular surface parameters. Results. MIG, IP-10, and MCP-1 were found clearly elevated in MGD subjects with higher MQ score than that in MGD subjects with low MQ score (MIG: $p=0.038$ , IP-10: $p=0.019$ , MCP-1: $p=0.040$ ). The meibomian function was found mostly positively correlated with level of MIG (MGE: $r=0.600$ , $p<0.001$ ; MQ: $r=0.579$ , $p<0.001$ ) and IP-10 (MGE: $r=0.719$ , $p<0.001$ ; MQ: $r=0.601$ , $p<0.001$ ). The tear stability was found negatively correlated with the level of MIG (NIKBUT: $r=-0.438$ , $p=0.005$ ; LLT: $r=-0.464$ , $p=0.003$ ) and MCP-1 (NIKBUT: $r=-0.425$ , $p=0.006$ ; LLT: $r=-0.761$ , $p<0.001$ ). The OSDI was positively correlated with IL-8, IFN-γ, and MIG. Conclusion. Chemokines in meibum were significantly evaluated in MGD subjects suffering from severe meibomian gland quality. These findings indicate that chemokines play roles in the pathogenesis of MGD, and molecules targeted by chemokines may develop as novel agents for MGD therapy, perhaps through inhibiting inflammation in meibomian glands and microvascular in the eyelid margin.

Metformin pre-treatment of stem cells from human exfoliated deciduous teeth promotes migration and angiogenesis of human umbilical vein endothelial cells for tissue engineering

BACKGROUND AIMS

Stem cells from human exfoliated deciduous teeth (SHED) play a significant role in tissue engineering and regenerative medicine. Angiogenesis is crucial in tissue regeneration and a primary target of regenerative medicine. As a first-line anti-diabetic drug, metformin demonstrates numerous valuable impacts on stem cells. This study aimed to explore metformin's impact and mechanism of action on SHED-mediated angiogenesis.

METHODS

First, cell proliferation; flow cytometry; osteogenic, adipogenic and chondrogenic induction; and proteomics analyses were conducted to explore the role of metformin in SHED. Subsequently, migration and tube formation assays were used to evaluate chemotaxis and angiogenesis enhancement by SHED pre-treated with metformin under co-culture conditions in vitro, and relative messenger RNA expression levels were determined by quantitative reverse transcription polymerase chain reaction. Finally, nude mice were used for in vivo tube formation assay, and sections were analyzed through immunohistochemistry staining with anti-human CD31 antibody.

RESULTS

Metformin significantly promoted SHED proliferation as well as osteogenic, adipogenic and chondrogenic differentiation. Proteomics showed that metformin significantly upregulated 124 differentially abundant proteins involved in intracellular processes, including various proteins involved in cell migration and angiogenesis, such as MAPK1. The co-culture system demonstrated that SHED pre-treated with metformin significantly improved the migration and angiogenesis of human umbilical vein endothelial cells. In addition, SHED pre-treated with metformin possessed greater ability to promote angiogenesis in vivo.

CONCLUSIONS

In summary, the authors' findings illustrate metformin's mechanism of action on SHED and confirm that SHED pre-treated with metformin exhibits a strong capacity for promoting angiogenesis. This helps in promoting the application of dental pulp-derived stem cells pre-treated with metformin in regeneration engineering.

Osteogenically differentiated mesenchymal stem cells promote the apoptosis of human umbilical vein endothelial cells in vitro

The absence of blood vessels in tissue engineered bone often leads to necrosis of internal cells after implantation, ultimately affecting the process of bone repair. Herein, mesenchymal stem cells (MSCs) and human umbilical vein endothelial cells (HUVECs) were cocultured to induce osteogenesis and angiogenesis. Based on the findings, the number of HUVECs in the coculture system increased in the growth medium group, but decreased in the osteogenic induction medium (OIM) group. Considering that the paracrine effects of MSCs had changed, we tested the genes expression of osteogenically differentiated MSCs. The expression of osteogenic genes in MSCs increased during osteogenesis. Further, the expression levels of pigment epithelial-derived factor (PEDF) gene and protein, an antivascular factor, were also increased. To verify whether MSCs promote HUVECs apoptosis via PEDF, PEDF was silenced via siRNA. The conditioned medium of differentiated MSCs with PEDF silencing significantly improved the proliferation and apoptosis of HUVECs. Based on further experiments, PEDF mediated the apoptosis and proliferation of HUVECs through p53, BAX/BCL-2, FAS, and c-Caspase-3. However, when PEDF was silenced with siRNA, the osteogenic potential of MSCs was affected. The results of this study provide a theoretical basis for the construction of prevascularized bone tissues in vitro.

Influence of Dipeptidyl Peptidase-4 (DPP4) on Mesenchymal Stem-Cell (MSC) Biology: Implications for Regenerative Medicine - Review

Dipeptidyl peptidase IV (DPP4) is a ubiquitous protease that can be found in membrane-anchored or soluble form. Incretins are one of the main DPP4 substrates. These hormones regulate glucose levels, by stimulating insulin secretion and decreasing glucagon production. Because DPP4 levels are high in diabetes, DPP4 inhibitor (DPP4i) drugs derived from gliptin are widespread used as hypoglycemic agents for its treatment. However, as DPP4 recognizes other substrates such as chemokines, growth factors and neuropeptides, pleiotropic effects have been observed in patients treated with DPP4i. Several of these substrates are part of the stem-cell niche. Thus, they may affect different physiological aspects of mesenchymal stem-cells (MSC). They include viability, differentiation, mobilization and immune response. MSC are involved in tissue homeostasis and regeneration under both physiological and pathological conditions. Therefore, such cells and their secretomes have a high clinical potential in regenerative medicine. In this context, DPP4 activity may modulate different aspects of MSC regenerative capacity. Therefore, the aim of this review is to analyze the effect of different DPP4 substrates on MSC. Likewise, how the regulation of DPP4 activity by DPP4i can be applied in regenerative medicine. That includes treatment of cardiovascular and bone pathologies, cutaneous ulcers, organ transplantation and pancreatic beta-cell regeneration, among others. Thus, DPP4i has an important clinical potential as a complement to therapeutic strategies in regenerative medicine. They involve enhancing the differentiation, immunomodulation and mobilization capacity of MSC for regenerative purposes.

Chemokine signaling in cancer-stroma communications

Cancer is a multi-faceted disease in which spontaneous mutation(s) in a cell leads to the growth and development of a malignant new organ that if left undisturbed will grow in size and lead to eventual death of the organism. During this process, multiple cell types are continuously releasing signaling molecules into the microenvironment, which results in a tangled web of communication that both attracts new cell types into and reshapes the tumor microenvironment as a whole. One prominent class of molecules, chemokines, bind to specific receptors and trigger directional, chemotactic movement in the receiving cell. Chemokines and their receptors have been demonstrated to be expressed by almost all cell types in the tumor microenvironment, including epithelial, immune, mesenchymal, endothelial, and other stromal cells. This results in chemokines playing multifaceted roles in facilitating context-dependent intercellular communications. Recent research has started to shed light on these ligands and receptors in a cancer-specific context, including cell-type specificity and drug targetability. In this review, we summarize the latest research with regards to chemokines in facilitating communication between different cell types in the tumor microenvironment.

Mechanism of dexmedetomidine regulating osteogenesis-angiogenesis coupling through the miR-361-5p/VEGFA axis in postmenopausal osteoporosis

AIMS

Postmenopausal osteoporosis (PMOP) is a growing health problem affecting many postmenopausal women. This study intended to identify the role of dexmedetomidine (Dex) in osteoporosis (OP).

MAIN METHODS

Microarray analysis was performed for the gene expression profiles of PMOP patients and postmenopausal healthy volunteers, and the most differentially expressed microRNA (miR)-361-5p was verified in clinic, and its diagnostic value in PMOP patients was analyzed. After establishment of OP model by ovariectomy, Dex treatment and overexpression of miR-361-5p or vascular endothelial growth factor A (VEGFA) were performed in OP rats or isolated bone marrow mesenchymal stem cells (BMSCs). Bone mineral density (BMD) related indexes and levels of osteogenesis-angiogenesis related genes were measured. The apoptosis and osteogenic differentiation of BMSCs were detected. After human umbilical vein endothelial cells (HUVECs) and BMSCs were cocultured, the angiogenesis of BMSCs was detected by Matrigel-based angiogenesis experiment.

KEY FINDINGS

miR-361-5p was highly expressed in PMOP patients and OP rats, with good diagnostic effect on PMOP. After Dex treatment, the expressions of miR-361-5p, VEGFA, BMD related indexes were increased in OP rats. In BMSCs, level of osteogenesis-angiogenesis related genes were increased after adding Dex, and the apoptosis was decreased after coculture of HUVECs and BMSCs. miR-361-5p could target VEGFA. After miR-361-5p overexpression + Dex treatment, the indexes related to osteogenesis and angiogenesis in OP rats and BMSCs were decreased, which were reversed after further overexpressing VEGFA.

SIGNIFICANCE

Dex can enhance VEGFA by inhibiting miR-361-5p, and then promote osteogenesis-angiogenesis, thus providing potential targets for PMOP treatment.

Hypoxia alleviates dexamethasone-induced inhibition of angiogenesis in cocultures of HUVECs and rBMSCs via HIF-1α

BACKGROUND AND AIM

Inadequate vascularization is a challenge in bone tissue engineering because internal cells are prone to necrosis due to a lack of nutrient supply. Rat bone marrow-derived mesenchymal stem cells (rBMSCs) and human umbilical vein endothelial cells (HUVECs) were cocultured to construct prevascularized bone tissue in osteogenic induction medium (OIM) in vitro. The angiogenic capacity of HUVECs was limited in the coculture system. In this study, the effects of the components in the medium on HUVEC angiogenesis were analyzed.

METHODS

The coculture system was established in OIM. Alizarin red staining and alkaline phosphatase staining were used to assess the osteogenic ability of MSCs. A Matrigel tube assay was used to assess the angiogenic ability of HUVECs in vitro. The proliferation of HUVECs was evaluated by cell counting and CCK-8 assays, and migration was evaluated by the streaked plate assay. The expression levels of angiogenesis-associated genes and proteins in HUVECs were measured by qRT-PCR and Western blotting, respectively.

RESULTS

Dexamethasone in the OIM suppressed the proliferation and migration of HUVECs, inhibiting the formation of capillary-like structures. Our research showed that dexamethasone stimulated HUVECs to secrete tissue inhibitor of metalloproteinase (TIMP-3), which competed with vascular endothelial growth factor (VEGF-A) to bind to vascular endothelial growth factor receptor 2 (VEGFR2, KDR). This effect was related to inhibiting the phosphorylation of ERK and AKT, which are two downstream targets of KDR. However, under hypoxia, the enhanced expression of hypoxia-inducible factor-1α (HIF-1α) decreased the expression of TIMP-3 and promoted the phosphorylation of KDR, improving HUVEC angiogenesis in the coculture system.

CONCLUSION

Coculture of hypoxia-preconditioned HUVECs and MSCs showed robust angiogenesis and osteogenesis in OIM, which has important implications for prevascularization in bone tissue engineering in the future.

Chemokines and Bone

Chemokines are a family of small proteins, subdivided by their conserved cysteine residues and common structural features. Chemokines interact with their cognate G-protein-coupled receptors to elicit downstream signals that result in cell migration, proliferation, and survival. This review presents evidence for how the various CXC and CC subfamily chemokines influence bone hemostasis by acting on osteoclasts, osteoblasts, and progenitor cells. Also discussed are the ways in which chemokines contribute to bone loss as a result of inflammatory diseases such as rheumatoid arthritis, HIV infection, and periodontal infection. Both positive and negative effects of chemokines on bone formation and bone loss are presented. In addition, the role of chemokines in altering the bone microenvironment through effects on angiogenesis and tumor invasion is discussed. Very few therapeutic agents that influence bone formation by targeting chemokines or chemokine receptors are available, although a few are currently being evaluated.