Migration Of Marrow-derived Mesenchymal Stem Cells Research Articles

Cadherin-6 is a novel mediator for the migration of mesenchymal stem cells to glioblastoma cells in response to stromal cell-derived factor-1.

Glioblastoma recruits various nontransformed cells from distant tissues. Although bone marrow-derived mesenchymal stem cells (MSCs) have been observed migrating to glioblastoma, the underlying mechanism driving MSC migration toward glioblastoma remains unclear. Tumor vascularity is critical in the context of recurrent glioblastoma and is closely linked to the expression of stromal cell-derived factor-1 (SDF-1). We demonstrated that cadherin-6 mediated MSC migration both toward SDF-1 and toward glioblastoma cells. Cadherin-6 knockdown resulted in the downregulation of MSCs capacity to migrate in response to SDF-1. Furthermore, MSCs with cadherin-6 knockdown exhibited impaired migration in response to conditioned media derived from glioblastoma cell lines (U87 and U373) expressing SDF-1, thus simulating the glioblastoma microenvironment. Moreover, MSCs enhanced the vasculogenic capacity of U87 cells without increasing the proliferation, cancer stem cell characteristics, or migration of U87. These results suggest that the current strategy of utilizing MSCs as carriers for antiglioblastoma drugs requires careful examination. Furthermore, cadherin-6 may represent a novel potential target for controlling the recruitment of MSCs toward glioblastoma.

Periostin in Cancer-Associated Fibroblasts Promotes Esophageal Squamous Cell Carcinoma Progression by Enhancing Cancer and Stromal Cell Migration

Cancer-associated fibroblasts (CAFs) in the tumor microenvironment are involved in the progression of various cancers, including esophageal squamous cell carcinoma (ESCC). CAF-like cells were generated through direct co-culture of human bone marrow-derived mesenchymal stem cells, one of CAF origins, with ESCC cells. Periostin (POSTN) was found to be highly expressed in CAF-like cells. After direct co-culture, ESCC cells showed increased malignant phenotypes, such as survival, growth, and migration, as well as increased phosphorylation of Akt and extracellular signal-regulated kinase (Erk). Recombinant human POSTN activated Akt and Erk signaling pathways in ESCC cells, enhancing survival and migration. The suppression of POSTN in CAF-like cells by siRNA during direct co-culture also suppressed enhanced survival and migration in ESCC cells. In ESCC cells, knockdown of POSTN receptor integrin β4 inhibited Akt and Erk phosphorylation, and survival and migration increased by POSTN. POSTN also enhanced mesenchymal stem cell and macrophage migration and endowed macrophages with tumor-associated macrophage-like properties. Immunohistochemistry showed that high POSTN expression in the cancer stroma was significantly associated with tumor invasion depth, lymphatic and blood vessel invasion, higher pathologic stage, CAF marker expression, and infiltrating tumor-associated macrophage numbers. Moreover, patients with ESCC with high POSTN expression exhibited poor postoperative outcomes. Thus, CAF-secreted POSTN contributed to tumor microenvironment development. These results indicate that POSTN may be a novel therapeutic target for ESCC.

ZO-1 regulates the migration of mesenchymal stem cells in cooperation with α-catenin in response to breast tumor cells

sMesenchymal stem cells are recruited from the bone marrow into breast tumors, contributing to the creation of a tumor microenvironment that fosters tropism for breast tumors. However, the intrinsic mechanisms underlying the recruitment of bone marrow-derived mesenchymal stem cells (MSCs) into the breast tumor microenvironment are still under investigation. Our discoveries identified zonula occludens-1 (ZO-1) as a specific intrinsic molecule that plays a vital role in mediating the collective migration of MSCs towards breast tumor cells and transforming growth factor beta (TGF-β), which is a crucial factor secreted by breast tumor cells. Upon migration in response to MDA-MB-231 cells and TGF-β, MSCs showed increased formation of adherens junction-like structures (AJs) expressing N-cadherin and α-catenin at their cell-cell contacts. ZO-1 was found to be recruited into the AJs at the cell-cell contacts between MSCs. Additionally, ZO-1 collaborated with α-catenin to regulate AJ formation, dependently on the SH3 and GUK domains of the ZO-1 protein. ZO-1 knockdown led to the impaired migration of MSCs in response to the stimuli and subsequent downregulation of AJs formation at the cell-cell contacts during MSCs migration. Overall, our study highlights the novel role of ZO-1 in guiding MSC migration towards breast tumor cells, suggesting its potential as a new strategy for controlling and re-engineering the breast tumor microenvironment.

The SDF-1/CXCR4 Signaling Pathway Directs the Migration of Systemically Transplanted Bone Marrow Mesenchymal Stem Cells Towards the Lesion Site in a Rat Model of Spinal Cord Injury.

It has been observed that bone marrow-derived mesenchymal stem cells (MSCs) migrate towards the injured spinal cord and promote functional recovery when systemically transplanted into the traumatized spinal cord. However, the mechanisms underlying their migration to the spinal cord remain poorly understood. In this study, we systemically transplanted GFP- and luciferase-expressing MSCs into rat models of spinal cord injury and examined the role of the stromal cell-derived factor 1 (SDF-1)/CXCR4 axis in regulating the migration of transplanted MSCs to the spinal cord. After intravenous injection, MSCs migrated to the injured spinal cord where the expression of SDF-1 was increased. Spinal cord recruitment of MSCs was blocked by pre-incubation with an inhibitor of CXCR4. Their presence correlated with morphological and functional recovery. In vitro, SDF-1 or cerebrospinal fluid (CSF) collected from SCI rats promoted a dose-dependent migration of MSCs in culture, which was blocked by an inhibitor of CXCR4 or SDF-1 antibody. The study suggests that SDF-1/CXCR4 interactions recruit exogenous MSCs to injured spinal cord tissues and may enhance neural regeneration. Modulation of the homing capacity may be instrumental in harnessing the therapeutic potential of MSCs.

Neuritin Promotes Bone Marrow-Derived Mesenchymal Stem Cell Migration to Treat Diabetic Peripheral Neuropathy.

The purpose of this study is to explore the effect and mechanism of neuritin overexpression in the bone marrow on peripheral neuropathy in type 2 diabetic (db/db) mice. We analyzed the impact of bone marrow neuritin overexpression on diabetic peripheral neuropathy and migration of bone marrow mesenchymal stem cells in db/db mice. Antagonists were used to inhibit the stromal cell-derived factor (SDF)-1α/C-X-C chemokine receptor type 4 (CXCR4)-phosphoinositide 3-kinase (PI3K)/Akt signaling pathway in primary cultured bone marrow mesenchymal stem cells. Immunofluorescence, transmission electron microscopy, Oil Red O staining, and transwell migration assays were used. Bone marrow-specific overexpression of neuritin in db/db mice was successfully established. Overexpression of neuritin in the bone marrow ameliorated hyperglycemia, prevented diabetic peripheral neuropathy, protected the ultrastructure of the sciatic nerve and intra-epidermal nerve fiber density, and promoted Schwann cell proliferation and remyelination in the sciatic nerve. Moreover, it ameliorated fat accumulation, adipocyte number, and vascular and nerve densities; decreased glutamate content in serum and bone marrow; restored gradient SDF-1α contents between bone marrow, blood, and sciatic nerve; and promoted impaired diabetic bone marrow mesenchymal stem cell migration. Neuritin improves bone marrow mesenchymal stem cell migration via the SDF-1α/CXCR4-PI3K/Akt signaling pathway in vitro. Overexpression of neuritin in the bone marrow can locally ameliorate neuropathy in the bone marrow. This improves the migration capability of bone marrow mesenchymal stem cells and repairs diabetic peripheral neuropathy, at least partly by activating the PI3K/Akt pathway through the SDF-1α/CXCR4 axis.

Sustained Release SDF-1α/TGF-β1-Loaded Silk Fibroin-Porous Gelatin Scaffold Promotes Cartilage Repair.

Continuous delivery of growth factors to the injury site is crucial to creating a favorable microenvironment for cartilage injury repair. In the present study, we fabricated a novel sustained-release scaffold, stromal-derived factor-1α (SDF-1α)/transforming growth factor-β1 (TGF-β1)-loaded silk fibroin-porous gelatin scaffold (GSTS). GSTS persistently releases SDF-1α and TGF-β1, which enhance cartilage repair by facilitating cell homing and chondrogenic differentiation. Scanning electron microscopy showed that GSTS is a porous microstructure and the protein release assay demonstrated the sustainable release of SDF-1α and TGF-β1 from GSTS. Bone marrow-derived mesenchymal stem cells (MSCs) maintain high in vitro cell activity and excellent cell distribution and phenotype after seeding into GSTS. Furthermore, MSCs acquired enhanced chondrogenic differentiation capability in the TGF-β1-loaded scaffolds (GSTS or GST: loading TGF-β1 only) and the conditioned medium from SDF-1α-loaded scaffolds (GSTS or GSS: loading SDF-1α only) effectively promoted MSCs migration. GSTS was transplanted into the osteochondral defects in the knee joint of rats, and it could promote cartilage regeneration and repair the cartilagedefects at 12 weeks after transplantation. Our study shows that GSTS can facilitate in vitro MSCs homing, migration, chondrogenic differentiation and SDF-1α and TGF-β1 have a synergistic effect on the promotion of in vivo cartilage forming. This SDF-1α and TGF-β1 releasing GSTS have promising therapeutic potential in cartilage repair.

Acute mobilization and migration of bone marrow-derived stem cells following anterior cruciate ligament rupture.

Little is known regarding acute local and systemic processes following anterior cruciate ligament (ACL) rupture. No study has elucidated whether bone marrow-derived mesenchymal stem cells (MSCs) are mobilized into circulation and recruited to the injured joint. In Part 1, Lewis rats were randomized to noninvasive ACL rupture (Rupture) or non-injured (Control) (n=6/group). After 72h, whole blood MSC concentration was assessed using flow cytometry. Synovial fluid and serum were assayed for stromal cell-derived factor (SDF)-1α and cartilage degeneration biomarkers, respectively. In Part 2, 12 additional rats were randomized and intravenously-injected with fluorescently-labeled allogenic MSCs. Cell tracking was performed using longitudinal, invivo and exvivo near-infrared (NIR) imaging and histology. Synovium SDF-1α and interleukin (IL)-17A immunostaining was performed. Serum was assayed for SDF-1α and 29 other cytokines. In Part 1, there was a significant increase in MSC concentration and synovial fluid SDF-1α in Rupture. No differences in cartilage biomarkers were observed. In Part 2, Rupture had significantly higher NIR signal at 24, 48, and 72h, indicating active recruitment of MSCs to the injured joint. Exvivo cell tracking demonstrated MSC localization in the synovium and myotendinous junction (MTJ) of the quadriceps. Injured synovia exhibited increased synovitis grade and higher degree of IL-17A and SDF-1α immunostaining. ACL rupture induced peripheral blood mobilization of MSCs and migration of intravenously-injected allogenic MSCs to the injured joint, where they localized in the synovium and quadriceps MTJ.

Systemically Infused Mesenchymal Stem Cells Show Different Homing Profiles in Healthy and Tumor Mouse Models.

Bone marrow‐derived mesenchymal stem cells (MSCs) can localize in injured, inflamed, and cancerous tissues after systemic infusion. However, the dynamic homing profile of MSCs in the peripheral blood is not well characterized. Here, using in vivo flow cytometry to noninvasively monitor the dynamics of fluorescence‐labeled cells, we found different clearance kinetics of systemically infused MSCs between healthy and tumor mouse models. The circulation times of MSCs in healthy mice and mice with subcutaneous tumors, orthotopically transplanted liver tumors, or metastatic lung tumors were 30, 24, 18, and 12 hours, respectively, suggesting that MSCs actively home to tumor environments. MSCs infiltrated into hepatocellular carcinoma (HCC) sites and preferentially engrafted to micrometastatic regions both in vivo and in vitro. The expression of epidermal growth factor, CXCL9, CCL25, and matrix metalloproteinases‐9 by HCC cells differed between primary tumor sites and metastatic regions. By characterizing the homing profiles of systemically perfused MSCs under physiological and cancerous conditions, these findings increase our understanding of the migration of MSCs from the circulation to tumor sites and constitute a basis for developing MSC‐based anti‐cancer therapeutic strategies. Stem Cells Translational Medicine 2017;6:1120–1131

Nitric Oxide Modulates Postnatal Bone Marrow-Derived Mesenchymal Stem Cell Migration.

Nitric oxide (NO) is a small free-radical gas molecule, which is highly diffusible and can activate a wide range of downstream effectors, with rapid and widespread cellular effects. NO is a versatile signaling mediator with a plethora of cellular functions. For example, NO has been shown to regulate actin, the microfilament, dependent cellular functions, and also acts as a putative stem cell differentiation-inducing agent. In this study, using a wound-healing model of cellular migration, we have explored the effect of exogenous NO on the kinetics of movement and morphological changes in postnatal bone marrow-derived mesenchymal stem cells (MSCs). Cellular migration kinetics and morphological changes of the migrating MSCs were measured in the presence of an NO donor (S-Nitroso-N-Acetyl-D,L-Penicillamine, SNAP), especially, to track the dynamics of single-cell responses. Two experimental conditions were assessed, in which SNAP (200 μM) was applied to the MSCs. In the first experimental group (SN-1), SNAP was applied immediately following wound formation, and migration kinetics were determined for 24 h. In the second experimental group (SN-2), MSCs were pretreated for 7 days with SNAP prior to wound formation and the determination of migration kinetics. The generated displacement curves were further analyzed by non-linear regression analysis. The migration displacement of the controls and NO treated MSCs (SN-1 and SN-2) was best described by a two parameter exponential functions expressing difference constant coefficients. Additionally, changes in the fractal dimension (D) of migrating MSCs were correlated with their displacement kinetics for all the three groups. Overall, these data suggest that NO may evidently function as a stop migration signal by disordering the cytoskeletal elements required for cell movement and proliferation of MSCs.

MicroRNA-195a-3p inhibits angiogenesis by targeting Mmp2 in murine mesenchymal stem cells.

MicroRNAs (miRNAs) modulate complex physiological and pathological processes, including the regulation of angiogenesis. Our previous study reported that bone marrow-derived mesenchymal stem cells (MSCs) are recruited into choroidal neovascularization lesions. miRNA-195 is highly expressed in MSCs, but its function remains unknown. In the present study, miR-195a-3p abundance was significantly decreased in hypoxia-treated murine MSCs; on the other hand, its overexpression reduced MSC proliferation and migration while increasing the activation of anti-angiogenic factor pigment epithelium-derived factor (PEDF). We further discovered that matrix metalloproteinase 2 (Mmp2) transcript is a target of miR-195a-3p, and that silencing Mmp2 phenocopied the reduced proliferation and migration of MSCs. The therapeutic potential of miR-195a-3p as an angiogenesis inhibitor was also demonstrated in a laser-induced choroidal neovascularization mouse model. These findings collectively indicate that miR-195a-3p is a negative modulator of angiogenesis, and could be used as an angiogenesis inhibitor. Mol. Reprod. Dev. 83: 413-423, 2016. © 2016 Wiley Periodicals, Inc.

Macroporous 3D scaffolds for studying mesenchymal stem cell migration and differentiation within cartilage defects

Event Abstract Back to Event Macroporous 3D scaffolds for studying mesenchymal stem cell migration and differentiation within cartilage defects Glendon C. Plumton1, Isaac M. Adjei1, Alfonso Martin-Pena2, Glyn D. Palmer2 and Blanka Sharma1 1 University of Florida, J. Crayton Pruitt Family Department of Biomedical Engineering, United States 2 University of Florida, Department of Orthopaedics and Rehabilitation, United States Introduction: Damaged cartilage is incapable of self-repair and continues to be a significant clinical challenge. Endogenous recruitment of native stem cells has received increased attention due to fewer regulatory burdens compared to cell delivery. One promising strategy is to combine biomaterials with surgical microfracture techniques to promote an endogenous repair response in cartilage defects[1]. Microfracture entails creating holes in the subchondral bone to facilitate bone marrow-derived mesenchymal stem cell migration[2], and the biomaterial provides a chondroconductive environment. However, the mechanisms of cellular migration and differentiation during this process remain largely unknown. Our goal is to develop a hydrogel system to control/study stem cell migration and differentiation in situ. We have developed a hydrogel in which internal porosity can be controlled and lentiviral vectors with conditionally active promoters can transfect cells infiltrating the hydrogel and enable tracking of chondrogenesis. Materials and Methods: Gelatin microspheres (150-300 µm) were added to a polymer solution of 10% w/v poly(ethylene glycol) diacrylate (MW 3400), 2.5 mg/mL sodium hyaluronate, and 0.5% Irgacure 2959 photoinitiator. The solution was cast into molds, crosslinked with UV light, incubated at 37°C to melt the gelatin microspheres, and imaged on a scanning electron microscope. Viral vectors were made to include Col2-Luc/EF1-GFP, or Col2-GFP/EF1-tdTomato. Viral vectors were mixed in polymer solution and equine MSCs (20 million cells/ml) and crosslinked. Nanoporous (n=5) and macroporous (n=3) hydrogels were produced, with media containing secreted luciferase collected at t=7, 10, 14 days and quantified using a bioluminescence assay. Confocal fluorescence microscopy was performed on the hydrogels. Nanoporous hydrogels containing Col2-GFP/EF1-tdTomato cells were imaged. Results and Discussion: A high degree of interconnected porosity was observed, and the architecture and porosity were adjustable. The viral vectors cause all viable MSCs to fluoresce green (EF1-GFP) or red (EF1-tdTomato), and MSCs undergoing chondrogesis will either secrete luciferase (Col2-Luc) or fluoresce green (Col2-GFP), depending on the reporter construct used.Secreted luciferase was found in all hydrogels with encapsulated Col2-Luc/EF1-GFP viral vectors, indicating that in situ transfection occurred. Using confocal imaging, transfected cellular clusters were identified due to GFP presence. Imaging of hydrogels with encapsulated Col2-GFP/EF1-tdtomato viral vectors demonstrated the ability to conditionally express GFP in Col2+ cells, enabling identification of MSCs undergoing chondrogenesis. Conclusion: These results support the development of a system to study the mechanisms of cellular migration and differentiation in biomaterial-enhanced microfracture repair. The feasibility of in situ transfection was established, and future studies will investigate migration and differentiation in vitro and in vivo using this platform. Insights gained from these studies could ultimately be used to develop more effective cartilage repair approaches in patients, as well as provide greater understanding of cell-material interactions in other systems where endogenous stem cells are harnessed for tissue repair .

Mechano growth factor E peptide promotes rat bone marrow-derived mesenchymal stem cell migration through CXCR4-ERK1/2

Mechano growth factor (MGF) is a splicing variant of insulin-like growth factor 1 (IGF-1). The unique C-terminal E domain of MGF (MGF-E) makes it distinct from the other variants of IGF-1. Our previous work demonstrated that MGF-25E induces the migration of rat bone marrow-derived mesenchymal stem cells (rMSCs) by altering their mechanical properties, which is accompanied by the activation of the extracellular signal-regulated kinase 1/2 (ERK1/2) pathway. However, the relationship between ERK1/2 activation and the change in mechanical properties has not been illustrated. In the present study, we determined that MGF-25E induced the migration of rMSCs by modulating CXCR4 to activate the ERK1/2 pathway. The analysis of the Young’s modulus and F-actin remodeling indicated that MGF-25E increased the stiffness and the F-actin polymerization of rMSCs through the activation of the CXCR4-ERK1/2 pathway. For the first time, this study clarified the signaling pathway that regulates the mechanical properties of rMSCs and is responsible for MGF-25E-promoted migration.

Matrix metalloproteinase-1-mediated mesenchymal stem cell tumor tropism is dependent on crosstalk with stromal derived growth factor 1/C-X-C chemokine receptor 4 axis.

Human bone marrow-derived mesenchymal stem cells (MSCs) have the unique ability to home toward injuries or tumor sites. We have previously shown that the tumor-tropic property is dependent on the intrinsic expression and activity of the matrix remodeling gene, matrix metalloproteinase 1 (MMP-1). Herein, crosstalk between MMP-1/protease activated receptor 1 (PAR-1) and the G-protein coupled receptor stromal-derived growth factor 1 (SDF-1)/C-X-C chemokine receptor 4 (CXCR-4) in facilitating cell migration was investigated. Gain-of-function and RNA interference (RNAi) technology were used to evaluate the interplay between the key players. The downstream effect on the tumor-tropic migration of MSCs was investigated using modified Boyden chamber assay. Neutralizing PAR-1 activation using monoclonal antibody and targeted knockdown of MMP-1 using RNAi resulted in decreased expression of SDF-1, which was not observed in control-RNAi-transfected cells. Overexpression of CXCR-4 failed to promote MSC migration; the percentage of migrated cells toward tumor cell conditioned medium was similar to the vector-transduced and the CXCR-4-transduced MSCs. Furthermore, inhibition of SDF-1/CXCR-4 signaling using AMD3100 reduced MSC migration through the deregulation of MMP-1 promoter activities, protein expression, and metalloproteinase activity. Collectively, our results showed that MMP-1-mediated MSC tumor tropism is dependent on crosstalk with the SDF-1/CXCR-4 axis.

The Involvement of CXCL11 in Bone Marrow-Derived Mesenchymal Stem Cell Migration Through Human Brain Microvascular Endothelial Cells

Bone marrow-derived mesenchymal stem cells (MSCs) transplant into the brain, where they play a potential therapeutic role in neurological diseases. However, the blood-brain barrier (BBB) is a native obstacle for MSCs entry into the brain. Little is known about the mechanism behind MSCs migration across the BBB. In the present study, we modeled the interactions between human MSCs (hMSCs) and human brain microvascular endothelial cells (HBMECs) to mimic the BBB microenvironment. Real-time PCR analysis indicated that the chemokine CXCL11 is produced by hMSCs and the chemokine receptor CXCR3 is expressed on HBMECs. Further results indicate that CXCL11 secreted by hMSCs may interact with CXCR3 on HBMECs to induce the disassembly of tight junctions through the activation of ERK1/2 signaling in the endothelium, which promotes MSCs transendothelial migration. These findings are relevant for understanding the biological responses of MSCs in BBB environments and helpful for the application of MSCs in neurological diseases.

Influence of TLR2 and TLR4 agonists on migration of human bone marrow mesenchymal stem cells

This study was aimed to investigate the influence of TLR2 and TLR4 agonists on the migration and adhesion activity of human bone marrow-derived mesenchymal stem cells (MSC) and to clarify the underlying mechanisms. The expression of TLR2 and TLR4 on MSC was detected by flow cytometry. The effects of TLR2 agonist (PAM3CSK4) and TLR2 agonist (LPS) on MSC migration and adhesion ability were evaluated with chemotaxis and adhesion test. The results indicated that expressive levels of TLR2 and TLR4 on surface of human bone marrow MSC were (24.5 ± 3.2)% and (91.3 ± 5.2)% respectively. Compared with the control group, the migration activity of MSC toward SDF-1 was decreased significantly in PAM3CSK4 group, while the adhesion activity of MSC was promoted by PAM3CSK4 exposure. However, both the migration activity toward SDF-1 and the adhesion activity of MSC were not changed significantly in LPS-treated group. Further, it was found that PAM3CSK4 did not affect the expressive level of CXCR4 on MSC, however, it could inhibit the spontaneous migration of MSC in dose dependent manner. It is concluded that activation of TLR2 can decrease the migration ability of MSC, which may associate with the decreased spontaneous migration ability and the increased adhesion activity of MSC.

Mechanical Stretch Upregulates SDF-1α in Skin Tissue and Induces Migration of Circulating Bone Marrow-Derived Stem Cells into the Expanded Skin

Skin and soft tissue expansion is a procedure that stimulates skin regeneration by applying continuous mechanical stretching of normal donor skin for reconstruction purposes. We have reported that topical transplantation of bone marrow-derived mesenchymal stem cells (MSCs) can accelerate mechanical stretch induced skin regeneration. However, it is unclear how circulating MSCs respond to mechanical stretch in skin tissue. MSCs from luciferase-Tg Lewis rats were transplanted into a rat tissue expansion model and tracked in vivo by luminescence imaging. Expression levels of chemokines including macrophage inflammatory protein-1α, thymus and activation-regulated chemokine, secondary lymphoid tissue chemokine, cutaneous T-cell attracting chemokine, and stromal-derived factor-1α (SDF-1α) were elevated in mechanically stretched tissues, as were their related chemokine receptors in MSCs. Chemotactic assays were conducted in vitro and in vivo to assess the impact of chemokine expression on MSC migration. MSC migration was observed in mechanically stretched skin. Mechanical stretching induced temporal upregulation of chemokine expression. Among all the tested chemokines, SDF-1α showed the most significant increase in stretched skin, suggesting a strong connection to migration of MSCs. The in vitro chemotactic assay showed that conditioned medium from mechanically stretched cells induced MSC migration, which could be blocked with the CXCR4 antagonist AMD3100, as effectively as medium containing 50 ng/ml rat recombinant SDF-1α. Results from in vivo study also showed that MSC migration to mechanically stretched skin was significantly blocked by AMD3100. Moreover, migrating MSCs expressed differentiation markers, suggesting a contribution of MSCs to skin regeneration through differentiation. Mechanical stretching can upregulate SDF-1α in skin and recruit circulating MSCs through the SDF-1α/CXCR4 pathway.

Involvement of PI3K and ROCK signaling pathways in migration of bone marrow-derived mesenchymal stem cells through human brain microvascular endothelial cell monolayers

Bone marrow-derived mesenchymal stem cells (MSC) represent an important and easily available source of stem cells for potential therapeutic use in neurological diseases. The entry of circulating cells into the central nervous system by intravenous administration requires, firstly, the passage of the cells across the blood–brain barrier (BBB). However, little is known of the details of MSC transmigration across the BBB. In the present study, we employed an in vitro BBB model constructed using a human brain microvascular endothelial cell monolayer to study the mechanism underlying MSC transendothelial migration. Transmigration assays, transendothelial electrical resistance (TEER) and horseradish peroxidase (HRP) flux assays showed that MSC could transmigrate through human brain microvascular endothelial cell monolayers by a paracellular pathway. Cell fractionation and immunofluorescence assays confirmed the disruption of tight junctions. Inhibition assays showed that a Rho-kinase (ROCK) inhibitor (Y27632) effectively promoted MSC transendothelial migration; conversely, a PI3K inhibitor (LY294002) blocked MSC transendothelial migration. Interestingly, adenovirus-mediated interference with ROCK in MSC significantly increased MSC transendothelial migration, and overexpression of a PI3K dominant negative mutant in MSC cells could block transendothelial migration. Our findings provide clear evidence that the PI3K and ROCK pathways are involved in MSC migration through human brain microvascular endothelial cell monolayers. The information yielded by this study may be helpful in constructing gene-modified mesenchymal stem cells that are able to penetrate the BBB effectively for cell therapy.

THE EFFECT OF HYPOXIA ON GLOBAL GENE EXPRESSION AND ALTERNATIVE SPLICING OF HUMAN MESENCHYMAL STEM CELLS

ObjectivesHypoxia preconditioning has become a novel strategy to improve the in vivo therapeutic potential of bone marrow-derived mesenchymal stem cells (MSCs). However, the underlying molecular mechanisms responsible for the hypoxia-induced...

Stroma‐directed imatinib therapy impairs the tumor‐promoting effect of bone marrow‐derived mesenchymal stem cells in an orthotopic transplantation model of colon cancer

Bone marrow-derived mesenchymal stem cells (MSCs) are reported to contribute to formation of tumor-promoting stromal cells. We reported recently that, in an orthotopic nude mice model of colon cancer, MSCs traveled to tumor stroma, where they differentiated into carcinoma-associated fibroblast (CAF)-like cells. We also found that CAFs express platelet-derived growth factor receptor (PDGFR) at a high level and that imatinib therapy targeting PDGFR in CAFs inhibits growth and metastasis of human colon cancer. These findings led us to examine whether the tumor-promoting effect of MSCs is impaired by blockade of PDGFR signaling achieved with imatinib. Orthotopic transplantation and splenic injection of human MSCs along with KM12SM human colon cancer cells, in comparison with transplantation of KM12SM cells alone, resulted in significantly greater promotion of tumor growth and liver metastasis. The KM12SM + MSC xenograft enhanced cell proliferation and angiogenesis and inhibited tumor cell apoptosis. When tumor-bearing animals were treated with imatinib, there was no significant increase in primary tumor volume or total volume of liver metastases, despite the KM12SM+MSC xenograft, and survival in the mixed-cell group was prolonged by imatinib treatment. Moreover, the ability of MSCs to migrate to tumor stroma was impaired, and the number of MSCs surviving in the tumor microenvironment was significantly decreased. In in vitro experiments, treatment with imatinib inhibited migration of MSCs. Our data suggest that blockade of PDGF signaling pathways influences the interaction between bone marrow-derived MSCs and tumor cells in the tumor microenvironment and, hence, inhibits the progressive growth of colon cancer.

Zoledronic acid blocks the interaction between mesenchymal stem cells and breast cancer cells: implications for adjuvant therapy of breast cancer

Zoledronic acid (ZA) reduces locoregional and distant metastases in estrogen receptor (ER)-positive breast cancer patients. Since ZA rapidly concentrates in the bone following i.v. administration, we hypothesized that this phenomenon involves the mechanism of action of ZA in bone tissue. Migration assays were carried out in fibronectin-coated Boyden chambers. Activation of signaling proteins was analyzed with a phosphoprotein array. Chemokines and growth factors were measured by immunoassays and real-time PCR. ZA significantly reduced in bone marrow-derived mesenchymal stem cells (MSCs) the activation of AKT and mitogen-activated protein kinase and their ability to migrate. Conditioned medium (CM) from ZA-treated MSCs showed a reduced capacity to promote the migration of ER-positive MCF-7 breast cancer cells as compared with CM from untreated MSCs. The levels of the chemokine (C-C motif) ligand 5 (CCL5, also known as RANTES - Regulated upon Activation, Normal T-cell Expressed, and Secreted) and interleukin (IL)-6 were significantly reduced in MSC-CM following treatment with ZA. Anti-RANTES and anti-IL-6 antibodies almost completely abolished the migration of MCF-7 cells induced by MSC-CM. Recombinant RANTES and IL-6 significantly induced MCF-7 cell migration and their combination showed a cooperative effect. Similar results were observed in different breast cancer cell lines. ZA might exert its antitumor activity by inhibiting MSC migration and blocking MSCs' secretion of factors involved in breast cancer progression.