Contribution Of Mesenchymal Stem Cells Research Articles

Mesenchymal Stem Cells Expressing Insulin-like Growth Factor-I (MSCIGF) Promote Fracture Healing and Restore New Bone Formation in Irs1 Knockout Mice: Analyses of MSCIGF Autocrine and Paracrine Regenerative Effects

Failures of fracture repair (nonunions) occur in 10% of all fractures. The use of mesenchymal stem cells (MSC) in tissue regeneration appears to be rationale, safe, and feasible. The contributions of MSC to the reparative process can occur through autocrine and paracrine effects. The primary objective of this study is to find a novel mean, by transplanting primary cultures of bone marrow-derived MSCs expressing insulin-like growth factor-I (MSC(IGF)), to promote these seed-and-soil actions of MSC to fully implement their regenerative abilities in fracture repair and nonunions. MSC(IGF) or traceable MSC(IGF)-Lac-Z were transplanted into wild-type or insulin-receptor-substrate knockout (Irs1(-/-)) mice with a stabilized tibia fracture. Healing was assessed using biomechanical testing, microcomputed tomography (μCT), and histological analyses. We found that systemically transplanted MSC(IGF) through autocrine and paracrine actions improved the fracture mechanical strength and increased new bone content while accelerating mineralization. We determined that IGF-I adapted the response of transplanted MSC(IGF) to promote their differentiation into osteoblasts. In vitro and in vivo studies showed that IGF-I-induced osteoglastogenesis in MSCs was dependent of an intact IRS1-PI3K signaling. Furthermore, using Irs1(-/-) mice as a nonunion fracture model through altered IGF signaling, we demonstrated that the autocrine effect of IGF-I on MSC restored the fracture new bone formation and promoted the occurrence of a well-organized callus that bridged the gap. A callus that was basically absent in Irs1(-/-) left untransplanted or transplanted with MSCs. We provided evidence of effects and mechanisms for transplanted MSC(IGF) in fracture repair and potentially to treat nonunions.

Contribution of mesenchymal stem cells, or fibroblast-like synoviocytes to the vicious circle leading to chronic inflammation in RA, through promotion of Th17 cells

Background and objectivesTH17 cells have been involved in the initiation and maintenance of inflammatory and autoimmune diseases, such as rheumatoid arthritis (RA).In this study, we hypothesised that interaction of T...

Mesenchymal stem cells and their microenvironment

Mesenchymal stem cells (MSC) are multipotent stem cells that hold promise for an expanding list of therapeutic uses, not only due to their ability to differentiate into all connective tissues including bone, fat and cartilage, but additionally due to their trophic and anti-inflammatory effects which contribute to healing and tissue regeneration. Ongoing research is starting to illuminate important aspects of the microenvironmental niche, which supports MSC self-renewal. In this review, we summarize recent findings on cellular structures and molecular pathways that are involved in regulation of MSC self-renewal versus differentiation, and in retention of MSCs within the niche versus mobilization and recruitment to sites of injury. In addition, the contribution of MSCs to the structure and function of hematopoietic and cancerous niches is discussed.

ENDOTHELIAL-LIKE CELLS DERIVED FROM MESENCHYMAL STEM CELLS ATTENUATE NEOINTIMAL HYPERPLASIA AFTER VASCULAR INJURY: PP.21.339

Objectives: The present study investigates the contribution of mesenchymal stem cells (MSCs) to neointimal formation, and whether endothelial-like cells differentiated from MSCs could attenuate intimal hyperplasia after vascular injury. Methods: Bone marrow-derived MSCs of SD rats were cultured in vitro routinely. Differentiation into endothelial-like cells was induced by cultivation of confluent cells in the presence of 50ng/ml vascular endothelial growth factor(VEGF). MSCs and endothelial-like cells were incubated with 20umol/L BrdU in 48 h for cells labeling. The labeling cells were injected via femoral vein on the day of balloon-induced carotid artery injury. Carotid arteries of all rats were examined by ultrasound biomicroscopy at day 7, 14 and 28 after the injury. Results: Flow cytometer analysis showed increased expression of CD31 and CD34, immunofluorescence analysis showed expression of endothelial-specific markers like vWF and VEGFR2 in endothelial-like cells. Ultrasound biomicroscopy showed significantly increases of IMT in the groups of PBS and MSCs compaired with endothelial-like cells group in 14 days after artery injured (0.10±0.02 mm vs 0.14±0.03 mm vs 0.13±0.02 mm, p < 0.01) and IMT significantly increased in 28 days after injury (0.16±0.02 mm vs 0.22±0.04 mm vs 0.23±0.05 mm, p < 0.01). Intimal/media (I/M) ratio were significantly reduced in endothelial-like cells group compared to PBS and MSCs groups (1.22±0.23 vs 2.52±0.64 vs 2.87±0.40, p < 0.001)(fig.1). Immunohistochemistry staining with anti-Brdu, a lot of Brdu-labeling cells were found in the adventitia, especially in the zone about vasa vasorum and few in the neointimal. Conclusions: These findings suggested that MSCs were able to differentiate into endothelial-like cells in vitro and cell therapy with MSCs could not attenuate the thickness of the neointima. Transplantation with endothelial-like cells derived from MSCs significantly suppressed intimal hyperplasia after vascular injury. A lot of transplanting cells were homing to adventitia.

Potential role of stem cells in management of COPD

Chronic obstructive pulmonary disease (COPD) is a worldwide epidemic affecting over 200 million people and accounting for more than three million deaths annually. The disease is characterized by chronic inflammation of the airways and progressive destruction of lung parenchyma, a process that in most cases is initiated by cigarette smoking. Unfortunately, there are no interventions that have been unequivocally shown to prolong survival in patients with COPD. Regeneration of lung tissue by stem cells from endogenous and exogenous sources is a promising therapeutic strategy. Herein we review the current literature on the characterization of resident stem and progenitor cell niches within the lung, the contribution of mesenchymal stem cells to lung regeneration, and advances in bioengineering of lung tissue.

Mesenchymal stem cell interactions with growth factors on kidney repair

To review the current knowledge of the contribution of mesenchymal stem cells (MSCs) during renal repair and the factors and mechanisms underlying these effects. Although many studies using MSCs as therapeutic agents have been published in recent years, our understanding is incomplete how migration, growth, and differentiation of adult MSCs are governed by interactions with resident renal cells, growth factors, and cytokines. Different laboratories have shown that extrarenal stem cells contribute to renal regeneration: MSCs migrate into injured renal tissue, are integrated into the tubular system, and differentiate into epithelial cells. Nevertheless, a couple of studies could not verify these results in all, but despite this they have shown a beneficial effect of administered MSCs on renal regeneration. It is well established that renal tubular epithelial cells secrete growth factors and cytokines. These factors participate in renal repair as paracrine regulators or chemoattractants to induce migration of extrarenal stem cells, whereas only limited data are available about the interactions between all key players during renal repair mechanisms. Although different studies demonstrate the effectiveness of MSC therapy, there are still open questions defining the mechanism of action during homing and differentiation and the long-term safety on the way to a therapeutic option.

Mesenchymal stem cells-derived vascular smooth muscle cells release abundant levels of osteoprotegerin.

Although several studies have shown that the serum levels of osteoprotegerin (OPG) are significantly elevated in patients affected with atherosclerotic lesions in coronary and peripheral arteries, the cellular source and the role of OPG in the physiopathology of atherosclerosis are not completely defined. Therefore, we aimed to investigate the potential contribution of mesenchymal stem cells in the production/release of OPG. OPG was detectable by immunohistochemistry in aortic and coronary atherosclerotic plaques, within or in proximity of intimal vascular smooth muscle cells (SMC). In addition, bone marrow mesenchymal stem cell (MSC)-derived vascular SMC as well as primary aortic SMC released in the culture supernatant significantly higher levels of OPG with respect to MSC-derived endothelial cells (EC) or primary aortic EC. On the other hand, in vitro exposure to full-length human recombinant OPG significantly increased the proliferation rate of aortic SMC cultures, as monitored by bromodeoxyuridine incorporation. Taken together, these data suggest that OPG acts as an autocrine/paracrine growth factor for vascular SMC, which might contribute to the progression of atherosclerotic lesions.

Mesenchymal stem cells-derived vascular smooth muscle cells release abundant levels of osteoprotegerin

Although several studies have shown that the serum levels of osteoprotegerin (OPG) are significantly elevated in patients affected with atherosclerotic lesions in coronary and peripheral arteries, the cellular source and the role of OPG in the physiopathology of atherosclerosis are not completely defined. Therefore, we aimed to investigate the potential contribution of mesenchymal stem cells in the production/release of OPG. OPG was detectable by immunohistochemistry in aortic and coronary atherosclerotic plaques, within or in proximity of intimal vascular smooth muscle cells (SMC). In addition, bone marrow mesenchymal stem cell (MSC)-derived vascular SMC as well as primary aortic SMC released in the culture supernatant significantly higher levels of OPG with respect to MSC-derived endothelial cells (EC) or primary aortic EC. On the other hand, in vitro exposure to full-length human recombinant OPG significantly increased the proliferation rate of aortic SMC cultures, as monitored by bromodeoxyuridine incorporation. Taken together, these data suggest that OPG acts as an autocrine/paracrine growth factor for vascular SMC, which might contribute to the progression of atherosclerotic lesions.

Human mesenchymal stem cells from bone marrow express tumor endothelial and stromal markers

Tumor development is a complex and dynamic process that involves malignant, vascular, and stromal cells. Endosialin is a tumor endothelial marker (TEM) present in the microvasculature and stroma of human tumors. Cancer-associated fibroblasts (CAF) have been implicated in promoting tumor development and have been associated with mesenchymal stem cells (MSC). Since stem/progenitor cells recruited either from bone marrow or residing in nearby tissues can contribute to pathological processes we investigated endosialin in MSC using a novel monoclonal antibody. Endosialin is highly expressed by CAF and human bone marrow-derived MSC. MSC can form networks in a tube formation assay that is inhibited by an anti-endosialin antibody. Immunohistochemistry for human endosialin in xenograft tumors following co-injection of MSC and cancer cells identified MSC in tumor stroma. MSC are a potential target for anticancer therapeutic intervention and endosialin expression offers a new tool for the identification of MSC. Endosialin expression by both CAF and MSC further implies the potential contribution of MSC to tumor stroma via differentiation into tumor stromal fibroblasts.

Mesenchymal stem cells and skin wound repair and regeneration: possibilities and questions

Adult mesenchymal stem cells (MSCs) have the capacity for self-renewal and for differentiating into a variety of cells and tissues. They may leave their niche to migrate to remote tissues and play a critical role in wound repair and tissue regeneration. Because of their multipotency, easy isolation and culture, highly expansive potential, and immunosuppression properties, these cells may be an attractive therapeutic tool for regenerative medicine and tissue engineering. Several studies have indicated a contribution of MSCs to reconstituting skin in cutaneous wounds, but problems still need resolution before MSCs can be widely used clinically. This review focuses mainly on the benefits of MSCs in skin wound healing and tissue regeneration and on the questions that remain to be answered before MSCs can be used in clinical practice.

Tales from the Crypt: Mesenchymal Stem Cells for Replenishing the Intestinal Stem Cell Pool

Studies have shown that Mesenchymal Stem Cells (MSC) contribute to replenishing the radiation-depleted intestinal stem cell (ISC) compartment after abdominal/pelvic radiotherapy. Coupling these findings with other encouraging results showing that MSC promotes healing in inflammatory bowel disease suggests that MSC may represent an attractive source for regeneration of gastrointestinal tissue. Nevertheless, controversy regarding the true contribution of MSC to the cellular pool of an injured organ versus promotion of healing through production of growth factors/cytokines raised questions regarding the true potential of these cells. Since MSC are known to be heterogeneous and some populations may represent tissue-specific stem cells or cells which have already committed to differentiation to a specific phenotype, it is important to find a means of identifying and enriching for subpopulations that are best suited for intestinal cell therapy. Thus, we examined the in vivo ability of clonally-derived MSC populations to contribute to the stem or mature epithelial pool of the intestine, and correlated these results with genomic analysis in an attempt to find a specific marker that enriches for such an MSC population. BM-derived Stro-1+ MSC clones were established by single cell deposition. Phenotypic characterization of the various clones showed that, despite many similarities, there was phenotypic variance between clones for some commonly expressed stem cell proteins, such as CD44 and c-kit. 6 of the clonally-derived MSC were transplanted into 55–60 day-old fetal sheep at a concentration of 106cells/fetus, and evaluated the recipient intestine at 2.5–3 months post-transplant for the presence of human organ-specific cells using fluorescent in situ hybridization and immunofluorescence. We found that MSC localized preferentially to the mucosal layer, distributed equally between the crypts and the villi, with no evidence of cell fusion. While 4 of the 6 clones had a similar level of intestinal engraftment of 1.5±0.4%, 2 of the clones exhibited enhanced engraftment of 5±0.65%. Dual staining with antibodies to cytokeratin and the ISC marker Musashi showed a direct correlation between the levels of donor contribution to the ISC pool and the levels of mature enterocytes within the villi, such that 1–4% of the Musashi+ cells within the crypt were donor-derived with the 4 clones exhibiting overall intestinal engraftment levels of 1.5%, whereas 12–14% of the total Musashi+ ISC population was donor-derived with the 2 clones exhibiting enhanced levels of intestinal engraftment. Since no correlation was found between the enhanced levels of engraftment and any of the phenotypic markers tested prior to transplant, transcriptome analysis using Affymetrix microarrays, and GeneSifter software was done in the hopes of identifying a marker that would allow selection of these cells. MSC did not express Mushashi, cytokeratin 2,18,19,20, or GPR49 prior to transplant, precluding their use for selection for transplant. MSC expressed calmodulin, caldesmon, B-catenin and cytovillin, proteins expressed by intestinal crypt cells. Unfortunately, the cytoplasmic location of these antigens prevents their use for selection. Nevertheless, EphrinB-2, a receptor expressed at high levels on ISC, was also found to be expressed on MSC. Studies are underway to confirm whether levels of EphrinB-2 correlate with the differentiation potential of the clones. Our studies demonstrate that MSC subsets have the ability to repopulate the ISC pool and generate differentiated intestinal cells and that combining in vivo functionality studies with genomic analysis may lead to identification of markers for enrichment of MSC that exhibit desired traits upon transplantation.

Abstract 1306: Late-outgrowth Endothelial Cells Attenuate Intimal Hyperplasia Contributed By Mesenchymal Stem Cells After Vascular Injury

Objectives: Mesenchymal stem cells (MSCs) from the bone marrow (BM) are pluripotent and have the capacity to differentiate into cardiomyocytes, endothelial cells (ECs), and smooth muscle cells (SMCs). Currently, MSCs are one of a number of cell types undergoing extensive investigation for cardiac regeneration therapy. However, it has not yet been determined whether this cell therapy also substantially contributes to vascular remodeling of diseased vessels, such as in intimal hyperplasia. Methods and Results: Human MSCs and a variety of progenitor and vascular cells were used for in vitro and in vivo adhesion experiments. To test the contribution of MSCs to intimal hyperplasia, MSCs from eGFP mice were injected via the tail vein of wild-type littermates after femoral artery wire injury. A model of direct BM transplantation of eGFP MSCs into the tibias of irradiated wild-type littermates was also conducted. Wire-induced vascular injury mobilized MSCs into the circulation. Compared to human aortic SMCs, MSCs exhibited a 2.8-fold increase in the adhesion capacity in vitro ( p &lt; 0.001), and a 6.3-fold increase in vivo ( p &lt; 0.001). In all animal models, immunostaining showed that a significant amount of eGFP MSCs contributed to intimal hyperplasia after vascular injury. Furthermore, MSCs were able to differentiate into cells of endothelial or smooth muscle lineage on the injured vessel wall. Co-culture experiments demonstrated that late-outgrowth ECs guided MSCs to differentiate towards an endothelial lineage through a paracrine effects rather than direct cell-cell interactions. In vivo , cell therapy with late-outgrowth ECs significantly attenuated the thickness of the neointima contributed by MSCs (intima/media ratio, from 3.2 ± 0.4 to 0.4 ± 0.1, p &lt; 0.001). Conclusions: This study raises concerns about the detrimental effects of stem cell therapy on injured vessel remodeling. Tissue regeneration therapy with MSCs or cell populations containing MSCs requires a strategy to attenuate the high potential of MSCs to develop intimal hyperplasia on diseased vessels.

Contribution of human bone marrow stem cells to individual skeletal myotubes followed by myogenic gene activation

Much attention is focused on characterizing the contribution of bone marrow (BM)-derived cells to regenerating skeletal muscle, fuelled by hopes for stem cell-mediated therapy of muscle degenerative diseases. Though physical integration of BM stem cells has been well documented, little evidence of functional commitment to myotube phenotype has been reported. This is due to the innate difficulty in distinguishing gene products derived from donor versus host nuclei. Here, we demonstrate that BM-derived stem cells contribute via gene expression following incorporation to skeletal myotubes. By co-culturing human BM-derived mesenchymal stem cells (MSC) with mouse skeletal myoblasts, physical incorporation was observed by genetic lineage tracing and species-specific immunofluorescence. We used a human-specific antibody against the intermediate filament protein nestin, a marker of regenerating skeletal muscle, to identify functional contribution of MSC to myotube formation. Although nestin expression was never detected in MSC, human-specific expression was detected in myotubes that also contained MSC-derived nuclei. This induction of gene expression following myotube integration suggests that bone marrow-derived stem cells can reprogram and functionally contribute to the muscle cell phenotype. We propose that this model of myogenic commitment may provide the means to further characterize functional reprogramming of MSC to skeletal muscle.

Non-Hematopoietic Bone Marrow Cells Can Be Mobilized and Differentiate into Cardiomyocytes after Myocardial Infarction: Possible Contribution of Mesenchymal Stem Cells.

Recent studies have suggested that bone marrow (BM) cells can contribute to regeneration processes in various tissues. Cardiomyocytes derived from BM cells have been observed after myocardial infarction (MI), and BM-derived cells mobilized by cytokines were capable of regenerating the myocardial tissue, leading to an improvement in survival or cardiac function after MI. However, the responsible BM cells have not been fully identified. The most likely candidates for the BM-derived stem cells with the ability to regenerate myocardial tissue are hematopoietic stem cells (HSC) and mesenchymal stem cells (MSC). The aim of this study was to determine the precise origin of the BM cells mobilized by cytokines to repair infarcted myocardium. Here, we used two independent clonal studies; we transplanted genetically marked single HSC or clonal MSC into lethally-irradiated recipient mice, induced MI, treated the mice with G-CSF, and analyzed the cardiac tissues. First, we transplanted single CD34−c-kit+Sca-1+lineage− side population (CD34−KSL-SP) cells or whole BM cells from mice ubiquitously expressing enhanced green fluorescent protein (EGFP) into lethally-irradiated mice, induced myocardial infarction (MI), and treated the animals with G-CSF to mobilize stem cells to the damaged myocardium. At 8 weeks post-MI, from 100 specimens we counted only 3 EGFP+actinin+ cells in myocardium of CD34−KSL-SP cells-transplanted mice, but more than 5,000 EGFP+actinin+ cells in whole BM cell-transplanted mice, suggesting that most of EGFP+actinin+ cells derived from non-hematopoietic BM cells. These results suggested that the major population of cells mobilized from the BM and active in the regeneration of cardiomyocytes was non-hematopoietic in origin. Next, clonally purified mesenchymal stem cells, CMG cells, transfected with a pMLC2v-EGFP plasmid encoding EGFP driven by the myosin light chain promoter were transplanted directly into BM of lethally-irradiated mice, MI was induced, and they were treated with G-CSF. As a result, a number of EGFP+actinin+ cells were observed in the ischemic myocardium, indicating that CMG cells had been mobilized and differentiated into cardiomyocytes. Together, these results suggested that the vast majority of BM-derived cardiomyocytes are of mesenchymal origin.

Titanium particles suppress expression of osteoblastic phenotype in human mesenchymal stem cells

Long-term stability of arthroplasty prosthesis depends on the integration between osseous tissue and the implant biomaterial. Integrity of the osseous tissue requires the contribution of mesenchymal stem cells and their continuous differentiation into an osteoblastic phenotype. This study aims to investigate the hypothesis that exposure to wear debris particles derived from orthopaedic biomaterials affects the osteoblastic differentiation of human mesenchymal stem cells (hMSC). Upon in vitro culture in the presence of osteogenic supplements (OS), we observe that cultures of hMSCs isolated from femoral head bone marrow are capable of osteogenic differentiation, expressing alkaline phosphatase, osteocalcin, and bone sialoprotein (BSP), in addition to producing collagen type I and BSP accompanied by extracellular matrix mineralization. Exposure of OS-treated hMSCs to submicron commercially pure titanium (cpTi) particles suppresses BSP gene expression, reduces collagen type I and BSP production, decreases cellular proliferation and viability, and inhibits matrix mineralization. In comparison, exposure to zirconium oxide (ZrO 2) particles of similar size did not alter osteoblastic gene expression and resulted in only a moderate decrease in cellular proliferation and mineralization. Confocal imaging of cpTi-treated hMSC cultures revealed patchy groups of cells displaying disorganized cytoskeletal architecture and low levels of extracellular BSP. These in vitro findings suggest that chronic exposure of marrow cells to titanium wear debris in vivo may contribute to decreased bone formation at the bone/implant interface by reducing the population of viable hMSCs and compromising their differentiation into functional osteoblasts. Understanding the nature of hMSC bioreactivity to orthopaedic wear debris should provide additional insights into mechanisms underlying aseptic loosening.