技术资料

OBJECTIVE: Bone marrow-derived mononuclear cells (BMCs) improve the functional recovery after ischemia. However,BMCs comprise a heterogeneous mixture of cells,and it is not known which cell types are responsible for the induction of neovascularization after cell therapy. Because cell recruitment is critically dependent on the expression of the SDF-1-receptor CXCR4,we examined whether the expression of CXCR4 may identify a therapeutically active population of BMCs. METHODS AND RESULTS: Human CXCR4(+) and CXCR4(-) BMCs were sorted by magnetic beads. CXCR4(+) BMCs showed a significantly higher invasion capacity under basal conditions and after SDF-1 stimulation. Hematopoietic or mesenchymal colony-forming capacity did not differ between CXCR4(+) and CXCR4(-) BMCs. Injection of CXCR4(+) BMCs in mice after induction of hindlimb ischemia significantly improved the recovery of perfusion compared to injection of CXCR4(-) BMCs. Likewise,capillary density was significantly increased in CXCR4(+) BMC-treated mice. Because part of the beneficial effects of cell therapy were attributed to the release of paracrine effectors,we analyzed BMC supernatants for secreted factors. Importantly,supernatants of CXCR4(+) BMCs were enriched in the proangiogenic cytokines HGF and PDGF-BB. CONCLUSIONS: CXCR4(+) BMCs exhibit an increased therapeutic potential for blood flow recovery after acute ischemia. Mechanistically,their higher migratory capacity and their increased release of paracrine factors may contribute to enhanced tissue repair. View Publication

Cell-matrix interactions are paramount for the successful repair and regeneration of damaged and diseased tissue. Since many tissues have an anisotropic architecture,it has been proposed that aligned extracellular matrix (ECM) structures in particular could guide and support the differentiation of resident mesenchymal stem and progenitor cells (MSCs). We therefore created aligned collagen type I structures using a microfluidic set-up with the aim to assess their impact on MSC growth and differentiation. In addition,we refined our aligned collagen matrices by incorporating the glycosaminoglycan (GAG) heparin to demonstrate the versatility of the applied methodology to study multiple ECM components in a single system. Our reconstituted,aligned ECM structures maintained and allowed multilineage (osteogenic/adipogenic/chondrogenic) differentiation of MSCs. Most noticeable was the observation that during osteogenesis,aligned collagen substrates choreographed ordered matrix mineralization. Likewise,myotube assembly of C2C12 cells was profoundly influenced by aligned topographic features resulting in enhanced myotube organization and length. Our results shed light on the regulation of MSCs through directional ECM structures and demonstrate the versatility of these cell culture platforms for guiding the morphogenesis of tissue types with anisotropic structures. View Publication

Dental pulp is a promising source of mesenchymal stem cells with the potential for cell-mediated therapies and tissue engineering applications. We recently reported that isolation of dental pulp-derived stem cells (DPSC) is feasible for at least 120h after tooth extraction,and that cryopreservation of early passage cultured DPSC leads to high-efficiency recovery post-thaw. This study investigated additional processing and cryobiological characteristics of DPSC,ending with development of procedures for banking. First,we aimed to optimize cryopreservation of established DPSC cultures,with regards to optimizing the cryoprotective agent (CPA),the CPA concentration,the concentration of cells frozen,and storage temperatures. Secondly,we focused on determining cryopreservation characteristics of enzymatically digested tissue as a cell suspension. Lastly,we evaluated the growth,surface markers and differentiation properties of DPSC obtained from intact teeth and undigested,whole dental tissue frozen and thawed using the optimized procedures. In these experiments it was determined that Me(2)SO at a concentration between 1 and 1.5M was the ideal cryopreservative of the three studied. It was also determined that DPSC viability after cryopreservation is not limited by the concentration of cells frozen,at least up to 2x10(6) cells/mL. It was further established that DPSC can be stored at -85 degrees C or -196 degrees C for at least six months without loss of functionality. The optimal results with the least manipulation were achieved by isolating and cryopreserving the tooth pulp tissues,with digestion and culture performed post-thaw. A recovery of cells from textgreater85% of the tissues frozen was achieved and cells isolated post-thaw from tissue processed and frozen with a serum free,defined cryopreservation medium maintained morphological and developmental competence and demonstrated MSC-hallmark trilineage differentiation under the appropriate culture conditions. View Publication

The metabolism of oxygen,although central to life,produces reactive oxygen species (ROS) that have been implicated in processes as diverse as cancer,cardiovascular disease and ageing. It has recently been shown that central nervous system stem cells and haematopoietic stem cells and early progenitors contain lower levels of ROS than their more mature progeny,and that these differences are critical for maintaining stem cell function. We proposed that epithelial tissue stem cells and their cancer stem cell (CSC) counterparts may also share this property. Here we show that normal mammary epithelial stem cells contain lower concentrations of ROS than their more mature progeny cells. Notably,subsets of CSCs in some human and murine breast tumours contain lower ROS levels than corresponding non-tumorigenic cells (NTCs). Consistent with ROS being critical mediators of ionizing-radiation-induced cell killing,CSCs in these tumours develop less DNA damage and are preferentially spared after irradiation compared to NTCs. Lower ROS levels in CSCs are associated with increased expression of free radical scavenging systems. Pharmacological depletion of ROS scavengers in CSCs markedly decreases their clonogenicity and results in radiosensitization. These results indicate that,similar to normal tissue stem cells,subsets of CSCs in some tumours contain lower ROS levels and enhanced ROS defences compared to their non-tumorigenic progeny,which may contribute to tumour radioresistance. View Publication

Current sources of mesenchymal cells,including bone marrow,fat and muscle,all require invasive procurement procedures,and provide relatively low frequencies of progenitors. Here,we describe the non-invasive isolation,and characterization,of a rich source of mesenchymal progenitor cells,which we call human umbilical cord perivascular cells (HUCPVCs). HUCPVCs show a similar immunological phenotype to bone marrow-derived mesenchymal stromal cells (BM-MSCs),since they are non-alloreactive,exhibit immunosuppression,and significantly reduce lymphocyte activation,in vitro. They present a non-hematopoietic myofibroblastic mesenchymal phenotype (CD45-,CD34-,CD105+,CD73+,CD90+,CD44+,CD106+,3G5+,CD146+); with a 1:300 frequency at harvest,a short-doubling time,and a clonogenic frequency of textgreater1:3 in culture. Furthermore,in addition to robust quinti-potential differentiation capacity in vitro,HUCPVCs have been shown to contribute to both musculo-skeletal and dermal wound healing in vivo. View Publication

Previous studies have demonstrated that normal mouse mammary tissue contains a rare subset of mammary stem cells. We now describe a method for detecting an analogous subpopulation in normal human mammary tissue. Dissociated cells are suspended with fibroblasts in collagen gels,which are then implanted under the kidney capsule of hormone-treated immunodeficient mice. After 2-8 weeks,the gels contain bilayered mammary epithelial structures,including luminal and myoepithelial cells,their in vitro clonogenic progenitors and cells that produce similar structures in secondary transplants. The regenerated clonogenic progenitors provide an objective indicator of input mammary stem cell activity and allow the frequency and phenotype of these human mammary stem cells to be determined by limiting-dilution analysis. This new assay procedure sets the stage for investigations of mechanisms regulating normal human mammary stem cells (and possibly stem cells in other tissues) and their relationship to human cancer stem cell populations. View Publication

MSCs are known to have an extensive proliferative potential and ability to differentiate in various cell types. Osteoblastic differentiation from mesenchymal progenitor cells is an important step of bone formation,though the pattern of gene expression during differentiation is not yet well understood. Here,to investigate the possibility to obtain a model for in vitro bone differentiation using mesenchymal stem cells (hMSCs) from human subjects non-invasively,we developed a method to obtain hMSCs-like cells from peripheral blood by a two step method that included an enrichment of mononuclear cells followed by depletion of unwanted cells. Using these cells,we analyzed the expression of transcription factor genes (runt-related transcription factor 2 (RUNX2) and osterix (SP7)) and bone related genes (osteopontin (SPP1),osteonectin (SPARC) and collagen,type I,alpha 1 (COLIA1)) during osteoblastic differentiation. Our results demonstrated that hMSCs can be obtained from peripheral blood and that they are able to generate CFU-F and to differentiate in osteoblast and adipocyte; in this study,we also identified a possible gene expression timing during osteoblastic differentiation that provided a powerful tool to study bone physiology. View Publication

Mature mammary epithelial cells are generated from undifferentiated precursors through a hierarchical process,but the molecular mechanisms involved,particularly in the human mammary gland,are poorly understood. To address this issue,we isolated highly purified subpopulations of primitive bipotent and committed luminal progenitor cells as well as mature luminal and myoepithelial cells from normal human mammary tissue and compared their transcriptomes obtained using three different methods. Elements unique to each subset of mammary cells were identified,and changes that accompany their differentiation in vivo were shown to be recapitulated in vitro. These include a stage-specific change in NOTCH pathway gene expression during the commitment of bipotent progenitors to the luminal lineage. Functional studies further showed NOTCH3 signaling to be critical for this differentiation event to occur in vitro. Taken together,these findings provide an initial foundation for future delineation of mechanisms that perturb primitive human mammary cell growth and differentiation. View Publication

Recent studies have shown that mesenchymal stem cells (MSC) with the potential for cell-mediated therapies and tissue engineering applications can be isolated from extracted dental tissues. Here,we investigated the collection,processing,and cryobiological characteristics of MSC from human teeth processed under current good tissue practices (cGTP). Viable dental pulp-derived MSC (DPSC) cultures were isolated from 31 of 40 teeth examined. Of eight DPSC cultures examined more thoroughly,all expressed appropriate cell surface markers and underwent osteogenic,adipogenic,and chondrogenic differentiation in appropriate differentiation medium,thus meeting criteria to be called MSC. Viable DPSC were obtained up to 120 h postextraction. Efficient recovery of DPSC from cryopreserved intact teeth and second-passage DPSC cultures was achieved. These studies indicate that DPSC isolation is feasible for at least 5 days after tooth extraction,and imply that processing immediately after extraction may not be required for successful banking of DPSC. Further,the recovery of viable DPSC after cryopreservation of intact teeth suggests that minimal processing may be needed for the banking of samples with no immediate plans for expansion and use. These initial studies will facilitate the development of future cGTP protocols for the clinical banking of MSC. View Publication

BACKGROUND: Mesenchymal stromal cells are multipotent cells considered to be of great promise for use in regenerative medicine. However,the cell dose may be a critical factor in many clinical conditions and the yield resulting from the ex vivo expansion of mesenchymal stromal cells derived from bone marrow may be insufficient. Thus,alternative sources of mesenchymal stromal cells need to be explored. In this study,mesenchymal stromal cells were successfully isolated from second trimester amniotic fluid and analyzed for chromosomal stability to validate their safety for potential utilization as a cell therapy product. DESIGN AND METHODS: Mesenchymal stromal cells were expanded up to the sixth passage starting from amniotic fluid using different culture conditions to optimize large-scale production. RESULTS: The highest number of mesenchymal stromal cells derived from amniotic fluid was reached at a low plating density; in these conditions the expansion of mesenchymal stromal cells from amniotic fluid was significantly greater than that of adult bone marrow-derived mesenchymal stromal cells. Mesenchymal stromal cells from amniotic fluid represent a relatively homogeneous population of immature cells with immunosuppressive properties and extensive proliferative potential. Despite their high proliferative capacity in culture,we did not observe any karyotypic abnormalities or transformation potential in vitro nor any tumorigenic effect in vivo. CONCLUSIONS: Fetal mesenchymal stromal cells can be extensively expanded from amniotic fluid,showing no karyotypic abnormalities or transformation potential in vitro and no tumorigenic effect in vivo. They represent a relatively homogeneous population of immature mesenchymal stromal cells with long telomeres,immunosuppressive properties and extensive proliferative potential. Our results indicate that amniotic fluid represents a rich source of mesenchymal stromal cells suitable for banking to be used when large amounts of cells are required. View Publication

Cell therapy is a novel promising option for treatment of ischemic diseases. Administered endothelial progenitor cells (EPCs) are recruited to ischemic regions and improve neovascularization. However,the number of cells that home to ischemic tissues is restricted. The GTPase Rap1 plays an important role in the regulation of adhesion and chemotaxis. We investigated whether pharmacologic activation of Epac1,a nucleotide exchange protein for Rap1,which is directly activated by cAMP,can improve the adhesive and migratory capacity of distinct progenitor cell populations. Stimulation of Epac by a cAMP-analog increased Rap1 activity and stimulated the adhesion of human EPCs,CD34(+) hematopoietic progenitor cells,and mesenchymal stem cells (MSCs). Specifically,short-term stimulation with a specific Epac activator increased the beta2-integrin-dependent adhesion of EPCs to endothelial cell monolayers,and of EPC and CD34(+) cells to ICAM-1. Furthermore,the Epac activator enhanced the beta1-integrin-dependent adhesion of EPCs and MSCs to the matrix protein fibronectin. In addition,Epac1 activation induced the beta1- and beta2-integrin-dependent migration of EPCs on fibronectin and fibrinogen. Interestingly,activation of Epac rapidly increased lateral mobility of beta1- and beta2-integrins,thereby inducing integrin polarization,and stimulated beta1-integrin affinity,whereas the beta2-integrin affinity was not increased. Furthermore,prestimulation of EPCs with the Epac activator increased homing to ischemic muscles and neovascularization-promoting capacity of intravenously injected EPCs in the model of hind limb ischemia. These data demonstrate that activation of Epac1 increases integrin activity and integrin-dependent homing functions of progenitor cells and enhances their in vivo therapeutic potential. These results may provide a platform for the development of novel therapeutic approaches to improve progenitor cell homing. View Publication

Human bone marrow multipotent mesenchymal stromal cells are progenitor cells that can be expanded in vitro and differentiate into various cells of mesodermal origin. They contribute to the bone marrow reticular niche,where mature B cells and long-lived plasma cells are maintained. Multipotent mesenchymal stromal cells were recently shown to modulate T- and B-cell proliferation and differentiation,dendritic cell maturation,and natural killer activity. These immunoregulatory properties encouraged a possible use of these cells to modulate autoimmune responses in humans. We studied the influence of bone marrow mesenchymal stem cells on highly purified B-cell subsets isolated from healthy donors and total B cells from pediatric systemic lupus erythematosus patients. Bone marrow mesenchymal stem cells promoted proliferation and differentiation into immunoglobulin-secreting cells of transitional and naive B cells stimulated with an agonist of Toll-like receptor 9,in the absence of B cell receptor triggering. They strongly enhanced proliferation and differentiation into plasma cells of memory B-cell populations. A similar effect was observed in response to polyclonal stimulation of B cells isolated from pediatric patients with systemic lupus erythematosus. This study casts important questions on bone marrow mesenchymal stem cells as a therapeutic tool in autoimmune diseases in which B-cell activation is crucially implicated in the pathogenesis of the disease. View Publication