Adherent Marrow Cells Research Articles

Human Chorionic Gonadotropin Improves the Proliferation and Regenerative Potential of Bone Marrow Adherent Stem Cells and the Immune Tolerance of Fetal Microchimeric Stem Cells In Vitro.

Nongonadal tissues express luteinizing hormone-chorionic gonadotropin receptors (LHCG-R) which are essential for their growth during fetal development. Adult mesenchymal stem/stromal cells (MSCs) have been shown to express functional LHCG-R outside pregnancy conditions, making them susceptible to hCG stimulation. In the present study we tested the effect of hCG treatment on bone marrow (BM) derived adherent stem cells in vitro, isolated from a parous women, mother of male sons, in order to evaluate its effect on maternal MSCs and in the same time on fetal microchimeric stem cells (FMSCs), to better understand the outcomes of this safe and affordable treatment on cell proliferation and expression of pluripotency genes. Our study highlights the beneficial effects of hCG exposure on gene regulation in bone marrow adherent stem cells through the upregulation of pluripotency genes and selection of more primitive mesenchymal stem cells with a better differentiation potential. Validation of these effects on MSCs and FMSCs long after parturition in vivo represents a close perspective as it could set the premises of a new mobilization strategy for the stem cell transplantation procedures in the clinical setting.

The Potential Role of Quorum Sensing in Clonal Growth and Subsequent Expansion of Bone Marrow Stromal Cell Strains in Culture.

Clonal development (clonogenicity) is an inherent property of a subset of postnatal bone marrow (BM) adherent stromal mesenchymal stem cells (MSCs) from which a multipotent progeny develops in culture. Our data suggest that clonogenicity and BM-MSC expansion are two distinct biological events. This hypothesis is based on the following observations: (1) the beginning of clonal growth is a property strictly dependent on serum and independent of the social context, (2) the expansion of individual clone is influenced by events deriving from a social context during initial growth, (3) clonogenic cells grown in a social context in presence of serum can emancipate themselves to generate a secondary different progeny, and (4) the ability of socially generated clones to develop an inherent potential for further growth suggests that quorum sensing may operate in BM-MSC cultures and determine the potential growth of clonal strains.

Electrotaxis: Cell Directional Movement in Electric Fields.

Electrotaxis plays an important role during embryogenesis, inflammation, wound healing, and tumour metastasis. However, the mechanisms at play during electrotaxis are still poorly understood. Therefore intensive studies on signaling pathways involved in this phenomenon should be carried out. In this chapter, we described an experimental system for studying electrotaxis of Amoeba proteus, mouse embryonic fibroblasts (MEF), Walker carcinosarcoma cells WC256, and bone marrow adherent cells (BMAC).

Electric field as a potential directional cue in homing of bone marrow-derived mesenchymal stem cells to cutaneous wounds

Bone marrow-derived cells are thought to participate and enhance the healing process contributing to skin cells or releasing regulatory cytokines. Directional cell migration in a weak direct current electric field (DC-EF), known as electrotaxis, may be a way of cell recruitment to the wound site. Here we examined the influence of electric field on bone marrow adherent cells (BMACs) and its potential role as a factor attracting mesenchymal stem cells to cutaneous wounds. We observed that in an external EF, BMAC movement was accelerated and highly directed with distinction of two cell populations migrating toward opposite poles: mesenchymal stem cells migrated toward the cathode, whereas macrophages toward the anode. Analysis of intracellular pathways revealed that macrophage electrotaxis mostly depended on Rho family small GTPases and calcium ions, but interruption of PI3K and Arp2/3 had the most pronounced effect on electrotaxis of MSCs. However, in all cases we observed only a partial decrease in directionality of cell movement after inhibition of certain proteins. Additionally, although we noticed the accumulation of EGFR at the cathodal side of MSCs, it was not involved in electrotaxis. Moreover, the cell reaction to EF was very dynamic with first symptoms occurring within <1min. In conclusion, the physiological DC-EF may act as a factor positioning bone marrow cells within a wound bed and the opposite direction of MSC and macrophage movement did not result either from utilizing different signalling or redistribution of investigated cell surface receptors.

Lab-to-clinic application of stem cell therapy for stroke

Stem cell therapy or “cell therapy” has been demonstrated to be a potent treatment intervention in animal models of acute ischemic stroke, and recently has been introduced as an experimental therapy in early phase clinical trials. Among the many stem cells, the bone marrow adherent cell type known as mesenchymal stem cells have emerged in laboratory studies as a safe and effective therapy for ischemic stroke and other brain diseases. In particular, a unique population of adherent bone marrow-derived cells, called MultiStem cells, display immunomodulatory effects and are a promising allogeneic cell therapy in acute ischemic stroke. Here, we describe the preclinical evidence supporting the use of MultiStem in the acute setting of ischemic stroke and the translation into an early phase clinical trial in ischemic stroke.

Lipocalin produced by myelofibrosis cells affects the fate of both hematopoietic and marrow microenvironmental cells

AbstractMyelofibrosis (MF) is characterized by cytopenias, constitutional symptoms, splenomegaly, and marrow histopathological abnormalities (fibrosis, increased microvessel density, and osteosclerosis). The microenvironmental abnormalities are likely a consequence of the elaboration of a variety of inflammatory cytokines generated by malignant megakaryocytes and monocytes. We observed that levels of a specific inflammatory cytokine, lipocalin-2 (LCN2), were elevated in the plasmas of patients with myeloproliferative neoplasms (MF > polycythemia vera or essential thrombocythemia) and that LCN2 was elaborated by MF myeloid cells. LCN2 generates increased reactive oxygen species, leading to increased DNA strand breaks and apoptosis of normal, but not MF, CD34+ cells. Furthermore, incubation of marrow adherent cells or mesenchymal stem cells with LCN2 increased the generation of osteoblasts and fibroblasts, but not adipocytes. LCN2 priming of mesenchymal stem cells resulted in the upregulation of RUNX2 gene as well as other genes that are capable of further affecting osteoblastogenesis, angiogenesis, and the deposition of matrix proteins. These data indicate that LCN2 is an additional MF inflammatory cytokine that likely contributes to the creation of a cascade of events that results in not only a predominance of the MF clone but also a dysfunctional microenvironment.

Optimization of nanofibrous silk fibroin scaffold as a delivery system for bone marrow adherent cells: in vitro and in vivo studies.

Electrospun silk fibroin nanofibrous scaffolds (ESFNSs) were successfully prepared by electrospinning of various Bombyx mori silk fibroin concentrations (10, 12, and 14% in formic acid). After characterizing the purified silk fibroin, the morphology, porosity, fibers' diameter, and uniformity of the prepared scaffolds were examined in detail. In addition, biological responses such as effects on bone marrow cell viability, cytotoxicity, and cell adhesion were evaluated in vitro. Biocompatibility and bioactivity properties of the ESFNSs were evaluated in vitro and in vivo by cell culturing and subcutaneous implantation in rat models for 7 and 28 days, respectively. According to the obtained results, no beaded fibers were seen in any of the prepared scaffolds, whereas ESFNS-10% provided more uniformity and porosity with nanoscaled fibers (90 ± 0.021 nm). Furthermore, the scaffolds also showed good cell adhesion and spreading (68.7 ± 11.8 and 7.6 ± 3.3 total length and width, respectively) with no detectable effect on cell viability and cytotoxicity. The in vivo biocompatibility evaluation indicated that the scaffolds did not stimulate detectable cellular inflammatory response (lymphocytes) and increased the total cell number (cellularity) in the implantation area. Furthermore, the results suggest the potential use of the prepared ESFNS-10% bone marrow cell constructs in direct implantation for tissue engineering applications.

The differentiation of human multipotent adult progenitor cells into hepatocyte-like cells induced by coculture with human hepatocyte line L02.

PurposeThe aim of this study was to establish an in vitro method to purify human multipotent adult progenitor cells (hMAPCs) and assess their possible differentiation into hepatocytes by coculture with human hepatocyte line L02.MethodshMAPCs were isolated by magnetic activated cell sorting (MACS) depletion selection using CD45 and GlyA microbeads. After indirect or direct coculture of hMAPCs and human hepatocyte line L02, the expression of albumin (ALB), alpha-fetoprotein (AFP), cytokeratin (CK) 18, and CK19 by hMAPCs was detected by immunocytochemistry.ResultsWith the MACS method, (5-10) × 104/mL hMAPCs could be separated from 1 × 106/mL bone marrow mononuclear cells. The purity of CD45-/GlyA- cells separated from bone marrow adherent cells was more than 98%, as determined by flow cytometry. In the coculture without cell-to-cell contact, hMAPCs expressed high AFP on day 1, and then tapered daily to low expression on day 7; ALB expression reached its peak on day 5, and remained high on day 7; CK18 was initially expressed on day 5 and was higher on day 7; CK19 was negative in all assays. In the coculture with cell-to-cell contact, ALB and CK18 were expressed by most cells while AFP appeared in only a few on day 5.ConclusionhMAPCs were induced to differentiate into mature hepatocyte-like cells by coculture with a hepatocyte cell line, either with or without cell-to-cell contact, but the former seemed more effective.

The Effects of Lipocalin (LCN2) on Hematopoiesis in Primary Myelofibrosis

Myelofibrosis (MF) is characterized by anemia, thrombocytopenia and marrow fibrosis. Malignant rather than normal hematopoietic progenitor cells (HPC) preferentially proliferate. A form of MF can also occur in patients with a prior history of PV or ET which is referred to as PV or ET related MF (PV-MF and ET-MF). In MF, excessive proliferation of marrow stromal cells occurs in response to cytokines elaborated by the malignant clone. Previously, we found that lipocalin-2 (LCN2) levels were elevated in patient plasmas with MPN, and a greatest degree of elevation was observed in the PMF plasma and PMF conditioned medium. We also found that LCN2 increased PMF HPC proliferation and increased numbers of JAK2V617F homozygous HPCs, but depressed normal BM HPC (Lu. et al, 2013 ASH meeting).In this study, a series of experiments were performed to further explore the effects of LCN2 on MF pathogenesis. ELISA data showed that plasma LCN2 levels not only were higher in all MF patients, plasma LCN2 levels in PV-MF as well as ET- MF were significantly greater than that in PV or ET plasma (p=0.0002 and p=0.0175, respectively). Importantly, in MPN patients, a non-parametric spearman correlation coefficient analysis suggested an inverse relationship between the patients’ hemoglobin levels and LCN2 levels (coefficient=-0.35, p<0.0001) and between platelet counts and LNC2 levels (coefficient=-0.26, p=0.0044). Immunofluorescence staining showed a greater proportion of PMF MNCs expressed LCN2. And immunohistochemical results revealed that LCN2 expressing cells were present in the PMF bone marrow and spleens samples and the LCN2 expression was restricted to cells belonging to the myeloid lineage rather than erythroid precursors or megakaryocytes. These data strongly confirmed that a higher level of LCN2 was expressed in MF patients. We then found that LCN2 significantly increased the generation of ROS (reactive oxygen species) in normal BM CD34+ cells but not PMF CD34+ cells (p<0.05). Furthermore, exposure of normal marrow to the LCN2 dramatically increased the CD34+/annexin V+ cell population in a dose dependent fashion. These apoptotic effects were blocked by addition of N-Acetyl-Cysteine (NAC), a ROS scavenger. By contrast, LCN2 did not increase the degree of apoptosis of PMF CD34+ cells when added at similar doses. These data indicate that LCN2 selectively promotes the survival of PMF CD34+ cells but leads to the apoptosis of normal BM CD34+ cells by increasing ROS. With 6 different individual BM samples, we demonstrated that PMF MNC cells that produce high levels of LCN2 as well as a recombinant form of LCN2 strongly promoted BM marrow adherent cells (MAC) proliferation. Similarly, LCN2 added to semisolid cultures of normal marrow cells resulted in the appearance of increased numbers of fibroblast-like cells. In addition, the ability of LCN2 to promote MAC proliferation was blocked by addition of NAC. These results suggest that LCN2 related generation of ROS induces MAC proliferation. The MAC in both control and LCN2 containing conditions expressed vimentin, Von Willebrand factor (VWF) and α-smooth muscle actin (a-SMA), while in LCN2 cultures expressed higher levels of CD105 (Endoglin) and CD106 (VCAM-1). These MAC therefore expressed features characteristic of mesenchymal stem cells, fibroblasts and endothelial cells. The MAC under control conditions expressed CD90+ on their cell surface, while incubation with LCN2 resulted in diminished cell surface CD90 expression, and its localization to the nucleus.We propose that LCN2 acts in an autocrine fashion to promote malignant PMF hematopoiesis as documented by its ability to preferentially favor the appearance of JAK2V617F homozygous hematopoietic colonies in vitro, but also acts in a paracrine fashion to suppress the proliferation of normal HPC and to affect the marrow microenvironment by promoting stromal cell proliferation. Our findings indicate that LCN2 affects these numerous biological effects by promoting the generation of ROS. We also propose that therapeutic strategies that can impair the actions of LCN2 or inactivate ROS are likely to be beneficial to MPN patients since they improve disease related cytopenias as well as impede the development of progressive marrow fibrosis. Such agents affecting this alternative therapeutic target might potentially be used alone or in combination with other presently available therapeutic modalities. DisclosuresNo relevant conflicts of interest to declare.

Stromal control of chronic lymphocytic leukemia cells

Stromal control of chronic lymphocytic leukemia cells Paul Faustin Seke Etet,1 Armel Herve Nwabo Kamdje,2 Jeremie Mbo Amvene,2 Yousef Aldebasi,3 Mohammed Farahna,1 Lorella Vecchio41Department of Basic Health Sciences, College of Applied Medical Sciences, Qassim University, Buraydah, Saudi Arabia; 2Department of Medicine, University of Ngaoundere, Ngaoundere, Cameroon; 3Department of Optometry, College of Applied Medical Sciences, Qassim University, Buraydah, Saudi Arabia; 4Laboratory of Cytometry, Institute of Molecular Genetics, CNR, University of Pavia, Pavia, ItalyAbstract: In the ongoing efforts to develop therapies against chronic lymphocytic leukemia (CLL), stromal factors allowing malignant cells to escape spontaneous and chemotherapy-mediated apoptosis, giving way to relapses, have been abundantly investigated. Bone marrow adherent cell types, collectively referred to as stromal cells, appear to be key players in such escape, mainly because CLL malignant cells, which rapidly undergo spontaneous apoptosis when cultured in vitro, survive, migrate, and resist cytotoxic agents in co-culture with bone marrow stromal cells. CLL displays variable clinical courses according to well-defined prognostic factors induced on malignant B-cells (CLL cells) or expressed by the transformed bone marrow stromal microenvironment. Particularly, a critical pathogenic role is played by proinflammatory factors, adhesion molecules, and signaling molecules involved in cell fate and stemness, such as Notch, Wnt, sonic Hedgehog, phosphoinositide 3-kinase (PI3K), protein kinase B (Akt), and the B-cell CLL/lymphoma 2 (Bcl-2) family of regulator proteins. As herein discussed, these molecules probably form a complex network favoring CLL cell survival, proliferation, and chemoresistance to anticancer therapy. Characterizing the sets of signaling pathways involved in the interactions between stromal cells and CLL cells may provide new tools for CLL clinical phenotyping and for re-sensitizing chemotherapy resistant cells.Keywords: chronic lymphoblastic leukemia, CLL, signaling pathways, cancer, stromal cells

Plasmodium induced by SU6656, an Src family kinase inhibitor, is accompanied by a contractile ring defect

We have shown that SU6656, a potent Src family kinase inhibitor, has the ability to induce multinucleation at a high frequency in diverse cells: rat skin fibroblasts, bone marrow adherent cells, 5F9A mesenchymal stem cell-like clones, 2C5 tracheal epithelial cells and MDCK epithelial cells from dog kidney. To gain insight into the mechanism of multinucleation, we observed the process by time-lapse and confocal microscopy. These multinuclei generally seem to exist independently in one cell without any connections with each other. By time-lapse microscopy, multinucleated cells were found to be formed through the mechanism of plasmodium: karyokinesis without cytokinesis. The observation of EGFP-actin transfected cells by time-lapse confocal laser scanning microscopy suggested that plasmodium occurred with deficient contractile ring formation. Although we examined the differentiation of these cells, the multinucleated cells could not be categorized into any type of cell in vivo known to exhibit multinuclei.

Isolation of therapeutically functional mouse bone marrow mesenchymal stem cells within 3 h by an effective single‐step plastic‐adherent method

Isolation of mouse mesenchymal stem cells (mMSCs), by the approach of plastic adherence, has been difficult due to persistent contamination by haematopoietic cells (HCs); we have observed that this contamination was due to engagement between HCs and mMSCs. The HCs can be lifted together with the mMSCs despite their insensitivity to trypsin digestion. Herein, we provide a single-step procedure to rapidly segregate mMSCs from HC contaminants using transient lower-density plastic adherence (tLDA). The tLDA was performed by replating bone marrow adherent cells at lower density (1.25 x 10(4) cells/cm(2)) than usual, allowing for transient adherence of no more than 3 h, followed by trypsin digestion. tLDA-isolated cells were evaluated by immunophenotyping, multi-differentiation potentials, immunosuppressive properties, and therapeutic potential as demonstrated by symptoms of osteoporosis. The single-step tLDA method can effectively eliminate the persistent HC contaminants; tLDA-isolated cells were phenotypically equivalent to those reported as mMSCs. The isolated cells possessed classic tri-lineage differentiation potential into osteogenic, adipogenic and chondrogenic lineages and had immunosuppressive properties. After intravenous transplantation, they migrated into the allogeneic bone marrow and rescued hosts from osteoporosis symptoms, demonstrating their therapeutic potential. We have developed a simple and economical method that effectively isolates HC-free, therapeutically functional mMSCs from bone marrow cell adherent cultures. These cells are suitable for various mechanistic and therapeutic studies in the mouse model.

Alteration in marrow stromal microenvironment and apoptosis mechanisms involved in aplastic anemia: an animal model to study the possible disease pathology.

Aplastic anemia (AA) is a heterogeneous disorder of bone marrow failure syndrome. Suggested mechanisms include a primary stem cell deficiency or defect, a secondary stem cell defect due to abnormal regulation between cell death and differentiation, or a deficient microenvironment. In this study, we have tried to investigate the alterations in hematopoietic microenvironment and underlying mechanisms involved in such alterations in an animal model of drug induced AA. We presented the results of studying long term marrow culture, marrow ultra-structure, marrow adherent and hematopoietic progenitor cell colony formation, flowcytometric analysis of marrow stem and stromal progenitor populations and apoptosis mechanism involved in aplastic anemia. The AA marrow showed impairment in cellular proliferation and maturation and failed to generate a functional stromal microenvironment even after 19 days of culture. Ultra-structural analysis showed a degenerated and deformed marrow cellular association in AA. Colony forming units (CFUs) were also severely reduced in AA. Significantly decreased marrow stem and stromal progenitor population with subsequently increased expression levels of both the extracellular and intracellular apoptosis inducer markers in the AA marrow cells essentially pointed towards the defective hematopoiesis; moreover, a deficient and apoptotic microenvironment and the microenvironmental components might have played the important role in the possible pathogenesis of AA.

Mouse mesenchymal stem cells can support human hematopoiesis both in vitro and in vivo: the crucial role of neural cell adhesion molecule

We previously established a mesenchymal stem cell line (FMS/PA6-P) from the bone marrow adherent cells of fetal mice. The cell line expresses a higher level of neural cell adhesion molecule and shows greater hematopoiesis-supporting capacity in mice than other murine stromal cell lines. Since there is 94% homology between human and murine neural cell adhesion molecule, we examined whether FMS/PA6-P cells support human hematopoiesis and whether neural cell adhesion molecules expressed on FMS/PA6-P cells contribute greatly to the human hematopoiesis-supporting ability of the cell line. When lineage-negative cord blood mononuclear cells were co-cultured on the FMS/PA6-P cells, a significantly greater hematopoietic stem cell-enriched population (CD34(+)CD38(-) cells) was obtained than in the culture without the FMS/PA6-P cells. Moreover, when lineage-negative cord blood mononuclear cells were cultured on FMS/PA6-P cells and transplanted into SCID mice, a significantly larger proportion of human CD45(+) cells and CD34(+)CD38(-) cells were detected in the bone marrow of SCID mice than in the bone marrow of SCID mice that had received lineage-negative cord blood mononuclear cells cultured without FMS/PA6-P cells. Furthermore, we found that direct cell-to-cell contact between the lineage-negative cord blood mononuclear cells and the FMS/PA6-P cells was essential for the maximum expansion of the mononuclear cells. The addition of anti-mouse neural cell adhesion molecule antibody to the culture significantly inhibited their contact and the proliferation of lineage-negative cord blood mononuclear cells. These findings suggest that neural cell adhesion molecules expressed on FMS/PA6-P cells play a crucial role in the human hematopoiesis-supporting ability of the cell line.

Transformation potential of bone marrow stromal cells into undifferentiated high-grade pleomorphic sarcoma

Bone marrow adherent cells contain conventional bone marrow stromal cells and mesenchymal stem cells and these cells constitute the hematopoietic microenvironment. Mesenchymal stem cells have the capacity to give rise to multiple mesenchymal lineage cells and even ectodermal lineage cells. In the present study, we investigated what types of tumor cells are inducible from BM adherent cells by chemical carcinogens. Bone marrow cells from neonatal C3H/HeN mice were collected within 24 h after birth and then cultured. Four days later, bone marrow adherent cells were obtained and the cells were treated with 3-methylcholanthrene. By this treatment, some transformed clones consisting of large spindle cells were obtained. The transformed cells were highly positive for CD44 and were positive for Sca-1, CD49d and CD106, whereas the cells were negative for hematolymphoid markers. The cell clones had the ability to support hematopoiesis in vitro. These results indicate that the transformed cell lines have the characteristics of BM stromal cells/mesenchymal stem cells. Moreover, during culture of the transformed cells, spontaneous bone nodule formation was observed. When the transformed cells were inoculated into immunodeficient mice subcutaneously, the neoplasms grew in the subcutaneous tissue of the mice. Microscopically and ultrastructurally, the neoplasms showed the typical morphology of undifferentiated high-grade pleomorphic sarcoma (UHGPS). Bone-related genes have been found to be expressed in both transformed cells and UHGPSs. The present study suggests that UHGPSs are derived from BM stromal cells, probably mesenchymal stem cells.

Six-Transmembrane Epithelial Antigen of the Prostate (STEAP1 and STEAP2)—Differentially Expressed by Murine and Human Mesenchymal Stem Cells

Mesenchymal stem cells (MSCs) have great potential for cell-based therapies. However, lack of cell-specific markers thwarts full realization of this as it prevents their identification in vivo, and subsequent purification. In the present study, to ensure cell purity multiple individual clones were derived from the bone marrow of BALB/b and BALB/c mice, and subsequently defined as MSCs by demonstrating their multipotentiality and self-renewal ability. In an effort to define the molecular signature of such MSCs and identify potentially cell-specific markers, an extensive genome-wide microarray analysis was performed comparing eight individual undifferentiated MSC clones to four different controls-corresponding differentiated MSC clones, bone marrow adherent cells, freshly isolated bone marrow cells, and embryonic fibroblasts. Strikingly, all MSC clones expressed differentially high levels of six-transmembrane epithelial antigen of the prostate (STEAP1 and STEAP2). Further, both STEAP members showed an extremely similar expression profile to stem cell antigen-1 (Sca-1) as demonstrated by two-dimensional hierarchical cluster analysis. Most importantly, differentially high levels of STEAP1 and STEAP2 proteins were also detected in human multipotent bone marrow adherent cultures. Thus, STEAPs may represent novel markers of MSCs in man as well as mice. Depletion of STEAP1 in human MSCs using RNAi resulted in decreased cell adhesion to tissue culture plastic. Further work is now needed to fully uncover its function in these cells, and to explore its potential as a marker of MSCs.

The Use of Human Mesenchymal Stem Cell–Derived Feeder Cells for the Cultivation of Transplantable Epithelial Sheets

To report the efficacy of human bone marrow-derived mesenchymal stem cells as a source of feeder cells for the cultivation of transplantable corneal epithelial cell sheets. Human mesenchymal stem cells (marrow adherent stem cells; MASCs) were cultured in alpha-modified Eagle's medium with 10% serum and were treated with mitomycin C. Expression of cytokines in MASCs was confirmed by reverse transcription-polymerase chain reaction. Human limbal epithelial cells were cocultured with MASCs or 3T3 feeder cells to compare colony-forming efficiency (CFE). Limbal epithelial cells were cultured on MASCs or 3T3 feeder cells at the air-liquid interface to allow stratification, and stratified epithelial sheets were analyzed by immunohistochemistry against cytokeratin 3 (K3), K15, p63alpha, and ABCG2. Rabbit limbal epithelial cell sheets were cultivated with MASC feeder cells and transplanted to the ocular surface of the limbal-deficient rabbits. Epithelial grafts were observed by slit lamp microscopy for 4 weeks and then evaluated by histology and immunohistochemistry against K3 and K4. MASC feeder cells expressed keratinocyte growth factor, hepatocyte growth factor, and N-cadherin. The CFE of human limbal epithelial cells was similar in MASC and 3T3 feeder groups. Stratified cell sheets were successfully cultivated with MASC feeder cells expressing K3, K15, p63alpha, and ABCG2. Transplanted epithelial sheets regenerated the corneal phenotype in limbal-deficient rabbits. MASC-derived feeder cells are suitable for the engineering of epithelial sheets, avoiding the use of potentially hazardous xenologic feeder cells.

Lung environment determines unique phenotype of alveolar macrophages

Alveolar macrophages (AM) are the most abundant antigen-presenting cells in the lungs, and they play a critical role in regulating pulmonary immune responses to inhaled pathogens and to allergens. However, compared with macrophages in other body sites, AM have an unusual phenotype that, in many respects, resembles the phenotype of dendritic cells (DC). Therefore, to more fully define the unique nature of AM, we compared the phenotype and function of AM with the phenotype and function of resident peritoneal lavage-derived macrophages (PLM). We found striking phenotypic differences between AM and PLM, particularly with regard to CD11c expression, and we also observed that AM had a significantly better antigen-presenting capability than PLM. Therefore, we investigated the role of the local airway environment in generation of the unusual phenotype of AM. We carried out cell transfer experiments to compare macrophage differentiation in the airways with that in the peritoneal cavity. We observed significant upregulation of CD11c expression on bone marrow macrophages and peritoneal macrophages when they were adoptively transferred into the airways. In contrast, CD11c expression was not upregulated after cell transfer into the peritoneal cavity, whereas CD11b expression was significantly increased. In vitro, culture of bone marrow-adherent cells with surfactant protein D (SP-D) or granulocyte/macrophage colony-stimulating factor (GM-CSF) induced significant upregulation of CD11c expression, and in vivo GM-CSF concentrations were significantly higher in bronchoalveolar than in peritoneal lavage fluid. Finally, GM-CSF(-/-) mice failed to develop CD11c(+) AM, but CD11c(+) AM were present in SP-D(-/-) mice. However, macrophages from GM-CSF(-/-) bone marrow could upregulate CD11c expression when transferred to the airways of wild-type mice. These results suggest that the airway environment promotes development of macrophages with unique DC-like characteristics and that this unusual phenotype is determined, to a large degree, by locally high concentrations of GM-CSF and, possibly, SP-D.

Extracellular Matrix Made by Bone Marrow Cells Facilitates Expansion of Marrow-Derived Mesenchymal Progenitor Cells and Prevents Their Differentiation Into Osteoblasts

We cultured MSCs on an ECM made by bone marrow cells to attempt to reconstitute the MSC niche. This ECM promoted replication of mesenchymal progenitors and retention of their multipotentiality. We conclude that the marrow ECM facilitates expansion of mesenchymal progenitors and hypothesize that it plays an important role in the maintenance of MSC stemness. Mesenchymal colony-forming cells of the bone marrow comprise mesenchymal stem cells (MSCs) and their transit amplifying progeny, which we term mesenchymal colony-forming units (MCFUs). These progenitors undergo self-renewal and can differentiate into many different cell types including osteoblasts. However, they lose their unique properties when cultured on tissue culture plastic. This indicates that a critical feature of the marrow microenvironment that facilitates retention of stem cell properties is missing in such culture systems. In other tissues, the extracellular matrix (ECM) forms part of the specialized niche that controls stem cell behavior. Therefore, we examined whether a marrow cell-derived ECM promotes retention of the stem cell characteristics of MCFUs in vitro. A cell-free ECM was prepared from cultured murine marrow adherent cells. The replication and multipotentiality of murine MCFUs maintained on this marrow cell-derived ECM were examined in vitro and in vivo and compared with the behavior of MCFUs maintained on plastic. The marrow cell-derived ECM was made up of collagen types I, III, and V, syndecan-1, perlecan, fibronectin, laminin, biglycan, and decorin, similar to the composition of the marrow ECM. This ECM preparation promoted MCFU replication, restrained their "spontaneous" differentiation toward the osteoblast lineage, and preserved their ability to differentiate into osteoblasts or adipocytes. Moreover, transplantation of MCFUs expanded on the marrow cell-derived ECM into immunocompromised mice generated five times more bone and eight times more hematopoietic marrow compared with MCFUs expanded on plastic. The marrow ECM facilitates expansion of MCFUs in vitro while preserving their stem cell properties. We hypothesize that the ECM made by bone marrow cells plays an important role in the maintenance of MSC function.

ApoE Gene Deficiency Enhances the Reduction of Bone Formation Induced by a High-Fat Diet Through the Stimulation of p53-Mediated Apoptosis in Osteoblastic Cells

Osteoblast apoptosis increased in the tibias of apoE(-/-) mice fed with a high-fat diet, decreasing bone formation. The expression of p53 mRNA in marrow adherent cells increased. LDL or oxidized LDL increased apoptosis in the calvarial cells of apoE(-/-) mice. The increase in p53-mediated apoptosis is apparently related to a high-fat diet-induced osteopenia in apoE(-/-) mice. The effects of high-fat loading and the apolipoprotein E (apoE) gene on bones have not been elucidated. We hypothesized that apoE gene deficiency (apoE(-/-)) modulates the effects of high-fat loading on bones. We assessed this hypothesis using wildtype (WT) and apoE(-/-) mice fed a standard (WTS and ApoES groups) or a high-fat diet (WTHf and ApoEHf groups). The concentration of serum lipid levels and bone chemical markers were measured. Histomorphometry of the femurs was performed using microCT and a microscope. Bone marrow adherent cells from the femurs were used for colony-forming unit (CFU)-fibroblastic (CFU-f) assay and mRNA expressions analysis. The apoptotic cells in the tibias were counted. TUNEL fluorescein assay and Western analysis were performed in cultures of calvarial cells by the addition of low-density lipoprotein (LDL) or oxidized LDL. In the ApoEHf group, the values of cortical bone volume and trabecular and endocortical bone formation of the femurs decreased, and urinary deoxypyridinoline increased. Subsequent analysis revealed that the number of apoptotic cells in the tibias of the ApoES group increased, and more so in the ApoEHf group. The ratio of alkaline phosphatase-positive CFU-f to total CFU-f was decreased in the ApoEHf group. p53 mRNA expression in adherent cells of the apoE(-/-) mice increased and had a significantly strong positive correlation with serum LDL. TUNEL fluorescein assay of osteoblastic cells revealed an increase of apoptotic cells in the apoE(-/-) mice. The number of apoptotic cells in the apoE(-/-) mice increased with the addition of 100 microg/ml LDL or oxidized LDL. The p53 protein expression in apoE(-/-) cells exposed to 100 microg/ml LDL or oxidized LDL increased. We concluded that apoE gene deficiency enhances the reduction of bone formation induced by a high-fat diet through the stimulation of p53-mediated apoptosis in osteoblastic cells.