Oncostatin M Maintains the Hematopoietic Microenvironment in the Bone Marrow by Modulating Adipogenesis and Osteogenesis

The bone marrow (BM) is an essential organ for hematopoiesis in adult, in which proliferation and differentiation of hematopoietic stem/progenitor cells (HSPC) is orchestrated by various stromal cells. Alterations of BM hematopoietic environment lead to various hematopoietic disorders as exemplified by the linking of fatty marrow with increased adipogenesis to anemia or pancytopenia. Therefore, the composition of mesenchymal stromal cell (MSC)-derived cells in the BM could be crucial for proper hematopoiesis, but the mechanisms underlying the MSC differentiation for hematopoiesis remain poorly understood. In this study, we show that Oncostatin M (OSM) knock out mice exhibited pancytopenia advancing fatty marrow with age. OSM strongly inhibited adipogenesis from BM MSC in vitro, whereas it enhanced their osteogenesis but suppressed the terminal differentiation. Intriguingly, OSM allowed the MSC-derived cells to support the ex vivo expansion of HSPC effectively as feeder cells. Furthermore, the administration of OSM in lethally irradiated wild-type mice blocked fatty marrow and enhanced the recovery of HSPC number in the BM and peripheral blood cells after engraftment of HSPC. Collectively, OSM plays multiple critical roles in the maintenance and development of the hematopoietic microenvironment in the BM at a steady state as well as after injury.     

Stromal stem cells from adipose tissue and bone marrow of age‐matched female donors display distinct immunophenotypic profiles

Adipose tissue is composed of lipid‐filled mature adipocytes and a heterogeneous stromal vascular fraction (SVF) population of cells. Similarly, the bone marrow (BM) is composed of multiple cell types including adipocytes, hematopoietic, osteoprogenitor, and stromal cells necessary to support hematopoiesis. Both adipose and BM contain a population of mesenchymal stromal/stem cells with the potential to differentiate into multiple lineages, including adipogenic, chondrogenic, and osteogenic cells, depending on the culture conditions. In this study we have shown that human adipose‐derived stem cells (ASCs) and bone marrow mesenchymal stem cells (BMSCs) populations display a common expression profile for many surface antigens, including CD29, CD49c, CD147, CD166, and HLA‐abc. Nevertheless, significant differences were noted in the expression of CD34 and its related protein, PODXL, CD36, CD 49f, CD106, and CD146. Furthermore, ASCs displayed more pronounced adipogenic differentiation capability relative to BMSC based on Oil Red staining (7‐fold vs. 2.85‐fold induction). In contrast, no difference between the stem cell types was detected for osteogenic differentiation based on Alizarin Red staining. Analysis by RT‐PCR demonstrated that both the ASC and BMSC differentiated adipocytes and osteoblast displayed a significant upregulation of lineage‐specific mRNAs relative to the undifferentiated cell populations; no significant differences in fold mRNA induction was noted between ASCs and BMSCs. In conclusion, these results demonstrate human ASCs and BMSCs display distinct immunophenotypes based on surface positivity and expression intensity as well as differences in adipogenic differentiation. The findings support the use of both human ASCs and BMSCs for clinical regenerative medicine. J. Cell. Physiol. 226: 843–851, 2011. © 2010 Wiley‐Liss, Inc.     

Histone demethylase KDM7A reciprocally regulates adipogenic and osteogenic differentiation via regulation of C/EBPα and canonical Wnt signalling

Recent emerging evidences revealed that epigenetic methylation of histone and DNA regulates the lineage commitment of mesenchymal progenitor cells. This study was undertaken to delineate the actions of histone lysine demethylase 7A (KDM7A) on osteogenic and adipogenic differentiation. Kdm7a expression was up‐regulated in primary marrow stromal cells and established stromal ST2 line after adipogenic and osteogenic treatment. Silencing of endogenous Kdm7a in the cells blocked adipogenic differentiation whereas promoted osteogenic differentiation. Conversely, overexpression of wild‐type Kdm7a in the progenitor cells enhanced adipogenic differentiation whereas inhibited osteogenic differentiation. However, the effect of KDM7A on cell differentiation was largely attenuated when the point mutation was made that abolishes enzymatic activity of KDM7A. Mechanism investigations revealed that silencing of Kdm7a down‐regulated the expression of the CCAAT/enhancer binding protein α (C/EBPα) and secreted frizzled‐related protein 1 (Sfrp1). Chromatin immunoprecipitation (ChIP) assay revealed that KDM7A directly binds to the promoters of C/EBPα and Sfrp1 and removes the histone methylation marks H3K9me2 and H3K27me2. Furthermore, silencing of Kdm7a activated canonical Wnt signalling. Thereafter, activation of canonical Wnt signalling through silencing of Sfrp1 in ST2 attenuated the stimulation of adipogenic differentiation and inhibition of osteogenic differentiation by KDM7A. Our study suggests that KDM7A balances adipogenic and osteogenic differentiation from progenitor cells through epigenetic control of C/EBPα and canonical Wnt signalling and implicates that control of KDM7A action has an epigenetic perspective of curtailing metabolic disorders like osteoporosis.     

Osteogenic growth peptide C-terminal pentapeptide [OGP(10-14)] acts on rat bone marrow mesenchymal stem cells to promote differentiation to osteoblasts and to inhibit differentiation to adipocytes

Cumulative evidence indicates that bone marrow mesenchymal stem cells (MSCs) are multipotent cells capable of differentiating to osteogenic and adipogenic lineages when stimulated under appropriate conditions. Whether OGP(10-14) directly regulates the progenitor cells differentiating into osteoblasts or adipocytes remains unknown. In the present study, we investigated the roles of OGP(10-14) in differentiation along these separate lineages using rat bone marrow MSCs. Our results showed that OGP(10-14) promoted osteogenic differentiation of the stem cells and concurrently inhibited adipocyte formation. OGP(10-14) increased alkaline phosphatase (ALP) activity and mineralized nodule formation, and stimulated osteoblast-specific mRNA expression of core-binding factor 1 (cbfa1). In contrast, OGP(10-14) decreased adipocyte numbers and inhibited adipocyte-specific mRNA expression of peroxisome proliferator-activated receptor-gamma 2 (PPARgamma2). These observations suggest that commitment of MSCs into osteogenic or adipogenic lineages is regulated by OGP(10-14).     

Differentiation Capacity toward Mesenchymal Cell Lineages of Bone Marrow Stromal Cells Established from Temperature-Sensitive SV40 T-Antigen Gene Transgenic Mouse

Stromal cell lines were established from bone marrow of temperature-sensitive T-antigen gene transgenic mice. These stromal cell lines consisted of fibroblasts, endothelial cells, and preadipocytes. We found that these stromal cell lines exhibited phenotypic changes depending on the inactivation of T-antigen and growth condition; one preadipocyte line was induced toward adipocytes and osteogenic cells, and several preadipocyte and endothelial cell lines were induced toward muscle cells and adipocytes. Some cell lines showed bipotential characters. These results indicated that stromal cells consisting of bone marrow hematopoietic microenvironment are derived from multipotent mesenchymal stem cells.     

Expression of vascular cell adhesion molecule-1 indicates the differentiation potential of human bone marrow stromal cells

Bone marrow stromal cells (BMSCs) are a mixture of cells differing in differentiation potential including mesenchymal stem cells, and so far no CD antigens were found to be predictable for the differentiation property of each BMSC. Here we attempted to isolate differentiation-associated CD antigens using 100 immortalized human BMSC (ihBMSC) clones. Among 13 CD antigens analyzed, only CD106/Vascular cell adhesion molecule-1 (VCAM-1) showed a clear correlation with the differentiation potential of each clone; CD106-positive ihBMSC clones were less osteogenic and more adipogenic than CD106-negative clones. This association was confirmed in primary BMSCs sorted by CD106, showing that the CD106-positive fraction contained less osteogenic and more adipogenic cells than the CD106-positive fraction. The evaluation of CD106 fraction of BMSC strains in early passages predicted clearly the osteogenic and adipogenic potential after in vitro induction of differentiation, indicating the usefulness of CD106 as a differentiation-predicting marker of BMSC.     

Phenotypic and functional comparison of cultures of marrow-derived mesenchymal stem cells (MSCs) and stromal cells

Mesenchymal stem cells (MSCs) are a population of pluripotent cells within the bone marrow microenvironment defined by their ability to differentiate into cells of the osteogenic, chondrogenic, tendonogenic, adipogenic, and myogenic lineages. We have developed methodologies to isolate and culture-expand MSCs from human bone marrow, and in this study, we examined the MSC's role as a stromal cell precursor capable of supporting hematopoietic differentiation in vitro. We examined the morphology, phenotype, and in vitro function of cultures of MSCs and traditional marrow-derived stromal cells (MDSCs) from the same marrow sample. MSCs are morphologically distinct from MDSC cultures, and flow cytometric analyses show that MSCs are a homogeneous cell population devoid of hematopoietic cells. RT-PCR analysis of cytokine and growth factor mRNA in MSCs and MDSCs revealed a very similar pattern of mRNAs including IL-6, -7, -8, -11, -12, -14, and -15, M-CSF, Flt-3 ligand, and SCF. Steady-state levels of IL-11 and IL-12 mRNA were found to be greater in MSCs. Addition of IL-1α induced steady-state levels of G-CSF and GM-CSF mRNA in both cell preparations. In contrast, IL-1α induced IL-1α and LIF mRNA levels only in MSCs, further emphasizing phenotypic differences between MSCs and MDSCs. In long-term bone marrow culture (LTBMC), MSCs maintained the hematopoietic differentiation of CD34⁺ hematopoietic progenitor cells. Together, these data suggest that MSCs represent an important cellular component of the bone marrow microenvironment. J. Cell. Physiol. 176:57–66, 1998. © 1998 Wiley-Liss, Inc.     

Isolation of a novel PDZ-containing myosin from hematopoietic supportive bone marrow stromal cell lines

Stromal cells in bone marrow provide an optimal microenvironment for hematopoiesis. The established stromal cell lines from bone marrow showed various cellular heterogeneities and differed in their hematopoietic supportive ability. By a differential display method, we cloned a gene whose expression levels were correlated with the hematopoietic supportive ability of stromal cells. Its deduced amino acid sequence shows a structure similar to myosins, except that it lacks an actin binding site. Interestingly, it contains a KE-rich sequence and a PDZ domain in the NH(2)-terminal, which are protein-protein interaction domains; therefore we termed this novel myosin Myosin containing PDZ domain (MysPDZ). Western blot analysis showed that its protein levels positively correlated with the supportive ability of stromal cells and immunostaining suggested that MysPDZ was present at cytoskeleton in a filamentous and/or network form. Thus MysPDZ may be involved in the maintenance of the stromal cell architectures required for cell to cell contact.     

Human bone marrow mesenchymal cells express NG2: possible increase in discriminative ability of flow cytometry during mesenchymal stromal cell identification

Background aimsMesenchymal stromal cells (MSC) exhibit non-specific hematopoietic cell and/or stromal cell markers (e.g. CD73, CD105 and CD166) that have been used to identify MSC by flow cytometry. Because a neural glial antigen, NG2 (a progenitor cell marker in the central nervous system), is expressed by several tissue cells originating in the mesenchyme but not hematopoietic cells, it might be useful for isolating and identifying MSC. We investigated NG2 expression on culture-expanded MSC by flow cytometry.MethodsHuman bone marrow (BM) samples taken from 12 donors were cultured for MSC to be used in up to nine serial passages. Using flow cytometry, the neural glial antigen NG2 and commonly used MSC markers CD73, CD105 and CD166, were analyzed on the surface of culture-expanded MSC. The multipotential differentiation of the MSC was examined by adipogenic and osteogenic induction.ResultsThe percentage of cells positive for NG2 was similar to the percentages of cells positive for CD73, CD105 and CD166 in all passages of BM samples. The mean fluorescent intensities of NG2 did not change with culture passage. The MSC was successfully differentiated into adipogenic and osteogenic lines. The cells showed no karyotypic abnormalities.ConclusionsNG2 seems to be a promising marker for investigating the biology of MSC.     

Structure and function of bone marrow environment

Bone marrow and spleen are the major hematopoietic tissue in adult mice. However, little is known about the specific mechanism regulating hematopoiesis within these tissues. Since Dexter et al. first described conditions to maintain bone marrow hematopoiesis, long term bone marrow culture (LTBMC) has been developed in order to analyze the mechanism of the maintenance of proliferation and differentiation of hematopoietic stem cells in vitro. Furthermore, several stromal cell lines which are able to support the growth and differentiation of hematopoietic lineage, has been established from LTBMC. Although it is well known that bone marrow stromal cell lines are able to produce colony stimulating factors, it has been suggested that the stromal cell factors which involve membrane bound moieties must have a key role in the regulation of hematopoiesis. We expect that monoclonal antibodies to the surface of bone marrow stromal cells could detect such a critical stroma-associated protein that bounds the cell surface of the bone marrow stroma.     

Phenotypical properties and ability to multilineage differentiation of adipose tissue stromal cells during subculturing

Morphological and immunophenotypical properties of human adult adipose tissue stromal cells (ATSC) at cultivation passage 0 and 4 as well as their ability to induced in vitro differentiation into adipogenic and osteogenic directions were studied in this work. It was shown that primary cultures of ATSC were characterized by the presence of the lower number of cells expressing mesenchymal markers (CD73, CD105) than the cells of the 4th passage, but contained endothelial progenitor cells expressing CD34 and capable to form capillary-like structures within extracellular matrix. Both cell populations could equally differentiate into adipogenic and osteogenic lineages.     

Phenotypical properties and ability to multilineage differentiation of adipose tissue stromal cells during subculturing

Morphological and immunophenotypical properties of human adult adipose tissue stromal cells (ATSC) at cultivation passage 0 and 4 as well as their ability to induced in vitro differentiation into adipogenic and osteogenic directions were studied in this work. It was shown that primary cultures of ATSC were characterized by the presence of the lower number of cells expressing mesenchymal markers (CD73, CD105) than the cells of the 4th passage, but contained endothelial progenitor cells expressing CD34 and capable to form capillary-like structures within extracellular matrix. Both cell populations could equally differentiate into adipogenic and osteogenic lineages.     

Analysis of matrix metalloproteinase activity during differentiation of mesenchymal stem cells isolated from different tissues of one donor

Mesenchymal stem cells established from bone marrow (FetMSC) and limb bud (M-FetMSC) of early human embryo, as well as spheroids derived these cells, were induced to undergo osteogenic and adipogenic differentiation. Differentiated cells exhibited the activity of metalloproteinase (MMP)-9, -2, and -1. Its activity was different in osteogenic and adipogenic cells, as well as in monolayer cultures (2D) and cell spheroids (3D). The direct correlation between the level of adipogenic differentiation and gelatinases MMP-9 and MMP-2 activities in both cell lines in 2D and 3D culture was shown. M-FetMSC cells in 2D culture 12 days in culture during showed low potential for adipogenesis and reduced activity of MMP-2 and MMP-9. The low level of adipogenic differentiation in 2D M-FetMSC culture was accompanied with increased MMP-1 activity and enhanced differentiation (3D culture) resulted in a significant increase of both MMP activities. MMP-1 activity varied oppositely. MMP-1 activity declined in 3D cultures with a higher level of adipogenic differentiation. The level of osteogenic differentiation was similar in both cell lines during 2D and 3D cultivation. MMP-1 and -9 activities in both cell lines were not associated with osteogenic differentiation. MMP-2 and MMP-2 activity in these cells remained unchanged. The results suggest MMP implication in FetMSC and М-FetMSC differentiation. The difference in MMP activities during the cell differentiation may be caused by variations in the microenvironment or ECM properties in 2D and 3D cultures.     

Stromal cells provide signals different from cytokines for STAT5 activation in hematopoietic cells

After detachment from the stromal cells, hematopoietic stem cells are thought to differentiate to the cytokine-dependent stages where their growth and differentiation are promoted by these cytokines. To examine the stromal regulation of hematopoietic stem cells, we previously established a primitive hematopoietic stem-like cell line, THS119, whose growth was dependent on the bone marrow stromal cell line, TBR59, and from which IL-3- (THS119/IL-3) or IL-7- (THS119/IL-7) dependent cell lines were then generated. Using these cell lines, we examined the difference in signals mediated by the stromal cells and cytokines. The cytokine-dependent cell lines (THS119/IL-3 and THS119/IL-7) showed induction of STAT5 phosphorylation and target genes for STAT5 such as CIS, pim-1, p21 and bcl-xL upon addition of IL-3 or IL-7. IL-3 or IL-7 also induced STAT5 phosphorylation and STAT5 target genes of the stromal cell-dependent cell line, THS119, in the absence of stromal cells at levels similar to the cytokine-dependent cell lines. However, quite interestingly, TBR59 stromal cells could not induce STAT5 phosphorylation of THS119 cells, although they did induce STAT5 target genes in THS119 cells. In addition, the mRNAs for STAT5 target genes in THS119 cells on the stromal cells seemed to be more stable than those in the cytokine-dependent cell lines. Expression of the antiapoptotic genes bcl-2 and bcl-xL was higher in the stromal cell-dependent cell line than in the cytokine-dependent cell lines. These results suggested that stromal cells and cytokines may provide different signals for growth and differentiation of the hematopoietic cells.     

Generation of murine stromal cell lines supporting hematopoietic stem cell proliferation by use of recombinant retrovirus vectors encoding simian virus 40 large T antigen.

The bone marrow is a complex microenvironment made up of multiple cell types which appears to play an important role in the maintenance of hematopoietic stem cell self-renewal and proliferation. We used murine long-term marrow cultures and a defective recombinant retrovirus vector containing the simian virus 40 large T antigen to immortalize marrow stromal cells which can support hematopoiesis in vitro for up to 5 weeks. Such cloned cell lines differentially supported stem cells which, when transplanted, allowed survival of lethally irradiated mice, formed hematopoietic spleen colonies in vivo, and stimulated lymphocyte proliferation in vitro. Molecular and functional analyses of these cell lines did not demonstrate the production of any growth factors known to support the proliferation of primitive hematopoietic stem cells. All cell lines examined produced macrophage colony-stimulating factor. The use of immortalizing retrovirus vectors may allow determination of unique cellular proteins important in hematopoietic stem cell proliferation by the systematic comparison of stromal cells derived from a variety of murine tissues.