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Mesenchymal stem cells

In previous studies, we described the gene expression of the MSC derived from bone marrow and umbilical cord blood. We demonstrated their similarities revealed by the gene expression profile, although there are differences in the expression of various genes, especially those related to bone formation and angiogenesis.

We have now isolated MSC from various other human tissues, including the umbilical vein, the saphena vein and the umbilical artery, and from various fetal tissues such as the liver, the gonads, the skin, the amniotic fluid, the muscle fascia, and the carotids. All the MSCs isolated from these tissues exhibit the capacity to give rise to osteocytes, chondrocytes and adipocytes in culture, and express a set of genes specific for MSC.

We are now focusing to separate the most primitive MSC from the remaining differentiated cellular population, using specific markers such as STRO1, CD146, CD106, CD73 and CD63, by flow sorting or by purification with magnetic beads labeled with the specific antibodies. The phenotype and the biological properties of the more primitive MSC are studied by analyses of surface expression of markers, by assay of colony efficiency formation, by in vitro and in vivo differentiation into osteocytes, chondrocytes and adipocytes, and by determining the gene expression profile and the pattern of expressed protein by proteomics approaches. Animal models suitable for MSC transplantation to perform the in vivo studies are in development.

Animal models

We are studying the behavior of MSC in vivo using animal models of various diseases, including post bone marrow transplantation graft versus host disease (GVHD), acute liver injury induced by carbon tetrachloride, chronic cardiac insufficiency induced by adriamycin, and in acute radiation disease.

Mesenchymal stem cells and liver regeneration

Human mesenchymal stem cell transplantation in an experimental model of heart failure

We will use an experimental model in rats to evaluate the potential impact of human mesenchymal bone marrow stem cells (hMSC) transplantation in chronic heart failure. The chronic heart failure will be induced in rats by using doxorubicin (15 mg/kg i.p. over 2 weeks). Four weeks after drug infusion, the left ventricular ejection fraction and volumes will be assed by 2D-echocardiography. The animals will be assigned to 3 groups: 1. controls (n=20); 2. One procedure of peripheral infusion i.v. of hMSC (tail vein, 4x106 cells, n=20); 3. Repeated procedures of hMSC peripheral infusion (tail vein, 4x106 cells, n=20): 1 infusion/week over 4 consecutive weeks. Four weeks after treatment, the animals will be submitted to a final 2D-echocardiographic left ventricular function evaluation, subsequent euthanasia and tissue collection for histological analysis.

Hematopoietic progenitors

The hemangioblast - the cell that originated endothelial and hematopoietic cells in the embryo - is a transient cell type that develops early and disappears quickly during embryonic development. In human postnatal life, CD133+, CD34+, or CD34+KDR+ cell subsets in bone marrow, peripheral blood and cord blood possess the functional activity of hemangioblasts and are capable to differentiate into both hematopoietic and endothelial cells. We are comparing the functional properties and gene expression profiles of pure populations of bone marrow, peripheral blood, and umbilical cord blood CD133+, CD34+, CD34+KDR+, CD133+KDR+, CD34-CD133+, CD34+CD133+ cells to study their capacity to form hematopoietic colonies on long term culture (LTC-IC), and endothelial colonies in matrigel plaques. Next, we will examine the gene expression profile of CD133+ and CD34+ cells in order to characterize them. We also intend to transplant these cells in animal models of hematopoietic and endothelial injury to evaluate their clinical potentials.

We are also examining the genes involved in the early differentiation of CD34+ cells either along the erythrocytic or the granulocytic-monocytic lines.

Embryonic Stem Cells

Embryonic stem cells (ES) are cells derived from the early embryo that can be propagated indefinitely in the undifferentiated state while remaining pluripotent. ES can be isolated from the inner cell mass of blastocysts, from the embryonic ectoderm and from primordial germ cells. When transfected back into early embryo, they contribute to all the tisues of the embryo except to the placenta; they are not, thus, able to generate a complex organism. Most of the knowledge of ES biology are based on research with mouse embryonal carcinoma stem cells. The culture and frozen storage of human embryonic stem cells remains difficult, slow and labor-intensive. The ability to direct ES into specific differentiation pathways and to obtain pure populations of differentiated phenotypes remains limited and is the object of great interest.

We are starting to study biological characteristics of donated ES lines to:

  • 1.Evaluate the ES gene expression profiles by quantitative and qualitative methods.
  • 2.Compare the ES gene expression profile with the gene expression profile of adult stem cells including hematopoietic stem cells (CD34+, CD133+) and mesenchymal stem cells from bone marrow and umbilical cord blood.
  • 3.Understand the genetic and molecular mechanisms involved in the initial phase of ES differentiation.
In the next phase of the project, we plan to isolate, characterize and propagate ES lineages derived from the inner cell mass of blastocysts from frozen embryos obtained from the Fertilization Clinic of the University Hospital.

Basic Research