Determination of phenotypical and biological characteristics of mesenchymal stem cells in pediatric myelodysplastic syndromes

The pluripotent stromal stem cells or so called Mesenchymal Stromal Cells
(MSC*s), located in the bone marrow, give rise to cells that form the
structural network in support and maintenance of normal hematopoiesis. The
growth and differentiation of hematopoietic stem cell progenitor cells rely on
instructive signals provided by a specialized micro-environment. MSC*s provide
signaling by cell-cell contact and release of soluble factors. They themselves
are influenced by the developing hematopoietic stem cell. The stromal cells
isolated from marrow can be expanded ex vivo for biological studies.
Myelodysplastic syndrome is a heterogeneous disease characterized by
hematomorphological dysplasia, cytopenia, cytogenetic abnormalities and
leukemic transformation. In children, MDS accounts for less than 10% of all
cancers and has some distinct characteristics that distinguish the disease from
its adult counterpart. The contribution of the non hematopoietic
microenvironment in MDS is controversial but there is increasing evidence to
suggest that bone marrow stromal defects occur both in adult and pediatric MDS
patients and that stromal cell/hematopoietic stem cell interactions may
influence the initiation and/or progression of MDS. Modification of stromal
precursors could be the result of infiltrating malignant cells, which generate
conditions favorable to the development of leukemia. As such, precursor MSC*s
may be functionally different in children with MDS and within the heterogeneity
of the disease, i.e. depending upon leukemic development. If our hypothesis is
true normal signaling and interaction may be restored following successful
hematopoietic stem cell transplantation. If so pre and post transplant analysis
may be of benefit in prediction of relapse.

1 To determine the phenotype and biological characteristics of mesenchymal
stem cells derived from pediatric MDS patients as determined by flow cytometric
analysis, cell culture and differentiation abilities analyzed by subtype of MDS
compared to de novo ANLL and normal pediatric controls.
2 To analyze functional characteristics of MSC's isolated from pediatric MDS
patients:
a. In relation to immune regulation of T and NK cell function
b. To compare cytokine and growth factor expression of MSC*s and the expression
of chemokine receptor profiles of MSC*s and HSC*s isolated from children with
MDS analyzed by subtype of MDS compared to de novo ANLL and normal control
marrows.
3 To compare chromosomal difference between patient HSC*s and MSC's in
children with different subtypes of MDS utilizing karyotyping and/or chromosome
painting techniques.
4 To analyze genetic profiles of cell proliferation, apoptosis and
differentiation of MSC*s isolated form children with MDS compared to MSC*s
analyzed by subtype utilizing gene array analysis compared to de novo ANLL and
pediatric normal controls.
5 To determine whether or not normally functioning MSC*s impact on
hematopoietic growth in MDS patients and whether MDS derived MSC*s support
hematopoietic growth of normal CD34+ cells (pre and post allogeneic HSCT) by
long-term culture (Dexter type).

Following informed consent 10-15 cc of additional bone marrow aspirate will be
withdrawn at or around the time of diagnosis or immediately before
hematopoietic stem cell transplantation (HSCT). At the same time 20 cc of EDTA
blood and 5cc plasma will be withdrawn with the routine diagnostic blood
sampling. All samples will be shipped to the LUMC, Leiden, the Netherlands for
subsequent analysis. For children <10kg the blood sampling will be reduced to
10cc EDTA blood and 5cc plasma. CD 34+ve hematopoietic stem cells (HSC*s) will
be isolated from bone marrow and used in the subsequent experiments. MSC*s will
be isolated and expanded ex vivo to provide sufficient cells for analysis.
Phenotypic and biological parameters will be investigated, inclusive of
cytokine production, chemokine receptor analysis, chromosome changes and
interaction with immune regulatory cells. These results will be compared to
CD34+ve HSC*s and MSC*s obtained at the time of routine bone marrow harvest
from consenting normal pediatric bone marrow donors and children with de novo
acute myeloid leukemia at the time of diagnosis.

Additional blood and marrow during routine diagnostic sampling confers no
additional risks.