Study of oncogenic transformation in ex vivo expanded mesenchymal cells, from paediatric bone marrow.

OBJECTIVES: Mesenchymal stromal cells (MSCs) have attracted considerable interest in both the scientific and clinical fields. In order to obtain a sufficient cell number for application, their in vitro expansion is necessary, but during this process their characteristics may be altered and cells may acquire oncogenic properties. We have investigated properties of MSC that may be related to oncogenesis, a critical parameter that has to be evaluated prior to MSC clinical use. MATERIALS AND METHODS: We studied the expression of p53, p16, RB, H-RAS and human telomerase reverse transcriptase (hTERT) in MSCs from bone marrow of children diagnosed with idiopathic thrombocytopenic purpura (ITP) and autoimmune neutropenia. The same cells were seeded in soft agar to confirm their anchorage dependence and were karyotypically analysed. Finally, MSCs were subcutaneously transplanted into SCID mice and their ectopic osteogenic as well as tumorigenic potential was evaluated. RESULTS: We have shown that MSCs derived from bone marrow of children with ITP and autoimmune neutropenia do not undergo transformation, the cells expressed normal levels of p53, p16, RB and H-RAS. Expression of hTERT was undetectable, chromosome content remained stable, and their anchorage dependence was confirmed. In an in vivo model, when MSCs were subcutaneously transplanted into SCID mice, no tumorigenesis was observed. CONCLUSIONS: These findings suggest that MSCs from bone marrow of children do not have oncogenic properties and, therefore, represent validate candidates for applications in regenerative medicine.

Could cord blood be a source of mesenchymal stromal cells for clinical use?

BACKGROUND: Cord blood (CB) has long been regarded as an easily accessible source of hematopoietic progenitors suitable for transplantation, but its efficiency as a source of mesenchymal stromal cells (MSC) remains controversial. The aim of this study was to assess CB as a potential source of MSC, to determine the optimal culture requirements for CB MSC expansion and to compare their functional and immunophenotypic characteristics with bone marrow (BM) MSC from children. METHODS: Mononuclear cells from 18 full-term CB samples and 23 BM samples from children were set in culture under MSC-inducing conditions. Their immunophenotypic characteristics were assessed by flow cytometry and their differentiation potential was evaluated. RESULTS: Isolation of CB MSC was achieved in 25% of the samples cultured under optimal conditions: high initial cell concentration, fetal calf serum (FCS) enrichment of the culture medium, high FGF-2 concentration and high sample volume. Isolated CB MSC were morphologically similar to the ones derived from BM, but appeared late in culture. An adherent cell layer was formed and reached confluency in 34 days (passage 1; P1) and needed 55 days subsequently (from P1 to P2). CB MSC retained their characteristics for two successive passages. Immunophenotypic analysis showed no expression of CD34 and varying expression of CD45, ranging from 0% to 17.83%, and CD105, from 49% to 83%. CFU-F colonies developed in one case. DISCUSSION: These findings suggest that CB cannot be considered a sufficient source of MSC for clinical use, although easily accessible. Further research should aim for alternative sources.

Properties and potential of bone marrow mesenchymal stromal cells from children with hematologic diseases.

BACKGROUND: Mesenchymal stromal cells (MSC) have become the focus of cellular therapeutics but little is known regarding bone marrow (BM) MSC derived from children. As MSC constitute part of BM stroma, we examined their properties in children with hematologic diseases. METHODS: BM MSC from children with non-malignant hematologic disorders and acute lymphoblastic leukemia (ALL) were isolated and expanded. MSC were immunophenotypically characterized and their functional characteristics were assessed by CFU-F assay and cell doubling time calculation. Their ability for trilineage differentiation was verified by molecular and histochemical methods. Apoptosis was evaluated and clonal analysis was performed. RESULTS: MSC were isolated from BM of all groups. They acquired the mesenchymal-related markers from the first passage, with a simultaneous decrease of hematopoietic markers. A very low percentage of apoptotic cells was detected in all passages. The proliferative and clonogenic capacity did not differ among groups, with the exception of ALL at diagnosis, in which they were defective. Histochemical and molecular analysis of differentiated MSC yielded characteristics for adipocytes, osteoblasts and chondrocytes. Clonal analysis in a number of BM samples revealed a highly heterogeneous population of cells within each clone. DISCUSSION: MSC from BM of children with hematologic disorders, with the exception of ALL at diagnosis, can be isolated in sufficient number and quality to serve as a potential source for clinical applications.

Quantitative assessment of PRAME expression in diagnosis of childhood acute leukemia.

PRAME is expressed at low levels in normal testes and highly in solid tumor cells and hematological malignancies. The purpose of this study was to investigate PRAME expression levels in children with acute leukemia with real-time PCR analysis. Seventeen children with newly diagnosed or relapsed acute leukemia (11 ALL, 4 AML, 1 acute myeloblastic leukemia secondary to MDS, 1 ALL at relapse) and a control group of seven children were studied. Overexpression of PRAME was found in 52.9% (3 AML, 6 ALL) of the patients studied. No important correlation between PRAME expression and the patients' prognosis was observed. The above findings indicate that PRAME expression in acute leukemia does not seem to be of prognostic significance, whereas it might represent a candidate marker for the monitoring of minimal residual disease.

Quantitative assessment of WT1 expression in diagnosis of childhood acute leukemia.

The purpose of this study was to investigate WT1 expression levels in childhood acute leukemia. Bone marrow from 14 children with acute leukemia at diagnosis and from 7 children with solid tumors without bone marrow involvement (control group) was studied. Five of the 14 patients (35.7%), expressed high levels of WT1. Four of the five WT1 positive patients with additional adverse prognostic factors, have succumbed to their disease. The results of this study are in accordance with the fact that high levels of WT1 expression have been reported in patients with an unfavorable outcome.

Pleuropulmonary blastoma: an aggressive intrathoracic neoplasm of childhood.

A case of a 4-year-old girl with pleuropulmonary blastoma is reported. Surgical resection of the tumor was performed and histologic examination revealed pleuropulmonary blastoma with rhabdomyosarcomatous differentiation. Postoperative chemotherapy was administered and 3 weeks after initiation of treatment protocol a second site of lesion in the retroperitoneum was revealed with extension to the mediastinum, which shared similar mesenchymal neoplastic characteristics to the previously diagnosed primary lesion. The girl died 4 1/2 months after initial evidence of disease because of brain metastasis, indicating a very aggressive neoplasm unresponsive to treatment.