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Accessible online at: www.karger.com/fdt Paper presented at the meeting ‘In Utero Stem Cell Transplantation and Gene Therapy’ organized by the Merieux Foundation, Lyon (France), 13–14 March, 2003. The rapid advances in biological sciences have allowed a better understanding and management of various diseases. Cellular therapies, cell engineering and gene therapies may improve and/or replace many conventional treatments. Unfortunately, the progress in the achievement of those goals is frequently marred by overly enthusiastic and poorly supported claims by some of the scientists involved in this rapidly developing cutting-edge research. There are a number of areas that should be of special concern. Above all, it is crucial to protect patients involved in experimental therapies and to preserve high standards of inquiry and scientific integrity. The increasing demand for stem cells for transplantation has resulted in the exploitation of new sources of human stem cells, including embryonic stem cells. New methods of human cell cloning have opened an area of embryonic research that is associated with major ethical problems and controversies. As a result, opponents of research on human embryos have raised politically powerful arguments against embryonic stem cell research, suggesting that adult stem cells may offer the same therapeutic promise. Unfortunately, there is accumulating evidence that adult stem cells exhibit time-dependent changes, which affect long-term engraftment and curative cell reconstitution. Moreover, recent studies show that adult stem cells have limited plasticity and extensive heterogeneity. These studies also suggest that enriched but impure cell populations may lead to a misinterpretation of in vitro results. Thus, it is impossible to draw a distinction between plasticity of adult stem cells and heterogeneity of stem cell types that may pre-exist within tissue. Consequently, the great excitement concerning trans-differentiation of adult stem cells has to be tempered by the new, conflicting findings. The scientific ‘dogma’ that adult stem cells can morph into many types of cells may be based on misinterpretation of somewhat uncritical interpretation of data. What was initially claimed to be cell re-programming in vitro has currently been recognized by many as simple cell fusion with enlarged nuclei and double chromosomes, typical of hybrid cells. It is also recognized that the number of adult stem cells is limited and that the engraftment as well as reconstitution is impaired due to telomere shortening and DNA replicative exhaustion. It is clear that new discoveries continue to refine the understanding of what adult stem cells are capable of doing and more relevant animal studies are needed to establish the suitability of these cells for therapy. Embryonic stem cells have been suggested as a virtually inexhaustible source of stem cells for therapeutic uses because they can be propagated easily in culture. Unfortu

Hematopoietic stem cell transplantation has been increasingly used to replace a defective hematopoietic system and to treat various genetic defects as well as malignant diseases. However, the limitations of conventional bone marrow transplantation have stimulated an intense interest in exploring the use of alternative sources of hematopoietic stem cells, including peripheral blood mononuclear cells (PBMC) and cord blood (CB). A major investigative effort of our laboratory has been focused on evaluating fetal bone marrow (FBM) for transplantation. The current study compares and characterizes the functional and phenotypic characteristics of FBM, CB, adult bone marrow (ABM), and PBMC by clonogenicity assays, immunogenicity, and the quantification of progenitor cells. There was a striking difference in the proportion of CD34+ cells in FBM, ABM, PBMC, and CB (24.6%, 2.1%, 0.5%, and 2.0%, respectively). The clonogenic potential, as measured by colony forming unit in culture (CFU-C) assay, was significantly higher in FBM when compared with ABM, PBMC, and CB (202.5, 73.5, 40.8, and 65.5 colonies/10(5) cells, respectively). There was a significant decrease in proliferative responsiveness in mixed lymphocyte reaction (MLR) assay of FBM and CB compared with ABM and PBMC. These observations indicate that each source of hematopoietic stem cells has different intrinsic properties closely correlated with ontogenetic age that is a vital determinant for phenotypic characteristics, lineage commitments, immunogenicity, and proliferative potentials.

We have previously reported that fetal bone marrow (FBM) has higher number of CD34+ cells, greater clonogenic capacity, and lowered immunologic reactivity compared to adult bone marrow (ABM), cord blood (CB), and peripheral blood lymphocytes (PBL). The present studies were designed to investigate whether similar ontogenetic differences exist in the expression of hematopoietic-related cytokines by stromal cells from FBM, ABM, and CB using RT-PCR. Stromal cells were prepared in long-term cultures supplemented with hydrocortisone to 80% confluency from specimens obtained from 8 FBM (n=8), collected from spontaneously aborted fetuses at gestational age of 18-20 weeks; 8 ABM (n=8) from allogeneic donors; 7 CB (n=7) samples. RNA was extracted from the stromal cells and reverse-transcribed into cDNA which was then subjected to PCR using specific primers for stem cell factor (SCF), GM-CSF, G-CSF, M-CSF, IL-3, IL-6, IL-10, IL-11, respectively. Quantitation of products was measured by densitometry using a Howtech Scanner. A strong expression of SCF and IL-11 was observed in the stromal cells from FBM compared to ABM and CB. Although M-CSF was not detected in any of 8 FBM specimens, it was highly expressed in all ABM and CB samples. IL-6 was detected in 6/8 ABM but in only 1/8 FBM and 0/7 CB. Although G-CSF was not observed in CB, it was expressed in all FBM and ABM specimens. In contrast, expression of GM-CSF, IL-3, and IL-10 from different sources of stromal cells was similar. These results strongly indicate that there are age-related changes in cytokine expression in stromal cells at different maturational stages. Further, these results suggest an important role for these cytokines in their capacity to regulate differentiation and proliferation of stem cells during ontogentic development, and these may provide better predictive information for treatment of hematologic diseases as well as selection of stem cells for transplantation.

Stem Cell Transplantation: Superiority of Fetal Bone Marrow Over Cord Blood and Adult Bone Marrow. • 1290