SCM012 Sigma-AldrichNDiff Neuro-2 Medium Supplement (200x)

The major obstacle to the widespread use of umbilical cord blood (UCB) in hematopoietic stem/progenitor (HSC) cell therapy is the low cell dose available. A cytokine cocktail for the ex vivo expansion of UCB HSC, in co-culture with a bone marrow (BM) mesenchymal stem cells (MSC)-derived stromal layer was optimized using an experimental design approach. Proliferation of total cells (TNC), stem/progenitor cells (CD34(+)) and colony-forming units (CFU) was assessed after 7 days in culture, while sole and interactive effects of each cytokine on HSC expansion were statistically determined using a two-level Face-Centered Cube Design. The optimal cytokine cocktail obtained for HSC-MSC co-cultures was composed by SCF, Flt-3L and TPO (60, 55 and 50 ng mL(-1), respectively), resulting in 33-fold expansion in TNC, 17-fold in CD34(+) cells, 3-fold in CD34(+)CD90(+) cells and 21-fold in CFU-MIX. More importantly, these short-term expanded cells preserved their telomere length and extensively generated cobblestone area-forming cells (CAFCs) in vitro. The statistical tools used herein contributed for the rational delineation of the cytokine concentration range, in a cost-effective way, while systematically addressing complex cytokine-to-cytokine interactions, for the efficient HSC expansion towards the generation of clinically significant cell numbers for transplantation.

Most clinical applications of haematopoietic stem/progenitor cells (HSCs) would benefit from their ex vivo expansion to obtain a therapeutically significant amount of cells from the available donor samples. We studied the impact of cellular interactions between umbilical cord blood (UCB) haematopoietic cells and bone marrow (BM)-derived mesenchymal stem cells (MSCs) on the ex vivo expansion and differentiative potential of UCB CD34(+)-enriched cells. UCB cells were cultured: (a) directly in contact with BM MSC-derived stromal layers (contact); (b) separated by a microporous membrane (non-contact); or (c) without stroma (no stroma). Highly dynamic culture events occurred in HSC-MSC co-cultures, involving cell-cell interactions, which preceded HSC expansion. Throughout the time in culture [18 days], total cell expansion was significantly higher in contact (fold increase of 280 + or - 37 at day 18) compared to non-contact (85 + or - 25). No significant cell expansion was observed in stroma-free cultures. CD34(+) cell expansion was also clearly favoured by direct contact with BM MSCs (35 + or - 5- and 7 + or - 3-fold increases at day 18 for contact and non-contact, respectively). Moreover, a higher percentage of CD34(+)CD38(-) cells was consistently maintained during the time in culture under contact (8.1 + or - 1.9% at day 18) compared to non-contact (5.7 + or - 1.6%). Importantly, direct cell interaction with BM MSCs significantly enhanced the expansion of early lymphoid CD7(+) cells, yielding considerably higher (x3-10) progenitor numbers compared to non-contact conditions. These results highlight the importance of dynamic cell-cell interactions between UCB HSCs and BM MSCs, towards the maximization of HSC expansion ex vivo to obtain clinically relevant cell numbers for multiple settings, such as BM transplantation or somatic cell gene therapy.

To harness the potential of ES (embryonic stem) cells for human therapy, technology to develop the large-scale expansion and differentiation of these cells is required. In the present study, we tested various conditions for the expansion and neural commitment of mouse ES cells, using a cell line with a fluorescent reporter, which allows the monitoring of these processes by flow cytometry. The expansion of the 46C ES cell line in the presence of two different media [serum-free ESGRO Completetrade mark and DMEM (Dulbecco's modified Eagle's medium) containing 10% (v/v) fetal bovine serum] was compared. Both media yielded similar cell fold increases at two different initial cell densities and were able to maintain neural commitment potential during expansion. The influence of inocula concentration in the presence of two different media on cell proliferation and efficiency of neural commitment was evaluated. Two different chemically defined serum-free media were tested: the more conventional N2B27 and the second-generation medium RHB-A (Stem Cell Sciences, Edinburgh, Scotland, U.K.). The kinetics of neural commitment was followed during 8 days in the presence of both media. Our results show that inocula concentrations between 5x10(3) and 10(4) cells/cm(2) are the most appropriate to achieve a better cell growth and more efficient neural commitment. We also show that cell culture in RHB-A medium results in higher rates of cell proliferation and neural commitment of ES cells, when compared with N2B27.

Pluripotent mouse embryonic stem (ES) cells multiply in simple monoculture by symmetrical divisions. In vivo, however, stem cells are generally thought to depend on specialised cellular microenvironments and to undergo predominantly asymmetric divisions. Ex vivo expansion of pure populations of tissue stem cells has proven elusive. Neural progenitor cells are propagated in combination with differentiating progeny in floating clusters called neurospheres. The proportion of stem cells in neurospheres is low, however, and they cannot be directly observed or interrogated. Here we demonstrate that the complex neurosphere environment is dispensable for stem cell maintenance, and that the combination of fibroblast growth factor 2 (FGF-2) and epidermal growth factor (EGF) is sufficient for derivation and continuous expansion by symmetrical division of pure cultures of neural stem (NS) cells. NS cells were derived first from mouse ES cells. Neural lineage induction was followed by growth factor addition in basal culture media. In the presence of only EGF and FGF-2, resulting NS cells proliferate continuously, are diploid, and clonogenic. After prolonged expansion, they remain able to differentiate efficiently into neurons and astrocytes in vitro and upon transplantation into the adult brain. Colonies generated from single NS cells all produce neurons upon growth factor withdrawal. NS cells uniformly express morphological, cell biological, and molecular features of radial glia, developmental precursors of neurons and glia. Consistent with this profile, adherent NS cell lines can readily be established from foetal mouse brain. Similar NS cells can be generated from human ES cells and human foetal brain. The extrinsic factors EGF plus FGF-2 are sufficient to sustain pure symmetrical self-renewing divisions of NS cells. The resultant cultures constitute the first known example of tissue-specific stem cells that can be propagated without accompanying differentiation. These homogenous cultures will enable delineation of molecular mechanisms that define a tissue-specific stem cell and allow direct comparison with pluripotent ES cells.