To further study the proliferation and multi‐differentiation potentials of adipose‐derived stem cells (ADSCs), the cells were isolated with improved methods and their growth curves were achieved with cck‐8. Surface protein expression was analyzed by flow cytometry to characterize the cell phenotype. The multi‐lineage potential of ADSCs was testified by differentiating cells with adipogenic, chondrogenic, osteogenic, and myogenic inducers. The results showed that about 5 × 10⁵ stem cells could be obtained from 400 to 600 mg adipose tissue. The ADSCs can be continuously cultured in vitro for up to 1 month without passage and they have several logarithmic growth phases during the culture period. Also, the flow cytometry analysis showed that ADSCs expressed high levels of stem cell‐related antigens (CD13, CD29, CD44, CD105, and CD166), while did not express hematopoiesis‐related antigens CD34 and CD45, and human leukocyte antigen HLA‐DR was also negative. Moreover, stem cell‐related transcription factors, Nanog, Oct‐4, Sox‐2, and Rex‐1 were positively expressed in ADSCs. The expression of alkaline phosphatase (ALP) was detected in the early osteogenic induction and the calcified nodules were observed by von Kossa staining. Intracellular lipid droplets could be observed by Oil Red staining. Differentiated cardiomyocytes were observed by connexin43 fluorescent staining. In order to obtain more stem cells, we can subculture ADSCs every 14 days instead of the normal 5 days. ADSCs still keep strong proliferation ability, maintain their phenotypes, and have stronger multi‐differentiation potential after 25 passages. Copyright © 2008 John Wiley & Sons, Ltd.

The study of myelodysplastic syndromes (MDS) in murine models has now indicated the possible involvement of the bone marrow microenvironment in the generation of dysplastic hematopoietic cells. However, there is scant work on patient samples and the role of hypomethylating agents on the bone marrow stromal cells of MDS patients is unclear. We show that human MDS-MSCs exhibit phenotypic, transcriptomic and epigenetic abnormalities. Stimuli provided by MDS-MSCs impaired the growth and function of healthy HSPCs, which is further sustained autonomously in HSPCs for significant periods of time resulting in a failure for active hematopoietic engraftment across primary and secondary transplant recipients (chimerism: 0.34–91% vs 2.78%, engraftment frequencies: at 0.06 ± 0.02 vs full engraftment for MDS-MSC vs healthy groups, respectively). Hypomethylation of MDS-MSCs improved overall engraftment in most of the MDS-MSC groups tested (2/7 with p < 0.01, 3/7 with p < 0.05 and 2/7 with no significant difference). MDS-MSCs that fail to respond to hypomethylating therapy are associated with patients with rapid adverse disease transformation and this further suggests that MDS-MSCs may be an integral part of disease progression and have prognostic value as well as potential as a therapeutic target.

The successful expansion of hematopoietic stem and progenitor cells (HSPCs) from umbilical cord blood (UCB) for transplantation could revolutionize clinical practice by improving transplantation-related outcomes and making available UCB units that have suboptimal cell doses for transplantation. New cytokine combinations appear able to promote HSPC growth with minimal differentiation into mature precursors and new agents, such as insulin-like growth factor-binding protein 2, are being used in clinical trials. Molecules that simulate the HSPC niche, such as Notch ligand, have also shown promise. Further improvements have been made with the use of mesenchymal stromal cells, which have made possible UCB expansion without a potentially deleterious prior CD34/CD133 cell selection step. Chemical molecules, such as copper chelators, nicotinamide, and aryl hydrocarbon antagonists, have shown excellent outcomes in clinical studies. The use of bioreactors could further add to HSPC studies in future. Drugs that could improve HSPC homing also appear to have potential in improving engraftment times in UCB transplantation. Technologies to expand HSPC from UCB and to enhance the homing of these cells appear to have attained the goal of accelerating hematopoietic recovery. Further discoveries and clinical studies are likely to make the goal of true HSPC expansion a reality for many applications in future.

Mesenchymal stem cells (MSCs) can not only support the expansion of hematopoietic stem cells in vitro, but also alleviate complications and accelerate recovery of hematopoiesis during hematopoietic stem cell transplantation. However, it proved challenging to culture MSCs from umbilical cord blood (UCB) with a success rate of 20–30%. Many cell culture parameters contribute to this outcome and hence optimization of culture conditions is critical to increase the probability of success. In this work, fractional factorial design was applied to study the effect of cell inoculated density, combination and dose of cytokines, and presence of serum and stromal cells. The cultured UCB‐MSC‐like cells were characterized by flow cytometry and their multilineage differentiation potentials were tested. The optimal protocol was identified achieving above 90% successful outcome: 2 × 10⁶ cells/mL mononuclear cells inoculated in Iscove's modified Dulbecco's medium supplied with 10% FBS, 15 ng/mL IL‐3, and 5 ng/mL Granulocyte‐macrophage colony‐stimulating factor (GM‐CSF). Moreover, the UCB‐MSC‐like cells expressed MSC surface markers of CD13, CD29, CD105, CD166, and CD44 positively, and CD34, CD45, and human leukocyte antigens‐DR (HLA‐DR) negatively. Meanwhile, these cells could differentiate into osteoblasts, chondrocytes, and adipocytes similarly to MSCs derived from bone marrow. In conclusion, we have developed an efficient protocol for the primary culture of UCB‐MSCs by adding suitable cytokines into the culture system. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009

In most human somatic cells, the lack of telomerase activity results in progressive telomere shortening during each cell division. Eventually, DNA damage responses triggered by critically short telomeres induce an irreversible cell cycle arrest termed replicative senescence. However, the cellular responses of human pluripotent stem cells to telomere uncapping remain unknown. We generated telomerase knockout human embryonic stem (ES) cells through gene targeting. Telomerase inactivation in ES cells results in progressive telomere shortening. Telomere DNA damage in ES cells and neural progenitor cells induces rapid apoptosis when telomeres are uncapped, in contrast to fibroblast cells that enter a state of replicative senescence. Significantly, telomerase inactivation limits the proliferation capacity of human ES cells without affecting their pluripotency. By targeting telomerase activity, we can functionally separate the two unique properties of human pluripotent stem cells, namely unlimited self-renewal and pluripotency. We show that the potential of ES cells to form teratomas in vivo is dictated by their telomere length. By controlling telomere length of ES cells through telomerase inactivation, we can inhibit teratoma formation and potentially improve the safety of cell therapies involving terminally differentiated cells as well as specific progenitor cells that do not require sustained cellular proliferation in vivo, and thus sustained telomerase activity.