Nonhuman Primates: Embryonic Stem Cells and Transgenesis

Large animal models for foamy virus vector gene therapy

Foamy virus (FV) vectors have shown great promise for hematopoietic stem cell (HSC) gene therapy. Their ability to efficiently deliver transgenes to multi-lineage long-term repopulating cells in large animal models suggests they will be effective for several human hematopoietic diseases. Here, we review FV vector studies in large animal models, including the use of FV vectors with the mutant O6-methylguanine-DNA methyltransferase, MGMTP140K to increase the number of genetically modified cells after transplantation. In these studies, FV vectors have mediated efficient gene transfer to polyclonal repopulating cells using short ex vivo transduction protocols designed to minimize the negative effects of ex vivo culture on stem cell engraftment. In this regard, FV vectors appear superior to gammaretroviral vectors, which require longer ex vivo culture to effect efficient transduction. FV vectors have also compared favorably with lentiviral vectors when directly compared in the dog model. FV vectors have corrected leukocyte adhesion deficiency and pyruvate kinase deficiency in the dog large animal model. FV vectors also appear safer than gammaretroviral vectors based on a reduced frequency of integrants near promoters and also near proto-oncogenes in canine repopulating cells. Together, these studies suggest that FV vectors should be highly effective for several human hematopoietic diseases, including those that will require relatively high percentages of gene-modified cells to achieve clinical benefit.

Growth characteristics of the nonhuman primate embryonic stem cell line cjes001 depending on feeder cell treatment

Embryonic stem cells (ESC) hold tremendous potential for therapeutic applications, including regenerative medicine, as well as for understanding basic mechanisms in stem cell biology. Since numerous experiments cannot be conducted in human ESC because of ethical or practical limitations, nonhuman primate ESC serve as invaluable clinically relevant models. The novel marmoset (Callithrix jacchus) ESC line cjes001 was characterized using different stem cell markers. The cells were stained positively with Oct4, SSEA-3, SSEA-4, Tra-1-60, Tra-1-81, and Sox-2 underscoring their status as undifferentiated ESC. ESC are typically grown on mouse embryonic fibroblasts (MEF) as feeder cells whose proliferation is arrested either by treatment with Mitomycin C or by gamma-irradiation. To assess the impact of these treatments on the ability of MEF to support the growth of undifferentiated ESC, we used an MTT assay to evaluate the cellular metabolic activity of growth arrested feeder cells. There was a significant (p < 0.02) difference in gamma-irradiated cells displaying a higher metabolic activity compared to Mitomycin C inactivation. Also we quantified 69 soluble factors in the supernatant of both Mitomycin-treated and gamma-irradiated MEF by bead-based multiplex analysis, and thus established a profile of MEF-secreted factors. The time course of secretion was analyzed by monitoring the supernatant at 0, 6, 12, and 24 h after changing the medium. Comparing gamma-irradiated and Mitomycin-treated MEF suggested higher amounts of some cytokines including FGF or SCF by the former. We also assessed whether the method of inactivation had an effect on growth kinetics and differentiation of primate ESC. There appeared to be a trend to a lower number of differentiated ESC colonies on the gamma-irradiated feeder cells, suggesting that this may be the preferable method of growth arrest.

Large scale production of stem cells and their derivatives

Stem cells have been envisioned to become an unlimited cell source for regenerative medicine. Notably, the interest in stem cells lies beyond direct therapeutic applications. They might also provide a previously unavailable source of valuable human cell types for screening platforms, which might facilitate the development of more efficient and safer drugs. The heterogeneity of stem cell types as well as the numerous areas of application suggests that differential processes are mandatory for their in vitro culture. Many of the envisioned applications would require the production of a high number of stem cells and their derivatives in scalable, well-defined and potentially clinical compliant manner under current good manufacturing practice (cGMP). In this review we provide an overview on recent strategies to develop bioprocesses for the expansion, differentiation and enrichment of stem cells and their progenies, presenting examples for adult and embryonic stem cells alike.