Stem cell research: current uses and future challenges

Dear Reader,

Long before the existence of stem cells was proven, work with blood islands pointed to the ability of hemangioblasts to generate blood cells in the embryo. Stem cell research has known a dramatic leap forward with the development of embryonic stem cell lines from isolated cells from the inner cell mass of early embryos. Indeed, stem cells have demonstrated to be exciting tools that would permit the unlimited repair and replacement of abnormal, damaged, or absent cell types and tissues (Thomson et al. 1998). A second major breakthrough came when Yamanaka's group showed the production of induced pluripotent stem cells from adult stem cells upon lentiviral introduction of four transcription factors (Takahashi and Yamanaka 2006), circumventing the ethical controversies associated with deriving stem cells from embryos as pointed out in the review from Schotanus et al. (this issue).

In the first review article appearing in this issue, Schauwer et al. (this issue) explore, among others, the applications for bone-marrow-derived mesenchymal stem cells and adipose-derived stromal vascular fraction cells in the treatment of musculoskeletal pathologies that are currently in use in horses. The differential efficacies of various approaches are still being investigated. Further optimization of stem-cell-based therapies should focus on cellular origin, isolation, enrichment, and processing as well as on the timing, route of administration, formulation, and dosing.

We still have a long way to go before reaching a full understanding of stem cell biology and translation of these findings into the clinic. Efforts to characterize the molecular mechanisms responsible for the variability encountered between human embryonic stem cells and induced pluripotent stem cell lines have initially focused on expression level variations in protein-coding genes. In addition, Lammens et al. (this issue) explore various recent studies providing evidence that also long non-coding RNAs (regulatory RNA not translated into protein) are key regulators in the maintenance of the stem cell pluripotent state.

Finally, it is of great concern, as described in De Bakker et al. (this issue), that little information is available regarding short-term and long-term safety of stem cell therapy in veterinary medicine. These authors point out that a few studies in horses and dogs have currently investigated the possible adverse reactions, such as increased thickening of the injured region after mesenchymal stem cell injection and the tumorigenic potential.

I hope the readers of Veterinary Quarterly will enjoy reading these informative articles as much as I have.