Stem cell therapies for neuromuscular diseases.

The promise of stem cells for therapy of a variety of disease conditions is one of the most heavily marketed commodities of modern biotechnology. Interest in this prospect has opened up and destabilized a large area of developmental biology, challenging some of its major tenets, and becoming a source of controversy. Much of the disagreement arises from apparently simple conflicts of findings, which may have as much to do with differences of interpretation as of actual data. However, outside a few favoured situations, the practical significance of most of the findings is marginal, with only trivial levels of stem cell participation in tissue reconstruction. Currently, much of the effort in stem cell research is devoted to identifying sources of stem cells and the diversity of fates they can be induced to adopt. Areas that are in need of development are those concerned with delivery to target tissues, improvement of conversion to the desired cell types and effectiveness of functional integration of these cells into the target tissue. Of these hurdles, perhaps the most important is the efficient delivery of stem cells to the appropriate sites. The most promising results in this respect have been achieved by either targeted injection to discrete sites or, for more diffuse targets, delivery via the intermediary of a bone marrow transplant. For the latter especially, we need a degree of improvement that can only come from a better understanding of the mechanisms involved.