Initially the term mesenchymal stem cells (MSCs) described cells isolated from bone marrow stroma that could give rise to bone and cartilage but has expanded to include cells from many different tissues with varying levels of multipotency. In the late 1990s the term MSC was used to describe any cells able to stick to plastic culture dishes and differentiate into other cell types in vitro, whether they came from stromal compartments of bone, fat or other tissues. Many of these MSCs did not behave as stem cells in vivo. A 2016 study showed that various cell populations from different tissues with very different gene expression and differentiation abilities were all classed as MSCs.
In 2006 the International Society for Cellular Therapy released a position statement proposing the term multipotent mesenchymal stromal cell instead of mesenchymal stem cell, unless the cells met the accepted criteria of stem cells, which is that capacity to self renew and differentiate into specific cell types in vivo. A commentary in Nature in 2018 called for “a coordinated global effort to improve understanding of the biology of the cells currently termed MSCs, and a commitment from researchers, journal editors and others to use more-precise labels.” The commentary encouraged more specific terms to describe the source of cells rather than using the misleading umbrella term. One company that is refraining from the MSCs term and using ‘adipose-derived regenerative cells’ instead is San Diego, California company, Cytori Therapeutics.
Despite disagreement in the scientific community about the nature of MSCs a 2016 report found that almost half of 351 US companies selling putative stem-cell therapies directly to customers mention MSCs in their marketing materials. There is concern that this catch-all term for cells that are actually different makes it easier for companies to sell unproven treatments.
Rather than their ability to differentiate into new cell types in the body, many of the therapeutic functions of MSCs are associated with their secretion of paracrine factors which can have anti-inflammatory and/or pro-angiogenic effects.