Mesenchymal Stem Cells: The Workhorse of Regenerative Medicine

Prolific Stem Cell and Cell Therapy Blogger Alexey Bersenev (@cells_nnm on Twitter) has recently written a post on his Cell Trials blog titled "Trends in cell therapy clinical trials 2011 – 2013".  If you are interested in Stem Cells and Cell Therapy, it is highly likely that you already know Alexey.  He is one of the most passionate and dedicated technologists in the area.  If you don't know him,  you can follow his activities at the above links, as well as at his Stem Cell Assays blog and among several LinkedIn Discussion groups.  Alexey reported that his own research shows that Cell Therapy Clinical Trials that are listed in international databases have doubled from 2011 to 2013, going from of 161 to 324. Alexey evaluated the data by the split between industry and academia (three academic trials in 2013 for every industry-sponsored trial), by country, by region, as well as by cell type and clinical indication.  His analysis is very important because with his technical background and expertise (Alexey is an MD/PhD researcher who has been doing hands stem cell research or therapeutic cell manufacturing as his day job for several years), if anyone can correctly categorize a trial, it is Alexey.

When tweeting highlights of his Cell Therapy Clinical Trials blog post (above inset) an astute follower of his picked up on the fact that Mesenchymal Stem/Stromal Cell (MSC) trials are out-pacing the other cell types.  This fact is consistent with another often-cited recent manuscript printed in the journal Regenerative Medicine titled "The Global Landscape of Stem Cell Clinical Trials" (free download available here).  This manuscript also creates its own database and analyzes the various types of trials, with the conclusion that "most of the increase (in Cell Therapy Clinical Trials) since 2006 was due to trials using MSCs".

So WHY are MSC trials outpacing other cell sources?  There are several reasons for this.  We believe this is likely due mostly to:

1. MSC researchers enjoy a tremendous data set generated over the last 20 years, and the safety profile of MSCs in early stage clinical trials has been very good.  This accumulated data has created a more straight-forward regulatory path with MSCs when compared to many other cell types such as pluripotent stem cell (PSC)-derived therapies.  PSCs are still in their infancy from the clinical trial side, and the next 10 years should considerably de-risk these cells.
2. Many MSC trials are performed with undifferentiated cells, and the manufacturing processes are simpler, more standardized, and more robust than many differentiated cell products.  This leads to more straight forward CMC (Chemistry, Manufacturing and Controls) filings when compared to newer cell types that have complicated differentiation pathways that have never been scaled up.  The standardization over the last several years has led to greater robustness, with more consistency around cost of goods. 
3. Finally, due to their robust signaling activity, MSCs demonstrate usefulness in a wide range of clinical indications (see Figure below borrowed from Viswanathan et al., Stem Cells Dev. 2014, Jan 14)  including cardiac, vascular, neurological, and various orthopedic regenerative applications, not to mention immunological applications (eg. GVHD) and more recently cancer therapies.  MSCs can be used alone or with other cell types to facilitate engraftment of these other cells by modulating host immune response to "protect" these cells.  Since a single manufacturing process can produce MSCs for use in a variety of clinical trials, clinical application of these cells is accelerated compared to other cell types.

Figure from Viswanathan et al, Stem Cells Dev. 2014 Jan 14.

Due to their tremendous therapeutic potential, the trend of MSC technology being incorporated into regenerative therapies will continue, and there is a strong need for affordable, abundant, and extremely well characterized MSC products to enable product development and successful clinical translation. New technologies such as bioprinting, cell and tissue engineering, synthetic biology/genetic manipulation, and of course, cell manufacturing sciences will continue to propel this field forward and further necessitate the need for the availability of large numbers (lot sizes in the billions) of clinically-translatable MSCs.

Do you think there are other driving forces behind MSC use in the clinic?  Please comment below.