Several years ago, we introduced the concept of a "Progenitor Helper Cell". At the time, all that was known was that MSC's needed to be present to help other cells like blood stem cells (CD34+). Experiments had shown that these blood stem cells (often used in bone marrow transplants) couldn't be grown outside the body unless MSC's were present.
You see, MSC's live in a "stem cell niche". In the bone marrow, this niche contains many other cells. There is evidence of chemical communication between MSC's and these other cells. Why? When we examined that question in 2005, it seemed logical that if MSC's had to be present to help other cells live outside the body, this would be a two way street. These other cells must have the ability to help MSC's. As a result, we coined the term, "Progenitor Helper Cells" (PHC's), for all of the other cells that assist MSC's.
In 2005, it only seemed a matter of time before we would understand how all the other cells in this stem cell niche helped MSC's get their work done. As it happens, research is now proving this concept. In one study published this week, MSC's and bone marrow cells were both needed to repair a rat pancreas in a diabetic mouse. This is a big deal, in that it means that the traditional concept of culturing MSC's in isolation and deploying them in isolation may be concept that isn't as effective as using the cells in a more natural way (meaning MSC's and PHC's together).
In summary, we believe that MSC's work with these other cells to act as "construction managers", overseeing or managing various parts of the repair processes. So it seems that "it takes a village" to both raise children and repair tissues.