Researchers at the Stanford University of School of Medicine have for the first time identified a single cell that is a common precursor to three important cell types: bone, cartilage and the stromal niche cells that support blood and immune cell growth. “Bone plays an under-appreciated role in everyday life,” says stem cell researcher Michael Longaker, MD, co-director of the Institute for Stem Cell Biology and Regenerative Medicine and a co-senior author on the research paper. “Every day, bone supports our daily activities, and there’s a lot more to bones then meets the eye. With this study, we are lifting the veil on how blood and bones are made” he says. The study was published online July 15, 2013 by the Proceedings of the National Academy of Science.
The interaction between stromal cells and blood cells may also lead to answers about certain diseases, they say. “The cells that support blood-forming stem cells and their immediate progeny control not only normal blood formation, but almost certainly control the early stages of pre-leukemia,” says Irv Weissman, MD, the director of the Institute for Stem Cell Biology and Regenerative Medicine and a co-senior author on the study. Weissman notes that, oddly enough, one of the cell types involved was discovered by him and his colleagues 26 years ago and led them to find the blood-forming stem cells in mice and humans. “Let’s hope that we can make even faster progress with these latest results, because a variety of blood diseases will almost certainly be affected by these cells.”
One of the key findings in this report is that the BCSPs make many types of stromal cells—the cells that support the blood and immune cells. Longaker, Chan and their colleagues focused on three types of stromal cells: one that supports all blood and immune stem cells, one that supports the formation of an immune cell called the B cell, and one that supports another, short-lived progenitor cell.
By Christopher Vaughan
“This helps us understand the mystery of how one stem cell can turn into such wildly different cell types as red blood cells, platelets, macrophages, and B and T cells,” Chan says. “This diversity is possible because there is also great diversity in the kind of stromal cells they are exposed to.” The researchers are now asking how such stromal diversity is generated, and think the answer may be found in a biochemical conversation between stromal cells and the blood forming cells.
The researchers call this newly discovered cell the bone, cartilage, and stromal progenitor (BCSP). “Without this cell, we would all be gelatinous blobs,” Chan explains. “Understanding the BCSP will give us insight into how bone and cartilage repair and regenerate themselves, how the hematopoietic system can be stimulated to fight infections and cancer, and how we can make more blood to be more fit or replace blood lost in accidents or surgery.”
“Bones provide the rigid framework for our body plan, cartilage lends flexibility to the joints so we can move around, and everything is fueled and aerated by blood, which is produced in bone marrow niches,” says postdoctoral scholar Charles Chan, PhD, who is a co-first author on the PNAS paper along with undergraduate Paul Lindau and medical student Wen Jiang, PhD. “Now, we have found the one cell that gives rise to these three tissue types.”