Adult stem cells are undifferentiated cells, found throughout the adult body, that multiply by cell division to replenish dying cells and regenerate damaged tissues. For example, the haematopoietic stem cell residing in the bone marrow has been estimated to undergo up to a 720 000-fold expansion during the process of mature blood cell production. Tissue specific adult stem cell types have been identified for several tissues (skin, gut epithelium, blood cells), while the stem cell types responsible for generation of many other adult tissues or cells still remain undiscovered.

The blood vessels are the part of the circulatory system that transports blood throughout the body. They are tubes formed by a single layer of simple squamous endothelial cells (ECs). The cellular origin of new vascular endothelial cells (ECs) during blood vessel growth in angiogenic situations such as wound healing or cancer is unknown.

The Finnish researchers have now identified and isolated previously unknown CD117+ adult vascular endothelial stem cells (VESCs). VESCs are a small subpopulation within vessel wall CD117+ ECs capable of undergoing clonal expansion while other ECs have a very limited proliferative capacity. They have demonstrated that a single vessel wall VESC by the phenotype Lin—CD31+CD105+Sca1+ CD117+ can produce in vitro tens of millions of daughter cells. Importantly, a single isolated VESC by the phenotype lin—CD31+CD105+Sca1+CD117+ can generate functional blood vessels in vivo. They have also shown that VESCs are present in tumor vasculature and in other neovascular tissues.

Isolated VESCs could be used in cell-based therapies to restore tissue vascularization in ischemic situation such as atherosclerosis and coronary artery disease. Importantly, neovascular blood vessel growth is a prerequisite for cancer growth and dissemination, and antiangiogenic therapies (such as Avastin) are already in clinical use. Since CD117+ VESCs are the very cells responsible for blood vessel growth in adults, they provide a novel specific target to block pathological angiogenesis and cancer growth.

This is a completely novel innovation and no direct competition exists. Endothelial cells are not yet used in cell transplantation therapies. The adult endothelial stem cells and their isolation methods described above will be the natural basis for EC isolation therapies. These cells are also the true biological target for all existing and future anti-angiogenic therapies.

Fields of applications:
-proangiogenic therapies to restore tissue vascularization in ischemic situations (atherosclerosis, coronary artery disease, diabetes)
-antiangiogenic therapies to inhibit vascular growth (cancer, other neovascular disorders)