Mesenchymal stem cells reside in virtually all post-natal organs and tissues

Mesenchymal stem cells (MSCs) are multipotent cells which can give rise to mesenchymal and non- mesenchymal tissues in vitro and in vivo. Whereas in vitro properties such as ( trans) differentiation capabilities are well known, there is little information regarding natural distribution and biology in the living organism. To investigate the subject further, we generated long-term cultures of cells with mesenchymal stem cell characteristics from different organs and tissues from adult mice. These populations have morphology, immunophenotype and growth properties similar to bone marrow- derived MSCs. The differentiation potential was related to the tissue of origin. The results indicate that ( 1) cells with mesenchymal stem characteristics can be derived and propagated in vitro from different organs and tissues ( brain, spleen, liver, kidney, lung, bone marrow, muscle, thymus, pancreas); ( 2) MSC long- term cultures can be generated from large blood vessels such as the aorta artery and the vena cava, as well as from small vessels such as those from kidney glomeruli; ( 3) MSCs are not detected in peripheral blood. Taken together, these results suggest that the distribution of MSCs throughout the post- natal organism is related to their existence in a perivascular niche. These findings have implications for understanding MSC biology, and for clinical and pharmacological purposes.