Mesenchymal stem cells form heart muscle

On August 3rd, 2009, the University of Miami Miller School of Medicine released a press piece that reported the results on a study by Joshua M. Hare, who is the director of the Interdisciplinary Stem Cell Institute at the Miller School. This study examined the ability of mesenchymal stem cells to fix ailing hearts.

Mesenchymal stem cells are found in lots of different places in our bodies. They are found in bone marrow stroma, fat, connective tissue, blood vessels, umbilical cord, and lots of other places too. These cells might come from “perivascular” cells, which are cells that hang around blood vessels. Nevertheless, mesenchymal stem cells have the ability to form bone, cartilage, fat, and muscle. They also have a fascinating capacity to hide from the immune system. They have groups of surface proteins that prevent cells from the immune systems from recognizing them as foreign, and therefore, mesenchymal stem cells from one person can be transferred into an unrelated person without fear of transplantation rejection.

Several experiments have shown that mesenchymal stem cells (MSCs) can differentiate into heart muscle if treated with the right chemicals (S. Tomita, et al., Circulation 1999;100:II-247–II-256; Also see H. Okura, et al., Tissue Eng Part C Methods, 2009). Transplanting MSCs into the hearts of laboratory animals that have had heart attacks can also help the fix the heart (D. Wolf, et al., J Am Soc Echocardiogr 2007;20:512-20). However, there is a raging debate over how MSCs help broken hearts get better.

Even though MSCs can form heart muscle in culture, they seem to do so rather poorly (Y. Zhang, et al., Interact Cardiovasc Thorac Surg. 2009 Dec;9(6):943-6). Also, several studies suggest that once MSCs are transplanted into ailing hearts, they do not differentiate into heart muscle with any efficiency worth bragging about and seem to help the heart by means of the chemicals they produce (Ryota Uemura, et al., Circulation Res 98 (2006): 1414-21).

There are, however, some reasons to suspect that this is not the end of the story. Engineering MSCs with various genes or administering MSCs with certain chemicals can push then to form heart muscle at higher rates (Yigang Wang, et al. Am J Physiol Heart Circ Physiol (nov 6, 2009, doi:10.1152/ajpheart.00765.2009). Also, in particular experiments, MSCs clearly form heart muscle (J. Tang, et al., Eur J Cardiothorac Surg 30 (2006): 353-61).

Clinical studies with MSCs for heart problems have been conducted but the data are limited. Initial studies were very encouraging (S. Chen, et al., Am J Cardiol 94 (2004): 92-5 and S. Chen, et al., J. Invasive Cardiol 18 (2006): 552-6). Now a new study has shown that MSCs not only help people who have had a recent heart attack, but that they turn into heart muscle and other heart tissues.  MSCs can also help form blood vessels and the increase of blood flow to the heart also helps an ailing heart.  This seems to be one of the main ways that bone marrow-based stem cells help hearts after a heart attack.  Therefore MSCs might be one of the best ways to treat bum hearts, but certainly more work needs to be done.