The laboratory of Massimiliono Gnecchi at the Fondazione IRCCS Policlinico San Matteo in Pavia, Italy has used the products of amniotic mesenchymal stem cells to treat heart attacks in laboratory rodents. The results are rather interesting.
In a paper published in the May 2015 edition of the journal Stem Cells Translational Medicine, Gnecchi and his colleagues grew human amniotic mesenchymal stem cells derived from amniotic membrane (hAMCs) in cell culture.
These cells were isolated from amniotic membrane donated by mothers who were undergoing Caesarian sections. The membranes were removed, and grown in standard culture media under standard conditions. Once the cells grew out, they were collected and grow in a medium known as DMEM (Dulbecco’s modified Eagle Medium). After the cells had grown for 36 hours, they culture medium was filtered, concentrated, and readied for use.
The first experiments included the use of this conditioned culture medium to treat H9c2 embryonic heart muscle cells with in culture and then expose the heart muscle cells to low oxygen conditions. Normally, low oxygen conditions kill heart muscle cells. However, the cells pre-treated with conditioned medium from hAMCs showed much more robust survival in low-oxygen conditions. This shows that molecules secreted by hAMCs had promote the survival of heart muscle cells.
Next, Gnecchi and his team used their conditioned medium to treat laboratory rats that had suffered heart attacks. Some of the rats were treated with conditioned culture medium from cultured skin cells and others with sterile saline. The culture medium was injected directly into the heart muscle. The rats treated with conditioned medium from hAMCs showed far less cell death than the other rats. The rats treated with the hAMC-treated culture medium also had vastly denser concentrations of new blood vessels.
It is well-known that mesenchymal stem cells from many sources are filled with small vesicles known as exosomes that are loaded with healing molecules. Mesenchymal stem cells release these exosomes when they home to damaged tissues. The culture medium from the hAMCs were almost certainly filled with exosomes. The molecules released by these cells helped promote heart muscle cell survival in the oxygen-depleted heart, and induced the recruited large numbers of EPCs (endothelial progenitor cells), which established large numbers of new blood vessels. These new blood vessels gave oxygen to formerly depleted heart tissue and promoted heart healing. The size of the heart scar was smaller in the rats treated with hAMC-conditioned medium.
Unfortunately there were no measurement of cardiac function so we are not told if this treatment affected ejection fraction, or other physiological parameters. Nevertheless, this paper does show that exosomes from hAMCs do promote the production of blood vessels and cell survival.