Human amniotic fluid stem cells (hAFSCs) have been isolated from the “water” that surrounds the baby when it is born. Amniotic fluid is the material is lost when a pregnant woman’s “water breaks.” If the amniotic fluid is retrieved before it ruptures, a specific stem cell population can be isolated from it, and these stem cells grow very well in culture, and can differentiate into a multiple of adult cell types.
When it comes to the heart, hAFSCs have a bit of a mixed record. One publication from Anthony Atala’s laboratory showed that implantation of hAFSCs into the heart of a laboratory animal after a heart attacked was followed by the formation of bony nodules in the heart tissue (see Chiavegato et al., J Mol Cell Cardiol. 42 (2007) 746-759). However, a follow-up publication, showed that the conditions used in the previous experiments caused the formation of bony nodules in the heart regardless of whether or not hAFSCs were implanted into the heart (Delo DM et al., Cardiovasc Pathol 2011 20(2):e69-78). Other papers showed that implanted cAFSCs could protect the heart from further deterioration (Bollini S et al., Stem Cells Dev. 2011 20(11):1985-94). However, a perennial problem is the poor retention of the cells in the heart after injection. Therefore, one group tried implanting hAFSCs into cellular goo (extracellular matrix). This caused the hAFSCs to stay put in the heart and differentiate into heart muscle cells and blood vessels (Lee WY et al., Biomaterials. 2011 32(24):5558-6).
On the heals of this success comes a paper from Taiwanese researchers who have embedded hAFSCs into polylactic-co-glycolic acid (PLGA) beads and implanted these into the heart of a laboratory animal after a heart attack. These beads are made of material that is completely biogradable, but the hAFSCs survive and grow well in them. Also, once they are implanted into the heart, the beads are large enough to prevent them from being displaced. Once the beads disintegrate inside the heart tissue, the cells are already so deeply implanted into the heart tissue, that they do not become washed out by circulating blood and other fluids.
The implanted hAFSCs differentiated into heart muscle cells and blood vessels. The blood vessels density in these hearts of the hAFSC implanted animals twice that of the control animals in the area of the infarct and almost three times that of the control outside the area of the infarct. The scar shrunk in the hAFSC-implanted hearts by ~30%, and the structure of the hAFSC-implanted hearts was much more robust and thick relative to the controls. Finally, the contraction of the heart muscle was (4 weeks after treatment) twice as strong in the hAFSC-treated hearts compared to the control. Ejection faction was not measured, and that is a deficiency in this paper, but all the cardiac parameters that were measured were vastly improved in the hAFSC-treated hearts relative to the untreated controls.
This paper shows that the porous PLGA beads are not toxic, deliver cells to the chosen target, and quickly disintegrate without affecting the target tissue, in this case the heart. Clearly hAFSCs have a part to play in the future of regenerative medicine.