Researchers at the Stem Cell Processing Laboratory at the University of Padua in Italy, in collaboration with researchers at INSERM (Institut National de la Sante et de la Recherche Medicale, the national French institute for health and biomedical research) in Paris have isolated c-Kit+ Lin- cells from both human and mouse amniotic fluid for the purposes of investigating the hematopoietic (blood-forming) potential of the cells, which was found to be unusually robust. Also known as “stem cell factor receptor”, the cytokine receptor c-Kit+ is expressed on the surface of hematopoietic stem cells although altered forms have been associated with some types of cancer. Recent independent studies have also demonstrated that Lin- hematopoietic stem cells contain a subpopulation of endothelial precursor cells which are capable of forming blood vessels.
In this particular study, amniotic fluid was collected from pregnant mice between 9.5 and 19.5 days after insemination, from which cells were isolated which were found to have markers similar to those of bone marrow stem and progenitor cells. In vitro, the cells were found to display a multilineage hematopoietic capability, generating erythroid, myeloid and lymphoid cells. In vivo, cells belonging to all 3 hematopoietic lineages were also generated after transplantation into immunocompromised hosts, and the cells were found to exhibit strong self-renewing properties, which is one of the primary traits of stem cells. Similar findings were also obtained from human amniotic fluid that was collected from volunteer human donors between 7 and 35 weeks of pregnancy during routine diagnostic amniocentesis procedures.
According to senior author Marina Cavazzana-Calva, M.D., Ph.D., of INSERM, “Building on observations made by other scientists, our reserach team wondered whether stem cells could be detected in amniotic fluid. We looked at the capacity of these cells to form new blood cells both inside and outside the body, and also compared their characteristics to other well-known sources of stem cells.” As Isabelle Andre-Schmutz, Ph.D., also of INSERM, adds, “The answer was a resounding ‘yes’. The cells we isolated from the amniotic fluid are a new source of stem cells that may potentially be used to treat a variety of human diseases.”
Amniotic fluid, also known as liquor amnii, is the liquid contained within the amnion, which is the membranous sac that surrounds an embryo, the primary purpose of which is protection during development. Amniotic fluid is known to contain a variety of substances, especially after the tenth week of human embryonic development at which time the fluid is rich in lipids, phospholipids, proteins, carbohydrates, urea and electrolytes, among other substances. Amniocentesis, in which fetal cells within the amniotic fluid are analyzed and screened for genetic defects in the developing fetus, is a routinely performed procedure precisely because such fetal cells are readily detectable within the fluid during gestation.
Previous research conducted by scientists at Wake Forest University and Harvard University in 2007 independently confirmed that amniotic fluid contains non-embryonic stem cells which differentiate into a variety of cell types including tissues of the liver, bone and brain. That same year Swiss researcher Dr. Simon Hoerstrup also demonstrated the ability of stem cells from amniotic fluid to differentiate into cardiac cells.
However, given the growing evidence that not only embryonic but also fetal stem cells can cause tumors, and especially in light of the recent medical publication that reported the condition of the Israeli boy who developed a life-threatening tumor that genetically matched the fetal stem cells that he had received as a therapy, it is especially important for scientists and physicians to be extra cautious about knowing whether or not even stem cells derived from amniotic fluid will cause tumors, since no “therapy” should generate more physical problems than those which it is meant to treat. As we have often stated on this website, ethics and politics aside, there are enough scientific hurdles which still need to be overcome before any embryonic, fetal, or pluripotent stem cell of any type (including the iPS cells, which are not stem cells but nevertheless exhibit pluripotency) can be safely and effectively used as a clinical therapy. Nevertheless, the discovery of stem cells within amniotic fluid that have now been shown to differentiate into a wide variety of tissue types offers yet another example by which stem cells can be obtained without the need for embryos. (Please see the related news article on this website, entitled, “Fetal Stem Cell Therapy Could Prove Fatal”, dated February 17, 2009, as originally reported by PLoS Medicine).
The recent findings on the hematopoietic potential of amniotic cells were published in the journal Blood, a publication of the American Society of Hematology, the world’s largest professional society that studies the causes and treatment of blood disorders.